HK1187574B - Hardfaced wearpart using brazing and associated method and assembly for manufacturing - Google Patents

Description

Hardfaced wear parts using brazing and related methods and assemblies of manufacture

Cross reference to related applications

This application claims priority from U.S. provisional patent application No. 61/472, 470, filed on 6/4/2011, and the entire contents of which are incorporated herein by reference and made a part hereof.

Technology neighborhood

The present invention relates to various embodiments of hardfaced components for abrasive environments formed using infiltration brazing or another brazing technique. More particularly, the present invention relates to products, systems, and methods related to these hardfaced components. For example, these hardfaced components may include wear resistant tools for biting into ground machinery (e.g., the tip of an excavator), mineral processing equipment such as the tip for a two roll crusher, trommel screens, or other abrasive applications.

Background

Examples of wear parts produced by penetration of hard particles are disclosed in US patent nos. US4884477, US4949598 and US6073518, and publications US20100278604, GB2041427 and WO 2008103688. Earlier documents describing more generally the infiltration process for making cemented carbides include US1512191 and DE420689C (r) ((r))1925, deutsches reich). The contents of these and all other documents referred to herein are hereby incorporated by reference in their entirety. The present invention seeks to overcome certain deficiencies of these and other prior devices and to provide new features not heretofore available.

Disclosure of Invention

Economical and efficient hardfaced wear parts are provided that are formed from a substrate, a thin shell, a plurality of hard particles held in a mold cavity defined between the substrate and the shell, and infiltrated brazing material that bonds the components into a composite wear part. Thin shells of metal are consumable because they typically corrode rapidly when these hardfaced parts are used. Methods for manufacturing these wear parts using infiltration brazing and consumable thin shells are also provided.

Aspects of the present invention relate to a hardfaced wear member comprising a steel substrate; a steel shell bonded to the substrate to define a cavity between the substrate and the shell; and a hard composite filling the cavity, the composite comprising a plurality of hardened particles infiltrated with a metal braze. Preferably, the hardfaced wear-resistant member is one in which the shell weighs substantially less than the substrate. Furthermore, preferably, the shell defines a reservoir outside the cavity, and more particularly, a flared reservoir outside the cavity. In some embodiments, the shell defines a funnel-shaped receptacle outside the cavity. In certain embodiments, the housing is welded to the substrate.

Aspects of the present invention relate to an article, such as a hardfaced wear part, including a substrate; a sheet metal shell connected to the substrate to define a cavity between a surface of the substrate and the shell; and a composite material filling the cavity and forming a coating on at least a portion of the surface of the substrate, the composite material comprising a hard particulate material infiltrated with a metallic brazing material.

According to one aspect, the shell has an opening providing access to the cavity for inserting hardfacing material and feeding the braze material. The shell may also include a reservoir connected to the shell and positioned outside the cavity in communication with the opening to initially contain the brazing material during manufacture.

According to another aspect, the housing may be attached to the surface of the substrate by welding or brazing. The housing may also include a conformal band in face-to-face contact with a portion of the surface of the substrate and around an entire perimeter of the housing such that the housing is connected to the substrate by welding or brazing at least at the conformal band. In such a configuration, the substrate may have a bonding surface in face-to-face contact with the conformal band, and at least a portion of the substrate within the mold cavity may be recessed relative to the bonding surface such that the composite material has an outer surface that is flush with the bonding surface.

According to yet another aspect, the brazing material may be bonded to the surface of the substrate and may also be bonded to the housing.

According to another aspect, the housing may include a front member having a front flange extending transversely from a rear edge of the front member and a rear member having a rear flange extending transversely from a front edge of the rear member, wherein the front and rear members are joined together to form the housing by welding or brazing the front and rear flanges.

According to yet another aspect, the particulate material may be or include tungsten carbide, and the metallic brazing material may be or include Ni-Cr-Si-B brazing alloy powder.

According to yet another aspect, the substrate may have a hole in the surface, and an insert rod may be received in the hole such that the hole is covered by the composite material.

Additional aspects of the invention relate to a tool having a surface at a tip of the tool and a bonding surface disposed proximate the surface, a composite hardfacing material forming a coating on at least a portion of the surface, and a sheet metal shell in contact with and surrounding the composite material. The composite hardfacing material includes a hard particulate material infiltrated with a metallic brazing material, wherein the metallic brazing material bonds with the surface to join the composite hardfacing material and the tool. The housing has a conformal band in contact with the bonding surface of the tool, and the housing is attached to the tool by at least welding or brazing between the conformal band and the bonding surface. A cavity is defined between the surface of the substrate and the shell, and the composite hardfacing material fills the shell.

Other aspects of the invention relate to a composite wear resistant tool comprising: a steel shell defining a mold cavity; a steel substrate partially filling the cavity to define a void between the shell and the substrate; and a hard composite at least partially filling the void and comprising a plurality of hardened particles infiltrated with a metal braze.

Other aspects of the invention relate to a hardfaced wear member comprising: a steel shell defining a mold cavity; a steel substrate only partially filling the cavity; and a hard composite in intimate contact with both the housing and the substrate to define a hard layer that protects the substrate from abrasion, and the composite includes a plurality of hardened particles infiltrated with a metal braze.

Still other aspects of the present invention relate to a hardfaced wear part for moving earth equipment comprising: a steel substrate; a steel shell substantially conforming to at least a portion of the surface of the substrate and defining a cavity therebetween; and a hard composite at least partially filling the cavity and bonded to both the shell and the substrate, the composite comprising a plurality of hardened particles infiltrated with a metal braze. Preferably, the shell has an average shell thickness, the substrate has an average substrate thickness, and the average shell thickness is substantially less than the average substrate thickness.

Other aspects of the invention relate to a composite wear resistant tool comprising: a thin metal shell defining an outer perimeter for a hard composite; a thick metal substrate defining a body for a tool, the substrate being at least partially surrounded by the housing; and a layer of hard particulate material infiltrated with a brazing alloy and defining a hard composite bonded to both the housing and the substrate.

Still other aspects of the invention relate to an article comprising: a substrate; a metal shell coupled to the substrate to define a cavity between a surface of the substrate and the shell; a hard material positioned within the mold cavity; and a metal brazing material which bonds the brazing material and the surface of the base material. As described above, the hard material and the metal brazing material may form a composite hardfacing material covering the surface of the substrate. In one configuration, the hard material may have a porous structure, such as a particulate material or a porous preform, and the porous structure is infiltrated with the metal brazing material to form the composite hardfacing material. In another configuration, the hard material may have a monolithic structure.

Aspects of the invention also relate to a method for use with a substrate, comprising: connecting a sheet metal shell to the surface of the substrate to define a cavity between the shell and the surface; placing a hard particulate material in the mold cavity against the surface; placing a metal brazing material in communication with the mold cavity; heating the brazing material to a temperature above the melting point of the brazing material and for a time sufficient for the brazing material to penetrate the particulate material in a molten state and contact the surface of the substrate; and cooling the brazing material to solidify the brazing material and form a wear-resistant composite coating on the surface of the substrate. The brazing material may be bonded to the surface and/or the housing after the brazing material is cured.

According to one aspect, the shell has an opening to the exterior of the shell and a flared receptacle is connected to the shell and positioned outside the cavity in communication with the opening, and the brazing material is placed in the receptacle in communication with the cavity. The container may be integrally formed with the housing.

According to another aspect, coupling the housing and the substrate includes welding or brazing the surfaces of the housing and the substrate. The housing may also include a conformal band that extends around a perimeter of the housing. In this configuration, connecting the housing and the substrate can include welding or brazing the conformal band to the surface of the substrate such that the conformal band is in face-to-face contact with a portion of the surface of the substrate surrounding the entire conformal band.

According to yet another aspect, the housing includes a front member having a front flange extending transversely from a rear edge of the front member and a rear member having a rear flange extending transversely from a front edge of the rear member. The method may also include joining the front member and the rear member together to form the housing by welding or brazing the front flange and the rear flange.

According to yet another aspect, the brazing material is heated to a temperature sufficient to melt the brazing material and for a time sufficient to allow the brazing material to penetrate the spaces between the hard particles, thereby bonding them together and to the substrate. For example, if tungsten carbon monoxide (WC) hard particles and pure copper or AWS BNi-2 are used, the brazing material may be heated to a temperature of about 2050F for a time period of 30 minutes to 1 hour in many applications. Heating may be accomplished in one configuration in a vacuum oven.

According to another aspect, the method also includes forming the housing, such as by welding or brazing multiple pieces of sheet metal together to form the housing. Other techniques may additionally or alternatively be used.

Other aspects of the invention relate to a method for manufacturing a composite wear resistant tool comprising the step of infiltrating a layer of hard particles confined between a substrate and a consumable sheet metal housing. The shell may be configured such that it confines the hard particles to a desired location on the substrate, and has a particular thickness and shape defined by the contours of both the substrate and the shell. The housing may also be configured such that it defines a receptacle for receiving the infiltration material to be melted during the infiltration step. Almost any tool or component that is currently case hardened by welding can be case hardened by the disclosed methods. These methods may include the step of selecting the particulate material in a type and size distribution to give the desired degree of wear resistance for the intended application. These methods may include steps in which the particulate material and its size distribution, as well as the type of osmotic material used, are selected to give the intended application a desired degree of abrasion resistance, while matching the differences in thermal and metamorphic expansion between the osmotic layer and the substrate so as to reduce or eliminate cracking and flaking.

Other aspects of the invention relate to a method of case hardening a metal part to produce a wear resistant composite product comprising: surrounding the component or a part of the component to be case hardened with a sheet metal casing; leaving a mold cavity; welding or high temperature brazing the shell to the substrate such that the mold cavity retains molten metal while being heated; at least partially filling the cavity with granular or powdery particles of an abrasive wear-resistant material; and then infiltrating the particles with a suitable low melting point material to bond the particles to each other and to the substrate by heating. More specific embodiments of the method include: providing a container integrated with the housing; placing a brazing alloy in the container; heating the combined assembly of the substrate, the shell, the particles of wear-resistant material, the container, and the brazing alloy such that the brazing alloy melts and flows into the gaps within the particles of wear-resistant material; and cooling the assembly such that the substrate, the shell, the particles of the wear-resistant material, and the braze alloy bond together to form a composite wear-resistant component.

Other aspects of the invention relate to a method comprising: connecting a metal shell to a surface of a substrate to define a cavity between the shell and the surface; placing a hard material in the mold cavity; placing a metallic brazing material in communication with the mold cavity; heating the brazing material to a temperature above the melting point of the brazing material and maintaining the temperature for a time sufficient for the brazing material to contact the brazing material and the surface of the substrate in a molten state; and then cooling the brazing material to solidify the brazing material and bond the material to the surface of the substrate. As described above, the housing may be formed of sheet metal. As also described above, the hard material may be infiltrated with the molten braze material to form a wear resistant composite.

Aspects of the present invention relate to an assembly comprising: a tool having a surface configured to bite into earth to move the earth; and a sheet metal shell coupled to the tool and having a conformal band conforming to at least a portion of the surface to define a mold cavity between the surface and the shell. The housing may also have an opening to the exterior of the housing. The housing is attached to the tool by welding or brazing the conformal band to at least a portion of the surface.

According to one aspect, the assembly is configured to form a wear resistant composite coating on the surface by: at least partially filling the mold cavity with a hard particulate material through the opening, placing a metallic brazing material in communication with the mold cavity, heating the assembly to a temperature above the melting point of the brazing material and maintaining the temperature for a time sufficient for the brazing material to penetrate the particulate material in a molten state and contact the surface of the tool, and cooling the assembly to solidify the matrix material and form a wear resistant composite coating on the surface. The assembly may also include a flared receptacle connected to the shell and positioned outside the mold cavity in communication with the opening, wherein the receptacle is configured to place the brazing material therein in communication with the mold cavity. After the process, the assembly may include a composite material that fills (or partially fills) the mold cavity and forms a coating on at least a portion of the surface of the tool, wherein the composite material includes a hard particulate material infiltrated with a metallic brazing material. The brazing material may be bonded to the surface and/or the housing.

According to another aspect, the assembly also includes a flare reservoir connected to the shell and positioned outside the cavity in communication with the opening. The flared container may be integrally formed with the outer shell.

According to yet another aspect, the conformal band extends around an entire perimeter of the housing and around an entire perimeter of the surface.

According to yet another aspect, the housing may include a front member having a front flange extending transversely from a rear edge of the front member and a rear member having a rear flange extending transversely from a front edge of the rear member, wherein the front and rear members are joined together to form the housing by welding or brazing the front and rear flanges.

According to another aspect, the tool has an aperture in the surface, and the assembly further includes an insert rod received in the aperture. In this configuration, spaces may be defined between the insert rod and the inner wall of the bore.

Other aspects of the invention relate to an assembly comprising: a tool having an operative surface; a sheet metal shell covering at least a portion of the operative surface and defining a cavity therebetween; and a plurality of spacers engaging the tool and the housing and separating the tool from the housing. The housing has an opening to an exterior of the housing.

According to one aspect, the assembly is configured to form a wear resistant composite coating on the work surface by: at least partially filling the mold cavity with a hard particulate material, placing a metallic brazing material in communication with the mold cavity, heating the assembly to a temperature above the melting point of the brazing material and maintaining the temperature for a time sufficient for the brazing material to penetrate the particulate material in a molten state and contact the operative surface of the tool, and cooling the assembly to solidify the matrix material and form the wear-resistant composite coating on the operative surface. After the process, the assembly may include a composite material at least partially filling the mold cavity and forming a coating on at least a portion of the operative surface of the tool, and the composite material comprises a hard particulate material infiltrated with a metallic brazing material, wherein the brazing material is bonded to the operative surface.

According to another aspect, the assembly may also include a wall extending from the shell and defining a receptacle connected to the shell and positioned outside the cavity in communication with the opening, wherein the receptacle is configured to place the brazing material therein in communication with the cavity.

Other aspects of the invention are directed to an assembly that may be used to form hardfacing material on a surface of a tool or other substrate. A metal shell is coupled to the substrate and has a conformal band conforming to at least a portion of a surface of the substrate to define a cavity between the surface and the shell. The housing also has an opening to the exterior of the housing. The housing may be formed of sheet metal in one configuration and may be welded or brazed to the substrate as described above.

Advantages of the invention will become more readily apparent after a consideration of the drawings and detailed description.

Drawings

Fig. 1-4 are perspective views of an embodiment of a wear member having an attached shell.

Fig. 5 is a top view of an embodiment of the wear member with an attached shell as shown in fig. 1-4.

Fig. 6 is a bottom view of the embodiment of the wear component with the attached shell as shown in fig. 1-5.

Fig. 7 is a left side view of the embodiment of the wear member with the attached shell as shown in fig. 1-6.

Fig. 8 is a right side view of the embodiment of the wear member with the attached shell as shown in fig. 1-7.

Fig. 9 is a front view of the embodiment of the wear component shown in fig. 1-8 with the shell attached and the hardfacing material visible within the shell and protecting a substrate.

Fig. 10 is a front view of an alternative embodiment of the wear part from a perspective similar to that of fig. 9, and in the form of a finished hardfaced wear part with an attached shell, with portions of the shell seen in fig. 9 removed.

Fig. 11-17 are views corresponding to fig. 1-7, respectively, but showing the finished hardfaced wear part of fig. 10.

Fig. 18 is a perspective view of another embodiment of a wear member with an additional shell including a container formed as a funnel.

Fig. 19 shows a perspective view of another embodiment of a two-piece housing, with the housing shown in an upright orientation.

Fig. 20 is a top view of the embodiment of the housing according to fig. 19, but including a wear member with a two-piece housing attached, with the wear member and housing shown in an upright orientation.

Fig. 21 is a left side view of the embodiment of fig. 20 with a wear member having a two-piece shell attached.

Fig. 21a is a left side cross-sectional view of the wear member of fig. 20 and 21 showing an attached two-piece shell having another configuration.

Fig. 22 is a cross-sectional view of the embodiment of fig. 20 and 21, taken generally along the line 22-22 in fig. 20.

Fig. 23 is a cross-sectional view of the embodiment of fig. 20 and 21, taken generally along the line 23-23 in fig. 20 and 21.

FIG. 24 is a cross-sectional view of the embodiment of FIG. 18 taken generally along a plane similar to the plane used to define the cross-sectional view of FIG. 22, but showing the substrate and housing in a horizontal orientation.

Fig. 25a-25j show various views as part of manufacturing a wear part generally in accordance with the embodiment of fig. 19-23.

Fig. 26 and 27 show perspective views of two different embodiments of an underlying substrate that may be used to manufacture hardfaced wear parts, and in fig. 26 and 27 the substrate, more particularly a tip, is oriented vertically.

Fig. 28 is a front view of the substrate and attached housing from a view similar to fig. 20 and 25c, and schematically shows two holes each including a hardened insert and two spacers.

FIG. 29 is a photograph of two hardened inserts used with the substrate shown in FIG. 28.

Fig. 30 is a plan view of the spacer of fig. 29.

FIG. 31 is a photograph of two examples of embodiments of the substrate shown in FIG. 27, each example shown having a weld station and ready to receive an appropriate amount of hard particles and infiltration braze powder.

FIG. 32 is a photograph of two examples of embodiments of the substrate and the housing shown in FIG. 28, each example shown having a housing filled with a penetration brazing powder.

Fig. 33 is a photograph of two examples from fig. 32 loaded into a furnace.

Fig. 34 is a photograph of an example from the examples of fig. 32 and 33 after the shell has worn away at the start of excavation.

Fig. 35 is a front view of the substrate and attached housing from a view similar to fig. 28, and schematically showing three apertures, and a central aperture including a hardened insert.

Fig. 36 is a cross-sectional view of the embodiment of fig. 35, taken generally along the line 36-36 in fig. 35.

FIG. 37 is a cross-sectional view of the embodiment of FIG. 36 with a plurality of particulate carbide particles filling a mold cavity defined between the substrate and the shell.

FIG. 38 is a cross-sectional view of the embodiment of FIG. 37 with brazing material filling a container formed by the shell over the carbide particles.

FIG. 39 shows a cross-sectional view of the embodiment of FIGS. 35-38 after an infiltration brazing cycle, with hardfacing surrounding and protecting the substrate.

Fig. 40 is a photograph of particulate carbide on the right and braze alloy powder on the left.

FIG. 41 shows a sample oven cycle chart with temperature on the vertical axis and time on the horizontal axis.

Fig. 42a-42k show various views as part of another embodiment of manufacturing a wear resistant component, with a different fig. 42a-42k showing selected processing steps as part of penetration hardfacing a twin roll crusher tip.

Fig. 43a-43f show various views as part of another embodiment of manufacturing a wear part, with different fig. 43a-43f showing selected processing steps as part of a twin roll crusher tip using infiltration hardfacing of a shell with an exhaust tube.

FIG. 44 shows a perspective view of another embodiment of a hardfaced wear member having a spherical configuration with a particularly complex surface shape.

Fig. 45a-45k show various views as part of another embodiment of making a wear resistant component, with different fig. 45a-45k showing selected processing steps as part of penetration case hardening a trommel screen for mineral processing.

Detailed Description

While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail preferred embodiments of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the various aspects of the invention to the embodiments illustrated and described.

In general, the present invention relates to the formation of composite or other wear resistant materials, such as wear resistant components, on the surface of a substrate using a metal shell using brazing and/or infiltration techniques, as well as articles formed using these techniques and methods and apparatus incorporating these techniques. For example, an article (e.g., a hardfaced wear component) formed using these techniques may include: a substrate; a sheet metal shell connected to the substrate to define a cavity between a surface of the substrate and the shell; and a composite material filling (or partially filling) the mold cavity and forming a coating on at least a portion of the surface of the substrate, and the composite material comprising a hard particulate material infiltrated with a metallic brazing material. In a more general example, an article formed using these techniques may include: a substrate; a metal shell coupled to the substrate to define a cavity between a surface of the substrate and the shell; a hard and/or wear resistant material positioned within the mold cavity; and a metal brazing material bonding the brazing material and the surface of the base material.

One embodiment of an article in the form of a hardfaced wear component 10 is shown in fig. 1-9 in the form of a mining tip. Unless otherwise indicated, the hardfaced wear-resistant component can comprise at least one of the structures, components, functionalities and/or variations described, illustrated and/or incorporated herein. The two basic components of the hardfaced wear part 10 include a primary tool that forms the structural component 12, or more generally the substrate 12, and an outer consumable metal shell 14 that forms a mold for the hardfacing material. Preferably, the base substrate 12 is formed of a metal, such as a steel alloy known in the art for use in ground engaging tools, and the housing 14 is made of sheet metal, such as a low carbon "soft" steel. The sheet metal housing 14 may be constructed of any material that can be formed or manufactured into a particular desired shape and that can withstand dissolution, melting, or undue weakening by the infiltrating material or temperatures generally required for infiltration brazing during the infiltration process. Various other components and configurations may be used to form the substrate 12 and to manufacture the hardfaced wear part 10 with the hardfacing material thereon. Examples of such components and structures include other types of tips, shrouds, or rotors; teeth for a bucket or dredge head; scrapers for soil levelers and scrapers; wear liners for various applications such as skids or truck bodies; earth-biting equipment such as used in mining, construction, or drilling; parts for mining processing equipment such as tips for twin roll crushers or trommel screens; and virtually any other desired components and structures. The present invention can also be used to replace damaged parts; the broken component may be a wear component such as a bite into the floor tool or a support structure such as a lip of a bucket.

The hardfacing material bonds with the base substrate 12 and protects the base substrate 12, but is not readily visible in fig. 1-8 because it is enclosed by the housing 14. Typically, the hardfacing material includes a hard material and a metallic brazing material that bonds the hard material to the substrate 12. The hard material generally has a higher hardness than the surface of the hard-facing substrate 12. The hard material may also have a higher wear resistance than the surface of the base substrate 12. As described in more detail below, the hardfacing material may be a composite formed of a hard material in the form of hard particles, and the hard particles are typically present in particulate (e.g., granular or powdered) form, such as tungsten carbide particles, infiltrated with an infusion metal brazing material, typically in granular or powdered form, such as a copper-based or nickel-based brazing alloy. It should be understood that "metallic" materials may include pure metals, as well as alloys and other materials that include one or more metals. In another embodiment, the hard material may be in the form of a porous material including a particulate material, a porous preform (e.g., a sintered preform), or other porous structure that may be infiltrated by the brazing material. Preferably, such porous materials may have a porosity of 5-50%, but may have a different porosity in other embodiments. In yet another embodiment, the hard material may be a solid, monolithic structure (or multi-piece structure), such as a tile, board, or other monolithic structure bonded to the surface of the substrate 12 by the brazing material. In each of these embodiments, the shell 14 is used to hold the hard material in a cavity 50 defined between the shell 14 and the outer surface of the substrate 12 in a position for brazing, such as against the surface of the substrate 12.

The housing 14 includes: a shell body 16, and an opening 17 opens to the outside of the shell body 16 and the cavity 50 is defined by the shell body 16; a container 18 communicating with the opening 17. In one embodiment, the receptacle 18 may be integrally formed with the housing body 16, or in another embodiment the receptacle 18 may be separately formed and engaged with the housing body 16. The container 18 is used only when the wear part 10 is manufactured and, as explained in more detail below, may be removed (e.g., cut away) or may simply be corroded away when the wear part 10 is in operational use. The shell 14 is joined to the substrate 12 by a conformal band 20, and the shell 14 is welded to the substrate 12 by the conformal band 20. The conformal band 20 can be in face-to-face contact with a portion of the substrate 12, surrounding a portion or all of the perimeter of the shell and the substrate, as described below. Alternatively, the housing 14 may be brazed to the substrate 12 if any of the brazing materials used to braze the housing 14 to the substrate 12 have a melting point temperature that is higher than the melting point temperature used to inject the brazing material. In other embodiments, the housing may be attached to the substrate 12 in another manner. For example, the housing may be placed on the substrate 12 using a ceramic felt or cloth gasket to seal the cavity and prevent the brazing material from leaking out during brazing.

Fig. 9 most clearly shows that the shell 14 has a shell thickness 22 that is significantly less than the nominal thickness of the base substrate 12. For example, the skin 14 may have an average skin thickness of about 0.105 inches, while the substrate 12 in FIGS. 1-9 may have a thickness in the range of 1.000 to 3.450 inches in the area covered by the skin. In one embodiment, the housing 14 may be constructed of sheet metal in the range of 16Ga (0.060 inches thick) to 10Ga (0.135 inches thick), which may be used in a wide variety of applications. In other embodiments, the housing 14 may have any other suitable thickness. For example, in further embodiments, the housing 14 may be constructed of steel or other metal plate having a thickness of about 0.25 inches, or may be cast or machined from bar stock, or otherwise formed. It should be understood that different portions of the housing 14 may have different thicknesses. Also visible in fig. 9 is a layer of composite hardfacing material, generally indicated at 24.

The relative thinness of the housing 14, when compared to the substrate 12, means that the housing 14 can be easily and relatively inexpensively formed. For simple shapes of the housing, a relatively low cost housing 14 may be made by cutting multiple pieces of sheet metal, welding or brazing the pieces together. Somewhat more complex shapes can be made by bending pieces of sheet metal into a particular configuration and then welding the bent sheet metal. The complex shape can be formed by, for example, deep drawing sheet metal forming, forming by the green (wire) method (rubber mat forming), hydroforming, and/or explosion forming. Precision ("lost wax") casting can also be used, but the cost of lost wax processes is generally not economical. For particularly complex shapes, the components of the housing may be formed by one or more of these methods, and then joined by welding or brazing.

Very little material is required to form an effective mold even for relatively large substrates. For example, if the mining tip 10, the weight of the shell 14 would only be approximately 41/2 pounds and the weight of the base substrate 12 would be 224 pounds. The particular weight of the mining tip and the housing for a particular size tip is only an example. There are many large variations depending on the size of the different tips used for different operations. However, all embodiments disclosed herein include a substrate and a housing, wherein the housing weight is significantly less than the substrate.

The shell is consumable, does not have a structural function in the finished product and often wears quickly when the resulting hardfaced wear part is used. Thus, the particular metal used to form the housing 14 need only be strong enough and resistant enough to dissolve to survive the high temperatures of the penetration brazing. Many readily available, relatively low cost sheet steels meet this criteria. Combining a minimum amount of material for 224 pounds of substrate, for example, less than 5 pounds of sheet steel, using readily available sheet steel, and using relatively easy manufacturing techniques to manufacture the thin metal shell 14, means that the cost of the shell 14 is often minimal when compared to the market value of the resulting hardfaced wear part 10.

In many applications, the tool substrate can be quite large and heavy, and the tool substrate is often transported or handled with the substrate in a particular orientation with respect to gravity. For example, a very heavy substrate may be held firmly on a bucket or in a fixture with the area to be case hardened facing upward. Other substrates may be supported by a base or a particular surface, with the area to be hardfaced facing up, sideways, or downward. Additional substrates may have multiple separate areas to be case hardened, facing in multiple different orientations.

The light sheet metal housing of the present invention can be easily moved to precisely align over a substrate and then welded to the substrate regardless of most orientations of the substrate. The thin metal shell can be easily attached to the underlying substrate by welding or high temperature brazing without the need for clamping or jigs, and the resulting joint is liquid tight even at the high temperatures required for infiltration brazing. In either case of the die related to penetration hardfacing, the molten metal brazing material should remain in the die. With the thin metal housing of the present invention, reliable attachment to the substrate can be achieved without the need for additional clamping or clamping. The resulting assembly is thus easier to place in an oven for penetration brazing and can penetrate hardfaced heavy objects significantly more easily.

Furthermore, the thin metal shell defining the mold for the infiltration hardfacing can be reliably combined from multiple parts and have side-facing openings and/or downward-facing openings that are later sealed by the underlying substrate fusion weld or high temperature brazing. This is very different from conventional graphite or ceramic molds used for infiltration brazing, which are more difficult to seal on an underlying substrate and generally require a large overlap area as shown in US 4933240. Even if these conventional graphite or ceramic molds are sealed to a substrate at room temperature, these seals can fail at the high temperatures required for penetration brazing, particularly when the substrate and the mold have different coefficients of thermal expansion. Thus, conventional graphite or ceramic molds are often made with an upward facing opening into which the substrate must be placed. This means that the substrate in these existing molds must be supported by the mold or suspended above the mold by a clamp or frame.

Supporting a heavy substrate by a mold can be difficult and may require the substrate to be in contact with the mold at locations where the hardfacing material is better applied. The use of clamps and frames results in heavier and larger assemblies, making it more difficult to place the mold and substrate combination into a furnace. The thin metal shell of the present invention does not have to support the substrate, allowing for a variety of embodiments with a variety of alternative orientations of the substrate and mold, and even a variety of differently oriented molds on a single substrate.

Fig. 10 shows the wear part 110, showing the wear part 10 of fig. 9 after removal of the container 18. This allows the wear member 110 to be transported and handled without any interference with the container 18. Fig. 11-17 correspond to fig. 1-7 and also lack container 18. For clarity of illustration, part numbers corresponding to those of FIGS. 1-9 have been used in FIGS. 10-17, but preceded by a "1," including the substrate 112, the housing 114, and a layer of hardfacing material 124.

It can be seen from fig. 10-17 that the thinness of the outer shell 114 allows the finished wear member 110 to closely match the desired final shape and weight of the wear member for operational use. For example, mining tips are sized and shaped to dig into a particular type of earth. The thinness of the housing 114 is particularly advantageous because the new unused tip 110 enclosed with the consumable housing 114 has a profile that will penetrate the earth material in a profile almost identical to that of the wear part 110 after wear of the housing 114. Similarly, mining equipment operates in a particular manner based on the weight of any attached bite into the ground tool, such as a tip on the bucket. The new unused tip 110, enclosed with the consumable housing 114, has a weight that is nearly the same as the weight of the wear part 110 after the housing 112 has worn. In the above example, the shell has a weight of about only 2% of the weight of the substrate. The difference in weight of the finished wear part according to this embodiment, with and without the consumable housing, after adding the weight of the hardfacing material, varies by less than 2%.

In the embodiment of fig. 1-9, container 18 is shown as a flared opening that is substantially coaxial with the long axis of substrate 12, and the long axes of housing body 16 and housing 14. Another embodiment may include a container substantially perpendicular to the long axis of the substrate, and the long axes of the housing body and housing. Such an embodiment is shown in fig. 18, where part numbers corresponding to those of fig. 1-9 have been used, but preceded by a "2", comprising a substrate 212, a housing 214, and a container 218 in communication with an opening 217 of the housing 212. Preferably, the container 218 is generally funnel-shaped, with a large mouth 218a, but a relatively small neck 218 b. This may minimize any resulting contamination in the housing 214 upon removal of the container 218, and this may make the wear member 210 more attractive when new. It may also allow different orientations of the substrate 212 and housing 214 during the injection brazing process as described below, so that various shapes of substrates and housings may also be received in specific processing equipment as described below. Finally, it may allow for a slightly different composite structure after injection brazing because of the different orientation of the substrate 212, housing 214, and container 218 with respect to gravity during injection brazing, when compared to the normal orientation of the substrate 12, housing 14, and container 18 during injection brazing.

It is generally simplest to locate any such container portion of the housing above the body of the housing. This configuration is generally most advantageous because it allows gravity to assist capillary action during the infiltration process. The effect of gravity may be obtained by increasing the height 218H of the neck of the funnel, increasing the effective "head" of molten brazing material contained in the corresponding funnel-shaped vessel. However, in some cases capillary action between the hardened particles and the molten braze material alone may be sufficient, even to allow the molten braze material to "move up" a suitable distance.

Another embodiment of a housing is shown in fig. 19 as a two-piece housing 314 having a two-piece conformal band 320. The two-piece housing body 316 of the housing 314 may initially be formed from a front half 326 and a rear half 328, with the front half 326 having a front flange 330 and the rear half 328 having a rear flange 332. A forward flange 330 extends transversely from the rear edge of the front half 326 and a rearward flange 332 extends transversely from the front edge of the rear half 328. The front flange 330 may be joined with the rear flange 332 by welding or brazing with a brazing material having a higher melting point temperature than the material intended for infiltration. In some constructions, the two-piece housing 314 may be more easily formed than a corresponding one-piece housing. In some configurations, the two-piece housing 314 may also be more easily joined to a corresponding substrate when compared to joining a corresponding one-piece housing.

In fig. 20 and 21, a two-piece housing 314 is shown engaged with a portion of a corresponding substrate 312 in the form of a pointed tip. Details of the external geometry of the substrate 312 can be seen because the housing 314 is shown as partially transparent. The outer geometry of the substrate 312 may include a body 334, with the body 334 defining a bonding surface 335 for welding or brazing with the two-piece conformal band 320. The substrate 312 may provide at least some recesses or other protrusions for the bonding of the hard materials. For example, in the embodiment shown in fig. 20 and 21, the substrate 312 has a step 336 slightly recessed from the outer surface of the body 334, and another recessed portion is a valley 338. Step 336 may define flange 340 and ramp 342. The distal end of the substrate 312 may be shaped to define an angled edge 344 and/or a rounded surface 346. In another embodiment, the substrate 312 may not provide any recesses or other protrusions for the hard material.

Cross-sectional views of the embodiment of fig. 20 and 21 are shown in fig. 22 and 23. The shell 314 extends smoothly away from the conformal band 320, defining a mold cavity 350 between the substrate 312 and the shell 314. The mold cavity 350 includes a recess defined by a valley 338 and other opposing recesses in which the distal end of the substrate 312 has a reduced thickness relative to the shell 314. The mold cavity 350 defines the resulting thickness of the hardfacing material bonded to the substrate 312, and the internal geometry of the shell 314 defines the final external geometry of the finished tip. In the embodiment of fig. 20-23, the hardfacing material that will bond with the substrate 312 extends generally fairly smoothly from adjacent portions of the substrate 312 that are generally flush with the outer surface of the substrate 312 and behind the resulting hardfacing material. In fig. 22 and 23, the inside surface of the housing 314 is flush with portions of the substrate 312. For example, at the conformal band 320, this provides a close fit with the bonding surface 335 to accurately position the housing 314 relative to the substrate 312. In other locations, such as the step 336, the flush mounting is simple because no hardfacing material is required, or even because no hardfacing material is required at these locations. The resulting hardfacing material 324 is flush with adjacent portions of the base substrate 12. For example, in the illustrated embodiment, the hardfacing material 324 is flush with the bonding surface 335, as well as other surfaces of the substrate 312 (e.g., step 336) that contact the inside surface of the housing 314. By not making the hardfacing material 324 protrude higher than the adjacent surface of the substrate 312, the amount of force required to push the tip 310 into the soil is reduced. The appearance of the hardfaced tip 310 is also better without a thick hardfacing layer protruding above the surrounding surface of the substrate 312. However, in another embodiment shown in FIG. 21a, the shell 314 may be flared outward from the conformal band 320 such that the hardfacing material that will bond with the substrate substantially increases the thickness of the tip, including enlarging the distal end of the tip relative to adjacent portions of the substrate 312, including relative to the bonding surface(s) 335.

Fig. 24 is a cross-sectional view of the embodiment of fig. 18, viewed from a similar perspective as the cross-sectional view of fig. 22, but with the substrate 212 shown in a horizontal orientation.

Fig. 25a-25j show various views as part of manufacturing the wear part 310. The various figures 25a-25j show alternative processing steps as part of the penetration case hardening bucket tip. Figure 25a shows a substrate 312 in the form of a point for a mining bucket of the type prior to attachment of any casing and prior to formation of any layer of hardfacing material on the substrate 312.

Fig. 25b, 25c and 25d correspond directly to fig. 19, 20 and 21. The substrate 312 is more generally referred to as the substrate 312 in light of the above. Only a portion of the substrate 312 is shown in fig. 25c and 25d, and is oriented substantially vertically when compared to the substantially horizontal orientation of the substrate 312 in fig. 25 a. The housing 314 is formed in two halves and then welded together along the flanges as described above. The housing 314 is mounted on the substrate 312 and then positioned along its bottom edge by welding as described above for the conformal band 320. Alternatively, the two halves of the housing 314 may be first clamped in place or otherwise held onto the substrate 312 and then welded together and/or with the substrate 312 to better match the various surface geometries of the substrate 312 and housing 314. When the steel shell 314 is engaged with the substrate 312, the steel shell and substrate define a mold cavity 350 between the substrate and the shell.

In fig. 25e, hard material in the form of hard particles 352 is introduced into the defined mold cavity 350 by pouring through the opening 317 communicating with the mold cavity 350, and the flaring of the container 318 makes it easier to pour into the hard particles 352. The hard particles 352 may be gravity-fed only to fill the mold cavity 350, or the hard particles 352 may be tamped and/or vibrated or otherwise packed positioned within the defined mold cavity 350. In another embodiment, different kinds of hard materials may be used, including those described above. Additionally, in another embodiment, the particles 352 may not completely fill the mold cavity 350, if desired. As shown in fig. 25f, the infiltration braze material 354 in powder form may then be poured over the layer of hard particles and held in the container 318 of the housing 314. In another embodiment, the brazing material 354 may be in a different form (i.e., not powdered), as described below. If the container 318 is substantially filled with the penetration brazing powder 354, as shown in fig. 25g, the container 318 may be sized to define a correct volume of penetration brazing material 354 relative to the defined volume of the mold cavity 350 and the layer 352 of hard particles held in the mold cavity 350. In fig. 25g, the entire assembly including the substrate 312, the shell 314, the layer of hard particles 352, and the layer of the infiltration braze material 354 is ready for an infiltration cycle as described below.

The permeation cycle of the kind shown in fig. 25h was carried out in one furnace. Preferably, the furnace is a vacuum furnace, but other types of furnaces may be used. The entire assembly of fig. 25g is placed in such a furnace for the infiltration cycle during which the entire assembly is heated to a temperature high enough to melt the infiltration braze powder 354. This causes the molten braze material to infiltrate the layer of hard particles 352 to form a composite 324 of hard particles 352 infused with the infused metallic braze material 354. The injection braze material bonds the substrate 312 and the hard particles 352.

The injection braze material may also be bonded to the housing 314, but this is not required. Thus, after infiltration, the shell 314 is typically permanently bonded to the substrate 312. When the resulting wear tip is used for excavation, the outer shell 314 simply wears away, exposing the permeable layer 324 to perform its wear-resistant function.

In fig. 25j, the container portion 318 of the housing 314 has been removed, leaving a finished product as the hardfaced wear member 310, and more particularly, the hardfaced tip 310.

Fig. 26 and 27 show two different embodiments of an underlying substrate that may be used to fabricate a hardfaced wear component. Fig. 26 shows the substrate 312 of fig. 25a in a vertical orientation. FIG. 27 shows another embodiment of the substrate 412 in the form of a point, with two holes 458 formed near the digging end of the substrate 412.

In this embodiment, the apertures 458 provide a plurality of surface intrusions that help to improve the bond between the substrate 412 and the resulting composite of hard particles and brazing material. The resulting infiltrated hard material in the apertures 458 alters how the resulting hard-faced wear component wears in use. In some embodiments, the resulting infiltrated hard material in the holes 458 helps maintain "sharpness" and excavation efficiency. Other advantages of this nature may be obtained by installing a prefabricated hard metal insert in the aperture 458.

Fig. 28 shows the embodiment of fig. 27 with the housing 414 welded to the substrate 412. Inserts 460 are schematically shown and are retained in each of the apertures 458. Appropriate spacing between the inner wall of the bore 458 and each insert 460 may be provided by one or more spacers 462. Two spacers 462 are shown mounted on each insert 460. In another embodiment, the spacer 462 may not be used. The spacing created by the spacers 462 can provide a transition between the substrate 412 and the insert 460 to resist cracking of the insert 460 due to differential expansion. The braze material formed in the space can be deformed to accommodate this difference in expansion and contraction, if desired. In yet another embodiment, the coefficient of thermal expansion of the permeating material may be selected to be between that of the insert 460 and that of the substrate 412 to assist in reducing cracking due to differential expansion, as similarly described below.

Two such inserts 460 are shown in fig. 29, and are preferably made of cemented tungsten carbide. In another embodiment, the insert(s) 460 may be one or more other carbides (e.g., chromium carbide, molybdenum carbide, vanadium carbide, etc.) in a sintered shape. Porous preforms of various carbides may also be used in another embodiment, including tungsten carbide (WC/W)₂C) Chromium carbide, molybdenum carbide, vanadium carbide and other carbides. In one embodiment, these porous preforms may be provided in the form of pure carbide. In another embodiment, the insert(s) 460 may be formed of ceramic or other material. If ceramic is used, one or more techniques may be used to enhance wetting and/or bonding of the braze material on the ceramic surface, including those described below. Preferably, the spacer 462 is constructed of steel and has a split collar 464 and a plurality of legs 466, and the split collar 464 is spring-like so that the spacer 462 remains in place when slid onto one of the inserts 460. One such spacer 462 is shown in detail in fig. 30.

FIG. 31 is a diagram of two examples of another alternative embodiment, each example including a substrate 512 in the form of a tip, and each example shown having a weld-positioned outer shell 514, and the outer shell 514 being prepared to receive an appropriate amount of hard particles and infiltrated brazing material, generally as described above. Fig. 32 shows two assemblies ready for a permeation cycle, and each assembly has a tip 512 and a shell 514 filled with hard particles (not shown) and brazing material 554. Optionally, a clamp 568 is detachably attached to each tip 512 to assist in stabilizing each tip 512 during operation and during loading and unloading from the furnace, as shown in FIG. 33.

A finished, partially worn substrate in the form of a hardfaced point 510 according to the embodiment of fig. 31-33 is shown in fig. 34. Hardfaced tip 510 is made by placing the assembly of fig. 32 and 33 in a furnace and then heating and cooling as part of an infiltration cycle as described below. The resulting hardfaced tip 10 is used for excavation to wear away the sacrificial shell 514, which is no longer visible in fig. 34. The gray background surrounding hardfaced tip 510 is a removable gauge that measures how much material wears when hardfaced tip 510 is used. As shown, the hardfaced tip 510 has been hardfaced such that the hardfacing material 524 is "above" the major surfaces of the tip 512, thus having a sharp angular transition of the outer surface, indicated at 524a, progressing from the tip 512 onto the hardfacing material 524. In certain applications, this angular surface configuration may provide particular advantages. In particular, the resulting enlarged digging end of the point with hardfacing 524 disposed above the surrounding surface of point 512 can effectively protect the adjacent non-hardfaced surface by a shadowing effect without the expense or weight of hardfacing. The selective addition of a hardfacing material can protect areas subject to substantial wear, and such hardfacing material may not be needed on other areas of the tip.

The thin metal shell of the present invention is particularly useful when a hardfacing material is added to a tip that has been produced by sand casting. Typically mining tip molds for use with green sand processes are to have significant dimensional variations, such as varying thicknesses of 0.060 inches in the area to which the casing of the present invention is to be attached corresponding to the conformal band described herein. Such green sand casting tips are therefore particularly difficult to seal with inflexible moulds, such as ceramic moulds and graphite moulds. However, the thin metal of the various shells disclosed herein can be easily deformed and bent as needed to allow the thin metal shell to be properly welded to the green sand casting tip.

Yet another embodiment is schematically shown in fig. 35, comprising a substrate 612 in the form of a pointed end having three holes 658, but with only a single insert 660 in the central one of the holes 658, and without any spacers. The outer shell 614 is filled with a mixture of hard particles and brazing material, and then the assembly is heated and cooled by an infiltration cycle to produce a hardfaced wear part. Fig. 36-39 show a cross-section through the central one of the holes 658, and show various processing steps, and the hard metal insert 660 is bonded to the hole 658 by these processing steps, while applying an external hardfacing to the substrate 612. These steps are shown in the cross-sectional views of fig. 36-39, and fig. 39 shows a cross-section of a finished hardfaced wear component 610 including a layer of hardfacing material 624 surrounding and protecting the distal end of the substrate 612. In other embodiments, the insert 660 may be received in a different aperture 658 and/or the substrate 612 may include multiple inserts 660 in multiple apertures.

The approximate relative thicknesses of the substrate 612, housing 614, and hardfacing 624 layers are shown in fig. 39. For example, thickness 672 is used to represent the substrate 612, thickness 674 is used to represent the shell 614, and thickness 676 is used to represent the layer of hardfacing material 624. Thickness 676 also represents the thickness of mold cavity 650. The sample values for these thicknesses are as follows:

substrate thickness 672 near conformal band: 3.450 inches

Shell thickness 674 of the entire shell: 0.105 inch

Case hardening thickness 676: 0.438 inch

Fig. 40 shows two powders, including granular carbide 52 on the right and braze alloy powder 54 on the left.

Tungsten carbide is particularly suitable for use asIs an example of hard particles that are part of a hardfaced wear component made in accordance with the present invention. May use, for example, WC or WC/W₂Pure carbides of C, and mixtures of various carbides. Also, suitable granular materials may be made from crushed cemented carbide materials, such as recycled machine tool inserts. The optimum size of the particulate material depends on the intended use of the wear part, but sizes in the range of-50 mesh to +70 mesh are suitable for many applications. The following alloys of tungsten carbide, titanium carbide and cobalt have been found to produce particularly effective hard-facing wear parts such as mining tips or tool tips:

other carbides that may be used as the hard particles in the composite include cast tungsten carbide (WC/W)₂C) Tungsten monoxide (WC), chromium carbide, titanium carbide, molybdenum carbide, vanadium carbide, columbium carbide, chromium albuginea beads or granules, and mixtures comprising these materials. As noted above, the hard material may be used in different forms, such as a porous preform, a monolithic member, or other structure. In another embodiment, the hard material may be formed of a ceramic material. If ceramics are used, one or more techniques may be added to enhance wetting and/or bonding of the ceramic surface by the brazing material. For example, the surface of the ceramic may be coated with a metallic or other material to enhance wetting by the brazing material. As another example, an active brazing technique may be used, wherein the brazing material includes a material (e.g., titanium) deposited on the ceramic surface to enhance wetting and bonding of the brazing material to the ceramic surface. Other types of hard materials may be used in other embodiments. As described above, the hard material may preferably have a higher hardness and better wear resistance to the surface of the base material to which the hard material is bonded.

A particularly good selection of brazing alloy powders includes Ni-Cr-Si-B brazing alloy powders conforming to Class BNi-2 in accordance with AWS A5.18.

Other types of brazing materials may be used as long as they are compatible with both the substrate and the hard particles, and are suitable for the particular brazing process. The brazing material may comprise a pure metal such as copper or silver, but may be a more typical standard brazing alloy with a nickel, copper or silver base. The brazing material may also include other copper rich alloys, and low melting point copper nickel alloys. Other types of brazing materials that may be used include pure copper, silicon bronze, titanium copper, chromium copper, phase separated bronze (spinometallic bronze), tin bronze, commercially available nickel-based brazing alloys (BNi-1, BNi-2, etc.), commercially available cobalt-based brazing alloys (e.g., BCo-1), or other types of brazing metals including precious metals and alloys. As mentioned above, in one embodiment, the brazing material may be provided in powder or other particulate form. In another embodiment, the brazing material may be in a different (e.g., non-powdered) form. For example, in one embodiment, the brazing material may be in the form of one or more cast or forged blocks of material. The blocks may be made to a predetermined weight for a particular brazing application and provide for quick and efficient installation of the brazing material in the assembly.

FIG. 41 shows an example of a furnace cycle for the brazing operation using a brazing material comprising tungsten carbide and Ni-Cr-Si-B brazing alloy powder, and the temperature is in the vertical axis. In general, the thermal cycle for the brazing operation involves first heating to a temperature slightly below the melting point temperature of the brazing material and holding to stabilize the temperature throughout the assembly (including thick and thin sections). The assembly is then heated (preferably rapidly) to a temperature above the melting point of the brazing material to melt the brazing material and allow it to penetrate the spaces between the hard particles. This time may be relatively short, for example 30 minutes to 1 hour in one embodiment. The temperature is then reduced to just below the solidus temperature of the brazing material to allow the brazing material to cure and bond with the hard particles and the substrate and remain until the temperature is stable throughout the assembly. Finally, the temperature reduction allows the component to be removed from the furnace. It will be appreciated that the length of time that the temperature must be maintained to stabilize throughout the assembly is affected by the size and geometry of the substrate and/or the housing, as larger/thicker components may require longer heating or cooling times. As shown, the temperature of the furnace and casting (e.g., assembly of substrate, shell, hard particles, and brazing material) increases and then decreases over time. The sample furnace cycle of fig. 41, as represented along the horizontal axis, takes about 7 hours, and the brazing step may be performed at about 2050 ° F for 30-60 minutes in one embodiment.

Fig. 42a-42k show various views as part of another embodiment of making a wear component 710. Various fig. 42a-42k show selected processing steps as part of a penetration hardfacing twin roll crusher tip. The resulting hardfaced roll crusher tip has a substrate and a thin metal shell that are substantially separate but bonded together by an injected composite hardfacing material with minimal contact between the substrate and the thin metal shell.

Fig. 42a shows a substrate 712 prepared by machining, casting or forging. A plurality of housing spacer holes 780 are drilled, formed, or formed in the substrate 712 as shown in fig. 42b, and corresponding housing spacers in the form of pins 782 are mounted in the holes 780 as shown in fig. 42 c. The pins 782 will be used to suspend the substrate 712 within a thin metal housing, and the desired spacing between the substrate 712 and the housing is defined by the length of the pins 782. The primary purpose of the pins 782 is to keep the shell 714 and substrate 712 properly separated until the mold cavities 750 are filled with hard particles 752. The pin 782 need only be large enough to remain after the filling step of the method disclosed herein. Thus, the pin 782 may be made from a variety of materials ranging from mild steel pins to pre-hardened cemented tungsten carbide pins.

Fig. 42d shows a sheet metal shell 714 that may be prepared by deep drawing, hydroforming, and/or cutting and welding as is known in the art of forming sheet metal molds. Next, the substrate 712 with protruding pins 782 is placed within a housing 714, as shown in fig. 42 e. Referring to fig. 42f, hard particles 752 may be placed in a mold cavity 750 defined between substrate 712 and shell 714, and optionally tamped, vibrated, or otherwise packed in mold cavity 750 to define a hard particle layer between substrate 712 and shell 714. In fig. 42g, the infiltrant material powder 754 is shown placed over the layer of hard particles, housed within a predetermined volume of a container 718, and preferably formed as an integral part of the shell 714. Reservoir 718 may be sized relative to mold cavity 750 to provide an optimal amount of infiltration material 754 to infiltrate and bond hard particles 752 into a composite hardfacing layer. This is shown graphically in fig. 42h, and the assembly is ready for an infiltration cycle.

Fig. 42i shows a furnace such as described above ready for an infiltration cycle. Fig. 42j shows the assembly of fig. 42i after the permeation cycle is complete (j), with the container 718 still in place. Preferably, the container 718 is removed from the shell 714 by cutting or other technique, leaving a finished wear-resistant composite product 710, as shown in fig. 42 k.

Although the housing 714 is shown as having a spherical lower surface that typically needs to be held in a fixture, other embodiments of similarly shaped housings may be self-supporting. In addition, housing spacing pin 782 may be omitted if substrate 712 is held by a heat resistant alloy fixture that also positions housing 714 in a desired position relative to substrate 712. Thus, substrate 712 is suspended above sheet metal housing 714 and within sheet metal housing 714 during the infiltration process. In other embodiments, any such fixtures that position housing 714 in a desired position relative to substrate 712 may be removed after hard particles 752 are packed into place. Hard particles 752 will not generally dissolve or melt during the infiltration process, and thus hard particles 752 will reliably support substrate 712 during the infiltration process. This allows the fixtures to be removed prior to placing any of the components, such as the assembly of substrate 712, shell 714, hard particles 752, and infiltration material 754, in a furnace. Other embodiments may suspend housing 714 from substrate 712. For example, housing 714 may be made to hang in a groove, not shown, in a stem of a hub formed as part of substrate 712.

The method according to the invention can be used with furnaces or retorts using hydrogen, argon, or other types of reducing or inert environments, instead of vacuum furnaces. When brazing in such non-vacuum furnaces, it is desirable to prevent the entrapment of gases within the hard particles as infiltration proceeds. The brazing powder can be melted completely simultaneously and seep down as a continuous molten layer, passing through the hard particles. The addition of a vent at a low point in the thin shell allows gas trapped in the hard particles to escape as the molten braze material seeps downward. Preferably, a breather tube or tubes are attached to the thin metal shell at a suitably low position, and the tube or tubes extend upwardly to a height greater than the final height of the molten brazing material at the final stage of penetration brazing.

An embodiment of a steel shell 814 for use in a non-vacuum furnace is shown in fig. 43a-43 f. Vent tube 884 extends from a low position of housing 814 to prevent gas entrapment during braze infiltration. Vent tube 884 is attached to housing 814 at a location or locations where gas entrapment occurs. Figure 43b shows a cross-sectional view of the substrate 812, the housing 814, and the vent tube 884. A hard particulate material 852 is poured into the mold cavity 850 and between the substrate 812 and the shell 814, as shown in fig. 43 c. Next, a permeating material 854 is added over the hard particle layer 852 as shown in fig. 43 d. In fig. 43e, the molten permeating material 854 is shown partially passing through the hard particle layer 852 and gas escaping through the vent tubes 884. Upon cooling, the hard particle layer and the permeable material form a composite 824, and at least some of the permeable material 854 fills the breather tubes 884, as shown in fig. 43 f. The breather tube 884 and the permeable material 854 can generally be easily cut away from the resulting hardfaced wear component 810.

Fig. 44 shows a spherical structure with a particularly complex surface shape. The wear part is not intended to represent any particular tool, but rather shows a complex tool that may be case hardened in accordance with the disclosure herein. For example, it may represent a infiltrated case-hardened grinding ball having a particularly complex profile. The finished wear-resistant composite product 910 includes a plurality of pre-formed hardfaced cemented tungsten carbide inserts, two of which are shown schematically in phantom at 960, bonded to an underlying substrate by the injected composite hardfacing material. Manufacturing the grinding balls 910 using known techniques would require complex multi-piece molds, possibly made using graphite or ceramic materials. The combination of the thin sheet metal mold, the preformed substrate, the hardened carbide particles, and the infiltration brazing results in a more economical method for manufacturing hardfaced tools with complex surface geometries.

Fig. 45a-45k show various views as part of another embodiment of making a wear part 1010. The various figures 45a-45k show selected processing steps as part of a rotary screen for mineral processing through case hardening. The resulting hardfaced trommel screen may have a substrate and a thin metal shell that are substantially separate but joined together by an injected composite hardfacing material with minimal contact between the substrate and the thin metal shell. Alternatively, the substrate and thin metal shell may be in contact at selected locations and the shell supports the substrate during permeation cycles. For example, a plurality of shoulders (not shown) may be formed at selected locations of the housing 1014, and a substrate may be placed on and supported by the shoulders. In other examples, conformal bands or conformal portions (not shown) of housing 1014 can be welded to substrate 1012.

Figure 45a shows a substrate 1012 that is typically prepared by machining, casting or forging. Fig. 45b shows a corresponding housing 1014, and in fig. 45c the substrate 1012 is shown supported in the housing 1014. A plurality of pins (not shown) may be used to suspend the substrate 1012 within the thin metal housing 1014, and the desired spacing between the substrate 1012 and the housing 1012 is defined by the length of the pins (not shown) similar to that shown in fig. 42.

Fig. 45d shows hard particles 1052 infused onto substrate 1012. Hard particles 1052 may be advanced into a mold cavity 1050 defined between the substrate 1012 and the shell 1014, and selectively tamped, vibrated, or otherwise packed into the mold cavity 1050 to define a layer of hard particles between the substrate 1012 and the shell 1014. In fig. 45e, the infiltration material powder 1054 is shown placed in the container 1018 over the hard particle layer 1052. Figure 45f shows the furnace ready for the permeation cycle. Fig. 45g shows the assembly of fig. 45e after complete loading with the appropriate amount of infiltration material powder and after heating and cooling through a complete infiltration cycle. Preferably, selected portions of the sheet metal are removed from the outer shell 1014 by cutting or other techniques, leaving the finished wear-resistant composite product 1010, as shown in fig. 45 h. For example, the upper edge 1018a of the surrounding wall may be cut away, and the upper cover 1018b defining a plurality of through-holes may be cut away.

If the type and size distribution of the shell material and the brazing material, as well as the particulate material in the hardfacing layer, are appropriately selected for the substrate material used for the tool, thermal and transition strains may be matched to prevent cracking of the hardfacing layer, and any hard metal inserts. In one embodiment, the brazing process may be designed such that the infiltration material has an overall coefficient of thermal expansion that is between the coefficient of thermal expansion of the hard particles and the coefficient of thermal expansion of the substrate. For example, many embodiments disclosed herein include a product having a steel substrate and a mild steel outer shell, and the product has a hardfacing layer of infiltration cast tungsten carbide particles. Similar to for AISI1008 steel, certain steels have a coefficient of thermal expansion of about 6.5 microinches per inch per ° F at temperatures below the austenitic range. Selecting copper or a copper-based alloy as the infiltrated material and selecting a particle size distribution that provides 50% cast tungsten carbide will produce an average coefficient of thermal expansion of 6.1 microinches per inch per ° F in the infiltrated material. Providing a permeable material having an average coefficient of thermal expansion that is relatively similar to the coefficient of thermal expansion used for the underlying substrate and the outer layer of sheet metal means that all components will expand and contract at approximately similar rates. This suppresses the tendency of the infiltrated material to crack and flake, particularly when cooled after the infiltration cycle, or when heated, which may occur later, when the hardfacing tool is used.

Such as the example shown in fig. 45h, the trommel may often have length and width dimensions in excess of 1 meter. Such articles provide a clear illustration of the distinct advantages that the present invention can provide with respect to overcoming the problem of thermal expansion during the infiltration process. The hard material that may be selected for wear resistance may have thermal expansion characteristics that are significantly different from those of a hardened steel material that may be used as the substrate, a low carbon steel material that may be used as the sacrificial housing, or a copper-nickel brazing alloy that may be used as the brazing material. As these articles become larger, for example 1 meter in length and width, the rate of thermal expansion of the various components becomes more important.

Ceramic and graphite molds have thermal expansion rates that are very different from the thermal expansion rates of the various steel alloys typically used as substrates for wear resistant components. This can lead to problems such as distortion of the finished part, unexpected variations in case hardened thickness, or even separation of the various parts of the mold assembly during the thermal process to allow the molten infiltration material to escape into the furnace. The low carbon steel material of the present invention is more likely to have a thermal expansion rate more similar to that of the various steel alloys typically used as such substrates. Thus, the steel alloy substrate, the low carbon steel thin metal shell, the hard particles having a particle size distribution that provides approximately 50% cast tungsten carbide, and the copper as the infiltration material provide significant advantages over the case hardening of known steel substrates that require the use of ceramic and graphite molds.

The following table provides several examples of thermal expansion coefficients for selecting hard materials, for mild steel (typical case materials), and copper (typical braze materials). It should be understood that this table provides examples for illustration and that other materials may be used as the hard material, the housing, the braze material, etc.

The combination of a steel substrate, a thin metal shell, and a properly selected mixture of hard particles having a particular size distribution, and a infiltrating material yields considerable advantages. This combination provides a greater ability to accommodate thermal and deformation strains and resulting dimensional changes, particularly when compared to conventional graphite or ceramic molds. The product and method of the present invention results in less risk of warping, less risk of unwanted thickness variations in the resulting case hardening, and less risk of leaking molten metal brazing material inside the furnace from damaged molds during infiltration cycles.

In addition, a material such as steel undergoes a phase change accompanied by a dimensional change. For example, when processing carbon and low alloy steels, the steels expand with increasing temperature. However, at about 1333 ° F, the steel begins to transform into a different crystalline structure. The transformation causes a reduction in size until the transformation is complete and then the material expands again (at a different rate) with further increase in temperature. Upon cooling, the transformation occurs again, with associated expansion-contraction-expansion of the dimensions, until the permeation cycle is complete. The disclosed method of using a thin metal shell as the mold more readily accommodates all of these expansions and contractions than when using a graphite mold or a ceramic mold. With the method of the present invention, both the substrate to be case hardened and the mold of the component housing the case hardened material are constructed of steel, so that both the substrate and the housing will undergo similar transformation, expansion and contraction. While there may be some variation with respect to the coefficient of thermal expansion and transition temperature, these variations are much smaller for thin metal molds and metal substrates than for graphite molds or ceramic molds and metal substrates. It is very difficult to use graphite or ceramic molds with metal substrates to make large flat trommel screens such as the example shown in fig. 45h without substantial risk of cracking and/or flaking of the hard-facing coating.

Furthermore, if the particulate material is intended to perform an abrasion resistant function, the particle size distribution may need to be considered to provide suitable abrasion resistance. Typically, for these cases, the size distribution must be such that the spacing between particles is less than the size of the abrasive particles encountered in the application. This prevents damage and loss of the hard particles. In an embodiment, a particle size of-50 to +70 mesh (as described above) may be sufficient for most applications, for example, if the abrasive particles in the application are not significantly smaller than 70 mesh. For finer abrasive particles, the particle size distribution should be made approximately equal to or smaller in size than the abrasive size.

The disclosed embodiments may also be used to renew or refurbish worn previously used hardfaced wear parts. For example, in one embodiment, a shell as described above is coupled to a substrate in the form of a hardfaced wear part, and the hard material (e.g., hard particles) is incorporated into the shell in close proximity to the substrate. The hard material may then be bonded to the substrate by brazing as described above. It should be appreciated that the braze material may be combined with the preexisting (worn) hardfacing material, the underlying base parent substrate, or both. In one embodiment, the hard material and/or the braze material may be the same as the user in the original hardfacing material.

Several disclosed embodiments show a steel substrate used to form a wear resistant component with a hard material covering all or substantially all of the outer operative surface (e.g., the ground-engaging surface) of the wear resistant component. This may allow the use of softer steel since the hardfacing material protects all of the steel. These embodiments provide advantages, particularly if the softer steel has better resistance to cracking, for example, the softer steel has a higher toughness than the other harder steels. Softer substrate materials may also have better solderability. Furthermore, softer substrate materials are generally easier to make into the initial substrate to be case hardened, and therefore it is cheaper to make these initial substrates composed of softer steel than similarly shaped initial substrates composed of harder steel.

It should be understood that the housing in any of the disclosed embodiments does not necessarily need to closely conform to the precise shape of the substrate. For example, the housing may be formed to provide greater thickness at high wear locations such as corners or corner edges of the tip. Similarly, a particular location on the substrate of the tool may be provided with a "rib" or "blade" by the resulting hardfacing layer. The ribs or vanes may help control the flow of abrasive material in which the assembly is operable, or direct the movement of earth material impacted by the resulting composite wear tool.

It should also be appreciated that any feature, component, structure, technique, etc., described with respect to one embodiment herein may be used or utilized with any other embodiment described herein, unless clearly indicated otherwise.

It is believed that the disclosure set forth herein encompasses multiple distinct inventions with independent utility. While each of these inventions has been disclosed in its preferred form, the specific embodiments thereof as disclosed and illustrated herein are not to be considered in a limiting sense as numerous variations are possible. Examples define the embodiments disclosed in the foregoing, but any example does not necessarily encompass all features and combinations that may be eventually requested. Where the description recites "a" or "a first" element or the equivalent thereof, such description includes one or more such elements, neither requiring nor excluding two or more such elements. Further, general designations such as first, second, or third used to distinguish between components and do not indicate a need or limitation in the number of components and do not indicate a particular location or order of the components unless otherwise specifically stated.

Claims (22)

1. A hardfaced wear member for abrasive applications, comprising:

a tool to be attached to a bite earth device and having a surface at a tip of the tool and a bonding surface disposed proximate to the surface at the tip;

a composite hardfacing material forming a coating on at least a portion of the at-the-tip surface, and the composite hardfacing material comprising a hard particulate material infiltrated with a metallic brazing material, wherein the metallic brazing material bonds with the at-the-tip surface to join the composite hardfacing material and the tool; and

a sheet metal housing in contact with and surrounding the composite hardfacing material, the housing having a conformal band in contact with a bonding surface of the tool, wherein the housing is connected to the tool by welding at least between the conformal band and the bonding surface,

wherein a mold cavity is defined between the surface at the tip of the tool and the shell, and the composite hardfacing material fills the shell.

2. The hardfaced wear component for abrasive applications of claim 1, wherein the weld is a braze.

3. The hardfaced wear component for abrasive applications of claim 1, wherein the housing has an opening to an exterior of the housing, and wherein the composite hardfacing material is exposed to the exterior of the housing through the opening.

4. The hardfacing wear-resistant member for abrasive applications of claim 3, further comprising a reservoir connected with the shell and positioned outside the mold cavity in communication with the opening.

5. The hardfacing wear component for abrasive applications of any of claims 1-4, wherein the conformal band contacts the bonding surface of the tool and surrounds an entire periphery of the housing, and the bonding surface is welded to the conformal band around the entire periphery.

6. The hardfaced wear component for abrasive applications of claim 5, wherein the weld is a braze.

7. The hardfaced wear component for abrasive applications of any of claims 1-4, wherein the metallic brazing material is bonded to the outer shell.

8. The hardfacing wear component for abrasive applications of any one of claims 1-4, wherein the housing comprises a front member and a rear member, and the front member has a front flange extending transversely from a rear edge of the front member, and the rear member has a rear flange extending transversely from a front edge of the rear member, wherein the front member and the rear member are joined together by welding the front flange and the rear flange to form the housing.

9. The hardfaced wear component for abrasive applications of claim 8, wherein the weld is a braze.

10. The hardfaced wear component for abrasive applications of any of claims 1-4, wherein the hard particulate material comprises tungsten carbide and the metallic brazing material comprises a Ni-Cr-Si-B brazing alloy.

11. The hardfaced wear part for abrasive applications of any of claims 1-4, wherein the tool has a hole in the surface at the tip, further comprising an insert rod received in the hole, wherein the hole is covered by a composite hardfacing material.

12. A ground engaging assembly for engaging a ground surface during operation of a ground engaging machine, comprising:

a tool to be attached to a ground engaging machine and having a surface; and

a sheet metal shell connected to the tool and having a conformal band conforming to at least a portion of the surface to define a mold cavity between the surface and the shell, and the shell further having an opening to an exterior of the shell,

wherein the housing is attached to the tool by welding the conformal band to at least a portion of the surface,

wherein the mold cavity is filled with a composite hardfacing material comprising a hard particulate material infiltrated with a metallic brazing material.

13. The assembly of claim 12, wherein the weld is a braze.

14. The assembly of claim 12, wherein the assembly is configured to form a wear resistant composite coating on the surface by: filling the mold cavity with a hard particulate material through the opening, placing a metallic brazing material in communication with the mold cavity, heating the assembly to a temperature above the melting point of the metallic brazing material and maintaining the temperature for a time sufficient for the metallic brazing material to penetrate the hard particulate material in a molten state and contact the surface of the tool, and cooling the assembly to solidify the metallic brazing material and form the wear resistant composite coating on the surface.

15. The assembly according to claim 12 or 14, further comprising a reservoir connected to the shell and positioned outside the cavity in communication with the opening.

16. The assembly of claim 15, wherein the receptacle is configured to place a metallic brazing material therein in communication with the cavity.

17. The assembly of claim 16, wherein the container has a flared shape and is integrally formed with the outer shell.

18. An assembly according to claim 12 or 14, wherein the conformal band extends around the entire perimeter of the housing and around the entire perimeter of the surface.

19. An assembly according to claim 12 or 14, wherein the outer shell comprises a front member and a rear member, and the front member has a front flange extending transversely from a rear edge of the front member, and the rear member has a rear flange extending transversely from a front edge of the rear member, wherein the front member and the rear member are joined together to form the outer shell by welding the front flange and the rear flange.

20. The assembly of claim 19, wherein the weld is a braze.

21. An assembly according to claim 12 or 14, wherein the tool has an aperture in the surface and further comprising an insert rod received in the aperture.

22. The assembly of claim 21, wherein a plurality of spaces are defined between the insert rod and an inner wall of the bore.