DE102012006998A1 - Producing wear-resistant film useful for producing wear-resistant coatings on components, comprises producing a green film comprising hard material particles, and compacting the green film - Google Patents

Abstract

Producing wear-resistant film, comprises (a) producing a green film comprising hard material particles, and (b) compacting the green film. Independent claims are also included for: (1) the wear-resistant film obtainable by the above method; (2) a composite material comprising the wear-resistant film, where the individual layers of the composite material comprise different proportions of the hard material particles and/or binder metal particles; (3) use of the wear-resistant film, the composite material or pre-sintered wear-resistant film produced from the wear-resistant film, for producing wear-resistant coatings on components; and (4) producing the wear-resistant component, comprising soldering, adhesively bonding or welding the pre-sintered wear-resistant film or the composite material on the component.

Description

Technical area

The present invention relates to the field of film production. In particular, the present invention relates to a process for producing wear protection films and a composite material comprising the wear protection film obtainable from the process. Furthermore, the present invention relates to the use of wear protection films and composite materials for the production of wear-resistant coatings on components. Moreover, the present invention relates to a method for producing wear-resistant components.

Background of the invention

To protect against high wear, in particular by abrasion, coating with hard material alloys is becoming increasingly important. The application of wear protection layers on mechanically loaded components also protects against corrosion or thermal damage. Thus, the life of such components can be increased significantly and the operating costs can be significantly reduced. In particular, composite materials, so-called metal-matrix composites (MMCs), which consist of a tough nickel, cobalt or iron metal matrix in which carbide materials such as carbides, borides or nitrides are incorporated are used. The best possible homogeneous distribution of the hard materials in the molten metal and a good bond between hard material and solder are of great importance for the quality of the resulting wear-resistant layers. The distribution of the hard materials, as well as the formation of the interface between material and solder and the formation of reaction phases in a molten metal alloy depends strongly on the materials to be mixed, the desired proportion of hard materials or the proportion of metal matrix on the hard metal alloy and the process conditions during of the manufacturing process. Therefore, reliable and simple methods have been and are being sought to produce such wear protection materials or wear protection coatings.

So z. B. in the patent US 6,649,682 B1 describes the application of an aqueous dispersion containing carbide carbide particles on the surface to be refined followed by treatment with a dispersion containing solder materials, wherein the wear protection layer is subsequently formed by heating the thus treated component on its surface.

In US 5,594,931 describes the production of prefabricated wear protection materials, which consist of at least two layers with different carbide and Lotmaterialanteilen, the layers are firmly connected by sintering.

In the published patent application US 2007/0017958 A1 is described in addition to multi-layer wear protection materials, the use of layered materials containing both hard metal particles, a metal alloy, a solder material and optionally a binder. The wear protection materials can be produced by slurrying the individual components in a solvent and then coating the material in layers. An alternative method that can be used to make metallic films is e.g. In WO 2007/147792 described.

The prior art discloses various methods for producing wear-resistant coatings. For example, in WO-A-2010040498 the production of wear protection layers described on the film casting. The process is divided into the following steps:
Slip preparation: Mixing of the hard materials, primarily tungsten carbide (eg the HC Starck product Makroline), with optionally a metallic binder which simultaneously acts as solder in the sintering process (preferably high-temperature Ni-based solders), with an organic binder, solvents and water organic additives such. B. plasticizers. The resulting intermediate is referred to as slip. Alternatively, the metallic binder is not processed in a slurry with the hard materials, but processed with the organic components to form a separate slip. Thus, a pure hard material slip and a pure slip of the metallic binder are obtained. As a result, a separate hard green sheet and a separate green sheet of the metallic slurry are then produced.

Film casting: The slip is filled in a casting shoe and poured onto a carrier film by means of a doctor blade. The carrier film moves at a defined speed relative to the doctor blade. The carrier foil forms a "green foil" with a defined thickness. As described above, the green sheet In addition to the organic components only the hard materials, only the metallic binder or mixtures of hard material and metallic binder included.

Debinding: In a debindering process, the organic constituents are expelled or burned out so that a layer remains only of hard materials and / or solder and / or mixtures of these components. Usually, a binder removal takes place by means of solvents and / or by thermal processes. For the products according to this document is a purely thermal debinding.

Sintering: In the sintering step, the layers of hard material and / or metallic binder are sintered to form a dense layer of hard material and metallic binder and optionally simultaneously soldered onto the surface to be coated. After debinding, there is only one layer of a mixture of hard materials and metallic binder, so that in this way the compression takes place essentially by the usual mechanisms of liquid phase sintering. If, after debindering, separate zones or layers of hard material and metallic binder are present-this is the case when hard material and solder are processed into separate slips and green films-densification by infiltration of the hard material layer with the metallic binder is preferred (Ni). based solder). The necessary capillary action is generated and adjusted by the distance between the hard materials. In addition, the packing density of the carbides has a significant influence on the wear properties of the coating or plate produced.

With regard to the optimization of the wear properties and the manufacturability, especially in infiltration processes, dense hard material layers, structures and plates, it has surprisingly been found that an increase in the carbide density (carbide concentration) leads to improved results. To some extent, this is possible by reducing the content of the organic additives in the green sheet.

Based on the above-mentioned methods according to the prior art, the object was to provide new processes for the production of wear films with further improved wear properties and an overall improved process control.

It has been found that the green sheet can be surprisingly densified further and thus the carbide distance in the green sheet can be further reduced if the green sheet, in addition to the above-described prior art method, is subjected to a densification step, for example by means of the cold isostatic pressing (CIP) method. is subjected. In essence, an isostatic pressure can be built up around the film which reduces the residual porosity of the green sheet.

In this way, the object underlying the present invention could be achieved. The inventive method, a higher packing density can be achieved within the green sheet, which in turn leads to an improved capillary action during the later infiltration and sintering process. Thus, the green sheet can be compacted as a single carbide and solder foil, as foils with solder and carbide content and as a layer structure (eg laminate) of carbide and solder foil.

Especially with a two-tape process control (separate hard material green film, also with low metal content such as Ni and a separate solder foil, also with low hard material content; WO-A-2010040498 This results in optimized wear resistance of the sintered layer or plate.

Description of the figures

1 : Microstructure of a wear protection layer of WC and Ni, produced via the film casting process including a subsequent CIP process.

Description of the invention

• a) Herstellung einer Grünfolie umfassend Hartstoffpartikel und
• b) Verdichten der Grünfolie.

The present invention is a process for producing wear protection films comprising the steps

• a) production of a green sheet comprising hard material particles and
• b) compacting the green sheet.

• a-1) Bereitstellung eines Schlickers umfassend Hartstoffpartikel und organischen Komponenten und
• a-2) Gießen des Schlickers zu einer Grünfolie hergestellt.

In a preferred embodiment of the method according to the present invention, the green sheet in step a)

• a-1) providing a slurry comprising hard material particles and organic components and
• a-2) Pour the slurry into a green sheet.

In a further preferred embodiment of the method according to the present invention, the slip comprises a binder suspension, hard material particles and optionally binder metal particles.

It has been shown that metal-coated hard material particles can be processed together with solder material powders in the presence of a binder suspension containing an organic binder and optionally a plasticizer to form a stable slip. The metal-coated hard material particles can be incorporated particularly well into the solder material matrix, wherein the cladding metal is chosen such that a slight wetting with the solder material takes place. Preferably, metals are used as the hard material particle shell, which are also contained in the solder material. The improved wettability of the metal-coated hard material particles results in improved incorporation of the particles into the solder material matrix. In addition, the reaction behavior of the solder with the hard material can be controlled or avoided by a suitable metal shell. This also applies with regard to the further processing steps that are necessary for the production of wear protection layers from the claimed wear protection films.

By pouring the slurry to the corresponding green sheet, the distribution of the metal-coated hard material particles in the solder material matrix is hardly influenced. This can be attributed to the use of an organic binder, whereby the good distribution of hard material in the metal matrix is stabilized during the production process of the films. A subsequent drying of the film or a debindering of the film at low temperatures below 400 ° C also affects the particle distribution of the film also not noticeable. The resulting film may further be presintered, that is, the film is subjected to a sintering step before being applied to a component to produce the anti-wear layer in a subsequent step. The pre-sintering of the film reduces film shrinkage in the production of wear-resistant layers on the desired component. However, this does not rule out that even non-pre-sintered or unbonded wear protection films can be applied directly to the respective component and then debinded and further processed. The pre-sintered films can also be easily glued to a component or using an additional solder on the component, for. B. by means of flame soldering, soldered or welded.

The wear protection films described here are thus particularly suitable for application to components by brazing or high temperature brazing, especially in vacuum furnaces. In the case of pre-sintered wear protection films, these can also be glued, soldered or welded. Even after the high temperatures during sintering, pre-sintering, brazing or Hochtemperaturlötprozesses the resulting wear protection layers show a nearly isotropic microstructure in the particle distribution and a very low porosity, resulting in low abrasion and high hardness over the entire surface to be refined of the component is reached. The pore formation is reduced by the good wettability of the metal-coated hard material particles by the solder material, since there is a good connection at the interface between the metal-coated hard material particles and the solder material. In particular, during sintering, presintering or soldering, phase reactions or diffusion processes can occur at the interface between the metal shell of the hard material particle and the solder material, in particular if the hard material particles have a metal shell. Through such diffusion processes or phase reactions, the wear protection layer is further stabilized during the manufacturing process, which includes a treatment at high temperatures, the pore formation in the wear protection layer is minimized. At the same time can be controlled or reduced by the choice of the metal shell, the reaction behavior of the solder with the hard material. In addition, the films according to the invention are easy to produce from a slurry by means of conventional film casting processes on an industrial scale.

Thus, a wear protection film containing hard material particles which have a metallic shell and solder material particles selected from the group of soft solders, brazing alloys or high-temperature solders is preferred.

In a further preferred embodiment of the process of the present invention, the slip further comprises i) from 0.1 to 10% by weight of binder suspension, the binder suspension preferably comprising from 1 to 60% by weight of organic binder and from 0 to 15% by weight of plasticizer, based on the total weight of the binder suspension, and ii) contains 90 to 99.9 wt .-% hard particles and optionally binder metal particles, wherein i) and ii) are each based on the total weight of the slurry.

The hard material particles preferably contain carbides and / or borides of transition metals with high melting points, in particular carbides of tungsten, titanium, vanadium, chromium, tantalum, niobium, silicon or molybdenum but also borides, carbonitrides or nitrides of these metals are suitable as hard material particles. Particularly preferred are the tungsten carbides, z. B. WC and / or WSC (tungsten carbides), wherein the WSC is a mixture of WC and W2C, which is in particular a eutectic structure of WC and W2C, titanium carbides, z. As TiC, tantalum carbides, vanadium carbides, z. B. VC, chromium carbides, z. B. Cr ₃ C ₂ , Cr ₇ C ₃ , Cr ₂₃ C ₆ , silicon carbides, z. B. SiC, molybdenum carbides, such as. B. Mo ₂ C or titanium borides, z. B. TiB ₂ , or mixtures of said hard material particles, wherein the tungsten carbides optionally mixed with tungsten borides, such as. As WB, are of particular importance. Particularly preferred hard material particles consist of the abovementioned carbides and / or borides. Particularly preferred are tungsten carbides of the form W2C / WC, wherein the particulate melt carbides have a particle shell of tungsten carbide (WC). A particularly preferred tungsten carbide with a WC shell is the Macroline tungsten carbide (MWC1 the AMPERWELD ^® powder series HC Starck GmbH). The hard materials described are also referred to below as hard metals.

Due to the high hardness, in particular the use of WSCs (tungsten carbide carbides) as hard material particles with regard to the production of wear protection layers is of great interest. Due to the strong phase reaction in nickel-based solders, preference is given to using the more thermally stable WSC, the Macroline tungsten carbide, as the hard material. The Macroline tungsten carbides have a core of WSC and a shell of WC, which largely protects the WSC core from reactions with the nickel base solder.

Furthermore, the use of hard materials in spherical form offers. Hard materials in spherical form are in particular obtainable by gas atomization or are produced in plasma from agglomerated hard materials.

The hard material particles are surrounded by a metal shell, wherein the metal shell supports the connection to the solder material and the incorporation into the slurry. Preferably, the shell has a similar composition as the solder material. In particular, the shell contains metals which are also contained in the solder material. Particularly preferred metals of the shell are nickel, cobalt, chromium, iron, copper, molybdenum, aluminum, yttrium or a mixture of these metals. Preferred mixtures in front of these cladding metals are cobalt / chromium, nickel / chromium, nickel / cobalt mixtures. Furthermore, the use of nickel-coated, chromium-coated or cobalt-coated hard material particles is particularly preferred. Metal-coated hard material particles are commercially available, for. B. nickel-coated or cobalt-clad tungsten carbide is marketed by H.C. Starck, Germany. In a particularly preferred embodiment, hard material particles of tungsten carbides are used, which can carry a WC shell and which are coated with a nickel-containing layer.

The metal-coated hard materials used are usually present in powder form. Powders having an average particle diameter of about 0.05 μm to 200 μm, preferably between 10 μm and 150 μm, are used, the ideal particle diameter varying depending on the application. The hard materials are preferably completely coated with a metal shell, although partially metal-coated particles can be used. However, the surface of the latter particles should preferably be provided with at least 50% with a metal coating. The metallic coating of the hard material particles takes place by deposition of the metal intended for the coating on the hard material particles by conventional methods.

Advantageously, the hard particles contain or consist of components selected from the group consisting of tungsten carbide, titanium carbide, tantalum carbide, silicon carbide, vanadium carbide, chromium carbide, molybdenum carbide, titanium boride, tungsten carbide, and tungsten carbide with a WC shell or shell of chromium carbide and any Mixtures thereof. In another preferred embodiment of the process of the present invention, components include or consist of selected from the group consisting of tungsten carbide, titanium carbide, tantalum carbide, silicon carbide, vanadium carbide, chromium carbide, molybdenum carbide, titanium boride, tungsten carbide, and tungsten carbide with a WC shell or a shell of chromium carbide and any mixtures thereof.

In a further advantageous preferred embodiment of the method of the present invention, the Hertstoffpartikel on a metallic shell comprising one or more metals selected from the group consisting of nickel, cobalt, chromium, copper, molybdenum, aluminum, yttrium and iron.

Furthermore, in a preferred embodiment of the method of the present invention, the green sheet additionally comprises binder metal particles, which are preferably selected from the group consisting of soft solders, brazing alloys and high-temperature solders.

Preferred solders in the context of the present invention are brazing alloys or high-temperature solders. In particular, solder powders from the group of nickel, titanium, cobalt, copper, tin or silver solders come into consideration as brazing materials. Suitable solders are z. B. brazing alloys, such as copper / tin solders, silver / cadmium / copper solders, silver / phosphor solders. Particularly preferred are high-temperature solders such. B. solders based on nickel or cobalt, such as nickel / chromium-containing solders or nickel / cobalt-containing solders. However, it can also be soft solders, especially tin-based solder, such. As tin / lead or tin / silver solders, the moreover more metals, such as. As antimony, bismuth and / or copper may contain. Furthermore, phosphorus additives are also common for common soft solders.

In a particularly preferred embodiment, metal-coated hard material particles are used in combination with nickel-containing solder materials. In particular, the nickel solders with additives such. As boron, chromium and silicon, hard particles, such as. As tungsten carbides, in particular the tungsten carbides, attack and thus render ineffective. By using metal-coated hard material particles, the dissolution of the hard material in the solder material can be reduced. With regard to the dissolution of tungsten carbides in nickel-based solders, the encapsulation of the WSCs with a tungsten carbide (WC) shell provides a remedy in particular. Accordingly, the use of nickel-coated tungsten carbides with a WC shell, such. B. MWC particularly suitable to produce particularly good wear protection layers.

The wear protection films described here generally contain, based on the total weight of the film, from 5% by weight to 95% by weight, preferably from 10% by weight to 90% by weight, of metal-coated hard material particles and 5% by weight. to 95 wt .-%, preferably 10 wt .-% to 50 wt .-%, of solder material particles. Particularly preferably, the films contain between 60% by weight and 80% by weight of metal-coated hard material particles and between 20% by weight and 40% by weight of solder material. The mixing ratio of the contained hard materials and solder materials can be varied depending on the respective wear protection application. The solder materials used can be selected based on the desired soldering temperature and on the material of the component to be coated. The solder materials should preferably have a solidus temperature above the decomposition temperature of organic additives used.

The wear protection films may also, based on the total weight of the film, 0.1 wt .-% to 99.9 wt .-%, preferably between 10 wt .-% and 90 wt .-% of metal-coated hard material particles and 0.1 wt .-% to 99.9 wt. %, preferably 10 wt .-% to 50 wt .-%, of solder material particles. Such wear protection films may also contain from 0.1% to 20% by weight of organic binders and plasticizers.

The described wear protection films can also be laminated with other hard material-containing and / or solder material-containing layers. Preferably, two or more films according to the invention, which are characterized by a different content of metal-coated hard material particles or solder material, are laminated to form a composite film.

Consequently, a further subject matter of the present invention is composite materials comprising at least one of the described wear protection films, wherein the individual layers of the composite contain different proportions of hard material particles and / or solder material particles. Such composite materials preferably have a layer with a proportion of between 40% by weight and 95% by weight, particularly preferably between 60% by weight and 90% by weight, of metal-coated hard material particles and from 5% by weight to 60% by weight. -% of solder material. Furthermore, the composite materials also have at least one further layer, which mainly contains solder material, preferably with a proportion of between 40% by weight and 100% by weight, particularly preferably between 60% by weight and 90% by weight. This layer may also contain hard material particles, in particular with a proportion by weight of between 10% and 40%, which are preferably also coated with metal. Also, such composite materials can be sintered on the component and / or pre-sintered. Sintered composite materials can also simply be glued, soldered or welded onto the component.

In a further embodiment, the claimed wear protection films may include, among other additives, organic binders and plasticizers. The proportion of organic binders and plasticizers is 0 wt .-% to 20 wt .-% based on the total weight of the film. In this case, organic binders and plasticizers are preferably used in a weight ratio between 100: 0 and 50:50. If an organic binder is contained in the wear protection film, this is particularly preferably with a Weight fraction between 0.5 wt .-% and 15 wt .-%, in particular between 2 wt .-% and 10 wt .-% before, the plasticizer is particularly preferably with a weight fraction between 0.1 wt .-% and 10 wt .-%, in particular between 0.5 wt .-% and 5 wt .-%, based on the total weight of the film before.

Preferred organic binders and plasticizers are those which decompose at temperatures below 400 ° C, preferably below 350 ° C. Suitable organic binders are z. As polymers with a low ceiling temperature, such. As halogenated polyolefins, in particular Teflon, polyacetals, polyacrylates or polymethacrylates or its copolymers, polyalkylene oxides, polyvinyl alcohols or its derivatives, polyvinyl acetates or polyvinyl butyrals. Particular preference is given to organic binders from the group of the polyalkylene carbonates, in particular polypropylene carbonate. The organic binder is used in particular during drying to connect the individual solid particles with each other. The binder should be readily soluble in the solvent and with other additives, such as. B. tolerated dispersants. Advantageously, the viscosity of the slurry is hardly increased by the addition of the binder and has achieved stabilizing effect on the suspension. The organic binder should preferably burn out without residue at low temperatures below 400 ° C.

In addition, the binder provides improved durability and improved handleability of the green sheet, in particular to reduce the formation of cracks during drying, for example.

As plasticizer (plasticizer) are z. As phthalates, such as. As benzyl phthalate, glues, waxes, gelatin, dextrins, gum arabic, oils, such as. As paraffin oil or polymers, such as. As polyalkylenes, especially polyethylene. However, preferred plasticizers are alkylene carbonates, in particular propylene carbonate. The plasticizer should in particular bring about the reduction of the glass transition temperature of the polymeric binder and a higher flexibility of the green film. The plasticizer penetrates into the network structure of the binder and thus reduces the viscosity of the slurry. By setting a suitable binder / plasticizer ratio and by combining various binders and plasticizers can be z. B. affect the tear strength and ductility of the green sheets. Also, the plasticizers used burn out preferably at low temperatures below 400 ° C completely.

As further additives which may be contained in the films, metallic binders such. As metal powder, which may preferably contain tungsten, tantalum, niobium, molybdenum, chromium, vanadium, titanium, manganese, iron, cobalt, nickel, copper, zinc, silver, cadmium, aluminum or tin, in question. Furthermore, metal oxides, such as. For example, silicates, alumina, zirconia or titanium oxide can be added. Such metallic additives should not exceed a proportion of at most 30 wt .-% of the total weight of the wear contactor film.

The wear protection films according to the invention may be flat films or else three-dimensionally formed films. The layer thickness of the films is between 10 .mu.m and 3000 .mu.m, in particular between 50 .mu.m and 2500 .mu.m, preferably between 200 .mu.m and 2000 .mu.m. A further subject of the present invention is a film casting process for the production of the wear protection films which is simple, industrially feasible and accordingly inexpensive is. For this purpose, first a binder suspension containing at least one solvent and an organic binder is prepared.

Suitable solvents are in particular organic solvents. However, the addition of water in certain cases may be appropriate. Preferred solvents are, for example, esters, ethers, alcohols or ketones, in particular methanol, ethanol, propanol, butanol, diethyl ether, butyl methyl ether, methyl acetate, ethyl acetate, acetone, methyl ethyl ketone (MEK) or mixtures thereof. Particularly preferred solvents are ketones, in particular from the group of alkyl ketones. Preferred organic binders are the compounds mentioned above, in particular polyalkylene carbonates. Furthermore, the binder suspension can also be added directly to a plasticizer. The resulting mixture is mixed in a mixing unit, such as. As a ball mill, mixed and homogenized.

The binder suspension thus prepared is then mixed with the hard material particles, which have a metallic shell, and the solder material and processed into a slurry. This can be z. B. in a tumble mixer or in a ball mill, wherein the ball mill is filled with grinding media, which preferably have a higher density than the hard material particles to be processed. The binder suspension is preferably initially introduced in the ball mill, but can also be added later. Furthermore, the metal-coated hard material powder and the solder material powder are filled in the ball mill, wherein the resulting mixture is ground and stirred until a stable slurry is formed. When using a ball mill, sufficient mixing and homogenization of the slurry generally takes between 4 hours and 48 hours. The slip can then be degassed at low pressure. The storage, degassing or other processing steps are preferably carried out with constant stirring in order to prevent sedimentation of the solid constituents of the slurry.

Of course, in alternative embodiments, the hard material and / or solder material particles may also be pre-alloyed and the binder suspension added. A continuous or portionwise addition of the binder suspension during the slip production is conceivable.

The resulting slip can then be cast into a film using conventional film casting techniques.

For the preparation of the slip, preference is given to using from 5% by weight to 60% by weight, preferably from 10% by weight to 30% by weight, of the binder suspension, based on the total weight of the slip (including solvent). The binder suspension comprises at least 1 wt .-% to 60 wt .-%, more preferably between 5 wt .-% and 40 wt .-%, of organic binder based on the total weight of the binder suspension and 0 wt .-% to 15 wt. -%, more preferably between 2 wt .-% and 10 wt .-%, of plasticizer based on the total weight of the binder suspension (including solvent). The binder suspension contains a sufficient amount of solvent to ensure at least a suspension of the individual components of the binder suspension. The use of larger amounts of solvent, which are needed for the suspension of the hard particles and the Lotmaterialpartikeln, is not contrary. However, binder slurry or solvent may also be added throughout the slurry production process as needed. Preferably, the amount of the solvent is metered so that slips arise with a high solids content.

Furthermore, 40 wt .-% to 95 wt .-%, preferably 70 wt .-% to 90 wt .-% of hard material particles and Lotmaterialpartikeln, based on the total weight of the slurry, added to the binder suspension. The weight ratio between hard material particles and solder material particles is preferably between 40:60 and 90:10, that is, the slurry preferably contains approximately between 25% by weight and 90% by weight, particularly preferably between 50% by weight and 80% by weight % of hard material particles and approximately between 5% by weight and 60% by weight, particularly preferably between 10% by weight and 40% by weight, of solder material particles. The hard material particles and solder material particles can be added together or separately. The particles can be supplied both as solid to the binder suspension or in pre-suspended form.

• i) eine Bindersuspension enthaltend ein Lösemittel und einen organischen Binder hergestellt wird,
• ii) die in Schritt i) hergestellte Bindersuspension mit Hartstoffpartikeln und Lotmaterialpartikeln ausgewählt aus der Gruppe der Hartlote oder Hochtemperaturlote versetzt und zu einem Schlicker verarbeitet werden und
• iii) der erhaltene Schlicker zu einer Folie gegossen wird, wobei dass zur Herstellung des Schlickers bezogen auf dessen Gesamtgewicht –0.1 Gew.-% bis –30 Gew.-% der Bindersuspension, wobei die Bindersuspension 0.1 Gew.-% bis 60 Gew.-% an organischem Binder bezogen auf das Gesamtgewicht der Bindersuspension und 0 Gew.-% bis 15 Gew.-% an Plastifizierer bezogen auf das Gesamtgewicht der Bindersuspension enthält und 60 Gew.-% bis 99.9 Gew.-% an Hartstoffpartikeln und Lotmaterialpartikeln eingesetzt werden, wobei das Gewichtsverhältnis zwischen Hartstoffpartikeln und Lotmaterialpartikeln zwischen 0:100 und 100:0 liegt, eingesetzt werden.

In an alternative embodiment, the green sheet can be made so that

• i) a binder suspension containing a solvent and an organic binder is prepared,
• ii) the binder suspension prepared in step i) is mixed with hard material particles and solder material particles selected from the group of brazing alloys or high-temperature solders and processed into a slurry, and
• iii) the slip obtained is poured into a film, wherein for the production of the slip based on its total weight -0.1 wt .-% to -30 wt .-% of the binder suspension, wherein the binder suspension 0.1 wt .-% to 60 wt. % of organic binder based on the total weight of the binder suspension and 0 wt .-% to 15 wt .-% of plasticizer based on the total weight of the binder suspension and 60 wt .-% to 99.9 wt .-% of hard material particles and Lotmaterialpartikeln be used wherein the weight ratio between hard particles and Lotmaterialpartikeln between 0: 100 and 100: 0 are used.

The slip or the binder suspension may contain other useful additives, in particular dispersants, defoamers or protective colloids, such. Example, polyester / polyamine condensation polymers, alkyl phosphate compounds, polyvinyl alcohols, dextrins or cellulose ethers.

When film casting by a slip casting method conventional film casting can be used. In this case, the slurry is filled into a reservoir under which a plastic carrier runs, which is carried out continuously at a controlled speed under the container. The slurry is poured from the reservoir onto the plastic film and coated with a casting squeegee to a certain thickness. As a result, a smooth and flat film is produced, which is then usually dried at variable temperatures, optionally stripped from the plastic film and rolled up or further processed or assembled. The method described is characterized by a high production rate and thus by low production costs, the quality of the films produced has a good consistency. Furthermore, simply different film thicknesses, in particular in the range between 10 .mu.m and 3000 .mu.m and film widths can be set. The maximum film width is determined by the specified Foliengießanlage specified. Due to the pronounced pseudoplastic behavior of the slurry, however, film widths of up to 400 mm can be produced without difficulty. The film thickness and width can be adjusted by the following parameters: cutting height of the doctor blade, filling height and thus casting pressure of the slip in the casting chamber, pulling speed of the plastic backing, casting shoe width and viscosity of the slip. The film thickness variation in width and length are usually less than 10% in this method. If structured plastic carriers are used as the casting base, even simple structures can be introduced into the wear protection foil.

An alternative method is the vacuum slip casting method, which is particularly suitable for the production of three-dimensionally shaped wear protection films. With vacuum slip casting, the process flow is considerably accelerated by applying a negative pressure. In this method, the slurry is poured into a porous mold, through which the solvent present is sucked by vacuum. The solids contained in the slurry deposit on the mold surface and thus form a three-dimensionally shaped film, which can be released from the mold after drying. In particular, very thin films of up to 1 μm in thickness can be obtained by the vacuum process, and the solvent removed can also be reused. The vacuum process can also be used industrially.

In a preferred embodiment of the manufacturing process, a suspension of solvent, such as. Example, an alkyl ketone, a binder, preferably polypropylene carbonate and a plasticizer, preferably propylene carbonate homogenized in a ball mill for several days and mixed. The prepared mixture of organic additives is the basis for the Foliengießschlicker. In the next step, a ball mill is filled with grinding media and weighed the binder suspension produced. The amount of grinding media used should be adjusted to the amount of solids in the slurry and the media should have a higher density than the hard material used. Then the hard material and solder powder are weighed. As hard materials, various tungsten carbides coated with nickel are preferably used. The soldering materials used are above all nickel / chromium solder powder, preferably NICROBRAZ solder powder (Wall Colmonoy). The resulting slurry is mixed with continuous stirring between 0.5 h and 24 h. Thereafter, the mixed slurry is transferred to a special casting vessel and degassed. Due to the high density of the powders used, the slurry must be constantly stirred slowly, so that sedimentation of the solid components is avoided. Then the degassed slurry is poured on a commercial casting machine to a solid and flexible carbide foil. As a support preferably a plastic carrier is used, in particular a silicone-coated plastic film, for example made of PET, which withstand the tensile forces during the casting process and should have low adhesion to the dried slurry or the green sheet, so that they can be easily removed. The produced wet film is dried in a circulating air drying channel, preferably at temperatures between 25 ° C and 85 ° C. With the described method, in particular green films with a density of between 2.5-15 g / cm ³ can be produced. The proportion of solid organic additives in the green film is preferably between 1 wt .-% and 25 wt .-%, in particular between 2 wt .-% and 10 wt .-% of the mass of the green sheet.

In a further preferred embodiment of the method according to the present invention, the green sheet is compacted by pressing, preferably by cold isostatic pressing. In this case, this pressing, in particular the cold isostatic pressing, in an advantageous embodiment by cold isostatic pressing at pressures between 1000 and 3000 bar, preferably between 1500 and 2500 bar and more preferably between 1600 and 1800 bar. It is furthermore preferred that the densification is carried out by cold isostatic pressing within 5 to 120 minutes, preferably 10 to 60 minutes, more preferably between 20 and 30 minutes.

Alternatively, the green sheet can be compacted by axial pressing or rolling processes.

In a particularly preferred embodiment, the densification of the green sheet is carried out at a temperature above the gas transition temperature of the organic binder, for example above 40 ° C, preferably above 50 ° C, in particular above 60 ° C, z. B. between 70 ° C and 200 °. The elevated temperatures facilitate the rearrangement processes during compaction and lead to improved results.

The densification of the green sheet in step b) of the process according to the invention particularly preferably leads to an increase in the density of at least 10%, preferably at least 20%, particularly preferably at least 25% and in particular at least 30%.

Another object of the present invention relates to a wear protection film obtainable by the method of the present invention.

Furthermore, a further subject matter of the present invention relates to composite materials comprising at least one wear protection film according to the subject matter of the present invention, characterized in that the individual layers of the composite contain different proportions of hard material particles and / or binder metal particles.

In a preferred embodiment thereof, at least one layer of the composite is a green sheet, the binder metal particles in an amount of more than 70 wt .-%, preferably more than 80 wt .-% and particularly preferably more than 90 wt .-%, in particular more than 95 wt .-%, each based on the total weight of the green sheet, and wherein the film was preferably compacted.

Another object of the present invention relates to the use of wear protection films or composite materials or pre-sintered wear protection films prepared therefrom for the production of wear protection coatings on components.

The production of wear protection films by means of film casting has many advantages. So z. B. using an organic binder, large amounts of hard material particles are easily mixed in the production of slip in a matrix of solder material. By using an organic binder, the film obtained is further stabilized, in particular against a mechanical stress, thereby increasing the handling of the film, in particular facilitates the further processing of the film.

The wear protection films described here are particularly suitable for the production of wear protection layers by brazing at over 450 ° C, preferably by high temperature brazing at over 900 ° C, wherein the production of a solid compound of the film with the component by liquid phase sintering, thereby forming a diffusion zone at the interface training takes place. This results in particularly coherent connections between the wear protection layer and the component. The liquid phase sintering is usually carried out under protective gas and / or under reduced pressure, with a small amount of hydrogen being often mixed in as oxidation protection. With the help of brazing and high-temperature brazing can be coated in particular metallic components that have a steel surface or have a metal surface, containing z. As iron, copper, molybdenum, chromium, nickel, aluminum, silver or gold, wherein the melting temperature of the surface or its solidus temperature should be above the liquidus temperature of the solder material contained in the wear protection film.

The binder-containing wear protection films can be applied directly to a component for the production of a wear-protection layer, debinded and then processed into the corresponding protective layer. However, the wear protection films are preferably pre-debinded and pre-sintered in order to minimize film shrinkage during the production of the wear protection layer on the component. Debinding means removal of the organic constituents required for film casting as far as possible without residue. However, if residues remain in the form of carbon, this leads to the formation of carbides in the following sintering process, which does not necessarily have to be troublesome. Debinding is carried out thermally according to a suitable temperature / time profile. The temperature rise should not exceed 400 ° C. Usually, the binder removal under nitrogen or argon takes place partly with a low hydrogen content in order to remove any oxygen present from the atmosphere. The complete debinding of the film can take up to a day.

A further preferred embodiment of the method of the present invention is characterized in that the wear protection film is debindered, preferably pre-sintered at temperatures below 400 ° C., preferably below 300 ° C. and optionally subsequently.

Two production methods of wear protection layers on a component will be described below by way of example. The first method is based on a green, filled with solder material hardfoil. The green foil is cut to size according to the component size and attached to the component surface. The attachment of the film can be done without further aids, but it can also be used adhesives, which can be removed preferably by thermal decomposition. In particular, the binder suspension can be used as an adhesive for applying the film to the component. Thereafter, the component is thermally treated with the green film. In the first thermal treatment step, the debinding process is preferably carried out at low temperatures of less than 350 ° C. The Debinding temperature is in preferred embodiments below the liquidus temperature of the solder material in the wear protection film. The organic additives used are preferably removed as completely as possible at reduced pressure (below one bar). In the subsequent sintering step, the debindered film is sintered onto the component surface in a high vacuum at about 10 ^-4 -10 ^-6 mbar. The maximum temperature and the holding time depend on the solder material used, wherein at least the liquidus temperature of the solder material has to be achieved. The liquidus temperature of the solder material should be below the melting temperature of the hard material. The sintering temperatures are normally in a range of 800 ° C and 2000 ° C, especially between 1000 ° C and 1500 ° C, preferably between 1050 ° C and 1200 ° C. The solder material used becomes liquid at the predetermined sintering temperature and wets the hard metal particles and the component surface. The applied high vacuum promotes the wetting of the hard metal particles and the carrier with the liquid solder and reduces the porosity in the generated wear protection layer. In this case, a pronounced diffusion layer is formed between the component surface and the produced wear protection layer. The diffusion layer determines the adhesion of the wear protection layer on the component surface.

In the second method, a presintered wear protection part is produced in a first step from the flexible green film produced analogously to the method just described. The pre-sintering of the green sheet is z. B. performed on a ceramic sintered substrate, such as Al ₂ O ₃ or ZrO ₂ . After the debindering cycle up to 400 ° C., a high vacuum is applied and the hard metal foil is sintered on the sintered substrate to form the solid particle composite material. The thus pre-sintered wear protection film can then be applied to the component and processed by liquid phase sintering analogous to the previous method for wear protection layer. Alternatively, the presintered material can also simply be glued to the surface of the component or soldered or welded using an additional solder.

The wear protection layers which can be produced with the aid of the wear protection films according to the invention are distinguished by a low porosity of preferably less than 5%, particularly preferably less than 1.5%, in particular less than 1%. The porosity can be optically determined on a wear protection layer section, the ratio of the area fraction of the pores to the area fraction of the solids on the cut surface being determined. Preferred wear protection layers that can be produced by the described methods have a density between 2.5 g / cm ³ and 25 g / cm ³ , preferably between 5 g / cm ³ and 15 g / cm ³ . The wear protection layers produced are characterized by a high hardness. Wear-resistant coatings with a Rockwell hardness of between 40 HRC and 70 HRC can be produced without problems, and preferred wear-resistant coatings have a Rockwell hardness of more than 50 HRC. The wear protection resistance of the produced layers can be checked by a two-body abrasive wear test ASTM G132-96 (Pin to Table) can be determined. B. by the standard rule ASTM G65-04 be determined.

In particular, the combination of organic additives, including organic binders and plasticizers having a low decomposition temperature, and solder materials having a liquidus temperature which is above the decomposition temperature of the organic additives may provide lower wear protection layers in conjunction with the metal-coated hard material particles evenly distributed in the solder material matrix Porosity and high hardness are generated. The liquidus temperature of the solder material is preferably above 100 ° C., more preferably above 200 ° C., in particular above 400 ° C., higher than the decomposition temperature of the organic binder or plasticizer. This is possible with wear protection films that are easy to produce on an industrial scale and can be easily processed by thermal treatment, in particular by separate debbbing at low temperatures and subsequent brazing, high temperature brazing or flame brazing at high temperatures to the respective wear protection layers.

In a preferred embodiment of the use according to the invention, the binder-containing wear protection film is applied directly to the component and then debinded at temperatures below 400 ° C or debiased before application to the component at temperatures below 400 ° C and then pre-sintered and then by liquid phase brazing the wear protection layer generated on the component.

Another object of the present invention relates to a method for the production of wear-resistant components, wherein a pre-sintered wear protection film according to an article of the present invention or of composite materials according to further articles of the present invention are adhered to the component, soldered or welded.

example

The organic constituents (solvent, optionally plasticizer, organic binder (see WO-A-2010040498 ) are first processed to a binder suspension.

Subsequently, Ni-coated tungsten carbides (Macroline) are added to the binder suspension for the hard-material film, and the components are homogenized to give the slip. For the solder foil, the binder suspension is mixed with a metallic binder, in this case Ni-base solder, to the slip. The two slips are then processed by the Foliengießverfahren to individual green sheets.

Typical composition of a hard-material film:

• Hard material: 98.2 mass% (eg Macroline)
• Plasticizer: 0.2% by mass
• Binder: 1.6% by mass

Typical composition of a solder foil:

• Ni base solder: 97.7 mass%
• Plasticizer: 0.3 mass%
• Binder: 2.0% by mass

The solder foil using Nicrobraze 130 as Ni base solder is referred to as "Ni-130" in Table 3 below.

Subsequently, the green Hartstofffolien additionally undergo a CIP process and so isostatically densified. The pressure used is 1800 bar.

The compacted hardfoil and uncompacted solder foil are then stacked (laminated) and subjected to an additional CIP process to form a hard and solder foil laminate.

The composite of compacted green sheets is then debinded and sintered directly on a sintered substrate or the furnace processes are run through on a component to be coated. In the first case, a wear protection plate, in the second a wear protection coating.

In this example, the green sheets are laid on a steel substrate only in the following sequence: steel - hard-material film (carbide tape (Ni-containing)) - solder film (Lottape); A reverse tape sequence is also conceivable.

The structure is debindered in a furnace process under hydrogen and sintered in a vacuum (10 ^-4 mbar to 10 ^-6 mbar) to a dense coating and soldered simultaneously to the steel. The final sintering temperature is between 1000 ° C and 1200 ° C.

The result is a dense wear protection layer of tungsten carbide (Ni-coated) and Ni-base solder on a steel substrate, as well as in 1 displayed.

It was thus possible to show that the green sheet density (green ink density) of a film containing hard material is increased by the CIP process used according to the invention, which reduces the porosity and the spacing of the hard materials. In wear tests after ASTM G65 / 04 Furthermore, a lower mass loss of these samples compared to the prior art was shown (see Table 3). Table 1: Slurry composition of various hard material compositions based on tungsten carbide The slip solid fuel org. additives solvent Schlicker Dimensions.% % Vol. Dimensions.% % Vol. Dimensions.% % Vol. Toilet tape 1 93.03 41.72 1.79 10.34 5.18 47.94 Toilet tape 2 92.73 40.51 1.78 10.04 5.49 49,45 Toilet tape 3 93.02 41.57 1.71 9.86 5.27 48.57 Toilet tape 4 93.02 41.57 1.71 9.86 5.27 48.57 Toilet tape 5 93.31 42.79 1.72 10.15 4.98 47.06

The slip compositions of Table 1 contain as solids the powders 1 to 3 designated in Table 2, as organic additives the plasticizers and binders indicated in Table 2 and additionally as solvent methyl ethyl ketone (MEK). The slip compositions indicated in Table 1 are prepared by means of the doctor blade. Formed into films and then dried, the solvent evaporated. The film composition is shown in Table 2.

The weight ratio of powder 1 to powder 2 for toilet tape 1 is 7: 3.

The weight ratio of powder 1 to powder 2 to powder 3 is 70:15:15 for WC-tape 3.

The weight ratio of powder 1 to powder 2 for toilet tape 4 is 7: 3.

Table 3 shows film laminates consisting of the hard-material films according to Table 2 and in each case one solder film. The laminate is subjected to a CIP process at 1800 bar. The ratio of the thickness of the brazing foil to the hard-material foil is 1: 2. The film laminates were sintered for 15 to 30 minutes at 1050 ° C to 1100 ° C at a pressure of 10 mbar. As the substrate material provided with the film laminates, low alloyed structural steel was selected.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 6649682 B1 [0003]
• US 5594931 [0004]
• US 2007/0017958 A1 [0005]
• WO 2007/147792 [0005]
• WO 2010040498 A [0006, 0014, 0073]

Cited non-patent literature

• ASTM G132-96 [0069]
• ASTM G65-04 [0069]
• ASTM G65 / 04 [0082]

Claims (19)

Process for the production of wear protection films comprising the steps: a) production of a green sheet comprising hard material particles and b) compacting the green sheet. A method according to claim 1, characterized in that the green sheet is produced in step a) a-1) providing a slurry comprising hard material particles and organic components and a-2) Pour the slurry into a green sheet. A method according to claim 2, characterized in that the slurry comprises a binder suspension, hard material particles and optionally binder metal particles. Method according to claim 3, characterized in that the slip, i) from 0.1 to 10% by weight of binder suspension, the binder suspension preferably containing from 1 to 60% by weight of organic binder and from 0 to 15% by weight of plasticizer, based on the total weight of the binder suspension, and ii) contains 90 to 99.9 wt .-% hard particles and optionally binder metal particles, wherein i) and ii) are each based on the total weight of the slurry. Method according to at least one of claims 1 to 4, characterized in that the hard material particles comprise or consist of components selected from the group consisting of tungsten carbide, titanium carbide, tantalum carbide, silicon carbide, vanadium carbide, chromium carbide, molybdenum carbide, titanium boride, tungsten carbide, and Tungsten carbide having a tungsten carbide shell or a shell of chromium carbide and any mixtures thereof. A method according to any one of claims 1 to 5, characterized in that the hard material particles comprise a metallic shell comprising one or more metals selected from the group consisting of nickel, cobalt, chromium, copper, molybdenum, aluminum, yttrium and iron. Method according to at least one of claims 1 to 6, characterized in that the green sheet additionally comprises binder metal particles, preferably selected from the group consisting of soft solders, brazing alloys and high-temperature solders. A method according to claim 7, characterized in that the binding metal particles are selected from solder material particles from the group nickel, cobalt, copper, tin and silver solder material, preferably a nickel-based high-temperature solder. Method according to at least one of claims 1 to 8, characterized in that the densification of the green sheet in step b) leads to an increase in density by at least 10%, preferably at least 20%, more preferably at least 25% and in particular at least 30%. Method according to at least one of claims 1 to 9, characterized in that the densification of the green sheet by pressing, preferably by cold isostatic pressing. A method according to any one of claims 1 to 10, characterized in that the compression by cold isostatic pressing at pressures between 1000 and 3000 bar, preferably between 1500 and 2500 bar, more preferably between 1600 and 1800 bar, takes place. Method according to at least one of claims 1 to 11, characterized in that the densification by cold isostatic pressing within 5 to 120 minutes, preferably 10 to 60 minutes, more preferably between 20 and 30 minutes, takes place. A method according to any one of claims 1 to 12, characterized in that the wear protection film entbindert, preferably at temperatures below 400 ° C, preferably below 300 ° C and optionally pre-sintered. Wear protection film obtainable by a process according to any one of claims 1 to 13. Composite materials containing at least one wear protection film according to claim 14, characterized in that the individual layers of the composite contain different proportions of hard material particles and / or binder metal particles. Composite material according to claim 15, characterized in that at least one layer of the composite is a green sheet, the binder metal particles in an amount of more than 70 wt .-%, preferably more than 80 wt .-% and particularly preferably more than 90 wt .-% , in particular more than 95 wt .-%, each based on the total weight of the green sheet, and wherein the film was preferably compacted. Use of wear protection foils according to claim 14 or of composite materials according to claim 15 or 16 or pre-sintered wear protection foils produced therefrom for the production of wear protection layers on components. Use according to claim 17, characterized in that the binder-containing wear protection film is applied directly to the component and then debinded at temperatures below 400 ° C or debinded before application to the component at temperatures below 400 ° C and then pre-sintered and thereafter by Liquid phase soldering the wear protection layer is produced on the component. A method for producing wear-resistant components, characterized in that a pre-sintered wear protection film according to claim 14 or composite materials according to claim 15 or 16 is soldered, glued or welded to the component or be.

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