HK1079246B - Hard metallic materials, hard metallic coatings, methods of processing metallic materials and methods of producing metallic coatings - Google Patents

Description

Hard metal material, hard metal coating, method for treating metal material and method for producing metal coating

Source of contract of the invention

The invention was sponsored by the U.S. government under contract number DE-AC07-99ID13727 issued by the U.S. department of energy. The united states government has certain rights in the invention.

Relevant patent data

This application is a continuation-in-part application of U.S. patent application 09/709918, filed on 9/11/2000, which is incorporated herein by reference.

Technical Field

The present invention relates to a hard metal material and a method of forming a hard metal material.

Background

Steel is a metallic alloy that may have special strength characteristics and is therefore widely used in structures where strength is required or is dominant. The steel may be used, for example, in skeletal supports for building structures, tools, engine components, and armor layers for modern weapons.

The composition of the steel varies depending on the use of the alloy. For purposes of the following description and claims, "steel" is defined as an iron-based alloy in which no other element (other than iron) is present in excess of 30 wt%, the iron content amounting to at least 55 wt%, and carbon limited to up to 2 wt%. In addition to iron, the steel alloy may include, for example, manganese, nickel, chromium, molybdenum, and/or vanadium. Accordingly, the steel generally contains small amounts of phosphorus, carbon, sulfur and silicon.

The atoms are regularly arranged in the steel and they are periodically stacked to form a 3-dimensional lattice which defines the internal structure of the steel. The internal structure (sometimes referred to as the "microstructure") of conventional steel alloys is always metallic and polycrystalline (consisting of many grains). The composition and the processing method are important factors influencing the structure and the performance of the steel. In conventional steel processing methods, an increase in hardness is accompanied by a corresponding decrease in toughness. Steels produced by conventional methods that increase the compositional hardness can result in steels that are very brittle.

Steel is typically formed by cooling a molten alloy. For conventional steel alloys, the cooling rate will determine whether the alloy chill forms an internal structure comprising mainly grains, or in a few cases an amorphous (so-called metallic glass) based structure. In general, it has been found that if cooling is performed slowly (i.e., at a rate of less than about 10 a)⁴K/sec) to form particles having a large size, and if cooling is performed quickly (i.e., at a rate greater than or equal to about 10 a)⁴K/sec), a microcrystalline internal grain structure is formed, or, in certain rare cases not found in conventional steel alloy compositions, amorphous metallic glasses are formed. When the alloy is rapidly cooled, the particular composition of the molten alloy will generally determine whether the alloy solidifies to form a microcrystalline grain structure or forms an amorphous glass.

Both the microcrystalline grain internal structure and the metallic glass internal structure can have the properties required for the specific application of the steel. In certain applications, the amorphous nature of the metallic glass provides desirable properties. For example, some metallic glasses may have particularly high strength and hardness. In other applications, the specific properties of the microcrystalline grain structure are preferred. Oftentimes, if the properties of the grain structure are preferred, these properties can be improved by reducing the particle size. For example, the particle size is reduced to nano-crystalline particles (i.e., particle size at 10A)^-9On the order of meters), the crystallite size can generally be improved (i.e., the particle size is 10 a)^-6On the order of meters). Generally, the formation of nano-sized grains is more problematic than the formation of micro-sized grains, and is generally not possible using conventional methods.

It is desirable to develop improved methods of forming nano-sized steel. Further, since it is often desirable to have a metallic glass structure, it is desirable to propose a method of forming metallic glass. Furthermore, it is desirable to develop methods of treating steels that increase hardness without a corresponding decrease in toughness.

Summary of The Invention

One aspect of the present invention includes a method of manufacturing a hard-metal material. An elemental mixture comprising at least about 55 weight percent Fe and at least one of B, C, Si and P is alloyed and cooled at a rate of less than about 5000K/s to form a metallic material having a hardness of greater than about 9.2 GPa. One aspect of the present invention includes a metallic material comprising at least 55% Fe and at least one of B, Si, P and C. The material has a total elemental composition of less than 11 elements, excluding impurities, and has a melting temperature of about 1100 to about 1250 ℃ and a hardness of greater than about 9.2 GPa. One aspect of the invention includes a method of forming a wire. The metal strip having the first composition and the powder having the second composition are rolled/stamped together, thereby combining the first composition and the second composition to form the wire rod having the third composition. The third composition contains at least 55 wt% Fe, and 2-7 other elements including at least one of C, Si and B.

One aspect of the present invention includes a method of forming a hardened surface on a substrate. A solid having a first hardness is processed to form a powder. The powder is applied to a surface of a substrate to form a layer having a second hardness. At least a portion of the layer comprises a metallic glass that can be converted to a crystalline material having a nano-particle size. In order to transform the metallic glass into a crystalline material, the layer is hardened to a third hardness, which is higher than the first hardness and also higher than the second hardness.

Brief description of the drawings

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a block flow diagram of a method of the present invention.

FIG. 2 is a block flow diagram of a process of the present invention.

FIG. 3 is an SEM micrograph of metal powder made by the method of the present invention.

Fig. 4 is a schematic partial cross-sectional view of a metallic material in a first processing step of the method of the present invention.

Fig. 5 is a view of the metallic material of fig. 4 at a processing step subsequent to that of fig. 4.

Fig. 6 is a schematic partial cross-sectional view of a metallic material substrate during a processing step of the processing method of the present invention.

FIG. 7 is a Fe-containing alloy formed by high velocity oxy-fuel deposition on 4340 alloy steel, 13-8 stainless steel and 7075 aluminum substrates₆₃Cr₈Mo₂B₁₇C₅Si₁Al₄Examples of the coating of (1).

FIG. 8 is the Fe shown in FIG. 7₆₃Cr₈Mo₂B₁₇C₅Si₁Al₄The cross-sectional porosity of the coating is shown schematically.

FIG. 9 is a graph of a deposition process containing (Fe) by plasma deposition (graph A), high velocity oxy-fuel deposition (graph B) and Wire-Arc deposition (graph C)_0.8Cr_0.2)₇₃Mo₂W₂B₁₆C₄Si₁Mn₂Schematic cross-sectional view of the porosity of the coating of (1).

FIG. 10 is a graph of Fe-containing deposition on a 330 micron thick, high velocity oxy-fuel₆₃Cr₈Mo₂B₁₇C₅Si₁Al₄The free surface of the coating of (a) is subjected to a pattern of x-ray diffraction scans.

FIG. 11 shows a graph of Fe content versus a thickness of 1650 microns₆₃Cr₈Mo₂B₁₇C₅Si₁Al₄The free surface (FIG. A) and the substrate interface (FIG. B) of the plasma sprayed layer of (1) are subjected to an x-ray diffraction scan.

FIG. 12 shows the results obtained for a composition of (Fe)_0.8Cr_0.2)₇₃Mo₂W₂B₁₆C₄Si₁Mn₂The free surface of a 0.25 inch thick coating formed by wire arc spraying of the wire was x-ray diffraction scanned.

FIG. 13 is a composition of Fe₆₃Cr₈Mo₂B₁₇C₅Si₁Al₄Atomized powder (upper curve), high velocity oxy-fuel ofGraph of data obtained from differential thermal analysis of the coating (middle curve) and the plasma sprayed coating. The curves illustrate the transition from glassy to crystalline for various test forms of the composition, as well as the melting temperature of the composition.

FIG. 14 is a graph of Fe for a 0.25 inch thick wire arc deposited wire₆₃Cr₈Mo₂B₁₇C₅Si₁Al₄A differential scanning calorimetry data plot of the coating. The figure shows the transition from glassy to crystalline in the coating.

FIG. 15 shows a composition comprising (Fe)_0.8Cr_0.2)₇₉B₁₇W₂C₂The composition of (a), the metallic material produced by the method of the present invention, SEM micrographs after 1 hour heat treatment at 700 ℃ (panel a), 750 ℃ (panel B) or 800 ℃ (panel C), and the diffraction pattern of the corresponding selected area.

FIG. 16 shows a composition comprising (Fe)_0.8Cr_0.2)₇₃Mo₂W₂B₁₆C₄Si₁Mn₂The composition of (a), the metallic material produced by the process of the present invention, SEM micrographs after 1 hour heat treatment at 600 ℃ (panel a), 700 ℃ (panel B) and 800 ℃ (panel C) and the corresponding diffraction pattern of the selected area.

FIG. 17 is an SEM micrograph of a coating comprising Fe₆₃Cr₈Mo₂B₁₇C₅Si₁Al₄Formed by HVOF deposition by the method of the invention, followed by a heat treatment at 600 c for 1 hour.

FIG. 18 shows a composition containing (Fe)_0.8Cr_0.2)₇₃Mo₂W₂B₁₆C₄Si₁Mn₂The x-ray diffraction patterns of the high velocity oxy-fuel coating were measured (panel a) and Rietveld refined (calculated, panel B) after subjecting it to a heat treatment at 750 c for 1 hour.

FIG. 19 Panel A is a cross-sectional view having a thickness of about 200 micronsFe of meter thickness₆₃Cr₈Mo₂B₁₇C₅Si₁Al₄Examples of coated steel strips. The coating is formed using high-rate oxy-fuel deposition. Figures B and C show the effect of the coating on the coated strip during bending.

FIG. 20 shows a coating of Fe about 200 microns thick₆₃Cr₈Mo₂B₁₇C₅Si₁Al₄A coated base metal plate, the coating being formed by high velocity oxy-fuel deposition. The plates formed in the same manner are used to indicate the formed plate (fig. a), the plate (fig. B) on the coating side which has been repeatedly hammered, or the plate (fig. C) on the substrate side which has been repeatedly hammered, and the plate (fig. D) which has been subjected to severe plastic deformation.

FIG. 21 shows a composition of (Fe)_0.8Cr_0.2)8₁B₁₇W₂The true stress/true strain measurement profile of a thin metal strip of the metallic glass of (1). This curve reflects the data obtained for the following cases: strain rate of 10 at 20 DEG C^-3s^-1(FIG. A); 450 deg.C (fig. B) strain rate of 10^-4Second of^-1(solid circle) and 10^-2Second of^-1(hollow circles); strain rate of 10 at 500 deg.C (fig. C)^-4Second of^-1(solid circle) 10^-2Second of^-1(hollow circle) and 10^-1Second of^-1(triangle); 550 deg.C (Panel D) Strain Rate of 10^-1Second of^-1(hollow circle) and 10^-2Second of^-1(filled circle).

FIG. 22 shows a composition of (Fe)_0.8Cr_0.2)₈₁B₁₇W₂Graph of true stress/true strain measurements after crystallization of thin metal strips. The curve reflects a strain rate of 10 at 750 deg.C^-4s^-1The data obtained. Heating the composition to a temperature above the crystallization temperature and below the melting temperature of the composition achieves crystallization.

Detailed description of the preferred embodiments

The disclosure of the present invention is submitted for the statutory purpose of promoting the U.S. patent Law "Advances in science and useful technology" (article 1, clause 8).

The invention includes methods of forming metallic glass steel materials and methods of forming steel materials having nanocrystalline-scale composite microstructures, methods of applying such steel materials, and also includes the steel material compositions. The method encompassed by the present invention is generally described by reference to the block diagram of fig. 1. In the first step (a) a mixture of elements is formed. The mixture includes a steel composition. One example of the mixture includes at least 55 wt% Fe and may also include at least one element selected from B, C, Si and P. In a particular aspect of the invention, the mixture includes at least two of B, C and Si. The mixture may include B, C and Si, which in certain embodiments of the mixture may include B, C and Si in an atomic ratio of B₁₇C₅Si₁. In a particular aspect of the invention, the mixture may comprise at least one transition metal, for example selected from W, Mo, Cr and Mn. Further, the mixture may include one or more of Al and Gd.

The mixture of the present invention preferably includes less than 11 elements, and may more preferably include less than 9 elements. Furthermore, the mixture may comprise as few as 2 elements. In particular embodiments, the mixture may consist of, or may consist essentially of, less than 11 elements. Moreover, the mixture may consist or consist essentially of as few as 2 elements. In general, the mixtures of the invention are composed of 4 to 8 elements.

Examples of mixtures which can be used in the process according to the invention are: fe₆₃Mo₂Si₁，Fe₆₃Cr₈Mo₂，Fe₆₃Mo₂Al₄，(Fe_0.8Cr_0.2)8₁B₁₇W₂，(Fe_0.8Mo_0.2)₈₃B₁₇，Fe₆₃B₁₇Si₁，Fe₆₃Cr₈Mo₂C₅，Fe₆₃Mo₂C₅，Fe₈₀Mo₂₀，Fe₆₃Cr₈Mo₂B₁₇，Fe₈₃B₁₇，Fe₆₃B₁₇Si₅，Fe₆₃B₁₇C₂，Fe₆₃B₁₇C₃Si₃，(Fe_0.8Cr_0.2)₇₉B₁₇W₂C₂，Fe₆₃B₁₇C₃Si₅，Fe₆₃B₁₇C₂W₂，Fe₆₃B₁₇C₈，Fe₆₃B₁₇C₅，(Fe_0.8Cr_0.2)₇₈Mo₂W₂B₁₂C₅Si₁，Fe₆₃B₁₇C₅W₅，Fe₆₃B₁₇C₅Si₅，(Fe_0.8Cr_0.2)₇₆Mo₂W₂B₁₄C₅Si₁，(Fe_0.8Cr_0.2)₇₃Mo₂W₂B₁₆C₄Si₁Mn₂，Fe₆₃Cr₈Mo₂B₁₇C₅，(Fe_0.8Cr_0.2)₇₅Mo₂B₁₇C₅Si₁，Fe₆₃Cr₈Mo₂B₁₇C₅Si₁Al₄，(Fe_0.8Cr_0.2)₇₅W₂B₁₇C₅Si₁，Fe₆₃B₁₇C₅Si₁，(Fe_0.8Cr_0.2)₇₃Mo₂W₂B₁₇C₅Si₁，(Fe_0.8Cr_0.2)₇₂Mo₂W₂B₁₇C₅Si₁Gd₁，(Fe_0.8Cr_0.2)₇₁Mo₂W₂B₁₇C₅Si₁Gd₂And (Fe)_0.8Cr_0.2)₇₄Mo₂W₂B₁₇C₄Si₁。

In step (B) of fig. 1, the mixture may be alloyed. Step (B) of forming the alloy may comprise, for example, melting the composition in an argon atmosphere.

In step (C) of fig. 1, the alloy may be cooled to form a hard material containing solids. To obtain a hardened steel solid, cooling a conventional steel alloy to form a solid material is generally at a rate of at least about 5000K/sec. For the purposes described herein, cooling at a rate of at least about 5000K/sec may be referred to as rapid cooling. Rapid cooling can be achieved by a number of different methods including, for example, melt spinning, gas atomization, centrifugal spraying, water atomization, and chill-quenching. Alternatively, step (C) of fig. 1 may include rapid cooling or may include slow cooling (cooling at a rate of less than or equal to about 5000K/sec) to form a hard solid material. Slow cooling of the alloy may preferably comprise cooling at a rate of less than about 5000K/sec, and methods such as arc melting, casting, sand casting, investment casting, and the like may be used. The cooling rate and resulting hardness of the hard metal material may vary depending on the particular composition of the mixture used to form the alloy. In particular embodiments, the hard metal materials made by the methods of the present invention may have a hardness of greater than about 9.2 GPa. Furthermore, unlike conventional steel compositions that are rapidly cooled to achieve high hardness, the particular alloy compositions described herein can achieve extremely high hardness (greater than about 9.2GPa) through slow cooling.

The hard solid material formed in step (C) of fig. 1 may have a melting temperature of, for example, between about 1100C and about 1550℃. The hard solid material formed in step (C) of fig. 1 is not limited to a specific form, and may be, for example, a cast material including, but not limited to, an ingot form. The fabrication of hard solid materials using the processing steps described in fig. 1 may include standard metallurgical processes including, but not limited to: arc melting, investment casting, sand casting, spray forming and spray rolling.

The measured hardness (GPa) of ingots having the selected compositions of the invention are shown in table 1. The ingot was sawn in half with a diamond saw, inlaid with a metallographic phase, and the hardness was measured, each reported hardness value representing the average of ten measurements. As shown in Table 1, the hardness of the resulting ingots was as high as 14.9 GPa.

Although the solid block form of the cooling alloy may have a very high hardness, the hardness may also be accompanied by a very low toughness. Due to the low toughness, the formed ingots can be very brittle and can break when subjected to impact, such as when struck with a hammer. However, further processing of the solid bulk material using the method of the invention (described below) produces a material that is extremely hard and also has a higher toughness than cast ingot forms, as opposed to the usual increase in hardness with a concomitant decrease in toughness produced by conventional steel processing.

TABLE 1

Hardness of ingot

Ingot casting composition	Hardness (GPa)
		FeBCSi	10.3
(FeCr)BWC	10.8
		FeBCSi	11.1
FeBCW	11.2
		FeBC	11.9
FeBC	12.1
		(FeCr)MoWBCSi	12.1
FeBCW5	12.3
		FeBCSi	12.3
(Fe0.Cr)MoWBCSi	12.3
		(FeCr)MoWBCSiMn	12.3
FeCrMoBC	12.5
		(FeCr)MoBCSi	12.7
FeCrMoBCSiAl	13.2
		(FeCr)WBCSi	13.4
FeBCSi	13.7
		(FeCr)MoWBCSi	14.0
(FeCr)MoWBCSiGd	14.4
		(FeCr)MoWBCSiGd	14.7
(FeCr)MoWBCSi	14.9

Additional and alternative processes performed on the alloy in step (B) of fig. 1 and the hard solid material in step (C) of fig. 1 are generally described with reference to the block diagram of fig. 2. The alloy produced by the method of the present invention may comprise a molten alloy as shown in step (D) of fig. 2. The molten alloy may be solidified in step (E) by rapid cooling or slow cooling according to the method described above. The solidified material may be subjected to a further processing step (F) to form a powder. Alternatively, the molten alloy of step (D) may be directly subjected to the powder forming step (F).

Processing the solid material of step (E) into powder form may include, for example, using a variety of conventional comminution or milling steps, or atomization methods, such as gas, water, or centrifugal atomization, to produce a metal powder. In a particular embodiment of the invention, the use of an atomisation process to process solid materials into powders is advantageous because such a process can produce a large number of stable, inactive powders having the desired size range in a single step. Atomization can produce particularly advantageous spherical powders because spherical particles flow easily and can pass through a thermal deposition apparatus in an improved path (see below). The spherical characteristics of the powder particles made of hard steel ingots having an alloy composition are shown in fig. 3.

In a particular form of the invention, the powder particles produced by atomization may form powder particles comprising at least a portion of amorphous microstructure. The composition of the present invention has a high glass state forming ability, and rapid solidification in the atomization process allows the direct production of amorphous glass particles. In particular embodiments, it may be desirable to make amorphous particles, thereby limiting or eliminating the need for re-melting of the particles during subsequent deposition. The specific compositions processed by the method of the invention can be made into powders containing up to 100% amorphous structure.

As shown in fig. 2, the metal powder obtained in step (F) may be made from the molten alloy of step (D) of the method of the present invention without including the solidification step (E). This direct powder forming may be achieved by rapid solidification methods such as radiation cooling, convection cooling or conduction cooling, or any of the above-described atomization methods for processing solid metallic materials into powder form may be used. The advantages mentioned above in connection with the atomization of solid material are also used for the atomization of molten alloy in the method according to the invention.

The metal powder of step F may be further subjected to a classification treatment (classifying the powder by particle size (not shown)) before the surface treatment step (H) of fig. 2. Such classification may include, for example, continuous screening and air classification steps. The particle size produced by the process of the present invention may be between about 10 and about 450 microns. Powder particle classification may be employed to achieve a particular particle size or range of sizes for the deposition process of a selected material. In particular embodiments, classification may be used to produce powders having particle sizes ranging from about 10 to about 100 microns.

Still referring to fig. 2, the powder produced by the method of the present invention may optionally be used to produce a wire in step (G), which in turn may be used for surface treatment in step (H). Referring to fig. 4 and 5, the wire forming step (G) in fig. 2 will be described in more detail.

Referring first to fig. 4, wire forming may include providing a metal strip 20, which may have a first composition, and providing a powder, which may have a second composition. The composition of the metal strip 20 and the composition of the powder 22 may be combined to form a desired wire composition for subsequent deposition or other use. The powder 22 is not limited to a particular powder and may include, for example, a powder made using the method of the present invention described above. The composition of the metal strip 20 is not limited to any particular composition and may be selected as an additive to the composition of the powder 22 to form the desired wire composition.

The metal strip 20 may be combined with the powder 22 and further processed to produce the wire 24 shown in fig. 5. The combination of metal strip and powder may include, for example, forming a core wire using a conventional rolling/extrusion process wherein the powder material forms the core 28 and the metal strip forms the skin 26 around the core 28. The wire 24 is not limited to a particular diameter and may be, for example, about 0.035 to about 0.188 inches in diameter. In a particular embodiment, the preferred wire diameter may be 1/16 inches.

The overall composition of the wire 24, including the composite composition of the core 28 and the skin 26, may include at least 55 wt% Fe. The overall composition of the wire 24 may preferably include less than 11 elements. In a particular embodimentThe overall composition of the wire 24 may consist essentially of less than 11 elements. Preferably, the overall composition of the wire 24 may include or consist essentially of 2-7 elements in addition to iron. The element other than iron in the total composition may include at least one element selected from C, B, P and Si. In particular embodiments, the wire 24 may include C, B, P and 2, 3, or all of Si. For example, the overall composition of the wire 24 may include, for example, C, Si and B in an atomic ratio of B₁₇C₅Si₁. The overall composition may further comprise one or more of W, Mo, Cr, Mn, Al and Gd.

Examples of the total composition that may be contained in the wire 24 include: fe₆₃Mo₂Si₁，Fe₆₃Cr₈Mo₂，Fe₆₃Mo₂Al₄，(Fe_0.8Cr_0.2)₈₁B₁₇W₂，(Fe_0.8Mo_0.2)₈₃B₁₇，Fe₆₃B₁₇Si₁，Fe₆₃Cr₈Mo₂C₅，Fe₆₃Mo₂C₅，Fe₈₀Mo₂₀，Fe₆₃Cr₈Mo₂B₁₇，Fe₈₃B₁₇，Fe₆₃B₁₇Si₅，Fe₆₃B₁₇C₂，Fe₆₃B₁₇C₃Si₃，(Fe_0.8Cr_0.2)₇₉B₁₇W₂C₂，Fe₆₃B₁₇C₃Si₅，Fe₆₃B₁₇C₂W₂，Fe₆₃B₁₇C₈，Fe₆₃B₁₇C₅，(Fe_0.8Cr_0.2)₇₈Mo₂W₂B₁₂C₅Si₁，Fe₆₃B₁₇C₅W₅，Fe₆₃B₁₇C₅Si₅，(Fe_0.8Cr_0.2)₇₆Mo₂W₂B₁₄C₅Si₁，(Fe_0.8Cr_0.2)₇₃Mo₂W₂B₁₆C₄Si₁Mn₂，Fe₆₃Cr₈Mo₂B₁₇C₅，(Fe_0.8Cr_0.2)₇₅Mo₂B₁₇C₅Si₁，Fe₆₃Cr₈Mo₂B₁₇C₅Si₁Al₄，(Fe_0.8Cr_0.2)₇₅W₂B₁₇C₅Si₁，Fe₆₃B₁₇C₅Si₁，(Fe_0.8Cr_0.2)₇₃Mo₂W₂B₁₇C₅Si₁，(Fe_0.8Cr_0.2)₇₂Mo₂W₂B₁₇C₅Si₁Gd₁，(Fe_0.8Cr_0.2)₇₁Mo₂W₂B₁₇C₅Si₁Gd₂And (Fe)_0.8Cr_0.2)₇₄Mo₂W₂B₁₇C₄Si₁。

The powder used for wire formation is not limited to a particular microstructure and may include about 0 to about 100% amorphous (metallic glass) structure. The powder for wire formation preferably includes a composition of: when this composition is alloyed with the surface of the metal wire, an alloy composition capable of forming a metallic glass can be produced. The final composition of the wire produced according to the invention is preferably: the powder occupies a volume fraction of about 10 to about 60%.

The particle size range of the powder for wire forming according to the method of the present invention is not limited to a specific value. Since no particular powder size is required for wire formation, wire formation according to the methods of the present invention may employ any unfractionated powder, or a classified powder including sizes outside the preferred particle size ranges for the various powder deposition processes.

Referring again to fig. 2, the powder produced in step (F) or the wire produced in step (G) may be used to treat the surface in step (H). In step (H), the metal material may be applied to the surface in a powder form or a wire form, thereby forming a layer or a coating layer on the surface. The use of the feed of the powder or wire produced by the method of the invention will be described in more detail with reference to figure 6.

As shown in fig. 6, a substrate 50 is provided to treat a surface 51. Surface 51 may comprise a metal surface, such as a conventional steel surface, an aluminum surface, a stainless steel surface, a tool steel surface, or any other metal surface. Alternatively, surface 51 may comprise a non-metallic material, such as a ceramic material. A powder or wire, for example, made using the above-described method, may be used as a raw material for deposition on the surface 51. Examples of the surface treatment method for depositing the raw material on the surface 51 include a thermal deposition process in which the raw material is charged into the deposition apparatus 52. The feedstock may be converted into a spray 54 that is sprayed onto surface 51 to form a layer of material 56. Thermal deposition is not limited to a particular process and may include, for example, a high pressure plasma system, a low pressure plasma system, a detonation gun system, a diamond coating system, a high velocity oxy-fuel (HVOF) system, a twin or single roll wire arc system, or a high velocity wire arc system. FIG. 7 shows a composition of Fe₆₃Cr₈Mo₂B₁₇C₅Si₁Al₄Example of a spray HVOF coating.

The jetted layer 56 may contain a microstructure that includes at least a portion of the metallic glass prior to any subsequent processing. The amount of amorphous structure within layer 56 depends on the deposition method, deposition conditions, and composition of the starting materials. The hardness of the jetted layer 56 may be greater than about 9.2 GPa. The layer 56 typically has a hardness of about 9.2 to about 15.0 GPa.

The hardness of the jetted layer can be affected by porosity. It is advantageous to produce a layer or coating with low porosity, since an increase in the porosity of the material leads to a corresponding decrease in its hardness. As shown in fig. 8, the porosity of layer 56 may be as low as 0.06%. Typically, the porosity of the layer 56 is less than or equal to about 5% (corresponding to a layer density of greater than or equal to 95%). FIG. 9 shows a coating made using three different coating deposition processes (Fe)_0.8Cr_0.2)₇₃Mo₂W₂B₁₆C₄Si₁Mn₂Porosity of the coating. The porosity of the plasma coating shown in graph a is 0.9%, the porosity of the HVOF coating shown in graph B is 0.7%, and the porosity of the wire arc coating shown in graph C is 3.3%. Table 2 shows the measured hardness of each of the three coatings shown in fig. 9. Those skilled in the art will appreciate that the porosity of the coating 56 may be increased if it is desired to add oxygen during the spray deposition of the coating, or if it is desired to spray using non-optimized spray parameters. It is sometimes desirable that the porosity of the coating is high, for example in order to absorb oil.

TABLE 2

Properties of coatings made using different spray processes

Performance of	HVOF coating	Plasma coating	Wire arc coating
				Porosity (%)	0.7	0.9	3.3
Hardness of sprayed layer	10.0GPa	11.0GPa	12.7GPa
				Hardness after 1h at 700 DEG C	14.5GPa	13.5GPa	13.5GPa

X-ray diffraction studies of the free surface side of the single-shot 330 micron thick coating revealed a lack of long-range order microstructure, as shown in figure 10, indicating that the coating had an amorphous structure. The jetted layer 56 may contain some measurable amorphous structure, may contain predominantly amorphous structure (greater than 50% microstructured), or may contain up to about 100% amorphous structure.

The presence of the metallic glass allows the formation of a coating 56 in the absence of any interfacial layer (e.g., adhesion layer) between the coating 56 and the surface 51, as shown in fig. 6, due to the lack of long range order microstructure in the metallic glass. Because of the presence of the amorphous structure within the coating 56, there is little or no mismatch in crystalline structure between the material of the surface 51 and the coating 56, and therefore no interfacial layer is required. Although fig. 6 shows the absence of an interfacial layer, it is to be understood that the present invention also encompasses embodiments in which an interfacial layer is present (not shown).

Although a single coating 56 is shown in fig. 6, it is to be understood that the present invention also encompasses coatings having multiple thicknesses (not shown). The jetted layer 56 can comprise a multilayer thickness of about 25 to about 6500 microns. If a powder feedstock is used, the coating 56 may preferably have a multilayer thickness of about 250 to about 350 microns. If wire stock is used, the coating 56 may preferably have a multilayer thickness of about 750 to about 1500 microns.

Coatings having a multi-layer thickness can be made by, for example, sequentially depositing individual layers according to the methods described above. X-ray diffraction scans of the free surface side (fig. 11A) and substrate surface side (fig. 11B after lift-off) of the 1650 micron thick multilayer coating showed that the amorphous structure was maintained during the multilayer plasma deposition process. Fig. 12 shows x-ray scanning results showing the amorphous structure of an 1/4 inch thick multilayer coating made by twin roll wire arc spray deposition.

Differential Thermal Analysis (DTA) was performed to show that the composition was Fe₆₃Cr₈Mo₂B₁₇C₅Si₁Al₄The conversion of atomized powder feedstock, HVOF coating and plasma spray coating from glassy to crystalline state. The DTA scan results, combined with Differential Scanning Calorimetry (DSC) measurements, shown in FIG. 13 indicate that the powder feedstock contains 46% glass structure, the HVOF coating contains 41% glass structure, and the plasma coating containsThere is a 86% glass structure. The DSC curve shown in FIG. 14 is composed of Fe₆₃Cr₈Mo₂B₁₇C₅Si₁Al₄1/4 inches thick. In addition to having a base hardness of at least about 9.2GPa, the increase in base toughness of the jetted layer 56 is related to the toughness of the solid form of the cooled alloy of the corresponding composition (described above). For example, the tensile elongation of the jetted layer 56 may reach about 60% when the maximum density is reached.

Referring again to fig. 2, once the metallic material is applied to the surface in step (H), the metallic material may be further processed in step (I) to devitrify some or all of the metallic glass in the metallic material to form crystals having a nano-size. The devitrification step (I) results in an increase in the hardness of the devitrified layer associated with the jetted layer.

The devitrifying step (I) may include subjecting the jetted layer to a heat treatment comprising heating above the crystallization temperature of the particular alloy to a temperature between and below the melting temperature of the laminate composition within 1 minute to about 1000 hours. The crystallization step (I) generally involves heating from about 550 ℃ to about 850 ℃ for between about 10 minutes to about 1 hour.

The metallic glass material is heat treated to enable a solid state phase transition in which the amorphous metallic glass can be converted to one or more crystalline solid phases. Solid state crystallization of amorphous glass structures enables uniform nucleation throughout the amorphous material, forming nano-crystallites within the glassy state. The devitrified metal matrix microstructure may comprise a steel matrix (iron with interstitial atoms dissolved) or a complex multi-phase matrix containing multiple phases, one of which is ferrite. This nanocrystalline-grade metal matrix composite grain structure enables a combination of mechanical properties that are superior to those of larger grain sizes or metallic glasses. The improved mechanical properties may include, for example, high strength, high hardness, and the specific composition of the present invention may allow the toughness to be maintained or even increased relative to materials comprising larger particle sizes or comprising metallic glasses.

The resulting structure of the devitrified material may include nanoscale crystallites having a particle size of about 50 to about 150 nanometers. Furthermore, the devitrified material may have second phase precipitates at the grain boundaries, the precipitates being on the order of 20 nanometers in size. Fig. 15, 16 and 8 show TEM micrographs of the microstructure of a material produced using the method of the present invention after heat treatment. Referring to FIG. 15, it shows the (Fe) content after 1 hour treatment at different temperatures_0.8Cr_0.2)₇₉B₁₇W₂C₂The nanocrystalline microstructure of the devitrified material of (1). FIG. 15 also shows the diffraction patterns of the selected regions for each of the three treatment cases. FIG. 16 shows the composition containing (Fe) after 1 hour treatment at different temperatures_0.8Cr_0.2)₇₃Mo₂W₂B₁₆C₄Si₁Mn₂The nanocrystalline microstructure and the diffraction pattern of the selected areas of the devitrified material.

The TEM micrograph shown in FIG. 17 is made with HVOF deposition followed by a heat treatment at 750 ℃ for 1 hour and contains Fe₆₃Cr₈Mo₂B₁₇C₅Si₁Al₄The nanocrystalline microstructure of the devitrified layer. TEM indicates a nanoscale structure with about 75 to about 125 nanocrystalline grains with 20 nm second phase precipitates at the grain boundaries. The sample shown in fig. 17 was used to obtain the x-ray diffraction scan data shown in fig. 18A, which was then refined as shown in fig. 18B to determine the nanocomposite structure summarized in table 3.

TABLE 3

Crystallized (Fe)_0.8Cr_0.2)₇₃Mo₂W₂B₁₆C₄Si₁Mn₂Information of (1)

As shown in Table 4, the hardness of the devitrified nanocomposites made by the process of the present invention can increase by as much as 5.2GPa relative to the corresponding glass material (prior to devitrification). As shown in table 4, the process of the present invention can be used to make hard glassy materials or hard nanocomposites having a hardness higher than the hardness of the corresponding ingot form, even for compositions having a hardness of less than 9.2GPa when formed into an ingot form.

TABLE 4

Alloy hardness in ingot, glassy and nanocomposite states

Different methods were used to determine the properties of the devitrified materials prepared by the process of the present invention. The ability to adhere to the underlying material was determined by conventional measurement methods including drop impact, bend, and particle impact erosion tests. The coating was able to pass all three tests described above. FIG. 19 shows a composition containing Fe₆₃Cr₈Mo₂B₁₇C₅Si₁Al₄The elasticity and plastic ductility (resilience) of the coating. Panel A shows a steel strip coated with about 200 microns thick coating material using HVOF deposition. FIGS. B and C show that the coated strip is deformed without cracking or peeling of the coating from the base metal.

FIG. 20 Panel A shows a flat plate coated with about 200 microns thick Fe₆₃Cr₈Mo₂B₁₇C₅Si₁Al₄Coating of (2). As shown, the coating was able to deform with the base metal during repeated peening on one side of the coating (fig. B) or peening on the base side (fig. C), indicating high ductility and toughness of the coating. Furthermore, when the sheet was severely deformed (fig. D), no visible cracking, chipping or peeling of the coating was observed.

The tensile properties of the coatings produced by the method of the invention were determined using thin strips of metal made to the composition to be tested. The metallic glass ribbon (fig. 21) and the devitrified ribbon (fig. 22) were subjected to different strain rates at a range of temperatures. The stress/strain curve of the metallic glass indicates that elongation as high as 60% can be obtained (fig. 21A). The devitrified thin ribbon can exhibit superelasticity with a maximum elongation of up to about 180% (fig. 22).

The methods described herein may be used in a variety of applications including, but not limited to, such applications as protective coatings and surface hardening. In these applications, the metal coatings produced by the methods of the present invention may be applied to the surfaces of components, equipment, and machinery to protect the surfaces from one or more of corrosion, erosion, or wear. Such applications may employ a sprayed layer comprising metallic glass or a devitrifying material comprising a nanocomposite structure. Furthermore, such applications may employ coatings having a partial metallic glass structure and a partial nanocomposite structure. Such partially glassy/partially nanocomposite coatings can be made, for example, by the following methods: the individual coating layers are formed sequentially and only a specific coating layer is heat-treated, or one or more layers are formed sequentially and only a portion of the one or more coating layers is heat-treated.

Due to the hardness of the sprayed metallic glass material produced by the method of the invention, the coating can be applied with the sprayed material without further devitrification. In other applications where high hardness is required, complete devitrification can be performed and up to 100% nanocomposite microstructures with very high hardness can be achieved. The increase in hardness produced by the method of the invention may be achieved without a concomitant decrease in toughness, and may even be accompanied by an increase in toughness. In compliance with the statute, the invention has been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the invention is not limited to the specific features shown and described, since the means herein described are presently preferred forms of putting the invention into effect. The scope of the invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted in accordance with the doctrine of equivalents.

Claims (10)

1. A method of manufacturing a hard metal material, comprising:

providing a mixture of elements, the mixture comprising at least 55 wt% Fe, and comprising B;

forming the mixture into an alloy; and

the alloy is cooled at a rate of less than 5000K/sec to form a metallic material having a hardness of greater than 9.2 GPa.

2. The method of claim 1, wherein the metallic material is in ingot form.

3. The method of claim 1, wherein the mixture comprises at least one transition metal selected from W, Mo, Cr, and Mn.

4. The method of claim 1, wherein the mixture comprises one or more of Al and Gd.

5. The method of claim 1, wherein the mixture further comprises one or more of P, C and Si.

6. The method of claim 1, wherein the mixture comprises B, C and Si in an atomic ratio of B₁₇C₅Si₁。

7. The method of claim 1, wherein the mixture comprises a composition selected from the group consisting of: fe₆₃B₁₇C₃Si₃，(Fe_0.8Cr_0.2)₇₉B₁₇W₂C₂，Fe₆₃B₁₇C₃Si₅，Fe₆₃B₁₇C₂W₂，Fe₆₃B₁₇C₈，Fe₆₃B₁₇C₅，(Fe_0.8Cr_0.2)₇₈Mo₂W₂B₁₂C₅Si₁，Fe₆₃B₁₇C₅W₅，Fe₆₃B₁₇C₅Si₅，(Fe_0.8Cr_0.2)₇₆Mo₂W₂B₁₄C₅Si₁，(Fe_0.8Cr_0.2)₇₃Mo₂W₂B₁₆C₄Si₁Mn₂，Fe₆₃Cr₈Mo₂B₁₇C₅，(Fe_0.8Cr_0.2)₇₅Mo₂B₁₇C₅Si₁，Fe₆₃Cr₈Mo₂B₁₇C₅Si₁Al₄，(Fe_0.8Cr_0.2)₇₅W₂B₁₇C₅Si₁，Fe₆₃B₁₇C₅Si₁，(Fe_0.8Cr_0.2)₇₃Mo₂W₂B₁₇C₅Si₁，(Fe_0.8Cr_0.2)₇₂Mo₂W₂B₁₇C₅Si₁Gd₁，(Fe_0.8Cr_0.2)₇₁Mo₂W₂B₁₇C₅Si₁Gd₂And (Fe)_0.8Cr_0.2)₇₄Mo₂W₂B₁₇C₄Si₁。

8. The method of claim 1, wherein the alloy has a melting temperature of 1100 ℃ to 1550 ℃.

9. The method of claim 1, wherein the mixture consists essentially of less than 11 elements.

10. The method of claim 1, wherein the mixture consists essentially of less than 9 elements.