DK158957B - COMPOSITION MATERIALS INCLUDING A CARBID MATERIAL, ITS MANUFACTURING AND USE - Google Patents

Description

DK 158957 B

The invention relates to a composite material of the kind set forth in the preamble of claim 1, a method of making this material which is of the kind set forth in the preamble of claim 5, and to the use of the composite material in wear resistant tools.

Since 1940, wear-resistant parts for wear-prone tools and equipment have been made of cemented carbide alloys consisting of a finely dispersed hard-carbide phase based on metals selected from groups IVB, VB 10 and VIB of the periodic system, cemented with cobalt or nickel or both. When prepared by compression of finely ground powders, followed by liquid phase sintering to achieve consolidation, the cemented carbide alloys have microstructures characteristic of hard carbide grains, generally in the range of 1 to 15 μπι.

The use of iron or steel as bonding materials has been found to be difficult since the finely divided state and the large specific surface of the dispersed 20 hard phases promote the formation of relatively brittle, binary insert alloys of tungsten and iron with carbon, the volume of bond is reduced and the sintered body is brittle to a greater or lesser extent, depending on the precision observed with respect to the composition and sintering parameters, and depending on the free carbon additions used to satisfy the affinity between iron and carbon.

Unlike cobalt and nickel, iron forms a stable carbide, Fe3C, and is more likely to form brittle binary carbides than cobalt or nickel bonding materials. Carbon transfer from the hard carbide phase (s) to iron is promoted by the presence of the liquid or plastic state of an iron or steel binder during liquid sintering, carried out at temperatures near, at or above the melting point of the binder.

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More recently, wear-resistant parts have been made by casting a liquid steel melt or a cast melt in a manufactured layer of relatively coarse particles, e.g. sintered, cemented carbide with a 5 grain size from approx. 3.2 mm to approx. 4.8 mm.

The method of the present invention differs from the melt steel casting method of U.S. Patent Nos. 4,024,902 and 4,140,170 and from the melt cast iron method of U.S. Patent No. 4,119,454 by two main factors: (1) a compact powder of steel or iron and graphite containing dispersed particles of sintered, cemented carbide, or a number of pieces of dimensioned sintered, cemented carbide, or primary, non-milled, macrocrystalline carbide crystals sintered at a temperature below the melting temperature of steel or cast iron, and (2) instead of the use of matrix alloy melting temperatures to achieve alloy density, high compressive unit pressures are used, both before and after sintering, thereby avoiding destruction of the dispersed hard phase particles by decomposition, melting or carbon diffusion reactions.

Casting methods also lack the well-known economic advantages that are characteristic of powder metallurgical methods, especially when a very large number of wear-resistant parts of either small or thin cross-section are to be produced. Due to the necessarily relatively high treatment temperatures and flow rates, excess amounts of undesirable binary carbides can also be formed, despite the use of relatively coarse small surface area carbide particles.

Since both the conventional powder metallurgical method of pressing and sintering of finely ground, steel-cemented carbide powders and methods involving casting of liquid steel or liquid cast iron in particulate cemented carbide previously placed in molds result in the foregoing described problems, it is desirable to develop a method by which a steel-cemented hard carbide alloy can be prepared substantially free of 3

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binary iron and tungsten binary deposit alloys in which the dispersed hard carbide phase is free of interface charge decomposition, melting or thermal cracking and is firmly bound in a steel matrix substantially free of macroporosity.

Accordingly, the object of the invention is to provide and prepare a material which has dispersed hard carbide material firmly and adherently bonded in a metallic matrix, by powder metallurgical technique in compression and high temperature and high pressure diffusion bonding, which material is substantially non-ferrous. machine machinable and has sufficient impact strength to be suitable for use as e.g. safety plates and components in padlocks.

From DE-Publication No. 2,722,271 there is known a process for preparing a composite material using an initial mixture of titanium carbide powder and a steel matrix. The mixture is cold-pressed and then vacuum-sintered at 1375 ° C, with the sintering appearing to be a liquid phase sintering. The resulting material is then hot pressed at 1275 ° C.

As can be seen from the following, the method of the present invention uses a sintering at a temperature at which the steel is not liquid and the sintered material is not subjected to any hot pressing 25 at 1275 ° C. In addition, according to the DE publication publication, it is a layered composite material with different carbide content sections, while the material made according to the invention has a metallic matrix molded around e.g. a tungsten carbide steel component.

30 In DE Publication 2,630,932, two examples of a hard composite material alone and a third example of a composite material containing only carbide particles in a steel matrix are given. Example 1 relates only to the formation of a composite material of cemented carbide and steel powder.

Example 2 relates to the formation of sintering a layer structure, the first layer containing a mixture of carbide and steel.

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powder, and where the second distinct layer contains steel powder. Example 3 relates to the formation of a structure by which molded diwolfram carbide is crushed and placed in a mold on which steel is molded around the carbide. In this specification 5, there is no mention that a tungsten carbide-steel matrix composite material is embedded in and bonded to another metallic matrix.

U.S. Patent No. 2,731,711 discloses the manufacture of cemented carbide and is not a composite material such as that of the invention, i.e. a composite material comprising steel-cemented carbide bonded to a metallic matrix. According to the patent, ball mill milling and liquid phase sintering are used; if such a technique was used in connection with the present invention, the formation of the undesirable eta phase would be increased.

US Patent No. 4,101,318 discloses the preparation of a composite material of a monocarbide grain, based essentially on a hexagonal solid solution (Mo, W) C embedded in a binder (30-80% by weight). ) of a hot-workable steel alloy. The starting powder contains 20 binder and carbides and preferably contains chromium and vanadium and is ground to increase the sintering activity of the iron powder. The powder mixture is sintered at a temperature not higher than that at which eta phase is formed.

The cemented carbide component is placed in a mold and a castable low alloy steel is cast around the carbide component.

According to this patent, the formation of eta phase is regulated by the chemical composition. According to the present invention, ball mill milling of the cemented carbide powder is avoided while wet milling is used according to patent 30, and according to the present invention a solid sintering technique is used, while according to the patent a sintering temperature which depends on the chemical composition is used.

Thus, the invention alleviates a number of disadvantages of the prior art and the stated object is achieved.

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The composite material according to the invention, as mentioned in the preamble of claim 1, is characterized in that the grain size of the carbide material is 0.04-0-0.08 mm and that the interface between the carbide material and the matrix is not thicker than 50 µm, preferably 0-40 μπι, and substantially free of eta carbides, and the carbide material optionally provided with a metal coating which forms a strong and adherent bond between the carbide material and the matrix, the carbide material and the matrix material being similar -10 species intermixed without significant grain size reduction, the interface formed by sintering the homogeneous mixture at a temperature below that at which the steel is at least partially liquid.

The process of the invention, as mentioned, is of the kind set forth in the preamble of claim 5, characterized in that carbide particles having a particle size in the range of 0.04-0.08 mm are used and that the sintering treatment is carried out at a temperature. below it, at which the steel is at least partially liquid.

Thus, the method of the invention comprises e.g. combining and blending sintered cemented tungsten carbide particles or primary, unpainted, macrocrystalline (i.e., more than 400 mesh) tungsten carbide crystals with a matrix of iron and graphite or steel powders, cold isostatic pressing of the material into a preform. -form to a desired shape, then sintering in solid state at a relatively low temperature, especially at a temperature below the steel melting temperature, preferably between 1037 ° C and 1232 ° C, and then hot isostatic pressing (HIP) of the sintered body at a temperature well below the melting point of the steel to obtain final compression or tightness increase. A diffusion bond is formed between the hard carbide particles and the surrounding steel powder that holds the wear-resistant hard carbide particles in place.

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A critical factor of the present invention is high pressure compression (or density increase), both cold and hot, to avoid process temperature which produces liquid state of the steel bonding phase and thus promotes the aforementioned undesirable reactions between the steel bonding material and hard, dispersed phase. The technique is improved in this regard by the use of a hard dispersed particle or particles with small specific surface area. The process also provides a significant advancement in production capability in the manufacture of relatively small size steel or carbide wear parts, of thin cross-section or complicated shape, as compared to the methods described in the aforementioned United States Patent Specifications. , in which molten steel or molten cast iron is poured into a form already filled with particles of cemented carbide.

Furthermore, both chemical control and flexibility with respect to the composition of the matrix alloy are superior to molten casting methods. The avoidance of the high 20 processing temperatures required for smelting and pouring steel or cast iron provides better mold economy as molds can be reused and better economics with respect to matrix metals which do not result in pour loss and recirculation costs. The process of the invention is well suited for forming parts which are to withstand both abrasive abrasive and impact forces. The process is ideally suited for the manufacture of abrasion resistant parts and cutting tools for equipment for agricultural purposes, road and highway construction and maintenance, crushing, grinding, excavation and treatment. Since the wear resistance of the products produced by this process is so high as to be practically non-machinable, they are also ideally suited for use as safety plates in safes or boxes. This durability in combination with the impact resistance of these materials also makes them suitable for use in padlocks.

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The nature of the invention will become more apparent from the following detailed description of the drawings, in which: FIG. Figure 1 shows a micrograph at 1500x magnification 5 showing a cemented carbide particle with a cobalt binder embedded in and bonded to a consolidated steel powder matrix; 2 is a cross-sectional perspective view of a wear-resistant plate with cemented carbide inserts embedded in and bonded to a consolidated steel powder matrix; and FIG. 3 shows a cross section of a portion of a cemented carbide knob cutting tool embedded in and bonded to a consolidated steel powder matrix.

Alloyed steel matrix powder, or a mixture of 15 iron and graphite powders containing 20 to 70% by weight of the finished mixture is combined and mixed with from 30 to 80% by weight hard carbide particles of W, Ti, Ta,

Nb or Zr, V, Hf, Mo, B, Si, Cr, or a mixture thereof, either as sintered, cemented carbide particles or 20 as primary, uncemented, unsintered, non-milled carbide crystals. There are set approx. 3% naphtha or other liquid hydrocarbon for the powder mixture during mixing to prevent segregation of higher density carbide particles during mixing and filling of the mold, especially when the dispersed hard phase is composed of hard carbide particles coarser than about 10 250 µm.

In the case of dispersed hard phase particles finer than approx. 250 µm, paraffin wax or other solid lubricant such as zinc stearate may be used, thereby reducing the possibility of component-particle segregation during mixing.

Then, the matrix powder containing the dispersed hard carbide phase is packaged in a preformed mold made of polyurethane or other elastomeric plastic material.

35 Powders of steel with various chemical compositions, e.g. carbon steel, alloy steel or stainless steel in powder form,

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s or elemental powders, e.g. of iron, copper or nickel, may also be packed in the same form together with the composite master-steel powder carbide mixture, at any desired location, adjacent to and in contact with the body containing the dispersed hard carbide phase, or the surrounding body, or including a dimensioned, sintered and cemented carbide insert. The packaged mold with a suitably designed cover is then sealed and placed in a rubber bag or balloon which is then evacuated, sealed and pressed isostatically, preferably at a pressure of approx. 2450 kg / cm2, but not less than approx.

700 kg / cm 2.

The compact powder form is then removed from the mold and heated in vacuo or in a protective or reducing gas atmosphere, e.g. hydrogen, to a temperature below the melting point of the steel matrix, preferably between 1037 ° C and 1149 ° C, between 20 and 90 minutes.

An alternative preforming method consists in packing the composite mixture containing preferably liquid hydrocarbon, e.g. naphtha, preferably 7% by weight, and methylcellulose, preferably 0.5% by weight, as pressing lubricant and green binder, in a steel preform.

The green preform is then air dried at room temperature in the mold, then removed from the mold and placed in a rubber bag which is then evacuated and closed, ready for cold isostatic compression as described above.

Compact materials thus sintered in the solid state retain some porosity. The shrinkage during sintering does not exceed 1%. However, it has been found that the density increase achieved by high pressure isostatic compression, followed by sintering as described above, is sufficient for the elimination of any interconnecting pore network and that the sintered bodies therefore meet the conditions for effective final density increase 35 at known hot isostatic pressing methods (HIP).

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Hot isostatic pressing for the purposes of the present invention is carried out in an inert atmosphere, preferably at from 870 ° C to 1260 ° C, or at any temperature below the steel melting temperature, for from 20 to 90 minutes at a minimum pressure of approx. 700 kg / cm 2, but preferably at a pressure of approx. 1050 kg / cm 2 for 60 minutes. Equally important is the formation of an alloy layer at the interfaces between cemented carbide particles and steel matrix. This interface alloy bond, first formed during sintering and later increased during hot isostatic pressing, consists of a thin interface between e.g. a 0.75% Js carbon steel matrix and dispersed, cobalt-cemented cartridge particles ranging in size from 3.2 mm to 4.8 mm. The bond is typically less than 40 μιη thick and no more than 50 thick. The interface alloy bond under these conditions is basically composed of cobalt and iron. The bond formation becomes significant, especially when the hard, dispersed phase consists of relatively coarse particles, because these tend to pull out if they are not securely anchored in 20 matrices.

Cemented tungsten carbide particle sizes constituting the dispersed hard phase are selected from the wide size range from 2.5 mesh to 100 mesh: (US Sieve Series), with preferred size ranges being -12 + 20 mesh, 25 -6 + 12 mesh and - 4 + 6 mesh. Specifically selected size ranges can be produced by known methods for crushing and selecting the size of sintered cemented carbide tool components, and which alloys are more common on the basis of a cobalt or nickel cemented tungsten carbide (WC), including 30 times containing Tic, TaC or NbC or combinations of these hard carbides.

A further useful aspect of the method of the invention is the application of a coating of an alloy or metal, preferably Corson bronze or nickel, to the surfaces of a dimensioned, sintered, cemented tungsten carbide insert of selected shape and size, or a number 10

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such inserts, which are then embedded in a steel or iron-graphite matrix powder at selected locations in a pre-forming mold, before the filled mold is compressed isostatically.

The Corson bronze coating used may have any of the nominal compositions listed in Table I:

Table 1

Corson Bronze Compositions A D

10 2.5% by weight Ni 10% by weight Mn 0.6% by weight Si 4% by weight Co 0.25% by weight Mn 86% by weight Cu residual Cu 15 After cold isostatic compression and with subsequent sintering and hot isostatic pressing of the compact carbide steel, the coating forms on the cemented carbide body autogenously provides a diffusion bond to increase the bond strength with which sized, cemented 20 carbide bodies are retained in the matrix. In this method, a cemented carbide body, or a number thereof, of specific shape and size can replace a dispersed, hard carbide phase of particulate nature, thereby forming a wear-resistant body or tool for cutting or drilling in metal or rock formations.

It is noted that the relatively low processing temperatures used in the process of the present invention in cases where steel matrix powder compositions which do not bind well to particles 30 of a dispersed hard carbide phase can result in an insufficient bond strength at the matrix-carbide particle interface. In such cases, e.g. when alloy steel powders which are known to be less sintering at the relatively low solid-state sintering temperatures used in the process of the invention have been found to be advantageous in coating

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the nickel or copper hard carbide particles, e.g. by known processes such as electro-free metal coating or by vacuum-vapor phase coating. Nickel coatings thus applied to the hard carbide fraction dispersed prior to mixing have been shown to improve the carbide particle bond strength. Such pre-coating of the hard carbide particles will also be advantageous when using stainless steel powders.

A further and useful part of the above described method is the incorporation of a dispersed hard carbide phase into a compressed steel or iron graphite powder consisting of non-milled macrocrystalline carbide crystals in size ranges between 60 and 400 mesh (US Sieve Series), and in preferred areas, e.g. -60 + 100 mesh, 15 -80 + 200 mesh or -150 + 325 mesh, instead of and replacing cemented carbide particles. The process of the invention for the composition and formation of macrostructured cemented carbide materials is exactly as described above.

The relatively low treatment temperature used results in a macrostructure substantially free of brittle iron and tungsten (eta phase) double carbides and coarse porosity. The tendency of liquid phase sintered, microstructured cemented tungsten carbide alloys, where e.g. a steel binder instead of the usual cobalt binder for developing eta-type brittle phases is well known. It is believed that the avoidance of liquid phase sintering and the consequent avoidance of carbon transfer promoted by such a process, as well as the uniquely small specific surface of the non-milled macrocrystalline carbide particles which form part of the dispersed hard phase, is essential for the successful formation of the two-phase steel carbide macrostructures produced by this method. It will be appreciated that liquid phase sintering 35 as mentioned herein means sintering at a temperature at which the steel binder is at least par.

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quite fluid. Therefore, the avoidance of liquid phase sintering according to the present invention does not apply to any metal or alloy having a lower melting point, e.g. copper or Corson bronze which can be added as a powder or a coating to promote seam bonding or density enhancement and which may be intentionally liquefied during sintering or hot isostatic pressing.

The use of non-milled, macrocrystalline hard-carbide crystals as a dispersed hard phase is a preferred embodiment of the process of the invention as an effective means of maintaining a hard phase of small specific surface. However, it is noted that substantially binder-free, hard aggregates of finer or ground hard car bites can be used in the aforementioned manner.

An important aspect of the aforementioned macrostructured bodies is the avoidance of ball mill milling or other comminution of the matrix carbide powder mixtures, or of each of these two materials separately, prior to cold isostatic compression, sintering and HIP. The 20 practices previously used, which have been widely considered essential to obtain good, commercially usable, cemented carbide structures, lead to increased reaction between carbides and iron-based matrix powders, resulting in the formation of brittle double carbides. The avoidance of powder milling also results in a cost reduction.

In the process of the invention, any of the macrocrystalline carbides or combinations or solid solutions thereof can be used, specifically WC, TiC, TaC or NbC, all of which exhibit the small specific surface and annular, block-shaped forms typical of these coarse crystalline mono- and binary carbides. It is known that primary macrocrystalline carbide materials can be finely ground together with cobalt or nickel to form cemented carbide microstructures upon liquid phase sintering in the temperature range from 1315 ° C to 1538 ° C, with the resulting dispersed hard carbide phases typically being between 1 μιη 13

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and approx. 10 / m. In contrast, the process of the invention results in dispersed single macrocrystalline linear carbide grains in size ranges selected from the much coarser extremes from 250 μια to ca. 40 μια.

The invention is further illustrated in the following examples.

Example 1

Wear-resistant cutting tips are made for use in rotary sugar cane cutting machines. A uniformly mixed mixture is prepared containing approx. 55% by weight approx. 3.3 mm to approx. 4.8 mm cobalt-cemented tungsten carbide - granules, approx. 44.67 wt% -100 mesh atomized iron powder and 0.33 wt% -325 mesh graphite powder. During the mixing, 5% by weight of naphtha is added to reduce to a minimum the segregation of the higher density cemented carbide particles. The moist mixture is manually compressed into an elastomeric polyurethane mold cavity with the desired tool shape, dimensioning under cold isostatic powder compression plus 1% sintering shrinkage. After cold isostatic compression at approx. 2450 kg / cm 2, the compressed preform is removed from the mold and vacuum sintered at approx. 1093 ° C for 60 minutes, then the sintered body is isostatically pressed at approx. 1232 ° C for 60 minutes at a pressure of approx. 1050 kg / cm 2 under helium.

Metallographic examination shows a matrix structure composed of mainly perlite and some ferrite, which is typical of conventional, slowly cooled 0.75% low porosity carbon steel. The cemented carbide-matrix interfaces 30 are occupied by bands having a width of approx. 5 μια of an alloy believed to be composed mainly of iron and cobalt.

The cemented carbide dispersed particles are unaffected by thermal cracking, and there is no evidence of dissolution, melting or decomposition of the dispersed carbide phase at or near the interfaces, these interfaces being sharp except for the above-mentioned 14

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iron-cobalt alloy diffusion zone. No potentially harmful concentrations of eta phase are observed. Test bodies are manually bent over a mandrel by hammering at room temperature and are found to have high impact resistance and to be substantially free of brittle fractures.

In the drawing, FIG. 1 is a micrograph of a typical area of a material made according to Example 1, but with the exception that the sintering is carried out at approx. 1150 ° C. A cobalt-cemented tungsten carbide granule 40 is shown metallurgically bonded to an alloyed carbon steel having a substantially perlittic structure 50 by means of an iron and cobalt diffusion zone 45. Dif fusion zone 45 is approx. 3 inches thick.

Example 2

A wear-resistant square plate of approx. 2580 cm2 with a thickness of approx. 9.6 mm and consisting of 60% by weight of unpainted -60 + 100 mesh macrocrystalline WC cemented with 40% by weight 0.75% C-steel containing 20% by weight Cu. A uniform dry blend of -60 + 100 mesh macrocrystalline WC crystals, -325 mesh graphite powder, -100 mesh iron powder and -325 mesh copper powder is dry blended non-milled to a uniform mixture and then wetted by mixing with liquid naphtha and methyl cellulose corresponding to 25 and 7, respectively. % and 0.5% by weight of the dry mixture, and then packed in a steel preform mold to a solid, green plate mold with dimensions corresponding to approx. 102% of the desired final dimension.

After air drying in the mold at room temperature, the compressed body is removed from the mold, placed in a rubber bag and further treated by cold isostatic compression, sintering and HIP as described in Example 1. Metallographic examination shows a macrostructure of macrocrystalline WC evenly dispersed in a steel matrix. . A 5 µm thick bond layer of unknown composition with WC boundary is observed

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sefladerne. These interfaces are free of brittle, binary carbide phases and cracking.

Example 3 A composite wear resistant body of steel having the dimensions of approx. 38.1 mm x 38.1 mm x 38.1 mm (cube form), comprising a dimensioned plate of sintered, cemented 5 percent by weight cobalt-tungsten carbide, suitably embedding the dimensioned plate of sintered, cemented, carbide in the green powder prior to iso-priming such that its outer surface is flush with the outer surface of the steel cube. A dry, unpainted mixture containing 97.25 wt% -100 mesh atomized iron powder, 2 wt% -325 mesh Cu powder and 0.75 wt% graphite is prepared and then mixed with naphtha and methyl cellulose corresponding to 5 and 0.3 respectively. % by weight of the dry mixture. This is then packed in an elastomeric form, upon which a square approx. A 645 mm2 sheet having a thickness of about 6.4 mm of sintered cemented carbide is pressed into the iron powder mixture so that the outer surfaces are congruent.

The mold is placed after closure in a rubber bag, evacuated, sealed and compressed isostatically at this point, removed from the mold, sintered and compacted hot and isostatically as in Example 1. Metallographic examination shows that the pre-installed sintered carbide plate is bonded through a 5 μπι interface bonding phase to the steel matrix surrounding it on three sides and that the entire structure turns out to be flawless and crack free.

FIG. 2 shows a wear plate 20 made in the manner described in this example, with the exception that three instead of one carbide insert (s) 30 are embedded in the plate 20 such that a surface 45 of each insert 30 is in substantially the same plane as the working end 35 40 of the tool 20. It is noted that the interface bond 35 is practically uniform and continuous, forming a 16

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tough and adherent bonding between the cemented carbide and the consolidated carbon steel and copper matrix 25.

For certain applications involving abrasion, depending on the corrosive nature of the environment in which the abrasive plate is used, the iron, carbon and copper powders used in this example can be replaced with stainless steel powders. or alloy steel.

FIG. 3 shows a cross section in another embodiment of a tool according to the invention. This tool 1 can be made substantially as described in Example 3, but with the exception that the cemented carbide insert 5 is allowed to have its working end 2 extending outwards and beyond the steel body 10 in the tool 1. As shown in this figure, the insert 5 is bonded to the steel body 10 by means of a diffusion fusion zone 15 formed by the interdiffusion of cobalt from the insert 5 and iron from the steel body 10 during the high temperature and high pressure sintering operations.

Claims (7)

A composite material comprising 30-80% by weight of a carbide material such as tungsten carbide, titanium carbide, tantalum carbide, niobium carbide, zirconium carbide, vanadium carbide, hafnium carbide, chromium carbide, boron carbide, silicon carbide or mixtures of these carbides and mixtures thereof or mixtures thereof 70% by weight of a matrix material comprising steel, steel and iron, steel and copper 10, and steel and nickel, the carbide material being embedded in and bonded to the matrix, characterized in that the grain size of the carbide material is 0.04-0.08 mm and that the interface between the carbide material and the matrix is no thicker than 50 μια, preferably 0-40 μιη, and is substantially free of eta carbides, and that the carbide material is optionally provided with a metal coating which forms a strong and adhesive bond. between the carbide material and the matrix, the carbide material and the matrix material being uniformly admixed without substantial grain size reduction, wherein s interface is formed by sintering the homogeneous mixture at a temperature below that at which the steel is at least partially liquid. Composite material according to claim 1, in which the carbide material is a cemented mixture with cobalt as a binder, characterized in that the interface contains iron and cobalt and has a thickness of 0-40 μιη. Composite material according to claim 1 or 2, characterized in that the carbide material contains tungsten carbide. Composite material according to claims 1-3, characterized in that the steel is an alloy steel or stainless steel. DK 158957 B A process for preparing a composite material according to claims 1-4 by mixing steel forming powder and hard carbide particles to form a homogeneous mixture which is cold pressed to form a compact preform which is then sintered at high pressure and elevated temperature, characterized in that carbide particles having a particle size in the range 0.04-0.08 mm are used and the sintering treatment is carried out at a temperature below that at which the steel is at least partially liquid. 10 Process according to claim 5, characterized in that the hard carbide particles are pre-coated with a metal coating prior to mixing with the steel forming powders. 15 Process according to claim 5 or 6, characterized in that the density increase of the compact preform is carried out by diffusion bonding by sintering the compressed preform at a temperature below 1375 ° C and below the melting temperature of the steel to obtain as little coherent porosity as possible. The preform is then isostatically pressed to the preform at a pressure above 700 kg / cm 2 at a temperature between 870 ° C and the steel melting temperature. Use of a composite material according to claims 1-4 wear-resistant tools.