MXPA99010407A - Tough-coated hard powders and sintered articles thereof - Google Patents

Abstract

A sintered material and the tough-coated hard powder (TCHP) to make such a material is comprised of core particles that consist essentially of a first metal compound having the formula MaXb. M is a metal selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, aluminum, boron and silicon while X represents one ormore elements selected from the group consisting of nitrogen, carbon, boron and oxygen. The letters a and b represent numbers greater than zero up to and including four. The core particles are surrounded by an intermediate layer consisting essentially of a second metal compound, different in composition from the first metal compound thereby forming coated particles. The material of the intermediate layer has a higher relative fracture toughness than the material comprising the core particles and is capable of bonding with the metal compound(s) forming the core particles and also being capable of bonding with iron, cobalt or nickel. The coated particles are surrounded by an outer layer of iron, cobalt, nickel, their alloys, their mixtures and their intermetallic compounds. The intimate liaison of multiproperty alloys within the TCHP grains allows the combination of normally conflicting sintered article performance characteristics (e.g., strength and hardness) at levels heretofore unseen in the powder metallurgical art.

Description

9 I HARD POWDERS WITH TENAZ COATING AND SINTERED ITEMS OF THEM CROSS REFERENCE OF RELATED APPLICATIONS This application is based on the provisional application with Serial No. 60 / 046,885 filed on May 13, 1997.

FIELD OF THE INVENTION The present invention relates to ceramic powders and sintered materials made from these powders. These materials find particular utility as forming members or metal formers, such as metal cutting and forming tools.

BACKGROUND OF THE INVENTION In the mid-1930s, tool steel alloys began to be replaced by sintered tungsten carbide powder tools, which quickly became the norm, due to their excellent hardness and inherent high tenacity and transversal mechanical resistance. The hardness of these materials improved the life of the tool and the tenacity and resistance helped to increase productivity by allowing higher feeds, speeds and higher forging parameters. The development and commercial availability of carbide tools increased significantly after World War II. Even these materials eventually wear out and the mechanism of such wear is not yet fully understood. The progressive wear causes variation in the materials that are formed and as a result of the need to maintain or preserve the dimensional tolerances of the parts, the tool must be replaced when it can no longer shape the part to the correct dimension. The time or the number of parts formed before said occurrence finally determines the limit of the life of the tool. The resulting loss of productivity during the change of the tool and the process of readjustment, production outside of specifications, reprocessing and non-compliance of the programs has been the driving force to obtain materials that provide a longer life of the tool. The life of the tool is determined by its resistance to various types of wear, its response to heavy loads and shock. In general, the higher the chip removal speed (high feeds and speeds), drawing pressures and P908 shaped and retains a long tool geometry, the better the tool will be. The upper cutting and shaping tools must be simultaneously hard, strong, rigid and resistant to chipping, fracturing, thermal decomposition, fatigue, chemical reaction with the workpiece and wear by attrition. In accordance with the above, the dominant mechanical properties that are sought in a sintered tool are strength, hardness, high elastic modulus, fracture toughness, low chemical interaction with the work piece and a low reaction coefficient to help the conformation of the work piece, while reducing heat buildup. In recent years, the powder metallurgy or powder metallurgy (PM) industry has grown significantly due to the ability of the powder to flow cold in a precision mold. This allows the mold to be reused, often at high volume, while drastically reducing machining, shaping and other process steps, because the sintered part is already very close to its intended configuration or "almost its net shape" . The increase of these parts, currently produced from aluminum, ferrous and copper powders, requires some of them P908 desirable attributes that the tools. For this reason, many PM articles suffer from additional forging, electrodeposition, i.e. plating, or heat treatment operations to develop localized hardness, toughness and strength. Many of these parts require resistance to shock and abrasion that demand the same mechanical properties that are required for the tools. In tools and hard articles, resistance to wear increases at the expense of resistance; Currently, the best tools show the best compromises and, therefore, they are limited to use in special applications. Beyond tungsten carbide, it has been found that various alloys, coating techniques and combinations of these allow to prolong not only the life of the tool but also to increase cutting speeds and feeds. Powder metallurgy and sintering have led to the development of new materials with improvements in hardness and toughness and add a hard coating to the sintered alloy such as chemical vapor deposition (CVD), physical vapor deposition (PVD), or chemical vapor deposition aided with plasma (PACV7D) has increased wear resistance.

P908 In the prior art much is taught about the preparation of coatings on powders, coating substrates and other improvements to hard materials. The prior art of tooling materials teaches six approaches that are currently known and that are in general use for the achievement of this improved resistance wear and tenacity; each has significant benefits and significant disadvantages: (1) mixing of hard and tough phase particles, (2) chemical vapor deposition coating (or other) of sintered substrates with hard phase layers, (3) combination of approaches (1) and (2), (4) cermet compacts (cerametals or cermets), (5) for a special type of tool (grinding and sanding media) chemically bond low concentrations of large particles of diamond or cBN to a substrate hard and abrasive but relatively weak and (6) Functional Gradient Materials (FGM). None of these solutions has provided the essential combination of the desired tool properties and only the chemical vapor deposition (CVD or PVD) approach is applicable today for some mechanical parts that require an increase in abrasion resistance.

P908 Mixed hard ternary systems? _ Tenacious. Despite the many auxiliary treatments and variations that exist and are taught in the art, mixing WC-TiN-Co hard alloy particles with the carbide powder prior to sintering has several disadvantages. Because these harder particles have a low mutual solubility with the binder, the transverse strength of the substrate rapidly falls to above 6-10 weight percent hard particles. The hardness and resistance to surface wear, in accordance with this, are also reduced, compared to a surface coating. The wear mechanism is also not greatly increased, due to the few hard particles (less than one per ten on the surface where they are needed) a weak bond with the binder and direct detachment.

Coatings Deposited by Chemical Vapor (CVD). These hard external coatings of intermetallic layers and hard cermets on the tool steels or substrates of sintered articles (after sintering) are appreciated for the high surface hardness they impart, which normally show values of 2400 Vickers (TiN) at 5000 Vickers (cubic boron nitride) up to 9000 (diamond). Still, for all P908 auxiliary treatments, variations and sintering aids that exist and are revealed in the art, including additional coating layers, locally affected substrate structures and dopants that reduce grain size or coatings, the external coating solution has several major disadvantages , which include the delamination and cracking of the coating during use (which comes from the different rates of thermal expansion of the coating and the substrate and the bending and surface loads) and the high process temperatures for the CVD required (9002 C - 1200a C) may not be consistent with the heat treatment necessary for the strength or geometry of the sintered part. The conventional coating by CVD of already sintered articles with several different coatings or layers allows them to withstand two or three unique challenges of the work piece. But since each layer must be deposited sequentially, the coating or the two remaining special coatings must remain covered until the outer layers have worn away. Therefore, only one of the design challenges of the coating of the concurrent substrate can be satisfied at the same time. Some tool categories, such as dies or spinning dies and nozzles, are even more prohibitively expensive, because there is an additional cost to ensure that CVD vapor is properly circulated through the die orifice. matrix for the deposition of the coating, where this is more necessary. The diffusion of CVD gas is low and the penetration is usually 0.5 to 10 micrometers or less. First, at these thicknesses, the coating wears down to the underlying carbide before most of the tolerance in the diameter of the wire or tube is used. Second, the normal reuse of the matrices at higher diameters should be done without the hard coating. In many cases, the extension of the total life of the tool may not be proportional to the cost of the added CVD. Currently, external coatings are the most common commercial solution to increase the performance of ordinary sintered tungsten carbide products. Increase the thickness of the deposition of the outer layers to obtain a longer life has a decreasing utility; it tends to increase the propensity to cracking and rounding of the sharp edges of the tool, adversely affecting the optimum cutting geometry or matrix.

Mixtures and Combined Coatings. The CVD coating and the mixing of hard alloy particles, a combination of (1) and (2) above, provides a very limited additional benefit, while having the same disadvantages.

Wax etals or Cermets Cermets are ceramic particles dispersed in an oxide or metal carbide matrix. The cermets combine the resistance to tin temperature of the ceramics with the tenacity and ductility of the carbides. They have approximately the same price as ordinary tungsten carbide and the wear is almost the same, with the exception of light finishing cuts, where they outperform ordinary carbide performance.

Sintered Abrasive Compounds. The fourth approach, taught in the German book by Dr.

Randall M. Liguid Phase Sintering, Plenum Press, New York 1985 (and practiced in Russia many years in advance) generates a class of super abrasive composites for grinding and sanding media and for tools with application in niches. These composites are produced by mixing diamond particles (or cubic boron nitride, cBN) and cobalt powders or by capturing them in a metallic electroplated deposit (nickel) and hot pressing them at lower temperatures. An alternative is to coat the diamond (or cBN) with an intermediate layer of a transition metal carbide former (which moistens the diamond) and chemically bind it to the others with a low melting, non-wetting metal binder. but ductile, such as cobalt, iron or nickel. The transition metal is only applied as a chemical bridge in thicknesses that are not intended to support structural mechanical load. The metals used as the main binder matrix have a good or sintering degree, that is, they have good sinterability, but they have relatively low melting points, elastic moduli and resistances. These materials have desirable applications in abrasive applications. In most of these applications, diamond represents 10 to 60 percent by volume of the composite. The binder coatings have several micrometers thick to aid processing at high temperatures (to avoid graffiti degradation of the diamond) and to dilute the diamond content but with great sacrifice in mechanical properties. The properties of these composites are governed by chemical considerations, not by mechanical considerations of elastic modulus, resistances or fracture toughness. In accordance with the above, with a large diamond particle size and a high concentration of binder, the mechanical properties of the composite are determined by the law of mixtures. Compositions are selected to ensure that the diamond particles are separated in the final microstructure, ensuring that there may be little diamond-diamond interaction. There is a slight increase in mechanical advantages, as found in the range of sintered carbide grain sizes from one micrometer to the nanoscale. The requirements for grinding or roughing tools are relatively large grains (from 50 to 600 micrometers) to increase the removal of metal, the binding of these particles to a wheel, the adequate separation between particles (low concentration of particles with large phase ligaments). binder) to allow the removal of the particles from the work piece and a great retention of the geometry of the grinding or roughing wheel. These materials form materials by abrading the work piece by the pure difference of hardness between the abrasive particles and the same work piece. These abrasive composites are sometimes used in cutting tools used to machine specialty materials of high hardness at relatively high speeds but with removal speeds of P908 chip (load) very low (see Figure 6). The cutting action of diamond cutting tools is very different from that of cemented carbide tools.

The limitation of diamonds or composites in cutting tools arises from their cutting behavior.

These composites operate as abrasives, where in general they perform by abrading the work piece, rather than by removing chips under a heavy load.

In this mode, the very hard diamond particle is retained by a tension bond. As it slides through the workpiece, the diamond is exposed to cut the opposite surface but, it resists wear while the matrix is eroded and progressively exposes the diamond. It is the projection of the diamond that is made the cut as long as it remains sharp. When the diamond becomes dull, that is, it loses its edge, it becomes rounded and the matrix is designed to fail. In this way, the diamond is extracted by the work piece and the matrix is eroded until another diamond is exposed. These hard and brittle abrasive composites are also used in some tool-type applications, such as drill bits and saws for masonry. These are also found in high-cost wire drawing dies and in some cutting tools, where their performance is allowed by the presence of steel or other P908 strong back, Functional Gradient Materials (FGM). The problem with the coated articles is the incompatibility between the mechanical, chemical or thermal properties of the layers. This problem is corrected by providing a gradual transition between incompatible layers, the FGM has one or more of the following variables: chemical composition, microstructure, density or variable forms of the same material. Another purpose is as coatings to modify the electrical, thermal, chemical or optical properties of the substrate on which the FGM is applied. The main disadvantages of these materials is their tendency to fail in places where the properties change and the difficulty in manufacturing these materials.

SUMMARY OF THE INVENTION The main objective of the present invention is to create sinterable particulate materials, called Hard Powders with Tenacious Coating (TCHPs) that provide an increase in the value above the hard article and the materials for currently known tools. The particles and articles made from them combine the best properties P908 mechanical strength, hardness, high elastic modulus, fracture toughness, low interaction with the work piece and low coefficient of friction that exists separately in conventional materials in an article of unique properties. It is a further object of the invention to reduce the cost of providing users with these materials. For example, tool inserts must be provided in considerable geometric variation to fit the various tool holders. In addition, the materials for currently available tools should be designed for very specific applications. Therefore, for each of these geometric variants material choices must also be offered (uncoated, coated CVD, coated PVD, cermet, ceramic, polycrystalline cBN, polycrystalline diamond). The combination of geometric variants and materials requires catalog costs, and necessary redundancy in the manufacture of the tool, expensive inventories of the supplier and the user with unique packaging and identification and sales effort to explain and sell the users the confusing arrangement. Another object of the present invention is to reduce the waste and cost associated with the present system, by providing general-purpose, high-performance tools at a reasonable cost. In addition, the process to manufacture the modalities P908 of the product of the invention has the object of reducing the production cost of the articles manufactured according to the invention. Another object is to provide a significant reduction in costs, by extending or prolonging the first-time life of the item and by reducing the manufacturing costs of the products they touch. The fact that the articles of the present invention are macroscopically homogeneous, instead of coated, offers users or suppliers the opportunity to reassort and economically use the initially worn items. Yet another object of the invention is to provide the same high-performance mechanical properties of the materials of the present invention in other hard article applications. Another object of the present invention is to provide a material having improved wear resistance and toughness, for use in a wide array of articles including tools (such as wire drawing dies, extrusion dies, forging dies, cutting and die cutting dies, shapes, forming rollers, injection molds, shears, drills, cutters for milling and turning, saws, helical drills, brushes or traction reamers, P908 reamers or rimmers, taps and dice); individual mechanical parts (such as, gears, cams, bearings, nozzles, seals, valve seats, pump impellers, winches, pulleys, bearings and wear surfaces); integrated co-sintered components for replacing coupling parts (connecting rods for internal combustion engine, bearings) and / or providing hard surface areas on mechanical parts of powdered metals (P / M) that replaced forged or machined steel parts with thermally treated zones (such as camshafts, transmission parts, parts of printers / copiers); heavy industrial articles (such as drill bits for deep well, teeth for mining equipment and earthmoving equipment, hot rollers for steel mills); and electromechanical components (such as reading heads for memory units, specialized magnets). In addition to providing these novel articles, the main objects of the invention are to provide novel composite particulate materials (ie, TCHP's), novel methods for producing said novel materials and methods for making articles from these materials. In order to achieve these and other objects, a sintered material comprising a plurality of P908 core particles consisting essentially of a first metal compound having the formula M ^. M is a metal selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, aluminum and silicon. X represents one more elements selected from the group consisting of nitrogen, carbon, boron and oxygen and a and b are numbers greater than zero up to and including 4. An intermediate layer surrounds each of the core particles and consists essentially of a second metal compound , of composition different from that of the first metallic compound. The second metal compound has a relatively superior fracture toughness and has the ability to bond with the first metal compound and also has the ability to bond to iron, cobalt or nickel. The core particle having on it the intermediate layer forms several coated particles. An outer layer overlaps the middle layer on the coated particles and functions as a binder. It is comprised of iron, cobalt, nickel, their mixtures, their alloys or their intermetallic compounds. Preferably, the coated particles have an average particle size of less than about 1 μm and, more preferably, less than about 1 μm. It is also preferred that the intermediate layer has a P908 thickness, after sintering, in the range of from 5% to 25% of the diameter of the core particles. It is also preferred that the outer layer has a thickness after sintering in the range of from 3% to 12% of the diameter of the coated particles. It is considered that with this outer layer thickness the deformation layers associated with dislocations in a coated particle are transmitted through the outer binder layer to the immediately adjacent intermediate layer. Preferably, the first metal compound consists essentially of a stoichiometric compound, such as, for example, TiN, TiCN, TiB2, TiC, ZrC, ZrN, VC, VN, cBN, Al203, Si3N4 or AlN. It is also preferred that the second metal compound consists essentially of WC or W2C and, most preferably, of WC. These materials have a fracture toughness greater than that of cubic boron nitride. A preferred embodiment of a sintered material comprises a plurality of core particles consisting essentially of cubic boron nitride with an intermediate layer on each of the core particles, the layer consists essentially of WC: The middle layer has a thickness, then of sintering, in the range from 5% to 25% of the diameter of the core particles. An outer layer comprising cobalt or nickel is superimposed on the layer P908 intermediate and the outer layer has a thickness, after sintering, in the range of from 3% to 12% of the diameter of the coated particles. The combination of the core particles, intermediate layer and outer layer forms a coated particle, which preferably has an average particle size of less than about 1 μm. Another embodiment of the present invention is a powder consisting essentially of a plurality of coated particles. Most coated particles have core particles that consist essentially of a first metal compound having the formula M ^. M is a metal selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, aluminum and silicon. X represents one more elements selected from the group consisting of nitrogen, carbon, boron and oxygen and a and b are numbers greater than zero up to and including four. The core particles coated with a surrounding layer consisting essentially of a second metal compound, of composition different from that of the first metal compound and having a relatively higher fracture toughness. The layer also has the ability to bind to the first metal compound and also has the ability to bind to a metal selected from the group consisting of iron, cobalt and nickel. From P908 preferably, the particles have an average particle size of less than about 2 μm and, more preferably, less than about 1 μm. It is also preferred that the layer surrounding the core particles, after sintering, have a thickness in the range of from 5% to 25% of the diameter of the core particles. The preferred compositions of the core particles and the surrounding layer (the intermediate layer) are the same for the powder form as for the sintered article. It is also preferred that the outer binder layer consists essentially of cobalt, nickel, its mixtures, its alloys or its intermetallic compounds, deposited on the outer surface of the second metal composite layer in the form of a continuous layer.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings are included to provide further understanding of the invention and are incorporated herein and constitute a part of this specification and, together with the description, serve to explain the principles of the invention. Figure 1 is a schematic representation of a sintered material, formed in accordance with a P908 aspect of the present invention. Figure 2 is a scanning electron microscope photomicrograph of a cross section of a sintered material formed in accordance with one aspect of the present invention at an increase of 20,000X. Figure 3 is a schematic representation of a device for forming or forming the powders, in accordance with an aspect of the present invention. Figure 4 is a schematic representation of the interior of the device of Figure 3, which represents the movement of the particles within this device during the deposition of the intermediate layer by chemical vapor deposition. Figure 5 is an end view of a component in a preferred embodiment of the device of Figures 3 and 4. Figure 6 is a graphic representation of the operational domain of the sintered material of the present invention, when used as a cutting tool. , with respect to conventional materials. Figure 7 is a compilation of the properties of the sintered materials described in the examples.

DESCRIPTION OF THE PREFERRED MODALITIES As embodied herein, the present invention is P908 a new type of material formed from powders. According to the invention, the powder is comprised of a plurality of core particles. It is intended that the core particles impart their physical properties to the overall powder structure. As it is incorporated here, the core particles consist essentially of a first metallic compound having the formula MaX,., wherein M is a metal selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, aluminum and silicon and X represents one more elements selected from the group consisting of nitrogen, carbon, boron and oxygen and the letters (a) and (b) represent numbers greater than zero to four. These metallic compounds are hard, resistant to wear and chemically resistant to most environments and workpieces. Significantly, for the present invention, the core material can be exposed, as for example, when the powder is sintered to form a cutting tool. The sintered article is formed by grinding, grinding and polishing the final shape of the article. This removes the intermediate layer of material on the core particles and exposes the core of the particles to the workpiece that will be machined. As it is more fully revealed later, this is a significant advantage.

P908 As incorporated herein, the core particles of the powders consist essentially of at least one stoichiometric compound. In some embodiments, the core compositions are different to impart the properties of the various core particles to the articles that will be formed therefrom. It is preferred that the metallic compound of the core consists essentially of a metal compound selected from the group consisting of: TiN, TiCN, TiB2, TiC, ZrC, ZrN, VC, VN, cBN, A1203, Si3N4 or AlN. These materials can be used in the form of powders, filiform crystals, crystals, filaments or the like available commercially, as the shape of the core particle can be technically significant. The core particle is covered with a layer of another metallic compound, called the intermediate layer. In this way, the material of the core particle must have some degree of compatibility with the material forming the intermediate layer applied thereto and must have a composition different from that of the intermediate layer. The powder embodiment of the present invention includes an intermediate layer applied to the outer surface of the core particle. The intermediate layer consists essentially of a second metallic compound, that is to say, one of composition different from that of the first P908 metallic compound that forms the core of the particle. The composite of the second intermediate layer has a fracture toughness relatively higher than that of the material forming the core. In addition, the second metal compound must have the ability to bind to the first metal compound and have the ability to bond to iron, cobalt, nickel, their mixtures, their alloys or their intermetallic compounds. Preferably, the second metal compound consists essentially of WC or W2C. As will be disclosed below, the combination of a relatively tough and strong intermediate layer and a hard core provides a powder and a sintered material formed therefrom with exceptional mechanical properties. This is also the case with the size and coating thicknesses of the coated particles. Specifically, particle sizes and layer thicknesses provide properties that are not explained by classical calculations of the law of mixtures. This will be described in more detail in the portion of the specification dealing with the sintered articles. In any case, it is preferred that the coated particles have an average particle size of less than about 2 μm and, more preferably, less than about 1 μm. It is also preferred that the intermediate layer has a thickness in the range of from 5% to 25% of the diameter of the particles Core P908 The thickness of the intermediate layer has a significant effect on the mechanical properties of the articles made therefrom. It is believed that when the coated particles (the core with an intermediate layer on it) have an average particle diameter, as measured graphically on a photomicrograph of a cross section, using the average free path method of less than about 2 μm , the resistance to movement of the displacement within adjacent sintered particles is improved, increasing the mechanical properties of the sintered article. Even using the classical mechanical approach, using finite element analysis, it is evident that increasing the thickness of a spherical WC shell surrounding a TiN sphere from about 0.1 μm to about 0.4 μm increases the theoretical tenacity by more than 40 μm. %. Additionally, it is preferred that the intermediate layer has a thickness, before sintering, in the range of from 3% to 200% of the diameter of the core particles. During sintering there may be a reduction in the thickness of the intermediate layer, due to the interaction with the core material, the particle-particle interaction, the phenomenon of grain boundaries and growth. In this way, to obtain the desired thickness P908 of the intermediate layer in the final sintered article, it may be necessary to have an initial thickness as high as 300% of the diameter of the core particle. A preferred form of the powder would have an outer binder layer applied thereto. Conventionally, metal binders are applied to the particles of the metal compound by grinding them with metal powders. This physical operation is long and when only a minor percentage of the powders is ground (eg, 6%) are of the binder metal, the time to smear the binder metal onto the surface of the remaining 94% of the particles adversely affects the economy of forming sintered articles using metal binders and can damage coated particles. The present invention contemplates applying said particles as a uniform coating on the outside of the particles of the metal compound, in the form of a continuous layer. According to the invention, the binder layer consists essentially of a metal selected from the group consisting of: iron, cobalt, nickel, their mixtures, their alloys and their intermetallic compounds. Preferably, the continuous dandruff of binder is deposited by chemical vapor deposition, sputtering, chemical deposition, electrodeposition, physical vapor deposition, carbonyl deposition, dew deposition of P908 solution or physical vapor deposition aided with plasma. Because cobalt and nickel are compatible with the preferred species of the core particle material and preferred material and materials for the intermediate layer and have superior properties at high temperatures, these are the preferred metallic binder compositions. Another embodiment of the present invention is a sintered material. This sintered material is comprised of a plurality of core particles consisting essentially of a first metallic compound having the formula MaXj. M is a metal selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium , molybdenum, tungsten, boron, aluminum and silicon. X represents one or more elements selected from the group consisting of nitrogen, carbon, boron and oxygen and a and b are numbers greater than zero up to and including four. Preferably, the first metal compound is predominantly stoichiometric and consists essentially of a metal compound selected from the group consisting of: TiN, TiCN, TiB2, TiC, ZrC, ZrN, VC, VN, cubic BN, Al_03, Si3N4, Si3N4 or AlN. These metallic compounds are hard and have other certain useful mechanical properties but, they have a limited tenacity to the P908 fracture (the ability to prevent the propagation of cracks). Other metal compounds may be operable with the present invention, however, the previously listed compounds are preferred. The selection of the compositions for the different portions of the particles can be based on conventional information such as the known characteristics of the candidate materials at the macroscopic level. For example, it is known that pro diffusion wear can be estimated for several materials by considering their standard formation free energy at operating temperature. Taken in the order of WC, TiC, TiN, and Al203, they have increasingly negative formation energy, therefore, it is seen that the TiN provides significantly reduced wear by diffusion compared to the normal WC cermets. In addition, the dissolution rates of various tool materials in the iron (the typical workpiece) at temperatures ranging from 1000 to 1100a C, differ strongly from one another. A comparison shows that a significant presence of TiN on the surface of the tool will ensure a strong decrease in the dissolution of WC in the iron; at 500a C, for example, the relative dissolution rates are: P908 WC: 5. 4 X 10 * TiC: 1. 0 TiN: 1. 8 X 10"3 A A112,003, 8 9 X Í O" 11 It is believed that these principles explain improvements in wear behavior of WC tools against iron, when the WC is associated with a TiN core.; that is, the exposed TiN core will exhibit less wear by diffusion to the iron than the WC. It is believed that a continuous WC particle coating is necessary to obtain a strong shell and high mechanical properties (Young's modulus of 696 GPa, compared to a value of 250 GPa for TiN). The core of TiN (which has a Vickers hardness Hv = 2400 compared to a value Hv = 2350 for the WC and that has a sliding friction coefficient μ = 0.125 compared to the value μ = 0.200 for WC) will reduce wear by friction against iron; The core will be exposed to the surface of the tool after its finish of grinding and polishing. It is also possible to make the core particles a plurality of different metal compounds, provided that each is compatible and different from the material comprising the layer covering the core particles. In this way, the properties of P908 an article comprised of sintered material, when core particles are exposed by removing or removing a portion of the intermediate layer of coverage, are determined primarily by the properties of the core particle, its concentration in the sintered material and their combinations. For example, if it is desired to shape the sintered article and shape it into a cutting insert, the sintered article could be ground or shaped by EDM (electric discharge machining) to expose the core particles. In a preferred embodiment, where the core particles are TiN and the intermediate layer is WC, the TiN friction coefficient, its strength and hardness to wear imparts said properties to the cutting insert while the total resistance of the insert and its resistance to propagation. of cracks are enhanced by the WC layer surrounding the TiN core particles. Significantly, the wear of the insert will not result in a decrease in the characteristics of this insert, because the TiN is not a coating that is finished by wear. This is an integral part of the insert material that renews the surface as it wears. A preferred core material is cubic boron nitride (cBN), however, this modality requires particles of specific size and thickness and layers to perform or achieve the P908 potential of the core particle cBN. It is believed that the extraordinary hardness of the cBN should be integrated into the article by using a surrounding load-bearing layer of another metallic compound of a composition and thickness such that the resulting stratified particle, when sintered, will have useful engineering properties as a structure. above its use as an abrasive. This embodiment of the sintered material includes an intermediate layer on each of the core particles of cBN, consisting essentially of WC or W2C. This embodiment also includes an outer layer that overlaps the intermediate layer on the coated particles. The function of the outer layer is to form a binder and bond the coated particles at reasonable sintering times and temperatures and convert them into a dense sintered material. As incorporated herein, the outer layer functions as a binder. It is comprised of iron, cobalt, nickel, their mixtures, their alloys or their intermetallic compounds. As indicated above with respect to the powder embodiment, the present invention contemplates applying these binders as a uniform coating on the outside of the particles of the metal compound, in the form of a continuous layer. The size of the core particles covered P908 with the intermediate layer (referred to collectively as "the coated particles") has a significant effect on the mechanical properties of the sintered material and on the articles made therefrom. As indicated above in the disclosure related to the powder, it is preferred that the coated particles have an average particle size of less than about 2 μm and preferably less than about 1 μm. It is also preferred that the intermediate layer has a thickness, after sintering, in the range of from 5% to 25% of the diameter of the core particles. In addition, it is believed that the thickness of the binder layer also affects the properties of the sintered material. It is preferred that the external binder layer has a thickness after sintering in the range of from 3% to 12% of the diameter of the coated particles. It is believed that a sintered material having these dimensions will have improved properties, because the stress fields associated with the dislocations in a coated particle are transmitted through the intermediate layer to the immediately adjacent core particle. It is known that the invention can operate with an intermediate layer having a thickness, after sintering in the range of from 3% to 200% of the P908 diameter of the core particles, however, a thickness in the range of from 5% to 25% is preferred. It is known that an increase in tenacity is the normal result of reducing grain size. The preferred diameter of the core particle is in the range of 0.1 nanometer to 1.0 micrometer. This range of particle sizes interact with the thickness of the intermediate layer. The resistance of a crystalline substance depends on the atomic union and the structure of the dislocation. Dislocations are linear defects in the atomic grid, which are normally fixed and immobile. In a mixture of two atomically bound crystalline materials, there are estimates of the upper and lower limit of the elastic modulus of the composite as calculated by the law of the mixtures and the inverse law of the mixtures. If it is subjected to an increasing load, the material elastically deforms until the dislocations of the grains begin to flow or to slip, which leads to the beginning of the permanent yield and the resistance limit. In particle sizes of approximately one micrometer and smaller, exceptionally high strengths are developed in these materials, mainly due to stresses or stresses of image displacement. There is a field of cylindrical deformation around P908 of each dislocation, which extends outward towards the surrounding grid. Theoretically, this deformation field around each dislocation must be balanced or balanced by opposing deformation fields, otherwise the dislocation will move away from the surfaces. When the size of the crystal is large compared to its deformation field, no image tensions are created around the dislocation unless it is on the surface of the crystal. In a sintered material having a binder that binds a plurality of crystalline particles, the image tension matches or is equal to the lower strength of the binder matrix but for large crystals this is a trivial correction, since most dislocations do not They are close to the surface. In submicrometric polycrystalline particles, the deformation field can extend to neighboring grains, whose atomic grid is probably not aligned with that of the grain of the deformation field. This field of compensatory deformation or balancer outside the surface of the grain restricts the movement of the dislocation, thus restricting the yield. As the size of the grains decreases, additionally, more dislocations will be closer to the surface and the P908 resistance can decrease. It is believed that when the thickness of the intermediate layer and the binder layer connecting the coated particles in the sintered material are sufficiently thin, then the deformation field actually passes through the binder matrix towards the neighboring particles. This creates a high resistance that ignores, that is, does not take into account the ligament material (in this case, the binder) between hard coated particles. In other words, the mechanical properties of the sintered article are independent of the properties of the binder phase, assuming that it is crystalline and very thin. The thickness of the intermediate layer must also be sufficiently thick with respect to the core to create a mechanical cell support matrix around and for all the core particles. Beyond this objective and the resistance to the expected image tension increases with 1.0 micron powders and smaller core, surprising resistance properties can be obtained in the sintered TCHP alloys, apparently due to the interaction of the particle size, the properties of the material of core and the properties and thicknesses of the intermediate layer and the binder. The reason for this is not yet completely P908 understood, but a tungsten carbide (WC) coating of 5 to 10 percent of a core particle of 1.0 micrometer or smaller is actually very thin and can act as if it were on its own much smaller, the tenacious phase particle (from 50 to 100 nanometers), effectively reaches the nanoscale mechanical properties at significantly larger and more manageable particle sizes. The TCHP structure with small hard core particle size and tenacious nanoscale shells separated by thin cobalt ligaments below a micrometer between grains, maximizes elasticity, hardness, fracture toughness and strength. The most interesting is the possible loss of the "composite or composite" character in the mechanical properties of the sintered TCHP, due to the thin binding ligaments. Even with a low hardness material (such as cobalt) the image tensions of the dislocations near the surface (and with submicrometric grains all are close to the surfaces), the properties of the composite are superior to those possible in abrasive composites. It may also be that the ligaments of the binder matrix become very thin and the strength of the composite becomes independent of the plastic properties of the cobalt binder, the strength P908 structural cell coatings can predominate and really approach the WC. The present invention provides sinterable metallic particulate materials which can be designed to offer an optimum balance of properties (eg, toughness, strength, low coefficient of friction and hardness). The operational improvements that can be expected in matrices and other tools manufactured from TCHP's are three: (a) a lower coefficient of friction at the interface between the work piece and the tool, which produces reduced heat, wear and characterization and it requires lower processing energy and auxiliary use of external lubricants, ultimately resulting in a longer tool life and better process control; (b) low reactivity with the iron, reducing sticking and wear by dilution of the flank or matrix and in turn prolonging the service life of the drawing die; and (c) a microstructure of the sintered tool in which the strong and tenacious coating material (eg, WC) on the particles forms a cellular support macrostructure for the tool, while at the same time providing a protective layer Perfect fit and tightly bonded to hard particulate cores (of, for example, TiN), keeping them in position and allowing P908 the optimal exposure and retention of the hard phase on the surface of the wear-resistant tool. This contrasts with articles produced by conventional methods (where the relatively low binder strength between the particles and the binder reduces the level of toughness and resistance to bending), reduces the level of toughness and resistance to bending (or in which a sintered article is fully coated to impart hardness (where the thin coating has a limited life or cracks.) The placement of the hard phase alloys in the interior, such as the core particle (instead of the outside), distributes the hard phase alloys (exposed on the external surfaces after finishing grinding) throughout the sintered microstructure in much greater proportions (or thicknesses) than is possible with any known conventional material. itself the resistance you desperate, reduces the chemical interaction with the work piece and decreases the coefficient of friction in a significant way. Increases the life of the tool by the constant renewal of surface grains that are worn or that are pulled by the opposite sliding surface.

P908 Also, the wear resistance and adhesion characteristics of most preferred core materials are known from their performance in conventional materials, so that their performance as d core particle materials is, in light of the present revelation, predictable. Because the particles are coated with known materials (eg, WC), the mixing and sintering of coated particles having several different core materials will facilitate the increase of multiple characteristics. In accordance with this, the cost of development and the tested are reduced, while providing a final material with unique properties. In this way, design a sintered microstructure, where each particle has a tenacious shell (the middle layer) that adheres very strongly to its neighboring particles to form a tenacious cellular support system throughout the substrate of the sintered article, produces an article sintered with the highest possible combination of strength, high elastic modulus, fracture toughness and hard alloy content. The resulting macrostructure of the article is a framework of cellular microstructure composed of shells of tough coated particles, strong, strongly interlaced, each containing and supporting one or more P908 chemically and mechanically bonded core particles, crystals, fibers or crystals, exposed in cross section on external surfaces during finishing grinding and polishing. This principle to optimize the combination of different materials for the core particles and the surrounding middle layer, allows the combination of the performance characteristics of the article, normally in conflict (ie, strength and hardness) at hitherto unknown levels in the technique of powder metallurgy. This concept provides a material designer with multiple tools (used individually or in combination) and a direct method that provides total and easy control to adapt the structure of the TCHP particle (thickness of the intermediate layer, size and core materials). ) and the mixing (integration of different "powders in the tool and in areas of the article) to satisfy many different unique conditions, combined and in specialty demand with a single item or tool." In addition, the use of a material was standard (such as WC) as a tenacious outer particle shell, dramatically reduces research, development and industrialization effort, because only a gas precursor to the reaction of the P908 material (eg tungsten carbide) to coat the dust particles, instead of several dozens of complicated precursor gases and reactants, used in multiple external substrate coatings. These particulate materials will sinter as if they were made of tungsten carbide particles, which are already known to bind very strongly to neighboring tungsten carbide particles with a binder, such as cobalt. In this way, the tenacious standard material in use for more than sixty years will permeate and reinforce the entire structure. The increase in the thickness of the tungsten carbide coating on the particle to satisfy more challenging resistance applications or decrease it in more critical wear applications, must solve most of the design challenges. Increasing the size of the core particle can easily be achieved to satisfy more severe wear resistance requirements or reducing it for higher strength applications. In use of different core particle materials with known characteristics (hardness, coefficient of friction) or found to perform better in specific applications (such as, for example, flank wear or crater wear) is also achieved By selecting the core material it is also possible to mix the above P908 thickness, diameter and powder parameters of the core material to solve most of the multiple criterion applications. It is also possible to transition the TCHP's gradually from the zones or layers rich in harder phases to those with more tough intermediate layer materials, using preheated sections of extruded wax / powder. This is a more flexible and effective approach than that used in the Functional Gradient Material (FGM) currently in use. The present invention can also be used to integrate different layers of powder (or mixtures) in different proportions of the same part to better resist multiple performance challenges. This is the last degree of refinement in microstructure design that is possible, with the exception of the gradient at the atomic level. The co-sintering, with other metal powders, provides the localized hardening in "non-hard" sintered parts, the TCHP will allow the steel parts that require technical treatment to be replaced by powdered metal parts (P / M), which require of a smaller number of manufacturing operations. Going now in detail to the attached drawings, the Figure 1 represents a sintered material in schematic cross section. In this modality there is one or more P908 particles of the hard metallic compound (10) with an intermediate layer of hard and tough metallic compound (14), such as, for example, tungsten carbide. The coated particle includes an outer layer of a suitable sintering binder (16), preferably metals of the iron group, usually cobalt or nickel. The resulting coated powder (18) is finally sintered in a finished or semi-finished article, of which a microsection is generally designated by the number 20. The microstructure of the sintered article (20) is a cellular framework of a layer of tightly interlaced unitary WC (14), each containing and supporting its own core of tightly bound metallic compound (10), held within the matrix (16) and exposed in cross section on the external surfaces (22) during the finishing grinding and polishing. The scanning electron microscope photograph shown in Figure 2 is of a unitary TCHP particle consisting of a core particle (6) of 1.6 micrometers of coated titanium nitride (7) with a thickness of about 0.25 micrometers (15 μm). cent) of W2C. This in one of the many TCHP grains placed in a resin metallurgical sample, shown in the bottom (9) and ground with stone. It is well known that hard alloy particles often do not sinter what P908 sufficiently close to the theoretical density due to (a) the irregularity of these grains (which cause poor fluidity, requiring hot pressing) and (b) to low plastic deformation during consolidation. The eight form of the core particle (6) shows typical concave irregularities in the samples. The CVD coating process normally fills the concavities as in (8), providing the coated particles with a rounder and smoother shape that in fact helps the fluidity and densification of the powders. This will reduce the processing cost, result in a more uniform and thinner binder layer and will help the densification of the powders, which in turn will increase the mechanical properties of the sintered article. The unique powders of the present invention were prepared in a chemical vapor deposition reactor (CVD). Due to the size of the particles that will be coated, the reactor includes components that prevent the agglomeration of the particles to be coated. A schematic representation of the reactor is presented in Figures 3-5. The CVD reactor system of Figure 3, consists of a rotating CVD reaction vessel (20), contained within an oven (22) to heat the powder and the reactant gases, the gases are supplied to the reactor.

P908 reactor and are evacuated through the gas inlet and outlet conduits (36, 26), respectively, at their opposite ends. The line (30) supplies the precursor tungsten exafluoride (WF6) while the lines (28) supply hydrogen with a purity of 99.999 percent, these are the two gases that react in the reaction vessel (20) to form the CVD coating, are connected to the rotary seal and to the inlet duct (36) by means of the flow meters (32). Line (28) also passes through a gas sparger (34), which contains isopropyl benzene with a purity of 99.9 percent. On the side of the outlet of the reactor (20) there is interposed a filter (38), in front of the evacuation conduit (26), the conduit is operatively connected to a vacuum system (not shown) and to a trap device (40) and a flow indicator (42). The reactor (20) may take the form of a cylinder of refractory metal or graphite, which has the ability to rotate at a variable speed, in the range of 50 to 150 rpm, depending on the diameter of the drum and the specific gravity of the powder which is going to be coated and the variation of its orientation; In this way, the angle of inclination (24) and the revolution speed can be adjusted to provide the appropriate residence time for the coated powder produced within the gaseous environment P908 reactive at high temperature (500-1600 ° C). There are four significant challenges during the practice of the CVD method to produce subchronic TCHP particulate matter: (1) the current cost of the tungsten hexafluorouro precursor gas (WF6); (2) control the harmful characteristics of the WF6; (3) the premature reaction of the precursors on other surfaces different from that of the core powder and (4) the disintegration of the agglomerates. The last three have technical solutions. Although other advantages of the processing cost can compensate or balance the first challenge, the ultimate success of the CVD will be determined by its cost with respect to other methods, such as deposition using metallic carbonyl. It was found that the solution to the previous third challenge (inefficient use of the reactants) was to keep the gas below the reaction threshold temperature until it is close to the core particles. This can be further improved by keeping the reaction gases separated, mixing them with each other and with the hot powders in turbulent form. It was found that microwave energy (but not induction frequencies) would warm the particles.

At a frequency of 2.45 GHz, heating for approximately 2 minutes at 500 watts produced an increase of P908 temperature of about 37-40 ° C. The concept of high heating rates in a turbulent and focused flow of reactants heated by the same powder (heated by microwave energy) in a quartz tube with recirculation, has a great attraction to achieve deagglomeration, mixing, recirculation and homogeneous covering of submicronic powders. Figure 4 illustrates a solution that was found to solve the problem of dust agglomeration. Fluidization in a rotating reactor normally does not apply the forces required to break or fragment the clods, which are continuously reformed. In fact, if left unattended, the agglomerates tend to classify themselves, according to their size, further preventing homogeneous processing. Additionally, a conventional horizontal rector has end zones that reduce the homogeneity of the coating thickness in the batch. As shown in Figure 4, a solution to the problem of agglomeration and end zones producing a non-uniform coating, involved the tilting of the reactor and the installation of a fixed guide 80 of the comb or rake type for (a) recirculate and homogenize the batch and (b) to apply a sufficient shear stress to deagglomerate it.

P908 Inside the furnace, the reaction chamber (62) is constructed of graphite, coated (60) with a quartz cylinder. The speed of rotation (66) must be such that the force of gravity acting on the powder of the core is barely greater than the centrifugal force, so that the falling dust grains, thus fluidized, maximize the exposure to gases reactants and accumulate on them the intermediate coating. The objective is for the core powder to flow, roll, cascade and roll by the proper combination of centrifugal force, gravity and rotational inertia from the rotation of the cylinder to maximize the exposure of the powder to the precursor gases. This implies a practical diameter (64) greater than 120 mm. To help break up or fragment the agglomerated lumps which prevent the deposition of homogeneous layers on each particle, the reactive gases can be introduced at a high flow rate or through the falling powder to break up the agglomerates with a shearing force. The shear is applied twice to the powder in two areas of the guide (80), shown in cross section (67) at the lower end of the drum. The first zone (68) apply light pressure and shear to the part of the powder that is trapped under the guide by rotating drum (60, 62). Between the drum and the zipper (67) P908 is formed by a progressive pinch angle (69) of 13 degrees, which applies enough compressive shear to break up the agglomerates. The second zone (70) consists of long angular teeth (72) which form the rack itself, cut squarely, with little bending or bending at the edges, in the stainless steel. This area (70) allows the compression powder to escape under a slight shearing force which serves to deagglomerate and further homogenize the particles for exposure during the next rotation. At a distance (74) of 5 mm from the quartz lining (60), the progressive angle of the teeth of the rack ends with a turning point that increases compression or pinching just as the openings of the teeth (72) reach its maximum. A small clearance (76) of 0.5-1.0 mm protects the quartz from being scratched by the zipper. The helical zone (80) of the rack provides a guide (78), shown at the lower end of the reactor (and shown at its upper end with dashed lines). This helical guide provides the lifting or lifting of dust to ensure lateral recirculation and homogeneity of the batch. Figure 5 shows the helical rack, so that the helical guide (78) is shown more clearly. On the upper platform they are cut P908 holes (92) to allow dust accumulated there to accumulate for their recirculation. The teeth of the rack (90) are also shown more clearly. As currently contemplated, the preferred embodiment of the invention utilizes pre-ground particle core powders, comprised of titanium nitride. This powder is coated by CVD with an intermediate layer of tungsten carbide. The use of cobalt binder for sintering is preferred. In a TiN / WC / Co system, there is a good solubility of the W in the Co and an efficient reaction between the C and the TiN, to form Ti (C, N), which leads to a strong base with grain boundaries TiN / WC and excellent mechanical properties of the sintered article, although this bond is less strong than that which is formed between the W and the Co. The TiN phase is located inside the material and does not cause any decrease in the performance coming from the surface wear (as is the case with traditional tools protected with a ceramic coating). Therefore, matrices, tools or other hard items made with the TCHP's could be reused for larger diameters or rectified for other applications. If subsequently it is determined that the formation of Ti intercalations (C, N) P908 should be minimized to increase the effectiveness of the binder, the increase in the thickness of the WC coating and the reduction of the sintering time and temperature can be used by vapor deposition of binder layers on the particles. On the other hand, at a hardness Vickers Hv = 3200 the Ti (C, N) is significantly harder than the TiN, Hv = 2400, or that the TiC, Hv = 2800. It can be shown that this is an advantage in certain applications. Zirconium nitride, SrN, harder than TiN has a friction coefficient two thirds less than that of TiN and is considered to be better at flank wear. This is also a preferred core material. Figure 6 depicts the compilation of the operational domains of various conventional tool materials and the expected operating domain of an embodiment of the present invention, used as a cutting tool material. By using conventional hard materials, the reduction of the particle size to the desired range and the application of a tough coating (such as the WC) in a thickness appropriate for the core, the TCHPs of the present invention expand the operational domains of these conventional materials. The extension or degree of increase in the speed of feeding the tool, is P908 say, the limit of the right side of the area defining the operational domain of the TCHPs of the present invention is based on the increase in tenacity provided by the tough coating and the use of hardness and other properties of the core material. Using a reactor system, such as the one depicted in Figure 3, sinterable composite particulates incorporating the present invention could be prepared by using each of the following alloys in the form of a powder with a diameter of 1.0-1.5 microns. Titanium nitride, titanium carbide, zirconium nitride, vanadium carbide, aluminum oxide and cubic boron nitride (other alloys such as titanium diboride, zirconium carbide, tantalum nitride and niobium carbide could also be used). The reactive ingredients of the chemical vapor, used for the deposition of WCx, are tungsten hexafluoride (WF6) in the presence of hydrogen and an aliphatic or aromatic carbon compound, the ingredients react at temperatures in the range of 500 ° C to 700 ° C , to form WCx coatings, with very reproducible characteristics. In the reactor, a low pressure (for example, less than 100 millibar) would be used to increase the difucibility of the reactive species in the gas and to allow a homogenous coating on the surface of the gas.

P908 powder. This technique is commonly called LPCVD (Chemical Vapor Deposition at Low Pressure). The reactor is operated at a sufficient speed to stir the core powder in a perpetual avalanche in free fall and the velocity of the reactive gas is adjusted as a function of other parameters (the pressure and the flow or total flow); A gas bubbler is used in those cases in which a liquid aromatic compound is used as the reactive ingredient. The target or white coating thicknesses, based on a desired 90-95 percent strength for all WCx sintered carbide and based on minimizing the residence time of the CVD, are in the range of 2 to 5 per percent of the average diameter of the particle. The operating parameters of the CVD are adjusted using a computer program, which allows its optimization, following the "main indicator", for example, the WCx coating thickness in different points of the reactor. The amount of WCx deposited on the powder is estimated by an EDX microanalysis of the treated powder, comparing the intensity peaks of tungsten and titanium and the WM: TÍK ratio (where M and K are the atomic ratio coefficients), determined on samples of particles taken at different points in the P908 oven and at different times. This provides clues about the homogeneity, deposition rate and characteristics of the surface WCx and interf cial characteristics of the WCx / core particle, before sintering. The cross-sectional thickness of the WCx coating is observed with an optical microscope and with a scanning electron microscope, using a specimen comprised of TCHP grains embedded in a resin and polished to expose a section of the grains; X-ray analysis is also used to show the presence of the WCx phase in the powder.

EXAMPLES Three series of sintered samples were prepared: a series made with particulate material of titanium nitride coated with WCx (incorporating to the present invention, (Formulations C, D, E and F), a series of reference bars made with powder of tungsten carbide without any coating (Formulation A), a comparative series made with a mixture of carbide powder and uncoated Tungsten Mark Appeals and the addition of TiN (Formulation B) and a standard Sandvick material (see column G) in Figure 7) coated with TiN, TiC, and Al203 (Formulation G). The tungsten carbide powder (WC) used P908 to produce the formulations is commercially available from H.C. Stark Company, as grade DS100 and has a typical average particle size of approximately 1. Oμm (± 0. lμm). The cobalt powder used was Starck grade II, which has a typical particle size of 1.5μm (± 0.2μm); The titanium nitride powder used was the Starck grade C, which has a typical particle size of 1. Oμm (varying from 0.8 to 1.2μm) and the nickel powder used is the commercially available one that has a typical particle size. of 2.2μm. The formulations incorporating the present invention were comprised of TiN core grains, coated by CVD with tungsten carbide (W2C) to a thickness of about 0.16μm, forming a composite particulate material (TCHP) having a particle size of about l.Oμm. The apparatus previously described with reference to Figures 3 to 5, was used to carry out the CVD coating of the TiN powder. It began to work with a helix angle of 20 ° and with the fixed comb at a pinch angle of 13 °. A suitable amount of TiN powder was introduced into the graphite reactor chamber. The system was purged, the hydrogen flow started and the internal pressure was adjusted to 11.25 Torr. Then energy was supplied to the electric furnace to carry the reactor drum, which rotates to 90 P908 revolutions per minute, at a temperature of approximately 550 ° C (approximately one hour). The flow meters of the WF6 supply and the eumeno sparger were then opened to provide a suitable molar ratio of reactants for depositing W2C onto the TiN powder substrate; the bubbler operated at 20 ° C and gaseous hydrogen was used as the carrier for the liquid eumeno .. The operation continued for a period of time sufficient to produce the desired thickness of W2C on the TiN particles, after which the flow meter of WF6 and the eumeno bubbler and the furnace was cooled in a hydrogen atmosphere. Formulation A is a binary mixture consisting of 94 weight percent WC and 6 weight percent Co; Formulation B is a ternary mixture consisting of 87 weight percent WC, 6 weight percent Co and 7 weight percent TiN; Formulation C consists of 84 weight percent of the TCHP composite described and 16 weight percent Ni; Formulation D consists of 84 weight percent of the TCHP composite and 16 weight percent of Co; and, formulation E consists of 90 weight percent of the TCHP composite and 10 weight percent of Co. Formulation B was formed in a bar P908 sintered with measurements of 53 x 16 x 11 mm and weighing approximately 130 grams, mixing the formulation with Acrawax C (an ethylenebistearamide processing aid available from Lonza Inc., of Fair Lawn, New Jersey) and hexane. It was milled in a ball mill for 16 hours with WC beads, vacuum dried, sieved at 300μm, cold pressed at 2000bar for five minutes and sintered with a residence time of 20 minutes at 1450 ° C. , in a vacuum of 1 to 3 Torr. The heating and cooling speeds applied were 150 to 200 ° C per hour and the total sintering operation required approximately two hours. Sample disks were prepared from formulations A, C, D, E and F. To prepare them, the formulation was mixed with a temporary camphor binder and an alcohol solvent, ground in a planetary ball mill for five minutes with Tungsten carbide balls, dried at 80 ° C for 15 minutes and sieved at 300μm. For samples A, C, and D, the discs formed were 10 mm in diameter and sintered at the vacuum conditions described above for samples A and B. To produce samples E and F, the formulation ground, dried and sieved was subjected to uniaxial pressing at 1400 ° C at a pressure of 200 kg / cm2, to form P908 discs measuring 50 mm in diameter. Several samples of each of the sintered articles described above were tested to evaluate each of several properties. The formulation, the sintering condition (vacuum or hot pressing), the shape of the article (bar or disc), the content of post-sintering binder and the values of the various measured properties are shown in Figure 7. The measurement of the Side wear and crater wear were on a standard material (CK 45) at a tangential surface velocity of 200m / min, a cut depth of 2mm and a feed rate of 0.2mm / rev. The values of hardness, resistance to bending and elastic modulus of Sample No. 1 are from the literature. In the preceding examples, it was found that the sintered samples embodying the present invention function in a manner that states that the metal powder constituent is especially well suited for the manufacture of tools and other articles, as contemplated herein. It will be appreciated that the ability to vary not only the composition of the metals used to produce the sinterable particulates of the invention (including any supplementary bonding agent or sintering aid), but also the relative thicknesses of P908 the core particle and the surrounding intermediate allows a high degree of control to be exercised over the properties exhibited by the particulate materials and the articles made from them. For example, by varying the thickness of the shell (for example, to a value that normal but not necessarily represents 5, 10 or 15 percent of the diameter of the TCHP particle), an optimum balance of hardness, toughness can be obtained , resistance, characteristic wear or wear and heat transfer capacity and can be imparted to the sintered product. The present invention provides a new class of powder materials, ie hard coated powders (TCHP's) that produce sintered articles that exceed the current compromised level of performance of conventional materials by combining the inherent transverse mechanical strength of metal carbides. (or of comparable tenacious metal compounds) with the superior wear resistance of hard metal compounds at the level of the core particle. Tools or articles made from these materials perform well at fairly wide intervals of conditions that today's specialized methods allow and their ratio of performance / price or proportion of value must increase significantly.

P908 The present invention has been disclosed in terms of examples and preferred embodiments. The scope of the invention is not limited thereto but is defined by the appended claims and their equivalents.

P908

Claims (40)

1. CLAIMS; 1. A sintered material comprising: a plurality of core particles, the core particles consist essentially of a first metal compound having the formula Ma k, wherein M is a metal selected from the group consisting of titanium, zirconium, hafnium , vanadium, niobium, tantalum, chromium, molybdenum, tungsten, aluminum and silicon; X represents one or more elements selected from the group consisting of nitrogen, carbon, boron and oxygen and a and b are numbers greater than zero and up to including four; an intermediate layer on each of the core particles, the layer consists essentially of a second metal compound, of composition different from that of the first metal compound and having a greater tenacity to the relative fracture, the second metal compound has the capacity of joining the first metal compound and having the ability to bind to a metal selected from the group consisting of iron, cobalt and nickel, thus allowing the formation of coated particles; and a binder which is superimposed on the intermediate layer on the coated particles, the outer layer comprises iron, cobalt, nickel, their mixtures, their alloys or their intermetallic compounds. P908 2. The sintered material according to claim 1, wherein the coated particles have an average particle size of less than about 2μm. 3. The sintered material according to claim 1, wherein the coated particles have an average particle size of less than about lμm. 4. The sintered material according to claim 1, wherein the intermediate layer has a thickness, after sintering, in the range of from 5% to 25% of the diameter of the core particles. The sintered material according to claim 1, wherein the intermediate layer has a thickness such that the deformation field associated with the dislocations in a coated particle is transmitted through the intermediate layer towards the immediately adjacent core particle. The sintered material according to claim 1, wherein the intermediate layer has a thickness, after sintering, in the range of from 3% to 200% of the diameter of the core particles. 7. The sintered material according to P908 claim 1, wherein the outer layer has a thickness, after sintering, in the range of from 3% to 12% of the diameter of the coated particles. The sintered material according to claim 1, wherein the outer layer has a thickness such that the deformation fields associated with the dislocations in a coated particle are transmitted through the binder to the immediately adjacent intermediate layer. 9. The sintered material according to claim 1, wherein the first metal compound consists essentially of a stoichiometric compound. The sintered material according to claim 1, wherein the first metal compound consists essentially of a metal compound selected from the group consisting of: TiN, TiCN, TiB2, TiC, ZrC, ZrN, VC, VN, AI2O3, Si3N4 and AlN . 11. The sintered material according to claim 1, wherein the second metal compound consists essentially of a metal compound selected from the group consisting of: WC and W2C. The sintered material according to claim 1, wherein the portions of the intermediate layer and the binder are removed to expose the P908 interior of the core particles. The sintered material according to claim 1, wherein the sintered material has a fracture toughness greater than that of cubic boron nitride. 14. A sintered material comprising: a plurality of core particles, the core particles consist essentially of a metal compound selected from the group consisting of: TiN, TiCN, TiB2, TiC, ZrC, ZrN, VC, VN, Al203, YES3N4 and AlN; an intermediate layer on each of the core particles, the layer consists essentially of a second metal compound, of composition different from that of the first metal compound and having a relatively superior fracture toughness, the second metal compound consists essentially of WC; and a binder that is superimposed on the intermediate layer on the coated particles, the binder comprises cobalt or nickel. 15. A sintered material comprising: a plurality of core particles, the core particles consist essentially of a plurality of metal compounds, each having the formula MQXJ-, wherein M is a metal selected from the group consisting of titanium , zirconium, hafnium, vanadium, niobium, P908 tantalum, chromium, molybdenum, tungsten, aluminum and silicon; X represents one or more elements selected from the group consisting of nitrogen, carbon, boron and oxygen and a and b are numbers greater than zero up to and including four; an intermediate layer on each of the core particles, the layer consists essentially of a different metal compound, of a composition different from that of the plurality of metal compounds that form the core particles and which has a superior toughness to relative fracture, the different metallic compound has the ability to bind to the metal compounds that form the core particles and have the ability to bind to a metal selected from the group consisting of iron, cobalt and nickel, thereby forming coated particles; and a binder which is superimposed on the intermediate layer on the coated particles, the binder comprises iron, cobalt, nickel, their mixtures, their alloys or their intermetallic compounds. 16. The sintered material according to claim 15, wherein the coated particles have an average particle size of less than about 2μm. 17. The sintered material according to claim 15, wherein the coated particles P908 have an average particle size of less than about lμm. 18. The sintered material according to claim 15, wherein the intermediate layer has a thickness, after sintering, in the range of from 5% to 25% of the diameter of the core particles. The sintered material according to claim 15, wherein the intermediate layer has a thickness such that the deformation fields associated with the dislocations in a coated particle are transmitted through the intermediate layer towards the immediately adjacent core particle. 20. The sintered material according to claim 15, wherein the intermediate layer has a thickness, after sintering, in the range of from 3% to 200% of the diameter of the core particles. 21. The sintered material according to claim 15, wherein the outer layer has a thickness such that the deformation fields associated with the dislocations in a coated particle are transmitted through the outer layer to the immediately adjacent intermediate layer. 22. The sintered material according to P908 claim 15, wherein the metal compounds that form the core particles consist essentially of stoichiometric compounds. 23. The sintered material according to claim 15, wherein the metal compounds forming the core particles consist essentially of metal compounds selected from the group consisting of: TiN, TiCN, TiB2, TiC, ZrC, ZrN, VC, VN, AI2O3, S3N4 and AlN. 24. The sintered material according to claim 15, wherein the different metallic compound consists essentially of WC. 25. The sintered material according to claim 15, wherein the portions of the intermediate layer and the binder are removed to expose the interior of the core particles. 26. The sintered material according to claim 15, wherein the sintered material has a fracture toughness greater than that of cubic boron nitride. 27. A sintered material comprising: a plurality of core particles consisting essentially of cubic boron nitride; an intermediate layer on each of the core particles, the layer consists essentially of WC, P908 the intermediate layer has a thickness, after sintering, in the range of from 5% to 25% of the diameter of the core particles; and a binder comprising iron, cobalt, nickel, their mixtures, their alloys or intermetallic compounds that overlap the intermediate layer, the binder has a thickness, after sintering, in the range of from 3% to 12% of the diameter of the coated particles, the combination of the core particles, the intermediate layer and the binder form a coated particle. 28. The sintered material according to claim 27, wherein the coated particles have an average particle size of less than about lμm. 29. A powder consisting essentially of a plurality of coated particles, most of the coated particles have: core particles consisting essentially of a first metal compound having the formula MaXj-), wherein M is a metal selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, aluminum and silicon; X represents one or more elements selected from the group consisting of nitrogen, carbon, boron and oxygen and a and b are P908 numbers greater than zero up to and including four; and a layer on each of the core particles, the layer consists essentially of a second metallic compound, of composition different from that of the first metallic compound and having a relatively superior fracture toughness, the second metallic compound has the capacity of join the first metal compound and have the ability to bind to a metal selected from the group consisting of iron, cobalt and nickel. 30. The powder according to claim 29, wherein the coated particles have an average particle size of less than about 2μm. 31. The powder according to claim 29, wherein the coated particles have an average particle size of less than about lμm. 32. The powder according to claim 29, wherein the layer has a thickness in the range of from 5% to 25% of the diameter of the core particles. 33. The powder according to claim 29, wherein the intermediate layer has a thickness, after sintering, in the range of from 3% to 200% of the diameter of the core particles. 34. The powder according to claim 29, wherein the first metal compound consists essentially P908 of a stoichiometric compound. 35. The powder according to claim 29, wherein the first metal compound consists essentially of a metal compound selected from the group consisting of: TiN, TiCN, TiB2, TiC, ZrC, ZrN, VC, VN, AI2O3, Si3N4 and AlN. 36. The powder according to claim 29, wherein the second metal compound consists essentially of WC or W2C. 37. The powder according to claim 29, which includes an external binder layer consisting essentially of a metal selected from the group consisting of: iron, cobalt, nickel, their mixtures, their alloys or their intermetallic compounds, the binder layer is deposited on the outer surface of the layer of the second metallic compound in the form of a continuous layer. 38. The powder according to claim 37, wherein the continuous layer of binder is deposited by chemical vapor deposition, sputtering, carbonyl deposition, chemical spray deposition of solution, electrodeposition or physical vapor deposition. 39. A powder comprising: a plurality of core particles consisting essentially of cubic boron nitride; P908 an intermediate layer on each of the core particles, the layer consists essentially of WC, the intermediate layer has a thickness, after sintering, in the range of from 5% to 25% of the diameter of the core particles; and an outer layer comprising cobalt or nickel which overlaps the intermediate layer, the combination of the core particles, the intermediate layer and the outer layer form the powder. 40. The powder according to claim 39, wherein the particles comprising the powder have an average particle size of less than about lμm. P908 SUMMARY OF THE INVENTION A sintered material is presented and the hard powder with hard coating (TCHP) for manufacturing said material is comprised of core particles consisting essentially of a first metal compound having the formula MaXj- ,. M is a metal selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, aluminum, boron and silicon, while X represents one or more elements selected from the group consisting of nitrogen , carbon, boron and oxygen. The letters a and b represent numbers greater than zero up to and including four. The core particles are surrounded by an intermediate layer consisting essentially of a second metallic compound, of composition different from that of the first metallic compound, thereby forming coated particles. The material of the intermediate layer has a fracture toughness relatively superior to that of the material comprising the core particles and has the ability to bind to the metal compound or compounds that form the core particles and also has the ability to bond to iron , cobalt or nickel. The coated particles are surrounded by an outer layer of iron, cobalt, nickel, their alloys, their mixtures or their intermetallic compounds. The intimate P908 Bonding of the alloys of multiple properties within the grains TCHP allows the combination of normally incompatible sintered article performance characteristics (eg strength and hardness) at levels hitherto unknown in the powder metallurgy art. P908