Abstract: A metal matrix composite comprising an iron aluminide binder phase and a ceramic particulate phase such as titanium diboride, zirconium diboride, titanium carbide and tungsten carbide is made by heating a mixture of iron aluminide powder and particulates of one of the ceramics such as titanium diboride, zirconium diboride, titanium carbide and tungsten carbide in a alumina crucible at about 1450.degree. C. for about 15 minutes in an evacuated furnace and cooling the mixture to room temperature. The ceramic particulates comprise greater than 40 volume percent to about 99 volume percent of the metal matrix composite.

Abstract: A composite material is disclosed along with the method of making the same. The material comprises a tough grade of cemented carbide granule dispersed with a hard brittle grade of cemented carbide granules to form a matrix. The quantity of hard, brittle cemented carbide granules is between 20% to 60% of the total composition. Such material functions to improve wear resistance without sacrificing toughness.

Abstract: According to the invention there is now provided a simple method of preparing a powder containing WC and cobalt and/or nickel. APT-powder and a powder of a basic salt of cobalt and/or cobalt are mixed in water or in mixed solvents. The suspension is stirred to react at temperatures ranging from room temperature to the boiling point of the solution whereby a precipitate is formed, which precipitate is filtered off, dried and finally reduced to a metallic powder.

Abstract: A process for the production of hard materials wherein hard constituent powders are coated with cobalt and/or nickel metal in solution by reducing the metals from a suitable compound such as an oxide, hydroxide or salt with a polyol while keeping the powder in suspension. The polyol functions both as a solvent and a reducing agent at the same time and is present in an amount of at least 5 times more moles polyol than moles metal. There is obtained an even distribution of the cobalt and/or nickel over the surface of the hard constituent powder without the formation of islands of pure metal.

Abstract: Processes are disclosed in which cemented carbide parts, having a wide range of initial carbon levels, and a wide range of sizes, can be carburized to a critical carbon level, and then slow cooled at various rates, to yield stratified enriched zones in the near-surface region of said parts. The enriched zones are characterized by the cobalt content decreasing, and the microhardness increasing, continuously through the enriched zones, and approaching values characteristic of the interior. The combination of stratified enriched zones in the near surface region and the 6% binder interior provide the toughness and deformation resistance required for heavy roughing applications.A wide variety of cemented carbides, having different compositions and WC grain sizes, can also be carburized and slow cooled using the same techniques to yield stratified binder enriched zones having the same hardness profiles and cobalt content profiles as described above.

Abstract: A compacted, single phase or multiphase composite article. Particles for use in the compacted article are produced by providing a precursor compound containing at least one or at least two metals and a coordinating ligand. The compound is heated to remove the coordinating ligand therefrom and increase the surface area thereof. It may then be reacted so that at least one metal forms a metal-containing compound. The particles may be consolidated to form a compacted article, and for this purpose may be used in combination with graphite or diamonds. The metal-containing compound may be a nonmetallic compound including carbides, nitrides and carbonitrides of a refractory metal, such as tungsten. The metal-containing compound may be dispersed in a metal matrix, such as iron, nickel or cobalt. The dispersed nonmetallic compound particles are no larger than about 0.1 micron in particle size and have a volume fraction greater than about 0.15 within the metal matrix.

Abstract: Cemented carbide inserts are available containing WC and cubic phases of carbide and/or carbonitride in a binder phase based on cobalt and/or nickel with a binder phase enriched surface zone. The binder phase content along a line essentially bisecting the rounded edge surfaces increases toward the edge and cubic phase is present. As a result, the edge toughness of the cutting inserts is improved.

Abstract: The present invention relates to cemented carbide bodies preferably for rock drilling and mineral cutting. Due to the fact that the bodies are built up of a core of eta-phase-containing cemented carbide surrounded by a surface zone free of eta-phase with low Co-content in the surface zone and successively increasing Co-content to a maximum in the outer part of the eta-phase-core they have obtained an increase in toughness and life at practical use.

Abstract: The present invention relates to a method of producing a sintered body comprising one or more hard constituents and a binder phase based on cobalt, nickel and/or iron by powder metallurgical methods milling, pressing and sintering of powders. At least part of the binderphase powder consists of non-agglomerated particles of spheroidal morphology having dimensions of 0.1 to 20 .mu.m.

Abstract: A high pressure injection nozzle member is formed of a super hard alloy or a hard material of carbide series mainly composing of a tungsten carbide as, wherein the tungsten carbon is composed of grains each having a diameter of less than 1 .mu.m. At least one kind of carbide or solid solution of carbide selected from Ti, Ta, V, Cr, Mo, Hf, or Zr by a weight % of less than 10.0% is added. A binding material essentially consisting of at least one of iron group elements by weight % of 0.2 to 2.0% may be further added. The super hard alloy or a hard sintered material has a high abrasion proof property and has a hardness more than about HRA 94.0. Nitride or nitride solid solution may be utilized in place of carbide or carbide solid solution. The nozzle member is particularly suitable for an abrasive water jet.

Abstract: Disclosed is a hard alloy with high hardness, high abrasion resistance, high corrosion resistance and high rigidity, which is excellent in performance in use for tools. The hard alloy contains more than 80% by weight of WC with less than 2 .mu.m of average particle size, more than 0.2% by weight and less than 2% by weight of Co and the remaining part of one or more metals, carbides, nitrides and carbonitrides of the metals in the IVa, Va and VIa families in the periodic table, such as 2.0 to 7.0% by weight of one or more of Mo and Mo.sub.2 C, and the alloy contains Co.sub.x W.sub.y C.sub.z in the sintered product. By the addition of Mo or Mo.sub.2 C and VC the growth of particles in the hard phase is inhibited and at the same time the wettability of WC--Co is increased.

Abstract: A watch exterior part is formed of cemented carbide or stellite alloy, and has a three-dimensionally curved as-sintered surface or a small hole with an as-sintered interior peripheral surface, or has a three-dimensionally curved polished surface obtained by polishing an as-sintered surface. The watch exterior part is manufactured by a method in which organic binder is milled into a material powder, and a molded body obtained by injection molding is subjected to a binder removing process and then sintered. By the manufacturing method, a watch exterior part formed of cemented carbide or stellite alloy has a high strength and a complicated configuration such as a three-dimensional curved surface and a small hole, without applying secondary machining operations such as discharge operations.

Abstract: A method for forming a wear surface on a metal substrate has a slurry which includes wear resistant particles, powdered steel, and binder system positioned on the metal substrate by retaining walls for a time sufficient for drying the slurry and forming a composite material of preselected thickness "T". The retaining walls are then removed and the substrate and the composite material are heated and passed through a rolling mill compressing the composite material.

Abstract: Method of making sintered insert for milling and turning formed of a titanium-based carbonitride containing hard constituents and binder phase metal comprising milling at least one hard constituent with binder phase metal, adding a second hard constituent at a later time during milling, pressing and sintering the pressed constituents to form the insert.

Abstract: The present invention relates to cemented carbide bodies preferably for wear demanding rock drilling and mineral cutting. The bodies are built up of a core of eta-phase-containing cemented carbide surrounded by a surface zone free of eta-phase where the binder phase content in the outer pan of said zone is lower than the nominal and, in addition, constant or near constant, and the binder phase content in the inner part of the eta-phase free zone closer to the eta-phase core is higher than the nominal. According to the method of the invention, bodies comprising evenly distributed eta-phase are subjected to a partly carburizing treatment with a carbon activity, a.sub.c, close to 1.

Abstract: The invention provides a method for manufacturing sintered parts, which uses as a debinder solvent a substance harmless to the human body and which can enhance the strength of an injection-molded product.

Abstract: A high pressure injection nozzle member is formed of a super hard alloy or a hard material of carbide series mainly composing of a tungsten carbide as, wherein the tungsten carbon is composed of grains each having a diameter of less than 1 .mu.m. At least one kind of carbide or solid solution of carbide selected from Ti, Ta, V, Cr, Mo, Hf, or Zr by a weight % of less than 10.0% is added. A binding material essentially consisting of at least one of iron group elements by weight % of 0.2 to 2.0% may be further added. The super hard alloy or a hard sintered material has a high abrasion proof property and has a hardness more than about HRA 94.0. Nitride or nitride solid solution may be utilized in place of carbide or carbide solid solution. The nozzle member is particularly suitable for an abrasive water jet.

Abstract: A sintered titanium-based carbonitride alloy contains hard constituents based on, in addition to Ti, W and/or Mo, one or more of the metals Zr, Hf, V, Nb, Ta or Cr in 5-30% binder phase based on Cobalt and/or nickel. The content of tungsten and/or molybdenum, preferably molybdenum in the binder phase is >1.5 times higher than in the rim and >3.5 times higher than in the core of adjacent hard constituent grains. The alloy is produced by a particular method.

Abstract: A spray powder for thermal spraying onto a substrate to provide a hardfacing, and a part with such hardfacing on the surface thereof, that is corrosion-resistant and abrasion-resistant. The spray powder comprises between about 75 to about 90 weight percent of tungsten carbide. The powder further comprises between about 10 and 25 weight percent of a nickel-based alloy, which includes Mo, and optionally, includes one or more of Fe, C, Cr, Mn, Co, Si and W.

Abstract: A sintered product useful for abrasion- and impact-resistant tools and the like is provided comprising an iron-group metal binder and refractory metal carbide particles, e.g. tungsten carbide, formed in situ during sintering by the exothermic reaction of a carbide-forming refractory metal powder with a carbon source mixed therewith. The sintering is carried out at an elevated temperature and at a pressure at which diamond is stable in the presence of a liquid phase comprised substantially of an iron-group binder metal, refractory metal, and dissolved carbon. The product may optionally contain diamond, up to about 95% in volume, enabling its properties to be tailored for a wide range of applications.

Abstract: Method of forming and a new class of tool steel macrocomposites having improved thermal fatigue resistance and improved wear resistance, formed of tool steel powder mixed with carbide powder under hot isostatic pressing.

Abstract: This invention discloses a process for preparing rare earth containing hard alloy, comprising preparing metal carbide powder containing rare earth metals or cobalt powder containing rare earth metals by using wet coprecipitating method; according to the composition of alloy, at least one kind of the metal carbide powder containing rare earth metal and cobalt powder containing rare metals being mixed homogeneously with other raw materials, shaping and finally sintering under high temperature. The process of the invention is simple technologically. The properties of the products produced by the process of the invention are good, stable and repeatable.

Abstract: The invention relates to a composite hard metal body of hard material, a binder and embedded reinforcing material, as well as to a process for the production of the composite hard metal body by methods of powder metallurgy.In order to create a composite hard metal body with improved toughness under load, improved hardness and a lower fracture susceptibility, the invention proposes to build in monocrystalline, preferably needle-shaped and/or platelet-shaped reinforcing materials, coated with an inert layer with respect to the binder metal phase and consisting of borides and/or carbides, and/or nitrides and/or carbonitrides of the elements of Groups IVa or Va or mixtures thereof and/or coated monocrystalline reinforcing material of SiC, Si.sub.3 N.sub.4, Si.sub.2 N.sub.2 O, Al.sub.2 O.sub.3, ZrO.sub.2, AlN and/or BN.

Abstract: A cermet alloy having a structure comprising a hard phase and a bonding phase, said hard phase comprising (1) at least one of MC, MN and MCN, wherein M is at least one element selected from Ti, Zr, Hf, Th, V, Nb, Ta, Pa, Cr, Mo, U and W and (2) at least one W-Co-B compound; said bonding phase comprising Co. The cermet has superior toughness and hardness, and can be worked by conventional sintering methods. The invention also includes a method for producing the cermet.

Abstract: An Ag-Cu-WC contact forming material for a vacuum interrupter comprising a highly conductive component comprising Ag and Cu and an arc-proof component comprising WC wherein the content of the highly conductive component is such that the total amount of Ag and Cu(Ag+Cu) is from 25% to 65% by weight and the percentage of Ag based on the total amount of Ag and Cu[Ag/(Ag+Cu)] is from 40% to 80% by weight; wherein the content of the arc-proof component is from 35% to 75% by weight; wherein the structure of the highly conductive component comprises a matrix and a discontinuous phase, the discontinuous phase having a thickness or width of no more than 5 micrometers and wherein said arc-proof component comprises a discontinuous grain having a grain size of no more than 1 micrometer.

Abstract: Disclosed are a high toughness cermet comprising a sintered alloy comprising 75 to 95% by weight of a hard phase of carbide, nitride or carbonitride containing Ti, at least one of W, Mo and Cr, and N and C, and the balance of a binder phase composed mainly of an iron group metal, and inevitable impurities,wherein the content of Ti in said sintered alloy is 35 to 85% by weight calculated on TiN or TiN and TiC, and the contents of W, Mo and Cr are 10 to 40% by weight in total calculated on WC, Mo.sub.2 C and/or Cr.sub.3 C.sub.2,the relative concentration of said binder phase at the 0.01 mm-inner portion from the surface of said sintered alloy is 5 to 50% of the average binder phase concentration of the inner portion, and the relative concentration of said binder phase at the 0.1 mm-inner portion from the surface of said sintered alloy is 70 to 100% of the average binder phase concentration of the inner portion, anda compression stress of 30 kgf/mm.sup.

Abstract: A non-magnetic, wear resistant composite of from 10 to 45 volume percent of titanium carbide or tungsten carbide particles bonded in a matrix of a nickel-titanium alloy wherein nickel comprises from 53 to 62 weight percent of the alloy with the remainder being essentially titanium.

Abstract: According to the present invention there is now provided a method of making a sintered titanium-based carbonitride alloy. According to the method, melt-metallurgical raw materials containing the metallic alloying elements for hard constituent-forming as well as binder phase-forming elements are melted and cast, using no intentional additions of the elements C, N, B and O, to form a pre-alloy which in solidified condition of brittle intermetallic phases with hard constituent-forming and binder phase-forming elements mixed in atomic scale. The pre-alloy is crushed and/or milled to powder with grain size <50 .mu.m. The powder is carbonitrided for simultaneous formation in situ of extremely fine-grained <0.1 .mu.m, hard constituent particles enclosed in their binder phase.

Abstract: A method of heating reactant materials in a plasma chamber to achieve a reaction temperature by enveloping the materials in a microwave induced electric plasma. The plasma chamber positioned in the microwave waveguide is filled with a gas and predetermined quantities of the reactant materials are placed in the chamber or reactor. A microwave produced electric field is passed through the gas to ionize it and produce an electric plasma that envelopes the reactant materials. The process may be used in a variety of high temperature chemical processes such as the production of tungsten carbide.

Abstract: A cutting insert of a sintered carbonitride alloy and with a complicated geometry, the insert having improved efficiency. This is obtained by giving the powder non-uniform compaction during pressing of the powder into a press-body so that the ultimate working edges will have a higher relative density than the surrounding, more "supporting" material in the press-body. By these means are often obtained surface defects in the form of cracks because of dissolved strains during the sintering.

Abstract: The invention relates to a method for the treatment and production of material, particularly for the treatment and production of free flowing, finely divided metal powder or metal matrix composite powder. The material is composed of tungsten carbide and at least two components, nickel and cobalt. According to the method of the invention the composite powder is first mixed with the organic binder in order to form powder agglomerate, which powder agglomerate is further subjected to sintering treatment in order to remove the binder and to improve the mechanical strength of the composite powder. Further the composite powder is subjected to classification and the classified composite powder is thermally treated at a high temperature in an at least one-step thermal treatment in order to melt the composite powder at least partially, and in order to mix the various components to each other.

Abstract: A tungsten carbide powder and cemented tungsten carbide article made from the powder are disclosed. The powder has a particle size of greater than 20 micrometers in diameter and no particles less than one-half the average particle size or greater than two and one-half times the average particle size.

Abstract: A method for producing a camshaft having a tubular steel shaft and a sintered cam piece joined to the shaft. The sintered cam piece has iron tetroxide film at its surface. The camshaft is produced by assembling a powder compact to the steel shaft to provide a camshaft assembly, sintering the assembly to provide an integral assembly, correcting bending to the assembly, annealing the assembly, grinding the cam piece and effecting vaporization treatment to the assembly at a temperature lower than the annealing temperature.

Abstract: A method is disclosed for producing tungsten carbide and a cemented tungsten carbide article therefrom which consists essentially of forming a uniform mixture of tungsten metal powder and carbon wherein the tungsten metal powder has an aveage particle size of from about 1 to about 4 micrometers in diameter, wherein the surface area of the carbon is no greater than about 12 m.sup.2 /g, and wherein the amount of the carbon is sufficient to react with essentially all of the tungsten to produce tungsten carbide in the subsequent heating step, heating the mixture in a non-oxidizing atmosphere at a temperature of at least about 1200.degree. C. for a sufficient time to produce tungsten carbide wherein the amount of free carbon is less than about 0.

Abstract: A method is disclosed for producing tungsten carbide-nickel powder which comprises forming a powder mixture consisting essentially of in percent by weight of about 0.1 to about 1.0 dimolybdenum carbide, about 1 to about 4 tungsten metal powder, about 80 to about 98% tungsten carbide and about 2 to about 20 nickel, wherein a sintered article produced from the powder has a relatively uniform microstructure.

Abstract: A method for producing metal carbide grade powders which comprises forming a wax mixture consisting essentially of in percent by weight about 5 to about 15 paraffin oil, with the balance being an esterified wax and paraffin, heating the wax mixture to a temperature above the melting point to melt the wax mixture and maintain it in the molten state, forming a powder-wax mixture consisting essentially of metal carbide powder, a binder metal, and the wax mixture while heating to a temperature above the melting point of the wax mixture to maintain the wax mixture in the molten state to result in a uniform distribution of the wax mixture on the carbide and binder metal particles, forming a slurry of the powder-wax mixture and water, attritor milling the slurry at a temperature below the melting point of the wax mixture, and removing water and agglomerating to produce metal carbide grade powder wherein a densified article made therefrom exhibits less linear shrinkage than articles made from carbide grade powder abs

Abstract: A method for manufacturing a dense cermet article including about 80-95% by volume of a granular hard phase and about 5-20% by volume of a metal binder phase. The hard phase is (a) the hard refractory carbides, nitrides, carbonitrides, oxycarbides, oxynitrides, carboxynitrides, borides, and mixtures thereof of the elements selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, and B, or (b) the hard refractory carbides, nitrides, carbonitrides, oxycarbides, oxynitrides, and carboxynitrides, and mixtures thereof of a cubic solid solution of Zr--Ti, Hf--Ti, Hf--Zr, V--Ti, Nb--Ti, Ta--Ti, Mo--Ti, W--Ti, W--Hf, W--Nb, or W--Ta. The binder phase is a combination of Ni and Al having a Ni:Al weight ratio of from about 85:15 to about 88:12, and 0-5% by weight of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Co, B, and/or C. The method involves presintering the hard phase/binder phase mixture in a vacuum or inert atmosphere at about 1475.degree.-1675.degree. C., then HIPing at about 1575.degree.-1675.degree. C.

Abstract: A drag bit with a faceted profile and method of its manufacture by which the facets provide for planar mold surfaces upon which cores having planar ends can completely contact the surface of the mold. The invention is particularly though not exclusively adapted to matrix body drag bits incorporating PDC cutters having tungsten carbide studs or cylinders which are mounted in wings, ribs or blades of the bit body. In accordance with a preferred embodiment of the present invention, the wings, ribs or blades have a small planar surface or facet at each PDC cutter location with each of the facets being at a consistent angular disposition with respect to the axis of the corresponding cutter stud. The facets are created by flat mold surfaces which facilitate the proper positioning and angular disposition of the cores which form the openings in the matrix for receiving the PDC cutters.

Abstract: An improved ceramic-metal composite comprising a mixture of a ceramic material with a ductile intermetallic alloy, preferably Ni.sub.3 Al.

Abstract: A microdrill bit is made of a tungsten carbide based cemented carbide which contains a binder phase of 6% by weight to 14% by weight of a cobalt alloy and a hard dispersed phase of balance tungsten carbide. The cobalt alloy contains cobalt, chromium, vanadium and tungsten and has weight ratios so as to satisfy the relationships of 0.04.ltoreq.(c+d)/(a+b+c+d).ltoreq.0.10 and 0.50.ltoreq.c/(c+d).ltoreq.0.95, where a, b, c and d denote weight ratios of tungsten, cobalt, chromium and vanadium, respectively. The drill bit is formed so as to have a Rockwell A scale hardness of 92.0 to 94.0.

Abstract: A method for producing metal carbide grade powders suitable for isostatic compaction which comprises combining a binder metal powder with an esterified wax and heating the wax to a temperature above the melting point of the wax to melt the wax and maintain it in the molten state to form a first mixture, with the amount of wax being sufficient to result in a level of wax in the subsequently produced second mixture of no greater than about 1/2% by weight, combining a metal carbide powder component with the first mixture while maintaining the wax in the molten state, forming a slurry of the second mixture and water, attritor milling the slurry at a temperature below the melting point of the wax, and removing water from the resulting attritor milled mixture to form the metal carbide grade powder.

Abstract: A tungsten carbide powder and cemented tungsten carbide article made from the powder are disclosed. The powder has a particle size of greater than 20 micrometers in diameter and no particles less than one-half the average particle size or greater than two and one-half times the average particle size.

Abstract: The present invention relates to a method of preparing an alloy for use as a cutting tool material comprising hard principles and binder phase by which a uniform distribution of the hard principles in the binder phase is obtained, and the resulting product.

Abstract: A composite material is disclosed along with the method of making the same. The material comprises a tough grade of cemented carbide granule dispersed with a hard brittle grade of cemented carbide granules to form a matrix. The quantity of hard, brittle cemented carbide granules is between 20% to 60% of the total composition. Such material functions to improve wear resistance without sacrificing toughness.

Abstract: The present invention relates to a method of sintering ceramics and ceramics obtained by said method. According to the present invention, the synthesis and sintering of ceramics can be simultaneously carried out by utilizing the reaction heat generated when at least one metallic element selected from metallic elements of IIb, IVb, Vb and VIb groups of the Periodic Table is combined with at least one nonmetallic element such as B, C N and Si without heat or by preliminarily heating the ceramics at temperatures remarkably lower than the usual sintering temperature ceramics thus-produced are superior in abrasion resistance and corrosion resistance.

Abstract: A hard metal composite is formed from a mixture of two or more pre-blended, unsintered hard metal composites in which the properties of each constituent are different. The constituent components are selected so that they have different grain sizes, different binder contents, different metal carbide or binders, or some combination of these. Primarily, the constituents are chosen on the basis of their properties and compatability, and are chosen to utilize the superior properties of one of the constituents without detrimentally affecting the desirable properties of the other. As an example, a pre-blended composite having a superior hardness may be dispersed in a second composite having a superior toughness with the resultant material having a hardness which approaches that of the harder constituent yet maintaining the toughness of the matrix constituent.

Abstract: High density compacts are made by providing a compactable particulate combination of Class 1 metals selected from at least one of Ag, Cu and Al, with material selected from at least one of CdO, SnO, SnO.sub.2, C, Co, Ni, Fe, Cr, Cr.sub.3 C.sub.2, Cr.sub.7 C.sub.3, W, WC, W.sub.2 C, WB, Mo, Mo.sub.2 C, MoB, Mo.sub.2 B, TiC, TiN, TiB.sub.2, Si, SiC, Si.sub.3 N.sub.4, usually by mixing powders of each, step (1); uniaxially pressing the powders to a density of from 60% to 95%, to provide a compact, step (2); hot densifying the compact at a pressure between 352 kg/cm.sup.2 (5,000 psi) and 3,172 kg/cm.sup.2 (45,000 psi) and at a temperature from 50.degree. C. to 100.degree. C. below the melting point or decomposition point of the lower melting component of the compact, to provide densification of the compact to over 97% of theoretical density; step (3); and cooling the compact, step (4).

Abstract: A apex seal is formed by cold pressing and sintering a mixture of Clevite and tungsten carbide powders to form a seal wherein harder rounded carbide particles are distributed within a softer matrix.

Abstract: An end mill formed of a tungsten carbide-base sintered hard alloy comprising a binder phase including a Co-base alloy, and a hard disperse phase consisting essentially of WC in proportions of:binder phase: 6-23 wt. %, andhard disperse phase: 77-94 wt %,the binder phase having a composition of:Cr: 1-15 wt. %,W: not more than 5 wt. %, andthe balance of Co and inevitable impurities, the hard disperse phase having a mean grain size of 0.5-2 .mu.m.

Abstract: The present invention relates to a sintered body for chip forming machining containing at least one hard constituent comprising a carbide, nitride and/or carbonitride of a metal of group IVB, VB or VIB in the periodical system and a binder metal based upon Co, No and/or Fe, in which the body comprises a core containing eta-phase or an intermediate phase, substantially free of carbon and/or nitrogen surrounded by a hard constituent- and binder phase-containing surface zone, free of said eta-phase or intermediate phase.