EP1095168A1

EP1095168A1 - Hard metal or ceramet body and method for producing the same

Info

Publication number: EP1095168A1
Application number: EP99941397A
Authority: EP
Inventors: Limin Chen; Walter Lengauer; Hans Werner Daub; Klaus Dreyer; Dieter Kassel; José Garcia; Georg Korb
Original assignee: Widia GmbH
Current assignee: Widia GmbH
Priority date: 1998-07-08
Filing date: 1999-06-26
Publication date: 2001-05-02
Anticipated expiration: 2019-06-26
Also published as: US6506226B1; EP1095168B1; ATE221140T1; WO2000003047A1

Abstract

The invention relates to a hard metal or ceramet body with a hard material phase consisting of WC and/or at least one carbide, nitride, carbonitride and/or oxicarbonitride of at least one of the elements from group IVa, Va, or VIa of the periodic table and a binding metal phase consisting of Fe, Co and/or Ni, said binding metal phase making up 3 to 25 mass %. In particular, WC crystallites should protrude beyond the hard metal or ceramet surface of the body by 2 to 20 mu m in order to improve the adhesion of surface layers that are applied.

Description

description

Carbide or cermet body and process for its manufacture

The invention relates to a hard metal or cermet body with a hard phase consisting of WC and / or at least one carbide, nitride, carbonitride and / or oxicarbonitride of at least one of the elements of the IVa, Va or Vla group of the periodic table and a binder metal phase Fe, Co and / or Ni, the proportion of which is 3 to 25% by mass.

The invention further relates to a method for producing such a hard metal or cermet body by mixing, grinding, granulating and pressing a starting mixture containing corresponding constituents and then sintering.

EP 0 344 421 A1 proposes a cermet which should either have an average grain size of the hard material phase in the surface layer compared to a core with a penetration depth of 0.05 mm, which is between 0.8 and 1.2 times that average grain size of the hard material phase in the cermet core or in the same penetration depth relates to a binder phase which corresponds to 0.7 to 1.2 times the average binder content of the cermet core or in which the hardness in the aforementioned penetration depth between the 0.95 and 1.1 times the average hardness of the cermet core. To produce this cermet, the starting mixture is sintered after grinding, mixing and pre-pressing, sintering in a first stage up to 1300 ° C or below under vacuum or an inert gas atmosphere, while in a second stage above 1300 ° C at a nitrogen pressure of 0.1 to 20 torr (13.3 Pa to 2.66 x 10 ³ Pa) is sintered, and the nitrogen pressure should also rise with increasing temperature. EP 0 368 336 B1 describes a cermet substrate with a hard surface layer in which the region with the maximum hardness is present at a depth between 5 μm and 50 μm from the substrate surface, and the substrate surface has a hardness of 20 to 90% of the maximum Hardness. To produce this cermet, the pre-pressed mixture is subjected to an initial temperature increase to 1100 ° C. in a vacuum, a subsequent temperature increase from 1100 ° C. to a temperature range between 1400 ° C. and 1500 ° C. in a nitrogen atmosphere, and a subsequent sintering in a vacuum.

EP 0 374 358 B1 describes a process for producing a cermet with 7 to 20% by weight binder phase and a hard phase made of titanium carbide, titanium nitride and / or titanium carbonitride with 35 to 59% by weight Ti, 9 to 29% by weight W, 0.4 to 3.5% by weight Mo, 4 to 24% by weight of at least one metal from Ta, Nb, V and Zr, 5.5 to 9.5% by weight N ₂ and 4, 5 to 12 wt .-% C. The formulated, mixed, dried and pre-pressed mass is sintered in such a way that the temperature is raised to 1350 ° C. in vacuo, the nitrogen atmosphere being set to 1 Torr (133 Pa) at 1350 ° C. , the nitrogen partial pressure is gradually increased together with the temperature increase from 1350 ° C. to the sintering temperature, the nitrogen atmosphere being set to 5 Torr (665 Pa) at the sintering temperature.

EP 0 492 059 A2 describes a cermet body whose hardness is at a penetration depth of not less than 1 mm higher than in the interior of the cermet, the binder content in a layer thickness of 0.5 to 3 μm compared to the core substrate being able to be minimized. The cermet should have a hard material coating in a thickness of 0.5 to 20 μm made of carbides, nitrides, oxides and borides of titanium and A1 ₂ 0 ₃ . To produce this body, a green body is first heated to a temperature between 1100 ° C and 1400 ° C under vacuum, then nitrogen gas let in up to a pressure at which the partial nitrogen pressure is between 5 and 10 Torr (665 and 1330 Pa), so that the substrate surface is denitrified. The sintering and the final cooling are carried out under a non-oxidizing atmosphere, such as a vacuum or an inert gas atmosphere. Finally, the body is coated using CVD or PVD.

To produce a high-viscosity cermet, EP 0 499 223 suggests that the relative concentration of the binder in a 10 μm-thick layer near the surface be 5 to 50% of the average mean content of binder in the cermet core and in the layer below it from 10 μm to 100 μm penetration depth adjust the binder content to 70 to 100% relative to the cermet core. In the process used for this purpose, the sintering is carried out under nitrogen gas at a constant pressure of 5 to 30 Torr (665 to 3.99 x 10 ³ Pa) and the cooling under vacuum at a cooling rate of 10 to 20 ° C / min.

EP 0 519 895 A1 discloses a cermet with a three-layer edge zone in which the first layer extends to a depth of 50 μm TiN, the next layer from 50 to 150 μm penetration depth with a binder enrichment and the next layer from 150 μm to 400 μm is formed with a binder depletion relative to the interior of the cermet core. For this purpose, the sintered body is in an atmosphere of N ₂ and / or NH _3, possibly in combination with CH ₄ , CO, C0 ₂ at 1100 ° C to 1350 ° C for 1 to 25 hours at atmospheric pressure or a pressure above 1.1 bar ( 1.1 x 10 ⁵ Pa) treated.

The cermets known from the prior art either have different binder contents on the surface, which is recognizable by their spotty appearance, or tend to adhere. tings of the binder with the sintered base, which leads to changes in the composition in the contact zone due to the associated reaction. Another disadvantage of the cermets known to date in the prior art is the poor adhesion of wear protection layers applied to the surface when the binder metal content is increased. If there is an increased nickel content in the surface, no CVD coating is possible at all. To influence the zone near the surface, a cermet is therefore proposed in DE 44 23 451 AI which has a hard material content of 95 to 75% by mass and 5 to 25% by mass of Co and / or Ni binder, the hard material phase consisting of carbonitrides with cubic Bl -Crystalline structure exists and 30 to 60 mass% Ti, 5 to 25 mass% W, 5 to 15 mass% Ta, of which up to 70 mass% can be replaced by Nb, 0 to 12 mass% Mo, 0 to 5 mass% V , 0 to 2 mass% Cr, 0 to 1 mass% Hf and / or Zr contains. The (C + N) content in the carbonitride phase should be> 80 mol%, the nitrogen content N / (C + N) being between 0.15 and 0.7. At a surface layer depth determined from 0.01 to 3 μm, the content of the binder phase in relation to the underlying cermet core area is less than 30% by mass. In this zone the titanium content is 1.1 to 1.3 times as large as in the underlying cermet core areas, whereas the sum of the contents of tungsten, tantalum and any proportions of molybdenum, niobium, vanadium and / or chromium in only 0 , 7 to 1 times the amount relative to the underlying cermet core areas. In an alternative embodiment of this cermet, the relative content of binder phase is 90% by mass, the relative Ti content is 100% to 120% and the sum of the contents of tungsten, tantalum and possibly molybdenum, niobium, vanadium, chromium is between 80 in the same surface zone % By mass and 110% by mass, each relative to the core of the cermet. This edge structure according to the above-mentioned document is produced by a process for cermet production, according to which the green compact produced by mixing, milling, granulating and pressing is first heated to the melting point of the binder phase under vacuum with a pressure below 10 ^"1 mbar (10 Pa). Upon further heating from the melting temperature of the binder phase to the sintering temperature, which is maintained for 0.2 to 2 hours, and a subsequent cooling to 1200 ° C., there is a gas mixture of N ₂ and Co with an N ₂ / (N ₂ + in the furnace atmosphere CO) ratio fluctuates between 0.1 and 0.9 under an alternating between a mean pressure of 10% and 80% of an average value in a period of between 40 and 240 sec. The mean pressure and the aforementioned ratio are selected depending on the binder content .

EP 0 687 744 A2 also describes a nitrogen-containing sintered hard metal alloy with at least 75% by weight and a maximum of 95% by weight of hard phase, which contains titanium, an element from the Via group of the periodic table and WC, the remainder of the binder phase made of nickel and cobalt. The alloy has 5% by weight to 60% by weight of titanium in the form of TiC and 30% by weight to 70% by weight of a metal in the form of a metal carbide. The cemented carbide alloy should have a soft, outermost surface layer, which consists of a binder phase and WC. Under this outermost layer is a 3 μm to 30 μm thick layer, which should consist essentially of WC with a low proportion of binder metal.

A sintered hard metal alloy of the composition mentioned at the outset likewise describes EP 0 822 265 A2. The sintered body produced from this should have an edge region which is divided into three layers, of which the outermost layer has a WC content between 0 and 30% by volume, the remainder of the binder phase middle layer 50 vol .-% to 100 vol .-% WC, rest of the binder phase, and a third bottom layer has a WC volume fraction between 0 and 30 vol .-%, rest of the binder.

It is an object of the present invention to provide a hard metal or cermet body suitable for a CVD or PVD coating, the surface of which has an improved adhesion for the layers of covalent hard materials, such as e.g. Diamond, cubic boron nitride, carbon nitride, fullerenes and metallic hard materials (carbides, nitrides, carbonitrides or oxicarbonitrides of the elements of the IVa to Vla group of the periodic table) as well as other layers which contain at least one of the elements B, C, N or 0 , guaranteed.

This object is achieved by a hard metal or cermet body according to claim 1, which according to the invention is characterized in that WC crystallites protrude from the body surface by 2 to 20 μm, preferably 5 to 10 μm. A coarse-grained surface morphology is created by these crystals, which creates the adhesion of applied surface layers by interlocking the crystallites with the deposited phases. These WC crystallites are so firmly integrated into the near-surface edge zone that they did not break out even during trial grinding work. The created surface roughness thus provides an ideal "anchorage" for the application of surface coatings.

Further developments of the invention are described in the subordinate claims.

The proportion of WC in the total hard material phase of the hard metal or cermet body is at least 50% by mass and a maximum of 96% by mass. The WC crystallites are preferably on the Body edge zone or surface connected with up to 50 vol .-% of a cubic phase of another hard material of different composition and binding metal parts. This cubic phase can essentially consist of carbides, nitrides, carbonitrides and / or oxicarbonitrides of at least one of the IVa, Va and / or Vla elements (except W) of the periodic system. The cubic phase can be single or multi-phase, in particular, for example, consist of Ti (C, N) and (Ti, W) C. Likewise, metals from the IVa, Va and / or Vla group of the periodic table, preferably W, Ta, Nb, Mo and Cr, can also be incorporated into the structure of the hard metal or cermet body, in particular in the edge zone near the body surface. The cubic phases in the edge zone can each have a homogeneous structure or a local core-edge structure, as is known in principle from cermets.

The present invention particularly includes cermet bodies whose phases with a cubic crystal structure 30 to 60 mass% titanium, 5 to 15 mass% tantalum and / or niobium, 0 to 12 mass% molybdenum, 0 to 5 mass% vanadium, 0 to 2 masses % Chromium, 0 to 1% by mass hafnium and / or zirconium, with up to 2% aluminum and / or metallic tungsten, titanium, molybdenum, vanadium and / or chromium being dissolved in the binder phase.

The edge zones near the surface can be constructed essentially homogeneously or have a gradient in the composition or surface zones near the surface of different compositions, an essentially first in an outer layer adjoining the body surface and reaching to a depth of between 2 μm and 3 μm Binder phase-free carbonitride phase is located, which adjoins an underlying middle layer with a thickness of 5 μm to 150 μm from an essentially pure WC-Co composition, and what is a third bottom layer with a thickness of connects at least 10 microns and a maximum of 650 microns, the proportions of the binder phase and the IVa and / or Va elements increase to the substantially constant value present inside the body and the tungsten proportion drops to the essentially constant value inside the body. The different layers of the sintered body described above merge continuously, titanium being preferably used as the metal of the carbonitride phase. The content of titanium and / or a further element of the IVa to Vla group of the periodic table, with the exception of tungsten, is maximum in the outer layer, then drops steeply to a minimum value during the transition to the middle layer and increases during the transition to the third lowest layer to a depth of penetration of approx. 800 μm from the surface gradually increases to an average value corresponding to the proportion of the total composition inside the body, which is below the titanium or other metal content in the outer layer. In a corresponding manner, the nitrogen content in the middle layer is minimal and increases to proportions above the average nitrogen content of the alloy which are present in the core interior as the transition to the outermost layer occurs. In contrast to this, the contents of tungsten and cobalt increase significantly during the transition from the outermost layer to the middle layer. The hard phase WC can possibly only be formed from (Ti, W) C or (Ti, W) (C, N) during sintering. The binder phase content in the middle layer is preferably at most 0.9 times the binder phase content in the interior of the body, while the tungsten content in this middle layer is at least 1.1 times the tungsten content in the interior of the body.

As an alternative to this, those edge zone areas are also possible in which the individual layers are not sharply separated from one another, but rather the respective metal and non-metallic Gradually change the proportion of tallies in the alloy over wide transition areas. The body characterized according to claim 9 fulfills the following conditions in three layers forming the edge region:

In an outer layer that adjoins the body surface or an edge zone with a penetration depth of 1 to a maximum of 3 μm and extends to a depth of between 10 μm and 200 μm, the tungsten and binder phase components are at most 0.8 times that of the total composition resulting portion. In this layer, the proportion of tungsten and the binder phase towards the inside of the body essentially increases continuously, whereas the proportion of nitrogen towards the inside of the body essentially decreases continuously. In an underlying middle layer with a thickness between 20 μm and 400 μm, as the depth of penetration progresses, the tungsten and binder phase contents pass through a maximum and the contents of elements of the IVa and / or Va group of the periodic table pass through a minimum. In a third, lowest layer, which reaches a maximum penetration depth measured from the body surface of 1 mm, the tungsten and binder phase components drop to essentially constant values inside the body, which correspond to the component in the overall composition, and the contents of elements the IVa and Va groups of the periodic table, in particular titanium, rise to essentially constant values. The nitrogen content remains essentially constant during the transition from the middle layer to the lowest layer down to the inside of the body.

The alloys of the bodies according to the invention can contain up to 2% by mass of chromium and / or molybdenum and in the hard material phase TiCN in an amount between 3 to 40% by mass of TiCN or up to 40% by mass of TiC and / or TiN.

The hard metal or cermet body according to the invention is preferably provided with at least one hard material layer and / or one ceramic layer (A1 ₂ 0 ₃ ) or diamond, cubic boron nitride or similar layers.

The manufacture of the above-described hard metal or cermet body is carried out as claimed in claim 11 or 12, the process techniques set out distinguishing between starting mixtures which already contain nitrogen and those which are free of nitrogen.

In the case of nitrogen-free mixtures of hard materials and binding metals, these are pre-pressed into a green body and first heated to a temperature between 1200 ° C and the sintering temperature in a vacuum up to about 1200 ° C and then in an inert gas atmosphere, after which at least temporarily at least when the sintering temperature is reached a nitrogen and possibly carbon-containing atmosphere is set at a pressure between 10 ³ and 10 ⁷ Pa, preferably between 5 x 10 ³ Pa and 5 x 10 ⁴ Pa. If the sintering temperature has not already been reached, the temperature is still increased to this temperature and maintained for a holding time of at least 20 minutes or only a slight cooling of at most 2 ° C./min is carried out in this time of at least 20 minutes. When the sintered body is finally cooled, the set nitrogen and possibly carbon-containing gas atmosphere is maintained until at least 1000 ° C is reached.

If the starting mixture contains nitrogen components of at least 0.2% by mass based on the total mass of hard material, the nitrogen-containing gas can also be introduced into the furnace atmosphere at a later time, at the latest when the sintering temperature is reached and depending on the nitrogen content in the starting mixture. In any case It must be ensured via the process control and / or the starting mixture that there are sufficiently high proportions of carbon and tungsten to form the WC crystallites on the surface. Possibly. the sinter holding time must be extended accordingly.

Further developments of the method are described in claims 13 ff.

Thus, in a variation of the method, it is also possible to remove the nitrogen and possibly carbon-containing atmosphere by introducing precursors, i.e. Nitrogen and possibly carbon-containing gases or possibly also by carbon-containing crucible materials in such a way that nitrogen and carbon are formed in situ under the prevailing temperature and pressure.

The size and frequency of the WC crystallites can be influenced with the period of time and with the gas composition at which the sintered body is above eutectic temperatures. Longer treatment times and a higher proportion of carbon lead to larger and / or more frequently occurring WC crystallites.

In one embodiment variant of the invention, the sintered body is heated to 1200 ° C. during the heating phase and this temperature is held for a period of at least 20 minutes, preferably more than one hour, before the further heating to the sintering temperature is continued.

Within the scope of the present invention there is also a procedure in which the body is first exposed to a vacuum in the warm-up phase up to approximately 1200 ° C., which is then replaced by an inert gas atmosphere (for example an inert gas atmosphere). The inert gas pressure of 10 ³ to 10 ⁴ Pa is maintained until the sintering temperature is reached, after which an atmosphere containing nitrogen and possibly carbon is set at a higher pressure of more than 10 ⁴ Pa above 1450 ° C., preferably close to 1500 ° C. .

According to a further embodiment, the sintered body made of a hard metal or a cermet can be subjected to a "pendulum annealing" after holding the sintering temperature for at least 0.5 hours, i.e. a temperature control in which the eutectic melting point is oscillated below and exceeded at least once, preferably several times, the temperature exceeding and falling below the eutectic point by at least 20 ° C., preferably at least 50 ° C. The heating and cooling rates and the rate at which the temperature falls below and exceeds the eutectic melting point are preferably at a maximum of 10 ° C./min. However, cooling and / or heating speeds between 2 ° C./min and 5 ° C./min are preferred.

In a further embodiment of the invention, the atmospheric gas mixture set after reaching the sintering temperature can be selected from N ₂ and CO with a ratio N ₂ / (N ₂ + CO) between 0.1 and 0.9.

Finally, within the scope of the present invention it is possible, after reaching the sintering temperature, to set a pressure in the nitrogen and possibly carbon-containing atmosphere which fluctuates in the mean value, the pressures deviating by 10 to 80% from an average value which is dependent on the binder content is chosen. A corresponding procedure is explained for example in DE 44 23 451 AI, to which reference is made. According to a development of the invention, the surface of the finished sintered body can be subjected to an etching treatment by means of gases or liquids, as a result of which the WC crystallites emerge more clearly through the formation of reliefs. In particular, this measure can be used to remove binder metal components on the substrate body surface which are undesirable in a diamond coating.

The present invention is further explained in the following with reference to the figures. Show it

1 is a temperature-time diagram,

2, 3 microstructures on a sintered body edge zone with different WC crystallites,

4 shows a scanning electron micrograph of the surface of the sintered body according to FIG. 2,

5 shows a diffractogram of the sintered body surface of an exemplary embodiment,

6, 7 representations of edge zone structures of different sintered bodies,

Fig. 8 is a temperature-time diagram in another

Execution variant,

9 is an illustration of a further edge zone structure of a sintered body,

10, 11 temperature-time diagrams with further examples for process temperature control. A WC-TiC-TiN-TaC-NbC-Co green compact with a composition with 1.3 mass% TiC was subjected to the temperature control shown in FIG. 1. First, the green body was heated for about 3 hours in a vacuum atmosphere to a temperature of 1200 ° C, which was then maintained for about half an hour. An inert gas was then admitted at a pressure of 5 × 10 ³ Pa and the heating was continued at 1485 ° C. until the sintering point was reached. When the sintering point was reached, the inert gas atmosphere was replaced by a nitrogen atmosphere under a pressure of 5 × 10 ⁴ Pa. The sintering temperature was maintained for about half an hour after which the furnace atmosphere was cooled to 1400 ° C. The temperature of 1400 ° C was maintained for about 5 hours after which the sintered body was cooled to room temperature. After reaching the sintering temperature until reaching 1000 ° C in the cooling phase, the nitrogen atmosphere was maintained under the pressure mentioned.

2 and 3 show microstructures of the sintered bodies treated in this way, of the same quantitative composition with different sizes of WC crystallite formation on the surface. 2 there was a higher carbon content in the starting mixture and in the gas atmosphere, which is why the WC crystallite formation on the body surface increased in the sintered body according to FIG. 4. In contrast, the sintered body according to FIG. 3 has fewer and smaller WC crystallites than that according to FIG. 2.

FIG. 4 shows a scanning electron micrograph of the surface of the sintered body according to FIG. 2, which shows that the WC crystallites are firmly integrated into the surface edge zones from which they protrude by 2 μm to 20 μm. Depending on the sintering conditions, ie according to the atmosphere setting, there are more or less large ones between the WC crystallites Share of face-centered cubic phase (Ti, Ta, Nb, W) (C, N) and binder phase. With the same sintered body alloy, one can see from the diffractogram according to FIG. 5 in addition to (hexagonal) WC components cubic face-centered phases (characterized by automotive) with a lattice parameter of 0.4368 nm. The proportion of tantalum and niobium carbides that can be estimated according to this is about 20 mol%. An inhomogeneous and / or at least two-phase structure of the face-centered cubic phase can be derived from the peak shape of the diffraction lines, in a manner similar to that known for cermets with a core-shell structure.

6 shows an edge zone structure of a sintered body of another mixture which has a (larger) proportion of TiC, namely 6% by mass. When this sintered body is treated in the same manner described above, larger proportions of face-centered cubic phase are formed between the WC crystallites protruding from the surface. The WC crystallites are significantly larger than in the case of sintered bodies which have only a lower carbide content in the starting mixture.

An edge zone structure of a further sintered sample is shown in FIG. 7. The starting mixture used there contained approximately twice the proportion of TiN as the pretreated sintered bodies. The structure according to FIG. 7 was obtained when the body was treated in accordance with FIG. 8. In contrast to the temperature control according to FIG. 1, after the holding time at the sintering temperature, the body is cooled to 1200 ° C. and then reheated to 1400 ° C. The temperature of 1400 ° C was maintained for about 2 1/2 hours before the body was cooled.

As can be seen from FIG. 9, WC crystallites protrude from the surface edge zone, which in an intermediate layer with an enrichment of face-centered cubic phase of carbides, Nitrides and carbonitrides of titanium, tantalum, niobium or tungsten border. This layer does not have to be strictly single-phase or homogeneous, but can consist of carbon-rich and low-carbon phases. Certain proportions of binder material are also incorporated into the intermediate layer. Inside the body, the sintered core joins the edge zone, which corresponds in its composition and its layer structure to the overall composition. The described edge structure, which differs in its structure from layers below, is formed in particular by heat treatments with changing temperatures, as can be seen, for example, from FIG. 8. If, on the other hand, a constant temperature is used after high sintering (see FIG. 1), such a face-centered cubic phase hardly forms; likewise, transitions from WC-Co microstructure areas to (Ti, Ta, Nb, W) (C, N) -rich intermediate zones are more continuous and less clear. It can also be clearly seen that the WC crystallites which can be seen in a sintered body according to FIG. 7 protrude far less from the body surface and are accordingly more integrated in the surface zones than in the other cases shown. However, also in the microstructure according to FIG. 7, a proportion of WC crystallite increasing towards the surface can be clearly seen.

Variations in the temperature control are shown in FIGS. 10 and 11. In the temperature profile shown in FIG. 10, the heating speed to temperatures up to 1200 ° C. and up to 1485 ° C. (sintering temperature) is chosen to be greater, namely with 5 ° C./min in comparison to the lower heating speed in the temperature profile according to FIG. 8. The cooling rate following the holding time to the sintering temperature was chosen to be 2 ° C./min. Both the heating rate from 1200 ° C to 1400 ° C and the cooling rate selected after a holding time of approx. 2 1/2 hours is 5 ° C / min. 11, in comparison to FIG. 1, a higher heating rate of 5 ° C./min in the first two heating phases was also chosen instead of the significantly lower heating rate shown in FIG. 1.

Claims

claims

1. Hard metal or cermet body with a hard material phase made of WC and / or at least one carbide, nitride, carbonitride and / or oxicarbonitride of at least one of the elements of the IVa, Va or Vla group of the periodic table and a binder metal phase made of Fe , Co and / or Ni, the proportion of which is 3 to 25% by mass, characterized in that from the body surface by 2 to 20 μm, preferably

Protrude 5 to 10 μm WC crystallites.

2. Tungsten carbide or cermet body according to claim 1, characterized in that the proportion of WC in the hard material phase is at least 50% by mass and a maximum of 96% by mass.

3. Tungsten carbide or cermet body according to claim 1 or 2, characterized in that the WC crystallites form a composite with up to 50 vol .-% of a cubic phase of a further hard material of a different composition and binder metal fractions at the edge of the body.

4. carbide or cermet body according to claim 3, characterized in that the cubic phase consists essentially of carbides, nitrides, carbonitrides and / or oxicarbonitrides of at least one of the IVa, Va and / or Vla elements, the periodic System, in particular of the Ti, wherein the cubic phase can be single or multi-phase.

5. hard metal or cermet body according to one of claims 1 to 4, characterized in that in the structure of the hard metal or cermet body also metals of the IVa, Va and / or Vla group of the periodic table, preferably W, Ta, Nb, Mo and Cr are included.

6. carbide or cermet body according to one of claims 1 to 5, characterized in that the phases with a cubic crystal structure in the hard material phase 30 to 60 mass% Ti, 5 to 15 mass% Ta and / or Nb, 0 to

12 mass% Mo, 0 to 5 masses! V, 0 to 2 mass% Cr, 0 to 1 mass% Hf and / or Zr contain and / or in the binder phase up to 2% Al and / or metallic W, Ti, Mo, V and / or Cr are dissolved.

7. hard metal or cermet body according to one of claims 1 to 6, characterized in that the cubic crystal structure of the hard material phase has a core-edge structure.

8. carbide or cermet body according to one of claims 1 to 7, characterized in that the body edge region consists of several layers with different compositions, wherein a) in an outer, adjoining the body surface and to a depth between 2 microns and 30 μm-reaching first layer, there is an essentially binder phase-free carbonitride phase, which b) adjoins an underlying middle layer with a thickness of 5 μm to 150 μm from an essentially pure WC-Co composition, and that c) in a third lowermost layer With a thickness of at least 10 μm and a maximum of 650 μm, the proportions of the binder phase and the IVa and / or Va elements of the periodic table increase to the essentially constant value present inside the body and the tungsten proportion drops to the essentially constant value inside the body .

9. hard metal or cermet body according to one of claims 1 to 7, characterized in that the body edge region consists of several layers with different compositions, wherein a) in an outer, to the body surface or to an edge zone with a penetration depth of 1 μm up to a maximum of 3 μm subsequent and in the hard material phase reaching a depth between 10 μm and 200 μm, the tungsten and binder phase fraction is a maximum of 0.8 times the proportion resulting from the total composition and in this layer the tungsten and Binder phase content increases substantially continuously towards the inside of the body and the nitrogen content decreases substantially continuously towards the inside of the body, b) that in an underlying middle layer with a thickness between 20 μm and 400 μm, the tungsten and binder phase contents reach a maximum and the contents of elements with increasing penetration depth the IVa and / or r Va group of the periodic table go through a minimum and c) that in a third lowest layer, which extends to a penetration depth measured from the body surface up to a maximum of 1 mm, the tungsten and binder phase fractions fall to essentially constant values inside the body and the contents increase to elements of the IVa and / or Va group of the periodic table to essentially constant values.

10. hard metal or cermet body according to one of claims 1 to 9, characterized in that at least one layer of a carbide, nitride and / or carbonitride of titanium or zirconium and / or of A1 ₂ 0 ₃ and / or of diamond, cubic boron nitride, carbon nitride (CN _X ), fullerenes or other at least one of the elements B, C, N and / or 0-containing compounds.

11. A method for producing a hard metal or cermet body according to one of claims 1 to 9, characterized in that a nitrogen-free mixture of hard materials and binder metals is pressed into a green body and in a vacuum or inert gas atmosphere to between 1200 ° C and Sintering temperature is heated, after which, at the latest when the sintering temperature is reached, a nitrogen and possibly carbon-containing atmosphere is set at least temporarily with a pressure between 10 ³ and 10 ⁷ Pa, preferably between 5 x 10 ³ Pa and 5 x 10 ⁴ Pa if necessary, heated to the sintering temperature and maintained for a holding time of at least 20 min or only a slight cooling of a maximum of 2 ° C / min is carried out in this time of at least 20 min and finally cooled, which when heating or at the latest when reached the sintering temperature set nitrogen and possibly carbon maintaining gas atmosphere is maintained until at least 1000 ° C is reached in the cooling phase.

12. A method for producing a hard metal or cermet body according to one of claims 1 to 9, characterized in that an at least 0.2 mass% nitrogen-containing mixture of hard materials and binder metals is preformed to form a body (green body) and on the sintering temperature is heated, the inert gas or vacuum atmosphere set during the heating at least temporarily from a temperature between 1200 ° C. and the sintering temperature by introducing nitrogen and possibly additionally carbon-containing gases under one Pressure of 10 ³ to 10 ⁷ Pa, preferably of 10 ⁴ Pa to 5 x 10 ⁴ Pa is exchanged for this gas pressure atmosphere, that the body is sintered for at least 0.5 h, preferably 1 h and then cooled, the heating off A gas atmosphere containing nitrogen at 1200 ° C or later is maintained until at least 1000 ° C is reached in the cooling phase.

13. The method according to claim 11 or 12, characterized in that the nitrogen and possibly carbon-containing atmosphere by introducing precursors, i.e. N- and possibly C-containing gases, or possibly by means of C-containing crucible materials, nitrogen and carbon being formed in the gas atmosphere in situ.

14. The method according to any one of claims 11 to 13, characterized in that heated to 1200 ° C during the heating phase and this temperature is held for a period of at least 20 min, preferably more than 1 h, before heating to the sintering temperature is continued.

15. The method according to any one of claims 11 to 14, characterized in that initially in the warm-up phase at about 1200 ° C, the previously existing vacuum through an inert gas atmosphere, preferably at a pressure of 10 ³ Pa to

10 ⁴ Pa, and only when the sintering temperature is reached is the nitrogen and possibly carbon-containing atmosphere set at a higher pressure, preferably> 10 ⁴ Pa.

16. The method according to any one of claims 1 to 15, characterized in that during or after the body has been held or has been at the sintering temperature for at least 0.5 h, the temperature during the cooling phase, preferably at least once, when passing through the eutectic melting point oscillating around the eutectic melting point falls below at least 20 ° C and then exceeds at least 20 ° C, preferably varied by at least 50 ° C.

17. The method according to claim 16, characterized in that the heating and cooling rate and the rate at which the temperature exceeds and falls below the eutectic melting point is up to 10 ° C / min.

18. The method according to any one of claims 11 to 17, characterized in that after reaching the sintering temperature and a holding time of at least 30 min, the atmosphere is cooled to about 1200 ° C and then the atmosphere is heated again at least once to about 1400 ° C, this temperature is held and then cooled again.

19. The method according to any one of claims 17 or 18, characterized in that the cooling speeds and / or heating speeds are between 2 ° C / min and 5 ° C / min.

20. The method according to any one of claims 11 to 19, characterized in that the gas mixture set after reaching the sintering temperature of N ₂ and CO with N ₂ / (N ₂ + CO) is between 0.1 and 0.9.

21. The method according to any one of claims 11 to 20, characterized in that after reaching the sintering temperature by a fluctuating in the mean pressures are set, which deviate 10% to 80% of an average.

2. The method according to any one of claims 11 to 20, characterized in that the sintered body is finally subjected to a surface etching treatment by means of gases or liquids.