EP1095168B1 - Hard metal or ceramet body and method for producing the same - Google Patents

Abstract

The invention relates to a hard metal or cermet 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 cermet surface of the by 2 to 20 mum in order to improve the adhesion of surface layers that are applied.

Description

The invention relates to a hard metal or cermet body a hard phase from WC and / or at least one carbide, Nitride, carbonitride and / or oxicarbonitride at least one the elements of the IVa, Va or VIa group of the periodic table and a binder metal phase on Fe, Co and / or Ni, their proportion 3 to 25 mass%.

The invention further relates to a method of manufacture of such a hard metal or cermet body with a WC content between 50 mass% and 96 mass% by mixing, Grinding, granulating and pressing a corresponding component containing starting mixture and subsequent 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 that 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 is between 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 at a depth between 5 µm and 50 µm from the substrate surface is present, and the substrate surface has a hardness of 20 to 90% of the maximum hardness. To make this Cermets becomes the pre-pressed mixture of an initial temperature increase to 1100 ° C in a vacuum, followed by an increase in temperature from 1100 ° C to a temperature range between 1400 ° C and 1500 ° C in a nitrogen atmosphere, and one then subjected to 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, the hardness of which is not less than 1 mm higher than in the interior of the cermet, the binder content being able to be minimized in a layer thickness of 0.5 to 3 μm compared to the core substrate. 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 Al ₂ O ₃ . To produce this body, a green compact is first heated to a temperature between 1100 ° C and 1400 ° C under vacuum, then nitrogen gas is admitted 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 layer close to the surface 10 µm thick to 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, optionally in combination with CH ₄ , CO, CO 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 have the surface either different binder levels what is recognizable by spotty appearance, or tend to stick of the binder with the sinter pad, what because of that associated response to changes in composition in the Contact zone leads. Another disadvantage of the so far after Cermets known in the prior art are those with increased binding metal contents poor adhesion from there in the surface applied wear protection layers. If nickel shares occur in the surface is not a CVD coating at all possible. To influence the surface near Zone is therefore proposed in DE 44 23 451 A1 a cermet which has a hard material content of 95 to 75 mass% and 5 to Has 25% by mass of Co and / or Ni binder, the hard material phase made of carbonitrides with a cubic B1 crystal 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) is between 0.15 and 0.7. In a 0.01 up to 3 µm determined surface layer depth is the content of Binder phase in relation to the underlying cermet core area less than 30 mass%. The titanium content is in this zone 1.1 to 1.3 times the size of the underlying cermet core areas, whereas the sum of the tungsten contents, 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 a alternative embodiment of this cermet is in the same Surface edge zone the relative content of binder phase 90 mass%, the relative Ti content 100% to 120% and the Sum of the contents of tungsten, tantalum and possibly molybdenum, niobium, Vanadium, chromium between 80 mass% and 110 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, grinding, 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., a gas mixture of N ₂ and Co with an N ₂ / (N ₂ + is in the furnace atmosphere CO) ratio varies between 0.1 and 0.9 under an alternating around a mean pressure of 10% to 80% of an average value in a period 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 one Sintered hard metal alloy with at least 75% by weight and maximum 95% by weight of hard phase, titanium, an element of Group VIa of the periodic table and WC, rest of the binder phase Contains nickel and cobalt. The alloy has 5 wt .-% to 60% by weight 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 supposed to be a soft, outermost surface layer own, which consists of a binder phase and toilet. Under this outermost layer is a 3 µm to 30 µm thick Layer consisting essentially of WC with low binder metal content should exist.

A cemented carbide alloy of the composition mentioned at the beginning also describes EP 0 822 265 A2. The one from here produced sintered body should have an edge area that divided into three layers, of which the outermost layer a WC content between 0 and 30 vol .-%, remainder binder phase, the middle layer 50 vol.% to 100 vol.% WC, remainder binder phase, and a third lowest layer has a toilet volume fraction between 0 and 30 vol .-%, the rest of the binder.

It is an object of the present invention, one for a CVD or PVD coating suitable carbide or cermet body to create an improved adhesion for the surface layers of covalent hard materials separated from the gas phase such as. Diamond, cubic boron nitride, carbon nitride, Fullerenes and metallic hard materials (carbides, Nitrides, carbonitrides or oxicarbonitrides of the elements of the IVa to VIa group of the periodic table) and others Layers which contain at least one of the elements B, C, N or O, guaranteed.

This task is performed by a hard metal or cermet body solved according to claim 1, characterized in accordance with the invention is that from the body surface around 2 to 20 microns, preferably Project 5 to 10 µm WC crystallites. Through this Crystals a coarse-grained surface morphology is generated, which determines the adhesion of applied surface layers Interlocking of the crystallites with the separated phases creates. These WC crystallites are in the edge zone near the surface so firmly integrated that they can also be used as a trial performed grinding work did not break out. The created one Surface roughness thus provides an ideal "Anchoring" for the application of surface coatings.

Further developments of the invention are in the subclaims 2 to 7 described.

The proportion of WC in the entire hard material phase of the hard metal or cermet body with at least 50 mass% and maximum 96 mass%. The WC crystallites are preferably on the Body edge zone or surface with up to 50 vol .-% one cubic phase of another hard material of different composition and binder metal parts connected. This cubic phase can essentially of carbides, nitrides, carbonitrides and / or Oxicarbonitriden at least one of the IVa, Va and / or VIa 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, in the structure of the hard metal or cermet body, especially in the marginal zone near the body surface also metals from the IVa, Va and / or VIa group of Periodic table, preferably W, Ta, Nb, Mo and Cr, included his. The cubic phases in the peripheral zone can each have a homogeneous structure or a local core-edge structure, as it is basically known at 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 mass% chromium, 0 contain up to 1 mass% hafnium and / or zirconium, in the binder phase up to 2% aluminum and / or metallic Tungsten, titanium, molybdenum, vanadium and / or chromium are dissolved.

The edge zones near the surface can be essentially homogeneous be built or a gradient in the composition have or near-surface marginal zones different Composition, being in an outer, attached to the body surface subsequent and to a depth of between 2 µm and 3 µm first layer a substantially binder phase free Carbonitridphase is located on an underlying middle layer with a thickness of 5 microns to 150 microns adjoins an essentially pure WC-Co composition and which is followed by a third bottom layer with a thickness of at least 10 µm and a maximum of 650 µm, the proportions of Binder phase and the IVa and / or Va elements on the inside of the body present, substantially constant value and the proportion of tungsten on the inside of the body essentially constant value drops. The different layers of the sintered body described above merge continuously about, preferably as the metal of the carbonitride phase Titanium is used. The content of titanium and / or another Element of the IVa to VIa group of the periodic table, tungsten except, is maximum in the outer layer, then falls steeply to a minimum when transitioning to the middle layer Value decreases and increases with the transition to the third lowest Layer up to a penetration depth of approx. 800 µm from the Surface gradually measured from a medium to that Proportion of the total composition corresponding value inside the body back on, but below the titanium or other Metal content in the outer layer. In corresponding Is the nitrogen content in the middle Layer minimal and rises at the transition to the outermost Layer on proportions above average nitrogen content of the alloy that are present in the core interior are. Contrary to this, increase at the transition from the outermost layer to the middle layer the contents of tungsten and cobalt. The hard material phase WC can possibly only formed from (Ti, W) C or (Ti, W) (C, N) during sintering. Preferably is the binder phase content in the middle Layer maximum 0.9 times the binder phase content inside the body, while the tungsten portion in this middle Layer at least 1.1 times that inside the body Proportion of tungsten.

As an alternative to this, such border zone areas are also possible, where the individual layers are not sharply apart are separated, but the respective metal and non-metal parts of the alloy gradually over wide transition areas to change. The body characterized according to claim 9 meets in three layers forming the edge area the following conditions:

In an outer, on the surface of the body or on one Edge zone with a penetration depth of 1 to a maximum of 3 µm subsequent and to a depth between 10 microns to 200 microns reaching the layer is the tungsten and the binder phase maximum 0.8 times that of the total composition resulting share. The tungsten mouth rises in this layer the binder phase portion to the inside of the body essentially continuously, whereas the nitrogen content at The body's interior essentially falls off continuously. In an underlying middle layer of a thickness between 20 µm and 400 µm pass through with increasing depth of penetration the tungsten and binder phase contents a maximum and Contents of elements of the IVa and / or Va group of the periodic table a minimum. In a third, lowest layer, the up to a depth of penetration measured from the body surface of a maximum of 1 mm, the tungsten and binder phase fractions fall to essentially constant values inside the body which correspond to the share in the total composition, and the contents of elements of the IVa and Va groups of the periodic table, Titanium in particular rise to essentially constant values. The nitrogen content remains at the transition from the middle layer to the lowest layer down to The inside of the body is essentially constant.

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

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

For the production of the carbide or cermet body described above is worked according to claim 8 or 9, wherein the Process techniques set out between starting mixtures distinguish in which nitrogen is already contained and those that are free of nitrogen.

In the case of nitrogen-free mixtures of hard materials with a WC content between 50 mass% and 96 mass% and binding metals, these are pressed into a green body and first in a vacuum to about 1200 ° C and then in an 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 at least temporarily 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.

Contains at least a nitrogen content in the starting mixture 0.2 mass% based on the total hard material mass, that can Nitrogen-containing gas also later, but at the latest when it is reached the sintering temperature and the nitrogen content in the starting mixture also to a lesser degree of partial pressure be introduced into the furnace atmosphere. In any case must about the process and / or the starting mixture be sure that enough carbon and Tungsten components for the formation of the WC crystallites on the surface available. Possibly. the sinter hold time is corresponding to extend.

Developments of the method are described in claim 10.

So it is also possible in a variation of the method that Nitrogen and possibly carbon-containing atmosphere Introduction of precursors, i.e. containing nitrogen and possibly carbon Gases or possibly also those containing carbon Crucible materials to adjust that under prevailing temperature and pressure nitrogen and carbon forms in situ.

With the time span and with the gas composition at which the sintered body is at above eutectic temperatures, can affect the size and frequency of WC crystallites become. This leads to longer treatment times and a longer one Share of carbon to larger and / or more frequently occurring WC crystallites.

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

Within the scope of the present invention there is also a process control at first in the warm-up phase until about 1200 ° C the body is exposed to a vacuum, which then by an inert gas atmosphere (e.g. noble gas atmosphere) is replaced.

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 can be made of a hard metal or a cermet after at least one Maintaining the sintering temperature of a "pendulum annealing" for 0.5 hours undergo, i.e. a temperature control in which at least once, preferably several times, the eutectic melting point is oscillating below and exceeded, the Temperature by at least 20 ° C, preferably at least 50 ° C, each exceeds and falls below the eutectic point. The heating and cooling rates and the Speed at which the temperature the eutectic Melting point falls below and exceeds at maximum 10 ° C / min. However, cooling and / or heating rates are preferred between 2 ° C / min and 5 ° C / min.

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, it is possible within the scope of the present invention after reaching the sintering temperature by an average fluctuating pressures of those containing nitrogen and possibly carbon Atmosphere, with pressures around 10 to 80% deviate from an average value which depends on the binder content is chosen. A corresponding procedure is explained for example in DE 44 23 451 A1, to which reference is made becomes.

According to a development of the invention, the surface of the finished sintered body using gases or liquids are subjected to an etching treatment, whereby the WC crystallites emerge more clearly through relief formation. In particular, this measure can be used to remove binder metal components serve on the substrate body surface, which at a diamond coating is undesirable.

Fig. 1

ein Temperatur-Zeit-Diagramm,

Fig.2, 3

Gefügeausbildungen an einer Sinterkörper-Randzone mit unterschiedlichen WC-Kristalliten,

Fig. 4

eine rasterelektronenmikroskopische Aufnahme der Oberfläche des gesinterten Körpers nach Fig. 2,

Fig. 5

ein Diffraktogramm der Sinterkörperoberfläche eines Ausführungsbeispieles,

Fig. 6, 7

Abbildungen von Randzonen-Gefügen unterschiedlicher Sinterkörper,

Fig. 8

ein Temperatur-Zeit-Diagramm in einer weiteren Ausführungsvariante,

Fig. 9

eine Abbildung eines weiteren Randzonengefüges eines Sinterkörpers,

Fig. 10, 11

Temperatur-Zeit-Diagramme mit weiteren Beispielen zur Prozeßtemperaturführung.

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

Fig. 1

a temperature-time diagram,

Fig. 2, 3

Microstructure formation on a sintered body edge zone with different WC crystallites,

Fig. 4

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

Fig. 5

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

6, 7

Images of marginal zone structures of different sintered bodies,

Fig. 8

a temperature-time diagram in a further embodiment,

Fig. 9

an image of another 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 those treated in this way Sintered body same quantitative composition with different large WC crystallite formation on the surface. at 2 was in the starting mixture and in the gas atmosphere has a higher carbon content, which is why 4 the WC crystallite formation on the Body surface appeared more. The sintered body after 3 has fewer and smaller toilet crystallites than that of FIG. 2.

Fig. 4 shows a scanning electron micrograph of the 2 that reveals the surface of the sintered body that the WC crystallites are firmly integrated into the surface edge zones from which they protrude by 2 µm to 20 µm. Between the WC crystallites are depending on the sintering conditions, i.e. after setting the atmosphere more or less large Proportion of face-centered cubic phase (Ti, Ta, Nb, W) (C, N) as well as binder phase. With the same sintered body alloy can be seen from the diffractogram according to FIG. 5 next to (hexagonal) WC proportions of face-centered cubic phases (marked by vehicle) 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%. From the peak shape of the diffraction lines can be an inhomogeneous and / or at least two-phase structure similar to the cubic face-centered phase as this is known from cermets with a core-shell structure is.

6 shows an edge zone structure of a sintered body another mixture that contains a (larger) proportion of TiC, namely 6 mass%. When treating this sintered body in the In the same way as described above, larger portions form face-centered cubic phase between those from the surface outstanding WC crystallites. The toilet crystallites are significantly larger than with sintered bodies, which are only a smaller one Have 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 about twice as large a proportion of TiN as the pretreated sintered body. The structure according to Fig. 7 was during a treatment of the body obtained according to Fig. 8. In contrast to the temperature control 1 is after the hold time the sintering temperature of the body cooled to 1200 ° C and thereafter reheated to 1400 ° C. The temperature of 1400 ° C has been maintained for about 2 1/2 hours before the body has cooled down.

As can be seen from Fig. 9 protrude from the surface edge zone WC crystallites out in an intermediate layer with a Enrichment of face-centered cubic phase from carbides, Nitrides and carbonitrides of titanium, tantalum, niobium or Wolframs adjoins. This layer does not have to be strictly single-phase or be homogeneous, but can be made of higher carbon and there are low-carbon phases. Are in the intermediate layer certain proportions of binder material are also incorporated. in the The interior of the body connects to the edge zone of the sintered core, which in its composition and its layer structure Overall composition corresponds. The outlined structure, those in their structure from layers below deviates, is particularly due to heat treatments with changing Temperatures such as those shown in FIG. 8 are recognizable, trained. In contrast, with a constant Temperature worked after high sintering (see Fig. 1) forms such a face-centered cubic phase is hardly apparent; transitions from WC-Co structural areas are also closed (Ti, Ta, Nb, W) (C, N) -rich intermediate zones more continuous and blurred. It is also clearly recognizable that the one The sintered body according to FIG. 7 recognizes WC crystallites far less protrude from the surface of the body and accordingly more in the surface zones are included as shown in the rest Cases. However, the structure is also 7 an increasing towards the surface WC crystallite content clearly visible.

Variations in the temperature control are shown in FIGS. 10 and 11. In the temperature profile shown in Fig. 10 is the heating rate to temperatures up to 1200 ° C and up 1485 ° C (sintering temperature) chosen larger, namely with 5 ° C / min compared to the lower heating speed at the 8. The temperature profile according to Fig. 8. Which depends on the holding time Sintering temperature subsequent cooling rate was with 2 ° C / min selected. Both the heating rate of 1200 ° C up to 1400 ° C as well as after a holding time of approx. 2 1/2 The cooling rate selected for hours is 5 ° C / min.

11 is compared to Fig. 1 also a higher heating rate of 5 ° C / min in the first two heating phases instead of that shown in Fig. 1 significantly lower heating rate selected Service.

Claims (10)

1. Hard metal or cermet body with a hard material phase of WC and/or at least one carbide, nitride carbonitride and/or oxicarbonitride of at least one element of groups IVa , Va or VIa of the classification of elements and a binder metal phase of Fe, Co and/or Ni, whose proportion amounts to 3 to 25 % by mass,
   characterised in that
   WC crystallites project from the body surface by 2 to 20 µm, preferably by 5 to 10 µm.
2. Hard metal or cermet body according to claim 1, characterised in that the WC-content in the hard material phase amounts to at least 50 % by mass and maximally to 96 % by mass and/or that in the texture of the hard metal or cermet body also metals of the groups IVa, Va and/or VIa of the classification of elements, preferably E, Ta, Nb, Mo and Cr are bound.
3. Hard metal or cermet body according to claim 1 or 2, characterised in that the WC crystallites at the body surface rim form a compound with up to 50 % by volume of a cubic phase of further hard material of a different composition and with binder metal parts, whereby preferably the cubic phase consists substantially of carbides, nitrides, carbonitrides and/or oxicarbonitrides of at least one of the elements of groups IVa, Va and/or VIa of the classification of elements, particularly of Ti, whereby the cubic phase can be a single-phased or multiphased and/or that the cubic crystal structure of the hard material phase has a core-rim structure.
4. Hart metal or cermet body according to one of claims 1 to 3, characterised in that the phases with cubic crystalline structure in the hard material phase contain 30 to 60 % by mass Ti, 5 to 15 % by mass Ta and/or Nb, 0 to 12 % by mass Mo, 0 to 5 % by mass V, 0 to 2 % by mass Cr, 0 to 1 % by mass Hf and/or Zr and/or in the binder phase up to 2 % Al and/or metallic W, Ti, Mo, V and/or Cr are dissolved.
5. Hart metal or cermet body according to one of claims 1 to 4, characterised in that the body-rim area consists of several layers with different composition, whereby

   a) in a first outer layer adjacent to the body surface and reaching to a depth between 2 µm and 30 µm a carbonitride phase essentially free of binder phase is present, which

   b) borders on an underlying intermediate layer with a thickness of 5 µm to 150 µm of a substantially pure WC-Co composition and that

   c) in a third innermost layer with a thickness of at least 10 µm and maximum 650 µm the contents of a binder phase and of the elements of groups IVa and/or Va of the classification of elements increase to the substantially constant value existing in the body interior and the tungsten content decreases to the substantially constant value in the body interior.
6. Hard metal or cermet body according to one of claims 1 to 4, characterised in that the body-rim-zone consists of several layers with different compositions, whereby,

   a) in an outer layer adjacent to the body surface or to a rim zone, with a penetration depth of 1 µm to maximum 3 µm, and reaching to a depth between 10 µm and 200 µm, in the hard material phase the content of tungsten and binder phase amounts maximally to 0,8 times the content resulting from the general composition and that in this layer the tungsten and binder phase content increases substantially continuously towards the body interior and the nitrogen content decreases substantially continuously towards the body interior,

   b) that in an underlying intermediate layer of a thickness between 20 µm and 400 µm, the tungsten and binder phase content run through a maximum with progressing depth and the contents of elements of the groups IVa and/or Va of the classification of elements run through a minimum and

   c) in a third innermost layer, which reaches to a penetration depth of maximum 1 µm measured from the body surface, the tungsten and binder phase contents decrease to the substantially constant values in the body interior and the contents of elements of groups IVa and/or Va of the classification of elements increase to substantially constant values.
7. Hard metal or cermet body according to one of claims 1 to 6, characterised in that at least one layer consists of a carbide, nitride and/or carbonitride of titanium or zirconium and/or of Al₂O₃ and/or diamond, cubic boron nitride, carbon nitride (CN_x), fuller's earth or another compound containing at least one of the elements B, C, N and/or O.
8. Method for the production of a hard metal or cermet body with a WC-content in the hard material phase between 50 % by mass and 96 % by mass according to one of claims 1 to 7, characterised in that a nitrogen-free mixture of hard materials and binder metals is prepressed into a green compact and heated in a vacuum or inert gas atmosphere to a temperature lying between 1200°C and the sintering temperature, after which at the latest when the sintering temperature is reached, a nitrogen-containing and optionally a carbon-containing atmosphere with a pressure between 10³ and 10⁷ Pa, preferably between 5 x 10³ Pa and 5 x 10⁴ Pa is set at least temporarily, optionally heated subsequently to the sintering temperature and the latter maintained over a holding time of at least 20 min, or in this time of 20 min only a slight cooling of maximum 2°C/min is performed, and finally cooled down, whereby the nitrogen-containing and optionally carbon-containing gas atmosphere set during heating or the latest when the sintering temperature was reached, is maintained in the cooling phase until at least 1000°C are reached.
9. Method for producing a hard metal or cermet body according to one of claims 1 to 7, characterised in that at least 0,2 % by mass of a nitrogen-containing mixture of hard materials and binder materials are preshaped into a body (green compact) and heated to the sintering temperature, whereby the inert gas atmosphere or vacuum set during heating, starting from a temperature of 1200°C to the sintering temperature, is at least temporarily replacing this gas pressure atmosphere by introducing nitrogen-containing and optionally in addition carbon-containing gases under a pressure of 10³ Pa to 10⁷ Pa, preferably of 10⁴ Pa to 5 x 10⁴, that the body is sintered for at least 0,5 hours, preferably for 1 hour and subsequently cooled down, whereby the nitrogen-containing atmosphere set during heating at 1200°C or later is maintained until in the cooling phase at least 1000°C are reached.
10. Method according to claim 8 or 9, characterised in that the nitrogen-containing and optionally carbon-containing atmosphere is set by introducing precursors, i.e. N-containing and optionally C-containing gases, or optionally by introducing C-containing crucible materials, whereby nitrogen and carbon are formed in the gas atmosphere in situ and/or that during heating the temperature is increased up to 1200°C and this temperature is maintained for at least 20 min, preferably for more than 1 hour, before continuing the heating up to the sintering temperature.

Images