EP1999087A1

EP1999087A1 - Sintered wear-resistant boride material, sinterable powder mixture for producing said material, method for producing the material and use thereof

Info

Publication number: EP1999087A1
Application number: EP07723199A
Authority: EP
Inventors: Hubert Thaler; Clemens Schmalzried; Frank Wallmeier; Christoph Lesniak
Original assignee: ESK Ceramics GmbH and Co KG
Current assignee: ESK Ceramics GmbH and Co KG
Priority date: 2006-03-24
Filing date: 2007-03-12
Publication date: 2008-12-10
Also published as: US20090105062A1; WO2007110149A1; DE102006013746A1; CN101410347A

Abstract

The invention relates to a sintered wear-resistant material based on transition metal diborides, comprising: a) as the main phase 80-98.8% by weight of a fine-grained transition metal diboride or transition metal diboride mixed crystal of at least two transition metal diborides or mixtures of such diboride mixed crystals or mixtures of such diboride mixed crystals with one or more transition metal diborides, wherein the transition metals are selected from the IV to VI subgroups of the periodic system, b) as the second phase 0.2 to 5% by weight of a continuous, oxygen-containing grain boundary phase, and c) as the third phase 1 - 15% by weight of particulate boron carbide and/or silicon carbide. Furthermore, the invention relates to a powdered sinterable mixture for producing such a sintered material, a method for producing the sintered material, preferably by pressureless sintering, and also the use of the sintered material for producing wearing parts in general mechanical engineering, in particular chemical plant engineering.

Description

SINTERED WEAR-RESISTANT BORIDE, SUSTAINABLE POWDER MIXTURE FOR THE MANUFACTURE OF THE MATERIAL, A MIXTURE FOR THE MATERIAL OF THE MATERIAL AND THE USE THEREOF

Field of the invention

The invention relates to a sintered wear-resistant material based on transition metal diborides, pulverulent sinterable mixtures for producing such a sintered material, method for producing such sintered sintered materials and the use of the sintered material for the production of wearing parts in general plant construction, in particular chemical plant construction, for Production of tools for machining as well as chipless machining and shaping, as well as electrode material for sliding contacts, welding electrodes and erosion pins.

Background of the invention

Titanium diboride has a number of advantageous properties, such as a high melting point of 3,225 ° C, a high hardness of 26-32 GPa (HV), excellent room temperature electrical conductivity and good chemical resistance.

A major disadvantage of titanium diboride is its poor sinterability. The poor sinterability is due in part to impurities, especially oxygen impurities in the form of TiÜ ₂ , which are contained in the commonly used titanium diboride powders, either by the carbothermal reduction of titanium oxide and boron oxide or by the known as Borcarbidverfahren reduction of me talloxide with Carbon and / or boron carbide are produced. Such oxygen impurities enhance grain and pore growth in the sintering process by increasing surface diffusion.

State of the art

Sintered titanium diboride materials can be made by the hot pressing process. For example, by axial hot pressing with sintered achieved temperatures above 1.80O ⁰ C and a pressure of> 20 MPa densities of above 95% of the theoretical density, wherein the hot-pressed material typically has a grain size of more than 20 microns. However, the disadvantage of the hot pressing method is that only simple body geometries can be produced thereby, while bodies or components with complex geometries can not be produced by this method.

On the other hand, components with more complex geometries can be produced via the pressure-loss sintering process. In this case it is necessary to add suitable sintering aids in order to obtain sintered bodies of high density. Possible sintering additives are, for example, metals, such as iron and iron alloys. By adding small amounts of iron, dense materials with good mechanical properties and high fracture toughnesses of more than 8 MPa m ^1/2 can be obtained. Such materials are described for example in EP 433 856 B l. However, these materials with a metallic binder phase, which are also referred to as cermets, have the disadvantage that they have a poor corrosion resistance to air or oxygen and in particular to acids and bases due to the metallic binder phase. Because of their reactivity to acids and bases, these materials can not be used in chemical plant engineering.

US-A-5,108,670 describes a method of making a titanium diboride sintered material having improved toughness which does not contain a metallic binder phase. For the production of the sintered material Titandi- is boride with up mixed to 10 wt .-% Chromdiborid, the mixture in the form of pressed and then θ in a powder bed consisting of Y ₂ ^* sintered ₃ Resins in a microwave oven, wherein the Y ₂ O ₃ then washed with reacts the TiB ₂ and forms a yttrium-titanium oxide phase, so that a TiB ₂ material is formed with oxidic second phase. Although a higher fracture toughness of about 6 MPa m ^{1/2 is} achieved with this material. The disadvantage, however, is that only a hardness of up to 18 GPa is achieved, which is very low for wear applications. In addition, the process of sintering in the powder bed is unsuitable for the production of large-volume components as well as components with thicker wall thicknesses, since a homogeneous distribution can not be achieved.

Object of the invention The invention is therefore based on the object of providing a sintered material which not only has good mechanical properties, such as high hardness, high strength and high toughness, but is also oxidation-resistant and corrosion-resistant, in particular to acids and alkalines , And if necessary, even at high temperatures has good mechanical properties. Furthermore, such a sintered material should be producible by a simple and inexpensive process, which also allows the production of moldings with complex geometries.

Summary of the invention

The above object is achieved by a sintered wear-resistant material based on Übergangsmetalldi- boriden according to claim 1, a powdered sinterable mixture for producing such a sintered material according to claim 8, a method for producing such a sintered material according to claims 15 and 16, and the use of the sintered material according to claims 22-26. Advantageous or particularly expedient embodiments of the subject of the application are specified in the subclaims.

The invention thus relates to a sintered wear-resistant

A material based on transition metal diborides, comprising a) as the main phase 80-98.8% by weight of a fine-grained transition metal diboride or transition metal diboride mixed crystal of at least two transition metal diborides or mixtures of such diboride mixed crystals or mixtures of such diboride mixed crystals with one or more a plurality of transition metal diborides, wherein the transition metals from the IV. to VI. B) as secondary phase 0.2 to 5 wt .-% of a continuous, oxygen-containing grain boundary phase, and c) as a third phase 1- 15 wt .-% particulate boron carbide and / or silicon carbide.

The invention further provides a pulverulent sinterable mixture for producing a sintered material based on transition metal diborides, comprising 1) 0.05-2% by weight of Al and / or Si as metallic Al and / or Si and / or an amount of an Al and / or Si compound corresponding to this content,

2) optionally at least one component selected from carbides and borides of transition metals of IV. To VI. Subgroup of the periodic table,

3) 0.5-19 wt% boron,

4) 0-15 wt .-% boron carbide and / or silicon carbide, and

5) as the remainder at least one transition metal diboride of IV. To VI. Subgroup of the periodic table, which is different from the transition metal boride of the above component 2).

The invention furthermore relates to a process for the production of such a sintered material by hot pressing or hot isostatic pressing or gas pressure sintering or spark plasma sintering of a pulverulent mixture as described above, optionally with the addition of organic binding and pressing aids.

The invention likewise provides a process for producing a sintered material as described above by pressure-sintering, comprising the steps:

a) mixing a powdery mixture as described above, optionally with the addition of organic binding and pressing aids in water and / or organic solvents for producing a homogenous powder suspension, b) preparing a powder granulate from the powder suspension, c) pressing the powder granules into green bodies high density, and d) pressure sintering of the green bodies obtained in vacuo or under protective gas at a temperature of 1,800 - 2,200 ⁰ C.

The sintered material according to the invention is suitable for the production of wearing parts in general plant construction, in particular in chemical plant construction due to its corrosion resistance to acids and bases, in thermal plant construction, in paper machines, in the milling and wear protection. The invention also relates to the use of the sintered material for the production of tools for machining as well as for non-cutting machining and shaping, forming technology and pulleys. Another use relates to the production of water and sandblast nozzles.

The sintered material according to the invention is likewise suitable as electrode material for sliding contacts, welding electrodes and erosion pins.

According to the invention, it has thus been found that the above-mentioned object is achieved by providing a sintered, wear-resistant, transition-metal diboride-based dense material whose matrix (main phase) consists of a fine-grained transition metal diboride or transition metal diboride mixed crystal or combinations thereof. As a second phase, the material contains an oxygen-containing, continuous grain boundary phase, which is formed as a thin continuous grain boundary film. At the triple points, larger portions or areas of the oxygen-containing second phase may be present. As a third phase, the material contains particulate boron carbide and / or silicon carbide, which acts as a grain growth inhibitor. The mixed crystal formation of the main phase has an additional grain growth inhibiting effect, so that a sintered material having good mechanical properties is obtained. The sintered material according to the invention has a surprisingly excellent corrosion resistance to acids and alkalis while retaining very good mechanical properties.

Detailed description of the invention

As mentioned above, the microstructure of the material according to the invention consists of a transition metal diboride or transition metal diboride mixed crystal of at least two transition metal diborides or mixtures of such diboride mixed crystals or mixtures of such diboride mixed crystals with one or more transition metal diborides. As a second phase, there is a continuous oxygen-containing grain boundary film with a small thickness of, for example, about 2 nm. At the triple points, larger proportions or ranges of the oxygen-containing second phase. As a third phase, particulate boron carbide and / or silicon carbide, which is predominantly located at the grain boundaries, is present in a small proportion. The boron carbide and / or silicon carbide additionally acts as a particle-reinforcing agent. If appropriate, small amounts of particulate carbon and / or particulate boron may also be present in the material. Furthermore, when using Al or Si or their compounds as sintering aids, low contents of these elements may be present in the main phase. The proportion of the oxygen-containing second phase is preferably up to 2.5 wt .-%.

The main phase preferably has an average particle size of less than 20 μm, more preferably less than 10 μm. The boron carbide and / or silicon carbide of the third phase preferably has an average particle size of less than 20 microns, more preferably less than 5 microns, and the proportion of this third phase is 1-15 wt .-%, preferably 1 -4 wt .-%.

The determination of the mean grain size of the main phase and of the average particle size of the boron carbide and / or silicon carbide is carried out by the line intercept length method on the etched cut.

The transition metals of IV. To VI. Subgroups are preferably selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W.

The main phase is preferably fine-grained TiB ₂ and / or ZrB ₂ and / or a mixed crystal of (Ti ₁ W) B ₂ and / or (Zr ₁ W) B ₂ and / or (Ti ₁ Zr) B ₂ , more preferably a mixed crystal of (Ti, W) B ₂ and / or (Zr ₁ W) B ₂ , including the ternary diborides (Ti, Zr, W) B ₂ . Particularly preferably, it is the mixed crystal (Ti, W) B ₂ or the mixed crystal (Zr. W) B ₂ .

The pulverulent, sinterable mixture according to the invention for producing a sintered material according to the invention contains the following components:

1) 0.05-2% by weight, preferably 0.2-0.6% by weight, of Al and / or Si as metallic Al and / or Si and / or an amount of an Al corresponding to this content. and / or Si compound. Al or oxygen-containing Al compounds, in particular Al ₂ O 3 or boehmite, are preferably used. 2) optionally, preferably ≥ 0.25 wt .-% of at least one component selected from carbides and borides of transition metals of IV. To VI. Subgroup of the Periodic Table, preferably tungsten carbide. Optionally, as component 2), transition metals of IV. To VI. Subgroup itself and oxides of such transition metals are used.

3) from 0.5 to 19% by weight, preferably from 1 to 5% by weight, of boron in elemental form,

4) 0-15% by weight, preferably 0.5-5% by weight of boron carbide and / or silicon carbide,

5) As the remainder at least one transition metal diboride of IV. To VI. Subgroup of the periodic table, which is different from the transition metal boride of the above component 2). As already mentioned above, the transition metals are selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W. The transition metal diboride of component 6) is preferably TiB ₂ and / or ZrB ₂ , more preferably TiB ₂ ,

The above components of the pulverulent mixture are preferably used in the highest possible purity and with a small particle size. For example, the transition metal diboride of component 5) preferably has an average particle size of not more than 4 μm, more preferably not more than 2 μm.

The sintered material according to the invention can be produced in a manner known per se by hot pressing, hot isostatic pressing, gas pressure sintering or spark plasma sintering of a pulverulent mixture as described above, optionally with the addition of organic binding and pressing aids. In this case, customary organic binders such as polyvinyl alcohol (PVA), water-soluble resins and polyacrylic acids and customary pressing aids such as fatty acids and waxes can be used.

To produce the sintered material according to the invention, at least one transition metal diboride of IV. To VI. Subgroup processed with the other powder-shaped components and optionally organic binding and pressing aids in water and / or organic solvents to form a homogeneous powder suspension. The homogeneous powder suspension is then transferred to a powder granules, preferably by spray drying.

This powder granulate can then be further processed by hot pressing or hot isostatic pressing to form a sintered material.

According to a preferred embodiment, the production of the sintered material according to the invention by Drucklossintern. In this case, a powder granules obtained as described above are pressed into green bodies of high density. For this purpose, it is possible to use all customary shaping methods, such as axial pressing or calcostatic pressing, but also extrusion, injection molding, slip casting and pressure slip casting. The green bodies obtained are then transferred in a vacuum or under protective gas at a temperature of 1,800-2,200 ° C., preferably 1,900-2,100 ⁰ C, more preferably about 2,000 ⁰ C, by pressureless sintering in a sintered material.

Preferably, the green bodies are annealed prior to pressure-sintering in an inert atmosphere at temperatures below the sintering temperature to remove the organic binding or pressing aids.

The materials obtained by pressure-sintering have a density of at least about 94% of the theoretical density, preferably a density of at least 97% of the theoretical density. Such density values ensure that porosity, if present, is present as closed porosity. Optionally, the sintered material may be densified by hot isostatic pressing to increase the density and to reduce the closed porosity.

The carbides of transition metals of the IV. To VI. Subgroup of the periodic table selected component of the powdery starting mixture reacts during the sintering process with the added boron to Übergangsmetallborid and boron carbide. The transition metal boride formed and / or the added transition metal boride of the above-mentioned component 2) can form a mixed crystal with the transition metal diboride of component 5) used, such as titanium diboride. This boride mixed crystal formation has a grain growth inhibiting effect. The boron carbide, both added and that formed, for example, from tungsten carbide and boron, also acts to inhibit grain growth. The Al and / or Si or their compounds act as sintering aids, the microstructure formed indicating a liquid-phase sintering process.

The sintered material according to the invention is outstandingly suitable for the production of wearing parts in general plant construction, in particular chemical plant construction, thermal plant construction, in paper machines, in grinding technology and in wear protection. Special applications of the sintered material according to the invention are tools for cutting machining as well as for non-cutting machining and shaping, for the forming technique and for deflection rollers. Furthermore, it is suitable for the production of water or sandblast nozzles, as well as electrode materials for sliding contacts, welding electrodes and erosion pins.

Brief description of the attached drawings

Figure 1 shows a light micrograph of the microstructure of the material obtained in Example 1;

Figure 2 is a photomicrograph of the microstructure of the sintered material obtained in Example 2;

Figure 3a shows a TEM brightfield image of a representative area of the microstructure of Figure 1;

Figures 3b and 3c show the EELS spectra associated with Figure 3a concerning the elemental qualitative composition of the investigated oxygen-containing secondary phase;

Figure 4a shows a TEM brightfield image of a representative (Ti, W) B ₂ - (Ti, W) B ₂ grain boundary of a representative region of the microstructure of Figure 1;

Figure 4b shows the oxygen distribution pattern associated with Figure 4a associated with EFTEM (Energy Filtering Transmission Electron Microscopy); Figure 4c shows the line scan of oxygen along the line drawn in Figure 4b; and

FIG. 5 shows a light micrograph of the microstructure of the sintered material obtained in Reference Example 1.

The following examples and Reference Example 1 illustrate the invention.

Example 1 :

450 g of TiB ₂ powder (d ₅₀ = 2 μm, 1.7% by weight of oxygen, 0.15% by weight of carbon, 0.077% by weight of Fe), 30 g of tungsten carbide powder (d 50 <1 μm ), 10 g of boron amorphous (purity 96.4%, d ₅₀ <1 micron), 8 g of boron carbide powder (d ₅₀ = 0.7 microns) and 2 g of Al ₂ O ₃ (boehmite as starting material) together with 10 g of Po - lyvinyl alcohol having an average molecular weight of 1,500 as a binder and 20 g of stearic acid as a pressing aid dispersed in aqueous solution and spray granulated. The spray granules are pressed at 1000 bar uniaxially to green bodies. The total oxygen content of a coked green body is 2.7%. The green bodies are heated at 10 K / min under vacuum to 2020 ⁰ C and 45 minutes held at sintering temperature. Cooling takes place with switched off heating power under Ar.

The sintered density of the obtained samples is 97.7% of the theoretical density.

A light micrograph of the microstructure is shown in Figure 1.

The resulting microstructure consists of a (Ti, W) B ₂ mixed crystal matrix, finely divided particulate B ₄ C, a Ti-Al-BO phase particulate in the triple points (Figures 3a, b and c, EELS spectroscopy) and a about 2 nm thick, continuous oxygen-containing amorphous grain boundary film (Figures 4a, b and c, EFTEM).

The hardness of the sintered body is 2,500 (HKO.1), the fracture toughness was determined by the SEVNB method and is 5.3 MPa m ^1/2 , the modulus of elasticity is 560 GPa and the breaking strength measured by the 4-point method is 500 MPa. Example 2:

450 g of TiB ₂ powder (d ₅₀ = 2 μm, 1.7% by weight of O, 0.15% by weight of C, 0.077% by weight of Fe), 30 g of WC (d ₅₀ <1 μm), 10 g boron amorphous (purity 96.4%, d ₅₀ <1 μm), 8 gB ₄ C (d ₅₀ = 0.7 μm) and 2 g Al ₂ O ₃ (boehmite as starting material) are mixed with 10 g polyvinyl alcohol with an average molecular weight of 1,500 as a binder and 20 g of stearic acid as a pressing aid dispersed in aqueous solution and spray granulated. The spray granules are cold isostatically pressed into green bodies at 1200 bar. The total oxygen content of a coked green body is 2.7%. The green bodies are heated at 10 K / min under vacuum to 2,060 ⁰ C and 45 minutes held at sintering temperature. Cooling takes place with switched off heating power under Ar.

The sintered density of the obtained samples is 98.7% of the theoretical density.

A light micrograph of the microstructure is shown in Figure 2.

The resulting microstructure consists of a (Ti, W) B ₂ mixed crystal matrix, finely divided particulate B ₄ C, a present in the triple points particulate Ti-Al-BO phase and an approximately 2 nm thick, continuous oxygen-containing amorphous grain boundary film.

Example 3:

436 g of TiB ₂ powder (d ₅₀ = 2 μm, 1.7% by weight of O, 0.15% by weight of C, 0.077% by weight of Fe), 44 g of WC (d ₅₀ <1 μm), 18 g of boron amorphous (purity 96.4%, d ₅₀ <1 micron) and 2 g of Al ₂ O ₃ (boehmite as starting material) together with 10 g of polyvinyl alcohol having an average molecular weight of 1,500 as a binder and 20 g of stearic acid as a pressing aid in aqueous solution dispersed and spray granulated. The spray granules are cold isostatically pressed into green bodies at 1200 bar. The green bodies are heated at 10 K / min to 2020 ⁰ C and 45 minutes held at sintering temperature. Cooling takes place with switched off heating power under Ar. Example 4:

The sintered bodies of Example 1 are post-densitized with 1,950 bar at 2,000 ⁰ C with a hold time of 60 minutes hot isostatic under argon. The density of the samples obtained is 99.1% of the theoretical density.

Samples of the materials prepared according to Example 4 were subjected to a corrosion test in 1 molar HCl at 100 ° C. The sample size was 20 x 3 x 4 mm. The samples were exposed to the corrosion medium for 90 minutes. After this time the corrosion rate was 1, 51 μg / mm ² h.

For comparison, this test was also performed on reference samples prepared from a sintered TiB ₂ material with 0.5% by volume Fe-Cr-Ni binder phase. The corrosion rate determined there on samples of the same dimensions as above was 5.26 μg / mm ² h, so that the material according to the invention from Example 4 has a corrosion rate reduced by a factor of 5.

Reference Example 1: (starting mixture without Al compound as sintering aid)

450 g of TiB ₂ powder (d50 = 2 μm, 1.7% by weight of O, 0.15% by weight of C, 0.077% by weight of Fe), 30 g of WC (d50 <1 μm), and 2O g B amorphous (purity 96.4%, d50 <1 micron) are dispersed together with 10 g of polyvinyl alcohol having an average molecular weight of 1,500 as a binder and 20 g of stearic acid as a pressing aid in aqueous solution and spray granulated. The spray granules are cold isostatically pressed into green bodies at 1200 bar. The green bodies are heated at 10 K / min in vacuo to 2.170 ° C and held for 45 min at sintering temperature. Cooling takes place with switched off heating power under Ar. The sintered body is subsequently recompressed at 1,950 bar Ar pressure for one hour at 2,000 ⁰ C. The density is 97.9% of the theoretical density.

A light micrograph of the microstructure is shown in Figure 5. The resulting microstructure consists of a (Ti, W) B ₂ mixed crystal matrix and particulate boron carbide, which lies partly in the grain boundary and partly in the mixed crystal grain. The average grain diameter is about 100 microns. For compacting to closed porosity here a higher sintering temperature was needed. The result is a coarse-grained structure.

Claims

claims

1. sintered wear-resistant material based on transition metal diborides, comprising a) as the main phase 80-98.8 wt .-% of a fine-grained transition metal or transition metal diboride mixed crystal of at least two transition metal diborides or mixtures of such diboride mixed crystals or Mixtures of such diboride mixed crystals with one or more transition metal diborides, wherein the transition metals from the IV. To VI. B) as the second phase 0.2 to 5 wt .-% of a continuous, oxygen-containing grain boundary phase, and c) as a third phase 1-15 wt .-% particulate boron carbide and / or silicon carbide.

2. Material according to claim 1, wherein the main phase a) has an average particle size of less than 20 microns, preferably less than 10 microns.

3. Material according to claim 1 and / or 2, wherein the boron carbide and / or silicon carbide of the third phase c) has an average particle size of less than

20 microns, preferably less than 5 microns.

4. Material according to at least one of claims 1 -3, wherein the proportion of the third phase c) 1 -4 wt .-% is.

5. Material according to at least one of claims 1 -4, wherein the second phase b) is present in a proportion of up to 2.5 wt .-%.

6. Material according to at least one of claims 1-5, wherein the transition metals of IV. To VI. Subgroup are selected from Ti, Zr, Hf, V,

Nb, Ta, Cr, Mo and W.

7. Material according to at least one of claims 1 -6, wherein it is the main phase a) fine-grained TiB ₂ and / or ZrB ₂ and / or a mixed crystal of (Ti ₁ W) B ₂ and / or (Zr, W) B ₂ and / or (Ti ₁ Zr) B ₂ , preferably a mixed crystal of (Ti, W) B ₂ and / or (Zr ₁ W) B ₂ , more preferably the mixed crystal (Ti ₁ W) B ₂ or the mixed crystal (Zr ₁ W) B ₂ .

8. A powdery sinterable mixture for producing a sintered material based on transition metal diborides, containing

1) 0.05-2% by weight of Al and / or Si as metallic Al and / or Si and / or an amount of an Al and / or Si compound corresponding to this content,

2) optionally at least one component selected from carbides and borides of transition metals of IV. To VI. Subgroup of the Periodic Table, 3) 0.5-19% by weight, preferably 1-5% by weight of boron,

4) 0-15 wt .-%, preferably 0.5-5 wt .-% boron carbide and / or silicon carbide, and

9. Mixture according to claim 8, wherein the proportion of component 1) 0.2-0.6 wt .-% is.

10. Mixture according to claim 8 and / or 9, wherein the proportion of component 2)> 0.25 wt .-% is.

1 1. A mixture according to any one of claims 8-10, wherein the transition metal diboride of component 5) has an average particle size of <4 microns, preferably <2 microns.

12. Mixture according to at least one of claims 8 to 1 1, wherein the transition metals of IV. To VI. Subgroup are selected from Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W.

A blend according to any one of claims 8 to 12, wherein component 2) is tungsten carbide.

14. Mixture according to at least one of claims 8-13, wherein the transition metal diboride of component 5) TiB ₂ and / or ZrB ₂ is.

15. A method for producing a sintered material according to at least one of claims 1 -7 by hot pressing or hot isostatic pressing or gas pressure sintering or spark plasma sintering a powdery mixture according to at least one of claims 8-14, optionally with the addition of organic binding and pressing aids.

16. A method for producing a sintered material according to at least one of claims 1-7 by pressure-sintering, comprising the steps: a) mixing a powdery mixture according to at least one of claims 9-14, optionally with the addition of organic binding and pressing aids in water and / or organic solvents to produce a homogeneous powder suspension) preparing b of a granulated powder from the powder suspension, c) pressing the granulated powder into green bodies of high density, and d) pressureless sintering the resulting green body in vacuum or under protective gas at a temperature of 1800-2200 ⁰ C. ,

17. The method of claim 16, wherein the preparation of the powder granules in step b) is carried out by spray drying.

18. The method of claim 16 and / or 17, wherein the preparation of the green body in step c) by axial pressing, cold isostatic pressing, extrusion, injection molding, slip casting or pressure slip casting takes place.

19. The method according to at least one of claims 16- 18, wherein the green body obtained in step c) are annealed prior to pressure-sintering in an inert atmosphere at temperatures below the sintering temperature.

20. The method according to at least one of claims 16-19, wherein the pressure-lock sintering in step d) at a temperature in the range of 1,900-2,100 ⁰ C, preferably about 2,000 ⁰ C is performed.

21. The method according to at least one of claims 16-20, wherein the pressureless sintered material is densified by hot isostatic pressing.

22. Use of the sintered material according to at least one of claims 1 -7 for the production of wearing parts in general plant construction, in particular chemical plant construction, thermal plant construction, in paper machines, in the milling technique and in wear protection.

23. Use of the sintered material according to at least one of claims 1 -7 for the production of tools for machining.

24. Use of the sintered material according to at least one of claims 1 -7 for the production of tools for chipless machining and shaping, forming technology and for deflection rollers.

25. Use of the sintered material according to at least one of the claims 1 -7 for the production of water or sandblast nozzles.

26. Use of the sintered material according to at least one of claims 1-7 as electrode material for sliding contacts, welding electrodes and Erodierstifte.