EP4496782A1 - Ceramic sintered body made of a sialon material, raw material mixture thereof, and manufacture thereof - Google Patents

Abstract

The present invention relates to a sintered body which is based on β-sialon as well as 15R-sialon and which, as a cutting material, exhibits a high cutting performance compared to workpieces made of nickel-based alloy or Heat Resistant Super Alloys (HRSA). To this end, a ceramic sintered body is disclosed which has a sialon phase and an amorphous or semi-crystalline grain boundary phase. The sialon phase has a proportion of 20 - 80 wt.% 15R-sialon polytypoid. The amorphous or semi-crystalline grain boundary phase optionally comprises a Yb-Al garnet, and constitutes up to 15 wt.% of the total sintered body. The sintered body is manufactured from an inorganic raw material mixture which comprises 40 to 57 wt.% of Si₃N₄; 40 - 55 wt.% of a mixture of AlN and Al₂O₃, the ratio of Al₂O₃ to AlN being in the range of 1-1.5:1, and 3 to 5 wt.% of Yb₂O₃ as a sintering aid.

Description

Ceramic sintered body made of a Sialon material, its raw material mixture and production

The subject of the invention is a sialon material whose sialon phase comprises ß-sialon and 15R sialon polytypoid. The Sialon material further comprises an amorphous or semi-crystalline grain boundary phase.

Sintered sialons are well-known, chemically stable materials with high mechanical strength over a wide temperature range. Sialons are therefore used as heat-resistant parts in machines. The high mechanical strength leads to low wear in abrasion-intensive processes. Sialones are therefore widely used as cutting agents in cutting tools.

Sintered moldings made of a/ß-Sialon, especially for use as a cutting tool, e.g. B. as cutting means are known from the prior art. The mixtures of a-sialon and ß-sialon enable the production of sintered moldings which, on the one hand, have a high hardness due to the granular a-sialon and, on the other hand, also have good toughness due to the needle-shaped ß-sialon grains.

The object of the invention is to provide a sialon sintered body that has high chemical resistance, high hardness and good fracture toughness. The sintered body is primarily intended for use in the machining of nickel-based alloys or Heat Resistant Super Alloys (HRSA). In addition, a method for producing a Sialon sintered body and the underlying inorganic raw material mixture should be provided.

The object is achieved by an inorganic raw material mixture according to claim 1, a Sialon sintered body according to claim 6, the method according to claim 10 and the use according to claim 14. The subordinate claims reflect preferred embodiments. Further preferred embodiments are described below. Designs can be freely combined with one another.

Unless otherwise stated, all percentages are based on weight (% by weight).

Unless otherwise stated, all information in mol% refers to the total mixture.

All components of the Sialon sintered body and also the inorganic raw material mixture can contain impurities. The purity of the starting materials is at least > 97%, ie each starting material can contain up to 3% by weight of impurities (based on the total amount of the respective starting material). The purity of the starting materials is preferably >99%, ie i Up to 1% by weight of impurities (based on the total amount of the respective starting material) is possible, particularly preferably the purity is > 99.7%, ie up to 0.3% by weight of impurities (based on the total amount of the respective starting material ) are possible. Ideally, the purity of the starting materials is > 99.9%, meaning there are almost no impurities (up to 0.1% by weight).

The impurities are preferably foreign metals in quantities of less than 1000 ppm. In a preferred embodiment, Fe ions are contained in the range between 10 and 1000 ppm, preferably between 10 and 500 ppm, particularly preferably between 10 and 100 ppm. A lower Fe content leads to disproportionately high raw material and manufacturing process costs. A higher Fe content leads to the formation of iron silicide, which negatively affects the fracture toughness of the sintered body. The levels of foreign metals are determined using X-ray fluorescence analysis.

Furthermore, the nitride components of the raw material mixtures can contain oxygen in amounts of less than 1.5% by weight, preferably less than 1% by weight, particularly preferably less than 0.7% by weight, based on the total amount of the respective starting material.

The grain sizes of the components of the sialon in the sintered sintered body are determined using SEM images. The maximum needle length, i.e. the maximum expansion of the grains, should not exceed 100 pm. The composition of the Sialon sintered body is determined using conventional X-ray analysis methods, for example XRD (DIN EN 13925-1 (2003-07) and DIN 13925-2 (2003-07)). Chemical analyzes of the metallic components of the sintered body according to the invention are carried out by energy-dispersive X-ray analysis (ISO 15632; DIN EN 1071-4) and X-ray fluorescence analysis (XRF; DIN 51001 (2003-08), DIN 51418-1 (2010-05), DIN 51418-2 ( 2015-03)). The oxygen content is determined using hot gas extraction (ASTM E 1409:2013).

Sialons are typically made by sintering a powdered mixture and consist primarily of silicon nitride, aluminum oxide and other inorganic starting materials such as: B. sintering aids. The sintered body, i.e. the material, the sintered body made from the starting materials, comprises a sialon phase and an amorphous or at least partially crystalline grain boundary phase. The sialon phase includes ß (beta) - sialon (Sie-zAlzOzNs-z where 0 < Z < 4.2) and 15R-sialon polytypoid (SiAUOzN^. The proportion of 15R-sialon polytypoid is 20 - 80% by weight , preferably 30 - 70% by weight, particularly preferably 40 - 60% by weight, based on the total weight of the sialon phase. The proportion of ß-sialon is preferably at least 10% by weight, particularly preferably at least 35% by weight. %. Particularly preferred is a proportion of ß-sialon of 40% by weight. The proportion of ß-sialon is a maximum of 80% by weight.

The proportion of 15R polytypoid leads to a sintered body that has a high level of chemical inertness, ie chemical reactions occur with or on the sintered body avoided by a high proportion of 15R polytypoid. However, a high proportion of 15R polytypoid leads to high brittleness of the sintered body. In the range of 40 to 60% by weight 15R, an optimal ratio of chemical inertness to fracture toughness of the sintered body can be obtained.

The detection limit in the X-ray analysis method for determining the composition of the sialon phase and for determining the individual sialons present in the sintered body is approximately 5% by weight. Up to 10, preferably up to 5% by weight, of further sialons, preferably selected from the list comprising a (alpha), 12H, 21R and/or 27R sialons, can be contained in the sialon phase.

The sintered shaped body consists of >80% by weight, preferably >85% by weight, of the sialon phase and up to 20% by weight, preferably up to 15% by weight of the amorphous or at least partially crystalline phase Grain boundary phase, based on the total weight of the sintered body. Particularly preferably, the sintered shaped body consists of >90% by weight of the sialon phase.

The proportion of grain boundary phase in the total weight of the sintered body is preferably <12% by weight, particularly preferably <10% by weight. In a preferred embodiment, the sintered shaped body consists of the sialon phase and the grain boundary phase, i.e. the sum of the proportions of the sialon phase and the grain boundary phase is 100% by weight. In order to be able to produce the densest possible sintered body, e.g. B. sintering aids added as additives. The amount of additives added influences the amount of grain boundary phase. In a preferred embodiment, the proportion of grain boundary phase is at least 5% by weight.

The sintered shaped body according to the invention is created by heat treatment, sintering, of a starting material mixture. This raw material mixture includes an inorganic raw material mixture and organic components. An inorganic raw material mixture for the production of sialons includes the components SisN4, AIN, AI2O3 and sintering aids.

To produce the sintered shaped body according to the invention, an inorganic raw material mixture is proposed, to which Yb2Ü3 is added as a sintering aid.

The use of Yb2Ü3 results in a sintered body that has high fracture toughness. This makes the sintered molded body according to the invention very suitable as a cutting agent for the machining of metallic workpiece materials. The high fracture toughness leads to increased stability of the cutting edge. The sintered molding thus withstands the stresses during machining even at high cutting speeds, increased feed and/or greater cutting depths, even in interrupted cuts.

The sintered body according to the invention, the sialon, is obtained from an inorganic raw material mixture which comprises the following components:

40 - 57% by weight SisN4 40 - 55% by weight of a mixture of AIN and AI2O3, the ratio of AI2O3 to AIN being in the range 1 - 1.5:1, preferably 1 - 1.25:1, particularly preferably 1 - 1.2:1 ,

3 - 5% by weight of Yb2O3 as a sintering aid.

In a preferred embodiment, the sum of the inorganic components is 100% by weight and the inorganic raw material mixture consists only of the components SisN4, AlN, Al2O3 and Yb2O3 as sintering aids.

The inorganic raw material mixture includes all inorganic components that are used to produce the sintered body according to the invention. In order to produce the sintered body, further organic components are added, such as: B. Dispersants, pressing aids and binders that are completely burned during heat treatment, debinding and sintering. These organic components preferably do not contain any metallic components. In a preferred embodiment, ammonium salts are used instead of sodium salts of the organic components.

In a preferred embodiment, the inorganic raw material mixture according to the invention comprises

45 - 54.5% by weight Si3N4,

42 - 50% by weight of a mixture of AIN and AI2O3, the ratio of AI2O3 to AIN being in the range 1 - 1.5:1, preferably 1 - 1.25:1, particularly preferably 1 - 1.15:1 .

- 3.5 - 5% by weight of Yb ₂ O ₃ .

In a preferred embodiment, the sum of the inorganic components is 100% by weight.

In a particularly preferred embodiment, the inorganic raw material mixture according to the invention comprises

- 47.5 - 51.5% by weight Si ₃ N ₄ ,

45 - 48% by weight of a mixture of AIN and AI2O3, the ratio of AI2O3 to AIN being in the range 1 - 1.5:1, preferably 1 - 1.25:1, particularly preferably 1 - 1.2:1 .

- 3.5 - 4.5% by weight of Yb ₂ O ₃ .

In a preferred embodiment, the sum of the inorganic components is 100% by weight.

The raw material mixture includes Yb2Ü3 as a sintering aid, which is used to produce high-density ceramics. When using more than 5% by weight of Yb2Ü3 based on the entire sintered body, the heat resistance, toughness and the hardness of the Sialon sintered body. In one embodiment, the proportion of Yb2Ü3 in relation to the inorganic raw material mixture according to the invention is 0.4 - 1.5 mol%, preferably 0.6 - 1.5 mol% and particularly preferably 0.6 - 1 mol%. %.

The sintered shaped body is produced from the inorganic raw material mixture according to the invention. For this purpose, the inorganic raw material mixture is first provided. One or more organic auxiliary substances are added.

The raw materials are first mixed and/or ground in a solvent. In one embodiment, the solvent is water. In a further embodiment, the solvent is an organic solvent, a mixture of several organic solvents or a mixture of one or more organic solvents and water. The solvent mixtures are preferably single-phase, i.e. the solvents dissolve completely into each other in the required amounts.

The powdery inorganic raw material mixture should comprise particles with an average particle size of 10 pm or less, preferably 5 pm or less, more preferably 3 pm or less. The inorganic raw material mixture is preferably placed in a mixing and grinding machine, such as a ball mill or a SiaN pot mill, with SisN grinding balls, and a solvent is added to the material which does not, at least substantially, dissolve the powdery raw material. Depending on the processing step, the grain sizes of the raw material mixture are referred to as agglomerates or primary particles. The D50 value of the primary particles, the ground raw materials, is determined using centrifugal sedimentation using the Particle Distribution Analyzer (DIN EN 725-5:2007, ISO 13320:2020-01).

The mixture is then ground and mixed until a slurry is formed and the desired primary grain size, i.e. the grain size of the raw material after grinding and before shaping, has been set. The mixing and grinding process usually takes at least 5 minutes, preferably 30 minutes, particularly preferably 1 hour to a maximum of 300 hours, preferably a maximum of 200 hours, particularly preferably a maximum of 100 hours.

In one embodiment, the SiaN powder has a primary grain size D50 0.25 <x <2.5 pm, preferably 0.25 <x <2.0 pm, particularly preferably D50 0.35 <x <1.0 pm. The primary grain size influences the shaping and the sintering activity.

In a further embodiment, the Si3N4 has a primary grain size D50 of 1.5 <x <2.0 pm.

After grinding, other organic auxiliary substances can also be added, which are mixed with the components mentioned.

The organic auxiliary substances to be added before or after grinding can be dispersants, binders, pressing aids and/or plasticizers. In one embodiment, the organic auxiliaries are used in an amount of 1 to 30% by weight the weight of the inorganic raw material mixture is added to the powdered raw material mixture or the slurry produced.

The mixture produced, the slurry, comprising the inorganic and organic raw materials in a solvent mixture are, in one embodiment, by a suitable process, such as. B. spray drying, subjected to granulation.

The mixture or granules are then shaped. All methods for bringing the state of the art into form can be used. In a preferred embodiment, the granules are brought into shape by pressing, preferably axial pressing, at 50 to 200 MPa. In a further embodiment, the shaping takes place using isostatic pressing.

Molding can also be done by using other methods such as injection molding, extrusion molding or slip casting.

The shaped mixture of starting materials is then debinded and sintered. In a preferred embodiment, sintering takes place under protective gas, such as. B. nitrogen and/or argon.

Debinding and sintering usually takes place in a heating device. The gas atmosphere during debinding and sintering is inert in one embodiment and comprises N ₂ , argon or a mixture of N ₂ and other inert gases, preferably Ar.

The debinding preferably takes place at 400 to 800 ° C and preferably lasts at least 5 minutes, preferably 30 minutes, particularly preferably 1 hour to a maximum of 100 hours, preferably a maximum of 50 hours, particularly preferably a maximum of 30 hours.

The exact contents of the individual sialon phase components and the proportion and composition of the amorphous or semi-crystalline grain boundary phase are set by the selected sintering parameters. During the production of the sintered body, during the sintering of the inorganic raw material mixture, the sintering aid Yb ₂ O3 is converted, among other things, into Yb-Al-garnet, Yb ₃ AI ₅ 0i ₂ , and accumulates in the amorphous or semi-crystalline grain boundary phase. The smallest possible proportion of Yb-Al garnet in the grain boundary phase is preferred. The lower the proportion of Yb-Al garnet in the grain boundary phase of the sintered body, the higher the wear and abrasion resistance of the sintered body. In a preferred embodiment, a maximum of 1.4% by weight of Yb-Al garnet can be detected in the grain boundary phase.

The Yb-Al garnet as a crystalline component stabilizes the grain boundary phase by increasing the softening temperature compared to a completely amorphous grain boundary phase. In a preferred embodiment, at least 0.02% by weight of Yb-Al-garnet can be detected in the grain boundary phase. The amount of Yb-Al garnet is determined by the sintering parameters, such as: B. influences the sintering temperature. At sintering temperatures up to 1950 ° C, lower proportions of Yb-Al garnet are obtained; at lower sintering temperatures, a higher proportion of Yb-Al garnet is obtained (see also Table 2). The proportion of Yb-Al garnet in the sintered body is preferably between 0.01 and 5% by weight, particularly preferably between 0.015 and 3% by weight, particularly preferably between 0.02 and 1.4% by weight the amount of crystalline phases in the sintered body.

With a lower sintering temperature, the proportion of crystalline grain boundary phase, and thus also the proportion of Yb-Al garnet in the grain boundary phase, is increased. In addition, a sintering temperature that is too low leads to a less dense sintered body with increased porosity and, as a result, lower abrasion resistance. The sintering temperature is therefore preferably more than 1600 ° C.

In addition to the sintering temperature, the cooling rate also affects the proportion of Yb-Al garnet in the amorphous and/or semi-crystalline grain boundary phase. The slower the cooling, the higher the proportion of Yb-Al garnet. The cooling rate is therefore preferably higher than 1000 ° C in 14 h, particularly preferably higher than 1000 ° C in 12 h, particularly preferably higher than 1000 ° C in 10 h. In one embodiment, the cooling rate is slower than 1000 ° C in 4 hours, preferably the cooling rate is in the range of 1000 ° C in 4 - 8 hours.

In addition to the proportions of crystalline phases, the sintering temperature also affects the grain size of the crystallites. These can be refined as part of a Rietveld refinement based on an X-ray diffractogram of the sintered body. Table 2 shows the average grain size of the individual crystalline phases (crystallite size). This is the average length of the congruent scattering domains in the sintered body. For the ß-Sialon phase, the higher the sintering temperature, the larger the crystallite size of the ß-Sialon phase. In addition, the Crystallite Size of the Yb-Al-Garnet phase in the sintered body according to the invention is smaller than the average Crystallite Size of the Sialon phases. The crystallite size of the Yb-Al-Grant phase is preferably at least 5 times smaller than the average crystallite size of the Sialon phases, particularly preferably the crystallite size of the Yb-Al-garnet phase is at least 10 times smaller than the average crystallite Size of the Sialon phases.

The shaped mixture of starting materials is sintered at a temperature between 1600 ° C and 1950 ° C, preferably between 1650 ° C and 1900 ° C, particularly preferably between 1750 ° C and 1875 ° C. At these sintering temperatures, the densest possible sintered body is obtained (> 99% of the theoretical density) and the proportion of Yb-Al garnet is in the preferred range.

In a preferred embodiment, the sintering takes place in a gas pressure sintering furnace under a pressure of at least 10 bar, preferably at least 50 bar, particularly preferably at least 75 bar and preferably at most 150 bar, particularly preferably at most 100 bar.

The sintering time is preferably at least 30 minutes and preferably a maximum of 3 hours, particularly preferably the sintering time is 45 minutes to 2.5 hours.

The final sintered Sialon sintered body can then be removed. Final processing is carried out using methods known in the prior art. In one In this embodiment, the sintered molded body is further processed by grinding into indexable inserts or solid shank milling cutters. The sintered molded body according to the invention can be processed into a cutting agent that has little contact with the workpiece material to be processed, e.g. B. nickel-based alloys or steels. Chemically resistant, hard cutting materials are required for machining Ni-based alloys. The alloys are highly heat-resistant and hard; very high temperatures arise during machining, which leads to reactions and rapid wear with conventional cutting materials. When machining nickel-based alloys or Heat Resistant Super Alloys (HRSA), no built-up edge is created, meaning that the material of the workpiece to be machined hardly or does not adhere to the cutting medium. In addition, the high proportion of 15R sialon polytypoid leads to a chemically very stable sintered body.

The present invention relates to a sintered body based on ß-sialon and 15R-sialon, which, as a cutting material, has a high cutting performance compared to. Workpieces made of nickel-based alloys or Heat Resistant Super Alloys (HRSA). For this purpose, a ceramic sintered body is shown which has a sialon phase and an amorphous or semi-crystalline grain boundary phase. The sialon phase has a proportion of 20 - 80% by weight of 15R sialon polytypoid. The amorphous or semi-crystalline grain boundary phase optionally comprises a Yb-Al garnet and accounts for up to 15% by weight of the entire sintered body.

The Yb2O3 from the raw material mixture serves, in addition to the Al-based additives and the SiO2 contained in the Si3N ₄ raw material, as a sintering aid. While the Al-based additives and the SiÜ2 can also be incorporated into the crystal lattice of the described sialon phases during the sintering process, the Yb remains in the grain boundary phase of the sintered body. This, and the Yb content, influences the properties of the grain boundary phase such as the glass transformation point and the bonding of the sialon phases with the grain boundary phase. This bond determines the dominant mechanisms for crack propagation in the sintered body and is therefore crucial for the fracture toughness of the sintered body. Therefore, the grain boundary phase of the sintered molding according to the invention contains at least 1.5% by weight, preferably 2% by weight, particularly preferably 2.5% by weight and a maximum of 5% by weight of Yb, calculated in the form of the sequioxide Yb2Ü3 and in relation to the total weight of the Sintered body.

The sintered shaped body is made from an inorganic raw material mixture containing 40 to 57% by weight of SisN ₄ ; 40 - 55% by weight of a mixture of AIN and AI2O3, the ratio of AI2O3 to AIN being in the range 1 - 1.5:1, and comprising 3 to 5% by weight of Yb2Ü3 as a sintering aid. Examples:

The following inorganic raw material mixtures (RM) were provided for the synthesis of sintered moldings.

Table 1 Composition of the inorganic raw material mixture

The starting materials, see Table 1, were mixed. SisN4 with an a-Si3N4 content of > 95%, an average grain diameter > 0.45 pm and an oxygen content of 1.2 - 1.4% by weight and Yb2O3 with a purity > 99.9%, one average grain diameter of approx. 5 pm, AI2O3 with a purity > 99.9%, an average grain diameter of 0.3 pm and AIN with an oxygen content of 0.6 - 1% and average grain diameter 1.2 - 1.7 pm are weighed, mixed with water and ground for at least 30 minutes in an agitator ball mill. The organic components are then added. The resulting ceramic slip (slurry) is granulated using spray drying. Shaped bodies were axially pressed at a pressure of approx. 1000 bar and debinded at 500 °C for 2 hours. The subsequent sintering took place according to the parameters from Table 2.

The sintered moldings were ground into cutting plates.

5 Table 2 Composition and properties of the sintered moldings

* the information refers to the proportion of the crystalline phases and was determined using Rietveld refinement, Topas Vers. 4.2, cif-files 00-048-1616, 00-042-0160, 00 023-1476

** the information refers to the result of the Rietveld refinement carried out to determine the crystalline phases (see *), the Crystallite Size was refined according to Gaus

10 “Results from experiments on machining nickel-based alloys (Inconel 718)

The measured values were determined in accordance with the following standard specifications: XRF: DIN 51001 (2003-08), DIN 51418-1 (2010-05), DIN 51418-2 (2015-03); XRD: DIN EN 13925-1 (2003-07), DIN 13925-2 (2003-07); Density: DIN EN 623-2 (1993-11), ISO 18754 (2020-04); Hardness: DIN EN 843-3 (2005-08), ISO 14705 (2016-12), ASTM C 1327 (2015); Fracture toughness: ISO 14627 (2012-07)

Claims

Patent claims 1. Inorganic raw material mixture comprising: 40 - 57% by weight Si3N ₄ 40 - 55% by weight of a mixture of AIN and AI2O3, the ratio of AI2O3 to AIN being in the range 1 - 1.5:1, and 3 - 5% by weight of Yb2O3, with the sum of the inorganic components being 100% by weight. 2. Raw material mixture according to claim 1, wherein the ratio of AI2O3 to AIN is 1 - 1.25:1, preferably 1 - 1.12:1. 3. Raw material mixture according to one of the preceding claims, comprising 45 - 54.5% by weight Si3N4, 42 - 50% by weight of a mixture of AIN and AI2O3, - 3.5 - 5% by weight of Yb ₂ O ₃ 4. Raw material mixture according to one of the preceding claims, comprising - 47.5 - 51.5% by weight Si ₃ N ₄ , 45 - 48% by weight of a mixture of AIN and AI2O3, - 3.5 - 4.5% by weight of Yb ₂ O ₃ 5. Raw material mixture according to one of the preceding claims, wherein the Si ₃ N ₄ powder has a primary grain size D50 0.25 <x <2.5 pm, preferably D50 0.25 <x <2.0 pm, particularly preferably D50 0.35 <x <1.0 pm or 1.5 <x <2.0 pm. 6. Ceramic sintered body comprising a sialon phase comprising ß-sialon and 15R-sialon, the proportion of 15-R-sialon polytypoid being 20 - 80% by weight of the sialon phase, and an amorphous or semi-crystalline grain boundary phase, where the grain boundary phase accounts for up to 15% by weight of the entire sintered body, the grain boundary phase having a maximum of 5% by weight of Yb, calculated in the form of the sequioxide Yb2Ü3 and in relation to the total weight of the sintered body. 7. Ceramic sintered shaped body according to claim 6, wherein the grain boundary phase contains at least 1.5% by weight, preferably 2% by weight, particularly preferably 2.5% by weight of Yb, calculated in the form of the sequioxide Yb2O3 and in relation to the total weight of the sintered shaped body, having. 8. Ceramic sintered shaped body according to claim 6 or 7, wherein the proportion of 15R sialon polytypoid is 30 - 70% by weight, preferably 40 - 60% by weight, based on the total weight of the sialon phase. 9. Ceramic sintered body according to claim 8, wherein the sialon phase additionally contains up to 10% by weight of 12H-, 21R-, 27R- or a-sialon, preferably up to 5% by weight of 12H-, 21R-, 27R or a-Sialon contains. 10. Ceramic sintered body according to one of claims 6 to 9, wherein the proportion of Yb-Al garnet in the sintered body is between 0.01 and 5% by weight, particularly preferably between 0.015 and 3% by weight, particularly preferably between 0. 02 and 1.4% by weight, based on the amount of crystalline phases in the sintered body. 11. Ceramic sintered body according to one of claims 6 to 10, wherein the crystallite size of the Yb-Al-garnet phase is smaller than the average crystallite size of the sialon phases, preferably at least 5 times smaller, particularly preferably at least 10 times smaller. 12. A method for producing the sintered sintered shaped body according to one of claims 6 to 11, with the method steps: (a) Providing a raw material mixture according to one of claims 1 to 5 (b) Addition of one or more organic auxiliaries (c) mixing and grinding the raw materials, preferably in at least one liquid selected from water and/or at least one organic solvent and, if necessary, adding one or more further organic auxiliaries (d) shaping the mixture (e) Debinding and sintering (f) Removal of the sintered sintered body 13. The method according to claim 12, wherein the sintering in process step (e) is carried out at 1600 °C to 1950 °C, preferably between 1650 °C and 1900 °C, particularly preferably at 1750 °C to 1875 °C. 14. The method according to claim 12 or 13, wherein the gas atmosphere is selected from N2 and/or a protective gas, preferably selected from N2 or a mixture of N2 and Ar and/or where the sintering takes place at a pressure between 10 and 100 bar. 15. Use of the ceramic sintered body according to one of claims 6 to 11 as a cutting means, preferably as an indexable insert or solid end mill.