Abstract: The invention relates to a polycrystalline SiC shaped body, which consists of 96% by weight to 99.5% by weight of hard-material grains having a core/shell structure, 0 to 0.1% by weight free carbon, remainder a partially crystalline binder phase; having the following properties: density at least 99.5% of the theoretical density, dark green coloring of ground sections or polished surfaces through characteristic light absorption in the orange spectral region at 1.8 to 2.2 eV, resistivity of at least 107 ohm·cm, and fracture toughness of at least 4.0 MPa.m½, measured using the bridge method.

Abstract: The invention relates to bearing materials of porous SiC having a trimodal pore composition and also a process for their production.The porous bearing material of pressureless-sintered SiC having from 3 to 10% by volume of independent closed pores having a trimodal pore composition consisting of micropores (M), fiber-shaped macropores (F) and spherical macropores (S), where the amounts in the pore system F-M-S (FIG. 1) are fixed by the trapezoidal area having the corner pointsa=10%M-80%F-10%Sb=10%M-10%F-80%Sc=40%M-10%F-50%Sd=40%M-50%F-10%Sand the micropores have a diameter of less than or equal to 5 .mu.m and the fiber-shaped macropores have a diameter of less than or equal to 30 .mu.m and a length of less than or equal to 80 .mu.m and the spherical macropores have a diameter of less than or equal to 70 .mu.m, and have a flexural strength of at least 250 MN/m.sup.2.

Abstract: A composite material includes boron carbide and titanium diboride in a volume ratio B.sub.4 C/TiB.sub.2 of from 90:10 to 10:90 parts and a proportion of elemental carbon greater than 2% by weight up to a maximum of 50% by weight, based on the boron carbide content. The composite material has a density greater than 92% TD, a hardness HK 0.1 greater than 2300, a four-point flexural strength greater than 400 MPa and a fracture toughness greater than 3.5 MPa.sqroot.m. The composite material is suitable for producing wear-resistant components or cutting tools.

Abstract: A process for producing shaped bodies of boron carbide, metal diboride and carbon, which includes(a) homogeneously mixing pulverulent boron carbide with at least one pulverulent monocarbide of an element Ti, Zr, Hf, V, Nb and Ta in an amount corresponding to from 2% to 6% by weight of free carbon, based on the total weight of the boron carbide;(b) shaping this mixture into green bodies of a density of at least 50% TD;(c) heating the preformed body thus obtained to from about 1250.degree. C. to 1450.degree. C. with exclusion of oxygen in a sintering furnace and maintaining it within this temperature range for from 10 to 120 minutes; and(d) subsequently sintering the preformed body by heating to from 2100.degree. C. to 2250.degree. C.

Abstract: Composite materials are provided based on titanium diboride and processes for their preparation.The composite materials contain(1) 70 to 98% by volume of titanium diboride,(2) 1 to 15% by volume of Fe.sub.2 B and(3) 1 to 15% by volume of Ti.sub.2 O.sub.3and have the following properties:density at least 93% of the theoretically possible density of the total composite material,hardness (HV10) greater than 1,900,bending fracture strength (measured by the three-point method at room temperature) at least 400 MPa andfracture resistance K.sub.IC (measured with a sharp incipient crack produced by the bridge method) of at least 4.5 MPa.sqroot.m.

Abstract: The invention relates to mixed sintered metal materials based on high-melting borides and nitrides and low-melting iron binder metals having the composition:(1) 40-97% by volume of borides, such as titanium diboride and zirconium diboride;(2) 1-48% by volume of nitrides, such as titanium nitride and zirconium nitride;(3) 0-10% by volume of oxides, such as titanium oxide and zirconium oxide, with the proviso that components (2) and (3) may also be present as oxynitrides such as titanium and zirconium oxynitride; and(4) 2-59% by volume of low-carbon binder metals, such as iron and iron alloys and to processes for preparing the same.

Abstract: The invention is a molded body of polycrystalline aluminum nitride having a density of at least 99.8% TD and comprising:______________________________________ at least 99 % by weight A1N up to 0.35 % by weight residual oxygen up to 0.35 % by weight residual carbon and up to 0.30 % by weight metallic impurities (Fe, Si, Ca, Mg). ______________________________________In the molded body, the aluminum nitride is present in the form of a single phase, homogeneous, isotropic microstructure having a maximum grain size of 5 .mu.m. The residual oxygen and the residual carbon are present in the form of a solid solution in the aluminum nitride lattice and ceramografically not detectable as separate phase(s) up to a manification of 2400 times. The molded bodies have a bending strength measured according to the 4-point method, at room temperature and up to about 1400.degree. C., of at least 500 N/mm.sup.2, a predominantly transcrystalline rupture modulus and a thermal conductivity at 300 K of at least 150 W/mK.

Abstract: The invention is a molded body of polycrystalline aluminum nitride having a density of at least 99.8% TD and comprising:at least 99% by weight AlNup to 0.35% by weight residual oxygenup to 0.35% by weight residual carbon andup to 0.03% by weight metallic impurities (Fe, Si, Ca, Mg).In the molded body, the aluminum nitride is present in the form of a single phase, homogeneous, isotropic microstructure having a maximum grain size of 5 .mu.m. The residual oxygen and the residual carbon are present in the form of a solid solution in the aluminum nitride lattice and caromografically not detectable as separate phase(s) up to a magnification of 2400 times. The molded bodies have a bending strength measured according to the 4-point method, at room temperature and up to about 1400.degree. C., of at least 500 N/mm.sup.2, a predominantly transcrystalline rupture modulus and a thermal conductivity at 300 K of at least 150 W/mK.