V. I. Subbotin

Synthesis and properties of ceramics in the SiC — B4C — MeB2 system

The effect of impurities and additives of titanium and zirconium borides on the structure and mechanical properties of SiC — B4C ceramics over a broad temperature range has been investigated. The ceramics was fabricated by hot pressing without a protective medium. Introduction of borides is accompanied by improvement in all the studied mechanical properties at room temperature, and the nature of hardening of the ceramics is practically independent of the type of SiC powders used. At high temperatures, the mechanical behavior of the ceramics is determined by the impurity composition: the ceramics obtained using abrasive powders loses strength beginning at 600°C, while using powders with decreased impurity content makes it possible to preserve the strength of the material up to a temperature of 1400°C.

Structure and properties of titanium–chromium diboride composites

Composites based on binary titanium–chromium diboride are produced by hot pressing. The influence of aluminum nitride additions on the composition, structure, and mechanical and tribotechnical properties of the materials is studied. It is shown that the introduction of up to 10 vol.% AlN into (Ti, Cr)B2 reduces porosity and improves mechanical and tribotechnical properties. The (Ti, Cr)B2–AlN composites were wetted by NiAl alloy and the interaction area was analyzed. The contact angles of wetting are close to zero in this system and terminal solid solutions form in the interaction area. This allowed (Ti, Cr)B2–AlN–NiAl metal ceramics to be obtained. The metal ceramics sintered in vacuum have fine structure consisting of (Ti, Cr)B2 and AlN grains and NiAl alloy.

Structure and Properties of Titanium Carbide Based Cermets with Additives of Other Carbides

The properties of wear-resistant cermets based on titanium carbide with additives of other carbides produced by two techniques are investigated. These techniques are: pressure sintering of powder mixture of the starting components (TiC, VC, Mo2C, NbC, Ni, and Cr) and pressure sintering of powder mixture of pre-synthesized solution of the starting carbides ((Ti, V, Mo, and Nb)C with additives of Ni and Cr. It is determined that cermets produced by the second technique possess more homogenous and fine-dispersed structure. The latter determines its higher mechanical strength, hardness, crack resistance, heat stability, and wear resistance, in comparison with the properties of cermets produced by the first technique.

Effect of grinding time on the structure and wear resistance of SiC–Al2O3 ceramics

The effect of time during which SiC–50% Al2O3 is ground in steel drums on the particle size and phase composition is studied. The optimum hot-pressing temperature leading to complete shrinkage is determined in relation to grinding time. The composition and structure of the hot-pressed ceramics and their influence on the wear resistance in friction against a steel counterface are analyzed. The wear resistance of the ceramics monotonically decreases from 23.4 to 3.8 μm/km when grinding time increases from 1 to 16 h and increases to 5.8 μm/km for a grinding time of 32 h. The friction surfaces of SiC–Al2O3 ceramics are examined, and their wear mechanisms are established.

Phase composition and properties of hot-pressed AlN–BN materials

The effect of hot-pressing temperature on the phase composition and properties of AlN–BN materials with addition of Y2O3 or SiC is studied. The composites have higher density and mechanical strength than the hot-pressed AlN–BN material without additions and retain its good insulating properties, thermal and chemical resistance, and adequate machinability.

Effect of Y2O3 and SiO2 additions on the phase formation and properties of the hot-pressed boron carbonitride composite

The dependence of phase composition and properties of the BCN composite with additions of Y2O3 and SiO2 (quartz glass) on hot-pressing temperature is studied. It is established that new strengthening phases form with the composite during reaction pressure sintering. The optimum conditions for producing the BCN composite are found. The BCN composite has high thermal strength, oxidation resistance, and electrical insulating properties.