Principles of Technology and Mechanical Properties of Structural Ceramics Based on the Ternary System SiC–B₄C–CrB₂

Abstract

The aim of this research was to work out the technology of ceramics for finding optimal sintering temperatures and to study their mechanical properties. Samples were prepared from powders with different volumetric ratio of the components. The powders underwent a prolonged co-milling in a vibratory mill, followed by uniaxial pressing, cold isostatic pressing (CIP) and pressureless sintering in a vacuum furnace under an argon atmosphere. Hot pressing (HP) was applied to some powder formulations. This study showed that it is advisable to carry out the first stage of the heat treatment up to 1550 °C under vacuum, with the aim of refining the grain surface from the oxygen-containing impurities due to their dissociation and evaporation. The studied area of formulations has a very narrow range of sintering (1940-1945 °C). It was established that the sinterability of the materials is affected by the amount of silicon carbide in the ternary system. Under pressureless sintering, the relative density of the material directly depended on the volume fraction of SiC. However, a change in the concentration of B₄C had no appreciable effect on the sinterability of the materials. The application of HP helped us to reduce the negative impact of large amounts of SiC. Under HP at temperatures close to T_eut, a certain decompaction of materials was observed with a significant amount of B₄C (3-5% loss in density).