SPECIFICS OF SINTERING AND DTA–TG ANALYSIS OF COMPOSITES OBTAINED IN cBN–MeSi2–Al SYSTEMS, WHERE Me – V, Cr, Mo, W

Abstract

Using the methods of high-temperature sintering under high pressures, the specifics of the formation of superhard BL group composites in cBN–МеSi₂–Al systems, where МеSi₂ – heat-resistant disilicides MoSi₂, VSi₂, CrSi₂, WSi₂, have been studied. The obtained high-strength ceramic matrix materials have been tested by X-ray phase method; their microhardness, crack resistance and Young’s modulus have been determined. Cutting plates made of these materials, demonstrating the highest operational characteristics in high-speed cutting (300 m/min) of AISI 316L and Inconel 718 steels, have been selected for DTA-TG analysis to study their thermal behaviour in air. Based on the obtained DTA-TG data, it has been found that the obtained superhard composites are heat-resistant, and the phase of their active thermal destruction falls on the temperature range 1100–1200 °C, which is primarily due to the oxidation of cBN grains. Among the oxidation products are higher oxides of d-elements, B₂O₃ and SiO₂ which are capable of forming borosilicate glass products.