SINTERING, PHYSICAL AND TECHNICAL CHARACTERISTICS AS WELL AS DTA-TG ANALYSIS OF CARBIDE-CONTAINING COMPOSITES OBTAINED IN cBN-MeCх-(Al) SYSTEMS, WHERE Me – Ti, Zr, V, Cr, Ta

Abstract

Under conditions of high pressures and temperatures for cBN-MeC_х-(Al) systems, where Me – Ti, Zr, V, Cr, Tа, the phase formation processes, certain physical and technical as well as thermal characteristics of the obtained superhard ceramic matrix composites have been studied. According to the results of XRD-analysis data, sintering in these systems is leads to the formation of minor amounts borides of d- elements, AlN, Al₂O₃, and the final sintered ceramics are non-porous with high Young modules (500-600 GPa) at a hardness of up to 43 GPa. All materials obtained can be used as cutting inserts for metal working by cutting. Using the DTA-TG analysis in air in the temperature range of 200-1300 °C, the processes of thermal and chemical destruction of sintered cBN-carbide materials have been analyzed. It has been experimentally established that visible oxidation processes for all superhard composites start at T > 800 °C, are accompanied by exothermic effects and, as a rule, a gain in the total mass of the sample. The oxidation proceeds in two stages, starting with the interaction of d-metal carbide with atmospheric oxygen and further oxidation of cBN grains. Among the reaction products after thermal treatment, B₂O₃ and the corresponding higher carbide-forming metal oxide have been registered.