Evolution of the Microstructure and Mechanical Properties of cBN-Based Cutting Tools with Silicides Compounds as Binder Phase

Abstract

Silicide based compounds are widely used for coatings due to their high melting temperature, oxidation resistance and moderate density. Employment of binders based on silicides of transitional metals can provide cBN-based cutting tools with higher chemical stability and better performance. The relationship between phase composition, microstructure and mechanical properties of novel polycrystalline cubic boron nitride (PcBN) materials were investigated. Three series of PcBN samples were made by high pressure high temperature (HPHT) sintering. Silicides of chromium-CrSi2, vanadium-VSi2 and molybdenum MoSi2 were used as a binder phase in each case, while aluminum was introduced to the mixture as an oxygen getter. During HPHT sintering at temperatures above 1850 C the formation of borides of binder phase were observed in cases with VSi2 and MoSi2. For system with CrSi2 binder, temperature of boride formation was found to be lower-1600 C. Materials with MoSi2 binder phase demonstrated the highest level of microhardness. Performance of materials were investigated in conditions of machining of stainless steel AISI 316L and Inconel 718.