Compositions,mechanical properties and microstructures of cBN-based composites sintered with Al or TiC

Abstract

Cubic boron nitride (cBN)-based composites were prepared from cBN–Al and cBN–TiC mixtures, respectively, under high pressure and high temperature (HPHT). During sintering, Al reacted with cBN and produced AlN and AlB₂, while TiC did not react with cBN. With increasing Al from 5–20 wt-%, the strength of the cBN-based composites decreased first, then increased. AlN and AlB₂ could strengthen the cBN-based composites to a certain extent. In the preparation from cBN–TiC, 10 wt-% addition of TiC was the optimal formulation to obtain the densest microstructure. Hardness of the two kinds of composites displayed different tendencies. On the other hand, cBN-based composites were treated at 1200°C for 1200 s. It was found that the isothermal oxidation process could be described by parabolic laws with slight oxidation scales formed on samples’ surfaces in different morphologies.