Effect of grain size and orientation degree on thermal shock resistance of BN-matrix textured ceramics under cyclic thermal shock

Abstract

Hexagonal boron nitride (h-BN) has a typical two-dimensional flake structure, so the anisotropy of h-BN grains caused by directional arrangement cannot be ignored when studying the thermal vibration resistance of materials under thermal cycling. In this paper, h-BN-matrix textured ceramics prepared with different holding time were selected, and the effects of thermal vibration temperature difference and thermal cycles on the phase and thermal vibration resistance of h-BN-matrix textured ceramics were studied. The results show that under the condition of high-frequency thermal cycling, the residual strength ratio (RSR) of BN-based textured ceramics is closely related to the holding time and showing obvious anisotropy. At the same time, there is a thermal vibration temperature range in which the internal stress will change from relief to re-accumulation.