Effects of h-BN on mechanical properties of reaction bonded β-SiAlON/h-BN composites

β-SiAlON/h-BN composites with improved machinability and thermal shock resistance were fabricated via a reaction bonding procedure using raw materials of Si, Al₂O₃, AlN and h-BN. Effects of h-BN on properties of the composites, including density, strength, hardness, fracture toughness, machinability and thermal shock resistance, were investigated. XRD analysis was performed to analyze the phase composition of the composites, and SEM was employed to analyze their microstructure. The results showed that the density of the composites went through a maximum value with h-BN content increased from 0 to 50 wt%. Vickers hardness of the composites with less h-BN addition was decreased without obvious strength loss. Fracture toughness of the composites was decreased with h-BN content increased from 0 to 50 wt%. Drilling hole and thread tapping test showed that the machinability of the composites with h-BN addition was commendable. Thermal shock resistance of the composites with h-BN content higher than 20 wt% was excellent, and the retained strength of the composites was decreased slightly with the temperature difference and thermal shock times increased.