The temperature dependence of hardness and toughness for polycrystalline diamond materials

Polycrystalline diamond materials (PCD), known for ultra-high hardness and wear resistance, are widely used in cutting tools, petroleum drilling, and grinding machines. However, its excellent performance is limited by its extreme brittleness and sensitivity to high temperatures. Studying the hardness and toughness of PCD materials is crucial for evaluating their potential applications under extreme conditions. The hardness and toughness of PCD materials under different temperature and load conditions are examined in this paper. Vickers hardness and dynamic elastic modulus tests were performed to develop a mathematical model for evaluating fracture toughness. The results show that the hardness of PCD materials decreases as the temperature rises from 20 °C to 600 °C, with the rate of decline becoming more pronounced at higher temperatures. The fracture toughness is initially weakened with rising temperature but increases with further temperature rise after 400 °C. At different temperatures, the fracture and crack propagation of PCD materials are closely related to factors such as stress conditions, cobalt bonding phase, grain boundary structure, and internal defects. In particular, the mode of crack propagation is predominantly transgranular fracture, with very few instances of intergranular fracture.