Effect of c-BN surface modification on the microstructure and mechanical properties of (Ti,W)C-based cermet tool materials

Alumina-coated cubic boron nitride (c-BN) particles (c-BN@Al₂O₃) were prepared using a heterogeneous nucleation method. Then, they were added to a (Ti,W)C-based cermet tool material after synthesis via vacuum hot-press sintering. The microstructure and mechanical properties of the (Ti,W)C-based cermet tool material with varying c-BN@Al₂O₃ contents were recorded and analyzed. The results show that with increasing c-BN@Al2O3 concentration, the relative density, flexural strength, fracture toughness, and Vickers hardness all increase first and then decrease, and the average grain size first decreases and then increases. The introduction of Al₂O₃ into the c-BN particles used for surface modification can improve the wettability and interfacial bonding strength between the c-BN and matrix particles, restrain the grain growth of the matrix particles, and improve the flexural strength of cermet tool materials. The addition of c-BN@Al₂O₃ also alters the crack propagation mechanism of the cermet tool material and introduces multiple toughening mechanisms to improve the fracture toughness of the cermet tool material. The high hardness of c-BN and Al₂O₃ is the main reason for the increase in hardness; however, excessive addition of such material reduces the relative density, resulting in a decrease in hardness.