Molecular dynamics simulation of the diffusion behaviour between Co and Ti and its effect on the wear of WC/Co tools when titanium alloy is machined

Abstract

In the process of machining titanium alloy, the high temperature and intensive stress at the tool/chip interface may activate atomic diffusion, which causes the tool to wear. In this paper, the temperature and stress at the interface were investigated using finite-element simulation. The diffusion behaviour of the Co/Ti interface at the atomic level was studied using molecular dynamics simulations. The results show that the cutting speed plays a notably important role in diffusion at the Co/Ti interface. The atomic diffusion across the interface becomes more significant with the increase in cutting speed, and a higher cutting speed corresponds to a thicker diffusion layer. The interfacial region exhibits an amorphous structural order at a high cutting speed; simultaneously, it was easier for the Ti atoms to penetrate into the Co atom side because of the larger interstices among the Co atoms. Turning tests were performed. The element diffusion was analysed based on the Auger electron spectroscopy depth profile. The simulation results were experimentally verified. The microscopic mechanism of the diffusion wear of the tool was revealed. This study contributes to a better understanding of the wear mechanisms of cutting tools in titanium alloy machining.