Atomic-scale interfacial diffusion of diamond into titanium: Phase transition and layer dependence

Abstract

The diffusion wear of diamond is a commonly recognized wear mode at high temperatures, while the atomic-scale diffusion behavior and the initiation mechanism are scarcely reported. In this work, we conduct a reactive molecular dynamics study to unveil the diffusion mechanism of diamond into titanium from an atomistic perspective. It is found that substantial diffusion of carbon atoms into titanium at a nanoscale temperature occurs at the temperature over 3000 °C, and the diffusion intensifies rapidly with the further increase of temperature. By studying the evolution of the phase transition, we find that the dangling atoms with a coordination less than two play a critical role in initiating the diffusion of diamond, and subsequently more sp-bonded carbon phases are involved in promoting the diffusion process during the non-equilibrium period. Moreover, the diffusivity of carbon atoms in diamond is found to have a strong layer dependence, which can be attributed to the unique phase composition and activation energy for self-diffusion. Eventually, an effective activation energy for the interfacial diffusion from diamond to titanium of 543.9 kJ/mol is obtained. This study provides a new insight into the initiation mechanism of the interfacial diffusion of diamond materials.