Temperature evolution and material removal mechanisms in nanosecond-pulsed laser ablation of polycrystalline diamond

A study of the single-pulsed laser ablation process for a polycrystalline diamond is presented. A simulation of the laser ablation process using a finite element model is carried out to understand the temperature evolution, material removal process and mechanisms, as well as the other physical phenomena associated with this process, that is, carbon phase transformation, liquid-phase ejection and vapour/plasma shielding effect. It is found that mass material removal can be achieved through surface evaporation under a higher laser pulse energy. It is further found that diamond graphitization under laser irradiation is responsible for heat losses due to the large heat accumulation in the graphitized diamond, while cobalt melting suppresses the evaporation of cobalt phase because of the heat consumption for solid-liquid transition. Crater depth and surface formation are also investigated experimentally on the polycrystalline diamond using single-pulsed laser ablation. The predicted crater depths are in reasonably good agreement with the corresponding experimental results.