Material removal and surface damage mechanisms in micro drilling of Nd: YAG material

Neodymium-doped Yttrium Aluminum garnet (Nd:YAG) materials enable the vital applications in both industrial and military fields. In this study, the nanoscratch and micro drilling tests were conducted to investigate the material removal and surface damage mechanisms of Nd:YAG. The brittle-ductile transformation and intermit-tent edge breaking mechanisms were elaborated in the nanoscratch tests. After the scratch load exceeded 37 mN, the material removal mechanism transforms from elastic-plastic deformation to brittle fracture. Subsequently, the various material removal and surface damage mechanisms were observed on the hole surface and hole wall in micro drilling, which was consistent with the scratch test results. On the hole surface, the discontinuous edge-breaking defects with a petal shape are the primary surface damages, which encircle the hole surface to form a sunflower shape. However, the hole wall quality primarily depends on the proportion of flaky exfoliation and the brittle fracture zones on the hole wall, and the hole wall roughness increased with the drilling speed and feed rate. This study aims to understand the material removal mechanisms and optimise the machining parameters in micro drilling of hard and brittle materials.