Chip morphology and surface integrity in ultraprecision cutting of yttria-stabilized tetragonal zirconia polycrystal

Yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) is an important material for dental, biomedical, and mechanical applications. In this study, Y-TZP was cut by a single-crystal diamond tool in the micro-nanometre scale. The chip morphology and machined surface/subsurface properties under various conditions were investigated by scanning electron microscopy, Raman spectroscopy and cross-sectional transmission electron microscopy. Two factors dominating the material removal were identified: (i) crystal grain refinement and (ii) tetragonal-to-monoclinic phase transformation, the mechanisms of which were established by experiments and finite element simulations. This study provides a possible solution to the rapid fabrication of small 3D features on Y-TZP with nanometric surface roughness and an ultra-fine-grained subsurface layer.