Laser remelting of zirconia surface: Investigation into stress field and microstructures

Investigation into the laser remelting of zirconia surfaces in a nitrogen gas environment is carried out. The thermal stress fields during and after the laser treatment process are predicted numerically. The microstructural and morphological changes in the laser-treated region are examined using optical microscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). The residual stresses are determined using the XRD technique. It is found that the residual stress predicted remains high along a depth of 50m below the laser-treated surface. The predictions of residual stress agree well with the XRD data. A fine dendritic structure is formed in the vicinity of the surface, which contributes to the surface hardness. In addition, transformation of t-ZrO₂ to c-ZrO ₂ at high temperature is accompanied by the formation of ZrN in the surface vicinity.