Laser-assisted, crack-free surface melting of large eutectic ceramic bodies

The modification of ceramic surfaces by directional laser melting is interesting because it can eliminate surface defects and thus improve the ceramics mechanical performance, as long as one prevents the formation of cracks. The feasibility of surface modification by laser-assisted melting on large t-ZrO₂-Al₂O₃ eutectic ceramic pieces was evaluated in this work. 0.4 mm thick, defect-free, resolidified layers were obtained on plates of 40 mm width by preheating at 1200 °C and processing at 1000 mm/h with a line-shaped CO₂ laser beam and 580 W/cm² irradiance. The surface finish was smooth, free from overlapping-track roughness. The resolidified layer had eutectic microstructure with lamellae-type Al₂O₃ and tetragonal ZrO₂(t-ZrO₂) colonies. The fracture tests of the samples confirmed the absence of crack-type resolidification defects and the removal of surface defects. Although no increase in average flexural strength was observed for surface resolidified samples, they showed significantly lower standard deviation.