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. 0.4mm thick, defect-free, resolidified layers were obtained on plates of 40mm width by preheating at 1200°C and processing at 1000mm/h with a line-shaped CO2 laser beam and 580W/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.