Study on laser-stricken damage to alumina ceramic layer of different surface roughness

This study examines the laser-stricken damage to different alumina ceramic surfaces of different roughness through multi-physical field coupling simulations and laser-striking experiments. The surfaces of different morphologies can be described by waves of different frequencies and amplitudes, and the waves which are discretized can be described by rectangular microstructures of different heights. In this paper, we found that the reaction of roughness surfaces to gauss lasers stricken on them could be simulated by the reaction of rectangular microstructures of different heights to laser strike. The simulation was carried out through the multi-physical field coupling method. The distribution of temperature and stress on rectangular microstructure were examined after being treated by high energy laser. It was found that overhigh temperature and stress were the main causes of laser-stricken damage, but there existed a critical rectangular column height value. The microstructure became increasingly prone to damage and fall-off with the increase of the rectangular column's height, but it became decreasingly prone to damage after the rectangular column reached the critical value. In the experiments, seven roughness zones of alumina ceramic layer were chosen as sample surfaces for laser-striking experiment. The results showed that there was a critical roughness value at a fixed laser energy density. As a result, the amount of particles falling off the surfaces caused by laser strike was rising when the roughness was increasing. However, the amount of particles falling off the surfaces was decreasing after roughness reached the critical value. The critical rectangular column height value in the simulation corresponded to the critical roughness value in the experiment. Therefore, an appropriate selection of roughness is an important factor for obtaining high laser-stricken damage threshold.