UV laser ablation of alumina ring faces for mechanical seal applications

Al2O3 Seal ring faces were treated by KrF excimer laser irradiation. Surfac e characteristics induced by laser irradiation depend upon laser fluence, t he number of laser pulses, the frequency ana duration of the laser pulses, the rotation rate of the ring, and the processing atmosphere. Microstructural analyses of the surface and cross section of the laser-proc essed seal faces showed that, at low fluence (1.8J/cm(2)), the surface is c overed by scale due to the melting/resolidification processes. At high flue nce (7.5 J/cm(2)), there is no continuous scaling on the surfaces. Material is removed by decomposition/vaporisation and the ablation depth is linearl y dependent on the number of pulses; on the surface, a network of microcrac ks forms. The evolution of surface morphology and roughness is discussed wi th reference to composition, the microstructure and physical and optical pr operties of Al2O3, and laser processing parameters.