UV laser ablation of alumina ring faces for mechanical seal applications

Al2O3 Seal ring faces were treated by KrF excimer laser irradiation. Surface characteristics induced by laser irradiation depend upon laser fluence, the 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-processed seal faces showed that, at low fluence (1.8J/cm(2)), the surface is covered by scale due to the melting/resolidification processes. At high fluence (7.5 J/cm(2)), there is no continuous scaling on the surfaces. Material is removed by decomposition/vaporisation and the ablation depth is linearly dependent on the number of pulses; on the surface, a network of microcracks forms. The evolution of surface morphology and roughness is discussed with reference to composition, the microstructure and physical and optical properties of Al2O3, and laser processing parameters.