Laser assisted densification of surface porosity in structural alumina ceramic

Alumina ceramics are extensively used in structural components due to excellent thermal and mechanical properties. The effective utilization of alumina ceramic in these applications necessitates the minimization of inherent processing defects such as porosity. Laser processing can be effectively used for densification of the surface porosity of these ceramics especially desirable for the applications where ceramics are exposed to high temperatures and aggressive environments. The present study discusses the influence of laser processing fluence on the surface porosity of the alumina ceramic irradiated with a continuous wave Nd: YAG laser beam. A detailed scanning electron microscopy characterization was carried out to indicate the mechanism of densification of porosity during laser irradiation based on development of solidification microstructures. Finally, a fractal geometry based approach was introduced to characterize the surface microstructures such that useful correlation can be developed for the prediction of surface porosity directly from the fractal dimensions. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.