Microwave glazing of alumina-titania ceramic composites for enhanced properties

Alumina-Titania ceramic composites are widely used and can be plasma spray deposited on softer substrates to attain enhanced properties. The application envelope of atmospheric plasma sprayed ceramic and ceramic composites can be widened considerably by reducing inherent surface defects by post processing them through other techniques like microwave (MW) irradiation. In microwave processing, high frequency microwaves penetrate into the bulk of the material and the volumetric interaction of the electromagnetic fields with the material results in dielectric (volumetric) heating. Ceramics are transparent to microwaves at low temperatures, however, start absorbing at higher temperatures resulting change in microstructure and material characteristics. In this study, plasma spray deposited alumina-titania ceramic composite was further processed (glazed) by subjecting to microwave radiation. The processed material is evaluated through XRD, SEM, microhardness survey, wear resistance, porosity and surface finish. Results indicate microwave irradiation induce compressive stresses in the material and possible flow of ductile gamma -Al2O3 phase during microwave heating yielding glazed surface. Healing of surface defects results in enhanced microhardness and surface finish as well as reduced wear rate of the glazed surface. Results are discussed.