POST-PROCESSING OF CERAMIC OXIDE AND METALLIC COATED SURFACES USING MICROWAVE GLAZING

摘要

In the material environment configuration, where the mechanical components and cutting tools are facing higher performance requirements, but are often restricted by their surface properties, these can be enhanced by applying industrial ceramics and/or metallic coatings. Thermal plasma spraying is one such pragmatic coating technique for ceramics and their oxides (TBC), and a high-velocity oxyfuel (HVOF) method for metallic coatings. Inherent presence of defects due to the cohesive strength, ultra-finely grained microstructure within the splates, porosity morphology, occurrence of cracks and defects calls for suitable modification of the coating microstructures in order to improve the quality and performance. In microwave heating (MH), energy is directly transferred to the material through an interaction of electromagnetic waves with molecules leading to volumetric heating. At low temperatures, ceramics are transparent to microwaves and absorb them at high temperatures resulting in a change in their microstructure and material characteristics. In this study, MH has been used for post-processing of plasma-sprayed alumina-titania, partially stabilized zirconia TBC coatings on the steel substrate, and HVOF-sprayed tungsten cobalt oxide metallic coatings on cemented carbide tools, and the resulting properties are evaluated. Results show a reduction in porosity, enhancement in microhardness, surface finish, and wear resistance of the glazed surfaces of coatings.