China Foundry (May 2011)
An investigation on bonding interface microstructure of ceramic coating prepared on AZ91D by evaporated pattern casting technique
Abstract
PbO-ZnO-Na2O ceramic coating was fabricated on the AZ91D Mg-alloy substrate surface by using of evaporated pattern casting (EPC) process. The ceramic coating was characterized through scanning electron microscopy (SEM) observation, energy dispersive X-ray spectrometer (EDS) and so on. The research was emphasized on the formation process of ceramic coating and the interface bonding conditions between ceramic coating and the substrate. Results show that the glass powder (PbO-ZnO-Na2O) melts when contacts with the high temperature liquid metal, and solidifies on the surface of the substrate with the decrease of temperature. Therefore, the ceramic coating was successfully prepared with the formation of the bonding interface with the substrate. Beside the influence of coating layer thickness, the vacuum level was also investigated. Further analysis indicates that oxide inclusions and decomposition products of foam pattern had a significant effect on the bonding interface. To obtain a good bonding interface between the ceramic coating and the substrate, the metal liquid oxidation and inclusions must be decreased and the decomposition products of foam pattern should be exhausted from the EPC coating completely.
