Rapid microwave sintering of protective ZrO2 coatings on reactive metal powder compacts

Electrophoretic deposition was used to create protective coatings of sub-micrometric ZrO2 particles on substrates made of conductive powders mixture (Ni+Al). In order to achieve the required mechanical properties, such coating requires a sintering stage. However, the rapid microwave sintering of thin zirconia layers usually requires some form of pre-heating or auxiliary heating of the material, in order to increase its loss factor. In this study, the heat released by the exothermal reactions of combustion synthesis occurring in the powders compact, is used to concurrently synthesize high-temperature rated aluminides and pre-heat and sinter the overlaying zirconia coating. Finite elements numerical simulation, fully coupling electromagnetic, heat transfer and chemical reactions application modes is used to investigate the temperature profile and power density distribution during the microwave sintering process, Experimental results show that the concurrent synthesis allows to form a thin alumina-based bond coat, which is expected to increase the high temperature resistance of the zirconia-coated aluminides.