Al2O3/YSZ Composite Coatings Prepared by a Novel Sol-Gel Process and Their High-Temperature Oxidation Resistance

In this study, a novel sot gel process has been utilized to fabricate Al2O3/YSZ (6 wt% yttria partially stabilized zirconia) composite coatings on Ni-based superalloy. The green coatings were obtained by electrophoretic deposition (EPD) in a suspension containing aluminium oxide sol, nano-Al2O3 and micro-YSZ particles, and then treated by so-called pressure filtration microwave sintering (PFMS) process. The as-sintered composite coatings were dense, uniform and crack-free and the phases mainly present alpha-Al2O3, m-ZrO2 and t-ZrO2 as aluminium oxide sot content decreasing. The cyclic oxidation tests at 1000 degrees C for 200 h demonstrate that both of high-temperature oxidation and spallation resistance for the coated samples were remarkably improved. These beneficial effects could be attributed to the special microstructure that micro-YSZ particles embedded in nano/submicron Al2O3 matrix. Meanwhile, the mechanisms of the inhibition of the oxygen diffusion and thermal match are further discussed.