Cyclic oxidation performance of Al2O3 and Y2O3-modified chromizing coatings

Three chromizing coatings were produced by chromizing on electrodeposited Ni-Al2O3 nano composite coating, pure Ni film and Ni-Y2O3 composite coating using pack cementation method at 1100°C for 3 h. The oxidation performance of these coatings was studied by the cyclic oxidation experiment. SEM observation indicates that compared to Y2O3 microparticles, the deposited Al2O3 nanoparticles are not only homogeneously dispersed in nanocrystalline Ni grains but also retarded the grain growth in the coatings during chromizing. Oxidation experiment results indicate that compared to chromizing coating formed on pure Ni film, the Al2O3 modified chromizing coating exhibite an increased cyclic-oxidation resistance due to the fast formation of a continuous chromia layer, together with the retarding effect of Cr outward diffusion by Al2O3 particles along grain boundaries in the chromizing coating. The dissolution and precipitation of Y2O3 microparticles not only have the same effect as Al2O3 particles to improve the cyclic-oxidation resistance, but also have reactive element effect to increase the cyclic-oxidation resistance.