Effect of aluminum concentration on microstructure and evolution behavior of oxide layer on NiAlSiY coating at 500

Abstract Three types of NiAlSiY coatings with different aluminum concentration were prepared. The isothermal oxidation behavior and mechanism of coatings at 500 °C were studied. The results indicate a multilayer oxide layer composed of NiO outer layer and Al2O3 inner layer is formed on the surface. The diffusion of aluminum in the coating and the phase transition from β-NiAl to γ'-Ni3Al promote the formation of Al2O3. Silicon plays an important role in the diffusion of aluminum by refining grains. When the aluminum is 21 wt.%, a dense Al2O3 layer can be formed on the NiAlSiY coating after oxidation for 30 hours.