High Temperature Oxidation Behavior of Co-Cr-Y2O3 Modified Aluminide Coatings on Ni-based Superalloy by Pack Cementation Process

The microstructure and high temperature oxidation behavior of Co-Cr-Y₂O₃ modified pack aluminide coatings on Ni-based superalloy GH586 were investigated. The results show that the specific Co-Cr-Y₂O₃ modified aluminide coating has a mass gain of only 0.36 mg/cm² after oxidation at 1000 °C for 100 h, which is much less than that of the substrate at 1000 °C. From X-ray diffraction, the phase of the coatings is mainly AlNi, and after oxidation at 1000 °C for 100 h the denser oxidation scale is composed of Al₂O₃, Cr₂O₃, and CoCr₂O₄. Surface and cross sectional morphologies were characterized by scanning electron microscope (SEM). The coating exhibits a better resistance to high temperature oxidation, compared to the oxidation film of GH586 without coating. Moreover, the growing Cr (W) rich phase is gradually gathered at the grain boundaries during the oxidation, and it is beneficial to providing more Cr element for the dense oxidation film, which is mainly attributed to the excellent high temperature oxidation resistance.