Isothermal oxidation behaviors of packed aluminide coatings of Ni-Cr-W superalloy at 1100℃

The isothermal oxidation behavior of packed aluminide coatings of Ni-Cr-W superalloy at 1100℃ was investigated. Results from scanning electron microscopy and X-ray diffraction indicate that the oxidation dynamics curve of packed aluminide coatings can be divided into two stages: initial rapidly stage and metaphase slowly stage. Oxides on packed aluminide coatings surface have a transformation process as following: crystal θ-A1₂O₃→equalaxial α-A1₂O₃→α-A1₂O₃→particle α-A1₂O₃→particle unite α-A1₂O₃ during the whole oxidation. During the initial stage of oxidation, carbides can be able to holdback coating degeneration caused by interdiffusion between Ni element and Al element.