NiCrAlY coatings were prepared using high-velocity oxygen fuel spraying (HVOF), and the coatings were removed from the substrate to achieve a uniform shape. Vacuum heat treatment (VHT) of the as-sprayed coatings was conducted at different temperatures (1000, 1100, and 1200 °C), and the specimens were subjected to isothermal oxidation exposure testing in air at 1100 °C for up to 21 h. The results show that the high temperature oxidation resistance of the coating increased gradually with the increase in VHT temperature, and the coating of VHT1200 had higher oxidation resistance. The high temperature oxidation resistance of the coating was related to the microstructure transformation of the coating. In VHT coatings, β-NiAl became a dispersed irregular block morphology. The γ’-Ni3Al in VHT1000 presented a granular morphology. However, in VHT1100 and VHT1200, γ’-Ni3Al became a lamellar morphology. This transformation of microstructure promotes the form of exclusive α-Al2O3 scale. With the increase in VHT temperature, the content of yttrium on coatings’ surface was increased and the pores were gradually eliminated. The concentration of yttrium on coatings’ surface prevented the formation of θ-Al2O3 and low porosity was beneficial in improving the internal oxidation of the coating.
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机译：使用高速氧气燃料喷涂（HVOF）制备幼亮涂层，并从基材中除去涂层以实现均匀的形状。在不同温度（1000,1100和1200℃）的时喷涂涂层的真空热处理（VHT），并在1100℃下在空气中进行样品在1100℃下进行等温氧化暴露测试。结果表明，随着VHT温度的增加，涂层的高温氧化性逐渐增加，VHT1200的涂层具有更高的抗氧化性。涂层的高温氧化抗性与涂层的微观结构转化有关。在VHT涂层中，β-nial成为分散的不规则嵌段形态。 VHT1000中的γ'-Ni3Al提出了颗粒形态。然而，在VHT1100和VHT1200中，γ'-Ni3al成为层状形态。这种微观结构的转化促进了独占α-Al2O3规模的形式。随着VHT温度的增加，涂层表面上的钇含量增加，孔逐渐消除。涂层上的钇的浓度防止了θ-Al 2 O 3的形成，低孔隙率有益改善涂层的内部氧化。
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