The purpose of this investigation was to evaluate the microstructure, high-temperature oxidation behaviour, and hardness of a seal coating under controlled exposures at 750 °C with different exposure times. The results reveal that the main phases in the coating are Ni, FeNi3, and hexagonal BN, with α-Al2O3 peaks appearing after 2-h oxidation. As the exposure time increases, the diffraction peak intensity of α-Al2O3 begins to decrease and Cr2O3 peaks appear after 200 h. After 1000 h, Cr2O3 becomes dominant with only small amounts of α-Al2O3 remaining. The high-temperature oxidation process of the coating includes three stages: the fast stage, transition stage, and slow stage. The oxidation rate is constant in each stage, and in the fast stage and slow stages with values of 7.59 × 10−4 and 8.37 × 10−5 mg2·cm−4·s−1, respectively. Initially, α-Al2O3 forms near the pores in the coating, followed by the formation of Cr2O3. As the exposure time increases, oxidation penetrates into the interior of the coating along phase boundaries to form island-shaped inner oxide layers with high concentrations of Cr, Ni, and Fe. Additionally, hardness increases with increasing oxide percentage.

中文翻译：

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NiCrFeAl-hBN密封涂层在高温氧化环境中的腐蚀行为

本研究的目的是评估密封涂层在 750 °C 和不同暴露时间的受控暴露下的微观结构、高温氧化行为和硬度。结果表明，涂​​层中的主要相为Ni、FeNi3和六方BN，氧化2h后出现α-Al2O3峰。随着暴露时间的增加，α-Al2O3 的衍射峰强度开始降低，200 小时后出现 Cr2O3 峰。1000 小时后，Cr2O3 占主导地位，只剩下少量的 α-Al2O3。涂层的高温氧化过程包括三个阶段：快速阶段、过渡阶段和缓慢阶段。每个阶段的氧化速率都是恒定的，在快速阶段和慢速阶段，氧化速率分别为 7.59 × 10-4 和 8.37 × 10-5 mg2·cm-4·s-1。原来，α-Al2O3 在涂层孔隙附近形成，然后形成 Cr2O3。随着暴露时间的增加，氧化作用会沿着相界渗透到涂层内部，形成岛状的内部氧化层，其中含有高浓度的 Cr、Ni 和 Fe。此外，硬度随着氧化物百分比的增加而增加。