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采用化学气相沉积(CVD)方法在单晶高温合金基体上制备了铬改性铝化物(Cr-Al)涂层,研究了1050℃下该涂层在空气中的高温氧化行为。采用X-射线衍射(XRD)、扫描电子显微镜(SEM)、能谱仪(EDS)等方法分析了Cr-Al涂层在高温氧化过程中相结构、显微组织和成分的演变规律,结果表明:经1050℃氧化300 h后,该涂层的氧化动力学曲线符合抛物线演变规律,Cr-Al涂层的涂覆提高了基体合金的抗高温氧化性能;高温氧化200 h内涂层保持良好的表面形貌,而经过300 h氧化后涂层出现了严重的氧化膜剥落现象;揭示了在高温氧化条件下Cr-Al涂层退化的相变过程,涂层区相结构转变过程为β-NiAl相→β-NiAl相(主)+γ′-Ni3Al相(次);扩散区相结构转变过程为β-NiAl相+析出相→β-NiAl相(主)+γ′-Ni3Al相(次)+析出相→γ′-Ni3Al相(主)+β-NiAl相(次)+析出相→γ′-Ni3Al相+析出相。
Chromium-modified aluminide (Cr-Al) coatings were prepared on single crystal superalloy substrate by chemical vapor deposition (CVD) method. The high-temperature oxidation behavior of the coatings at 1050 ℃ in air was investigated. The evolution of the phase structure, microstructure and composition of the Cr-Al coating during high temperature oxidation was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) After oxidation at 1050 ℃ for 300 h, the oxidation kinetics curve of the coating agrees with the parabolic evolution law. The coating of Cr-Al coating improves the high-temperature oxidation resistance of the matrix alloy. Surface morphology, and after 300 h oxidation coating showed a serious oxide film flaking phenomenon was revealed under high temperature oxidation of Cr-Al coating degradation of the phase transformation process, coating phase transition structure is β-NiAl Phase → β-NiAl phase (main) + γ’-Ni3Al phase (second); the transformation process of the phase structure in the diffusion zone is β-NiAl phase + precipitated phase → β-NiAl phase + Precipitated phase → γ’-Ni3Al phase (main) + β-NiAl phase (secondary) + precipitated phase → γ’-Ni3Al phase + precipitated phase.