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采用粉末共渗法在镍基高温合金表面获得约为300μm厚的铝硅涂层,考察了其在1050℃下混合硫酸盐(Na2SO4+25%K2SO4)中的热腐蚀行为,较为系统地研究了其热腐蚀动力学行为及其机制、熔盐作用下氧化膜的生长与破坏过程和热腐蚀不同时间后的腐蚀产物等。结果表明,相对于已有铝硅涂层在高温条件下(850~980℃)热腐蚀的相关研究,其在1050℃超高温下混合硫酸盐中的热腐蚀更加严重,这与超高温下熔盐对保护性氧化膜的熔解作用更强密切相关。在本实验条件下,铝硅涂层在1050℃下混合硫酸盐中热腐蚀70 h后已趋于失效,当热腐蚀90 h时其腐蚀层深度已达约75μm;此时,不仅涂层中Al和Ni直接与熔盐相互作用,而且Cr、Si也参与了与熔盐的反应,同时高温合金基体中的Ti也已扩散至表面。
The surface of the Ni-based superalloy was powder-infiltrated to obtain an Al-Si coating approximately 300μm thick. The hot corrosion behavior of the Al-Si coating was investigated systematically in mixed sulphate (Na2SO4 + 25% K2SO4) at 1050 ℃. Its hot corrosion kinetic behavior and its mechanism, the growth and destruction process of the oxide film under the action of molten salt, and the corrosion products after the hot corrosion at different times. The results show that compared with the existing research on hot corrosion of Al-Si coating at high temperature (850-980 ℃), the hot corrosion of mixed sulfate at 1050 ℃ ultra-high temperature is more serious. Salt is more strongly related to the melting of the protective oxide film. Under the experimental conditions, the Al-Si coatings tended to be ineffective after hot-etching at 1050 ℃ for 70 h, and the depth of corrosion layer reached about 75μm when hot-tempered for 90 hours. In this case, Al and Ni interact directly with the molten salt, and Cr and Si also participate in the reaction with the molten salt, and Ti in the superalloy matrix also diffuses to the surface.