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采用等离子喷涂技术在GH4169基体上制备了NiCr-Cr₂O₃-Ag-BaF₂/CaF₂高温固体自润滑涂层, 并对涂层进行了热处理. 通过SEM观察, XRD分析及拉伸实验, 对热处理前、后涂层的微观组织结构及结合强度进行了对比研究. 结果表明: 喷涂态涂层由Ni(Cr)相、Cr₂O₃相、Ag相和(Ba, Ca)F相组成, 组织形貌为粗大的层状结构, 结合强度为30.4 MPa; 经500和650℃热处理后, (Ba, Ca)F相转变为BaF₂和CaF₂相, 涂层内氟化物相与喷涂态相比更致密; 大量Cr₂O₃和NiO析出相的形成、长大使涂层内Ni(Cr)相细化; 在650 ℃下进行12或24 h热处理后, 涂层结合强度增至46.5 MPa; 热处理温度 为800 ℃时, BaF₂发生严重氧化, 致使涂层内组织疏松, 局部形成大面积孔洞, 涂层结合强度显著降低.

Foil air bearings are self–acting hydrodynamic bearings relying on solid lubricants to reduce friction and wear during sliding at start–up and shut–down when speeds are too low to allow the formation of a hydrodynamic air film. The service temperature of traditional solid lubricants such as graphite, PTFE and MoS₂ is limited to only about 300 ℃, The NiCr–Cr₂O₃–Ag–BaF₂/CaF₂ solid lubricants can make foil air bearings run from room temperature to 650 ℃ In this paper, the NiCr–Cr₂O₃–Ag–BaF₂/CaF₂ high temperature solid self–lubricant coatings were fabricated on GH4169 matrix using plasma spray technology. Microstructures and adhesive strengths of the coatings as sprayed and treated at 500, 650 and 800 ℃ were analyzed by SEM, XRD and tensile test. The results show that the as–sprayed coating consists of Ni(Cr) phase, Cr₂O₃ phase, Ag phase and (Ba,Ca)F phase and has coarse lamellar–likstructures, the adhesive strength reaches 30.4 MPa. After heat treatments at 500 and 650 ℃ (Ba, Ca)F phase transforms into BaF₂/CaF₂ phase, meanwhile the BaF₂/CaF₂ becames compacted. The formatin and growth of lots of black Cr₂Oand iO precipitations make Ni(Cr) phase refine. After heat treatment at 650 ℃ for 12 or 24 h, the adhesive strength increases to 46.5 MPa. But after heat treatment at 800 ℃ BaF₂ was oxidized, which makes the microstructures loose and the porosities are formed in a large area. The adhesive strength is decreased evidently.