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利用冷喷涂技术制备CoNiCrAlY涂层,并对涂层进行了真空预氧化处理。结合X射线衍射,扫描电镜,能谱分析等方法研究预氧化处理前后的CoNiCrAlY涂层在900℃的Na2SO4熔盐中的热腐蚀行为。结果表明:冷喷涂CoNiCrAlY涂层含氧量为0.12%(质量分数),孔隙率小于0.28%(体积分数)。真空预氧化处理在涂层表面生成厚约0.26μm连续、致密的α-Al_2O_3氧化膜;喷涂态涂层和预氧化涂层在热腐蚀150h后表面均生成了以α-Al_2O_3为主的致密连续氧化膜,保护了基体免受腐蚀破坏;真空预氧化处理有效减缓了S和O等元素向涂层内扩散的速率,从而提高了涂层的抗Na2SO4熔盐热腐蚀性能;高温热腐蚀对涂层的破坏作用远大于高温氧化。在相同温度下,涂层在单一Na2SO4熔盐中腐蚀时,Al的消耗速率约为高温氧化时的2倍。
The CoNiCrAlY coating was prepared by cold spray technique and the coating was vacuum pre-oxidized. The corrosion behavior of CoNiCrAlY coating before and after pre-oxidation treatment at 900 ℃ in Na2SO4 molten salt was studied by X-ray diffraction, scanning electron microscopy and energy spectrum analysis. The results show that the oxygen content of CoNiCrAlY coating is 0.12% (mass fraction) and the porosity is less than 0.28% (volume fraction). The vacuum pre-oxidation treatment produced a continuous and dense α-Al_2O_3 oxide film with a thickness of 0.26μm on the surface of the coating. The sprayed and pre-oxidized coatings formed dense continuous α-Al_2O_3 Oxide film to protect the substrate from corrosion damage; vacuum pre-oxidation treatment effectively slow down the elements such as S and O diffusion rate into the coating, thereby increasing the corrosion resistance of the coating Na2SO4 hot corrosion; hot corrosion of the coating The destruction of the layer is much larger than the high temperature oxidation. At the same temperature, the rate of Al depletion is about twice as high as that at high temperature oxidation when the coating is etched in a single Na2SO4 molten salt.