冷喷涂CoNiCrAlY涂层在Na_2SO_4熔盐中的热腐蚀行为

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。

Hot Corrosion Behavior of Cold-sprayed CoNiCrAlY Coating in Na2 SO4 Salt

CoNiCrAlY coatings were prepared by cold spray process .After deposition ,the pre‐oxida‐tion treatment of the coating was performed by vacuum heat‐treatment .The microstructure and phase constituent of coating were characterized by XRD ,SEM and EDS .The hot corrosion behavior of as‐sprayed and pre‐oxidized CoNiCrAlY coatings in molten Na2 SO4 at 900℃ was also studied .The re‐sults show that the as‐sprayed coating presents a dense structure with low porosity (less than 0 .28% , volume fraction) and low oxygen content (0 .12% ,mass fraction) .Vacuum pre‐oxidation treatment forms a continuous and denseα‐Al2 O3 layer on the coating surface ,with an average thickness of about 0 .26μm .As‐sprayed and pre‐oxidized coatings can protect the substrate from hot corrosion due to the formation of a continuous and dense α‐Al2 O3 layer .Moreover ,the vacuum pre‐oxidation treatment can alleviate the diffusion of S and O into coating ,and thus the hot corrosion resistance of coating is im‐proved .The damage of hot corrosion plays a more important role than high temperature oxidation . When corrosion in single Na2 SO4 molten salt with the same temperature ,the consumption speed of Al is two times of that in high temperate oxidation.