冷喷涂CoNiCrAlY涂层在Na_(2)SO_(4)熔盐中的热腐蚀行为

Hot Corrosion Behavior of Cold-sprayed CoNiCrAlY Coating in Na_(2)SO_(4) Salt

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。

C oN iC rAlY coatings were prepared by cold spray process.A fter deposition,the pre-oxidationtreatment of the coating was performed by vacuum heat-treatment.T h e microstructure and phaseconstituent of coating were characterized by X R D,S E M and EDS.T h e hot corrosion behavior of assprayedand pre-oxidized C oN iC rA lY coatings in molten Na2S04at900°C was also studied.T h e resultsshow that the as-sprayed coating presents a dense structure with low porosity(less than0.28%,volume fraction)and low oxygen content(0.12%,mass fraction).Vacuum pre-oxidation treatmentforms a continuous and dense crA l203layer on the coating surface,with an average thickness of about0.26jLtm.As-sprayed and pre-oxidized coatings can protect the substrate from hot corrosion due to theformation of a continuous and dense crAl203layer.M o reo ver,the vacuum pre-oxidation treatment canalleviate the diffusion of S and O into coating,and thus the hot corrosion resistance of coating is improved.T h e damage of hot corrosion plays a more important role than high temperature oxidation.When corrosion in single Na2S04molten salt with the same temperature,the consumption speed of A1is two times of that in high temperate oxidation