新型定向凝固高温合金750℃抗热腐蚀性能

Investigation on Hot Corrosion Resistance of a New Directional Solidification Superalloy at 750 ℃

研究了涂有75%Na2SO4+25%NaCl盐膜的新型定向凝固镍基高温合金在750℃的热腐蚀行为,采用X射线衍射仪和带能谱的扫描电镜分析腐蚀产物相组成以及微观结构.结果表明:该合金在开始阶段腐蚀速率较大,随着腐蚀时间的延长以及合金腐蚀层厚度的增加,腐蚀速率降低.腐蚀层可分为3个区域:外层是以TiO2和Cr2O3为主相对疏松的氧化层,中间层具有保护性的是富Cr层,内层是以Al,Ti为主的氧化物以及点状分布的硫化物.合金的热腐蚀主要由氧化-硫化共存伴随着表面腐蚀物挥发形成,在此过程中腐蚀持续向合金基体推进,使得腐蚀层不断增厚.

Hot corrosion resistance of a new directional solidification superalloy with a thin film of 75%Na2SO4＋25%NaCl was investigated at 750 ℃.The phase compositions of corrosion products were identified by X-ray diffractometer（XRD） and the surface and the cross-sectional morphologies of the samples were observed by scanning electron microscope（SEM）.The results showed that the hot corrosion rate is high.With the increasing of hot corrosion time and the thickening of hot corrosion layer,the hot corrosion rate is lower.The corrosion products can be divided into three layers.The loose external layer is mainly formed by TiO2 and Cr2O3,the intermediate layer is Cr-rich and the internal layer is mainly oxides of Al and Ti with the dot-like sulfide.The hot corrosion of the alloy is a coexist process of oxidation and vulcanization,accompanied by some volatility of corrosion products.During the process,the corrosion expands to the matrix of alloy and makes the corrosion layer thicken.