HastelloyC型铸造镍基合金的析出相及其对合金腐蚀行为的影响

Precipitated Phase in Cast Nickel-Base Hastelloy C Alloy and Influence of Precipitates on Corrosion Behaviour of the Alloy

本文采用金相显微镜、Ｘ射线衍射、电子探针和透射电子显微镜相结合的方法，研究了耐“氧化－还原”，复合介质腐蚀的含Ｃｒ、Ｍｏ、ｗ的ＨａｓｔｅｌｌｏｙＣ型铸造镍基合金中析出相的形态、成分、结构及形成条件。着重研究了析出相含Ｃｒ量和敏化时间对合金腐蚀行为的影响。结果表明，ＨａｓｔｅｌｌｏｙＣ型合金在８００～１２００℃范围内有ｐ相、μ相、Ｍ＿６Ｃ相及少量σ相析出，９００℃左右析出量相对少些。析出相数量越多，富Ｃｒ、Ｍｏ越严重，则合金的耐点蚀和晶间腐蚀性能越差。敏化时间延长，亦使合金耐点蚀和晶间腐蚀性能有所下降，但对合金的均匀腐蚀程度影响不大。

n this research,a combination of optical microscopo,x-ray diffraction spectrum,EMPA and TEM is used to invest igate the morphology,composition, structure and condition of formation of precipitated phase in cast Cr-Mo-W containing Hastelloy-C alloy aimed to use in “oxidation-reduction”composite harsh corrosive medium. The influence of chromium content of precipitated phase and sensitization time on the corrosion-resisistant property of the alloy is emphatically researched.Experimental resuIts show that,in Hastelloy-C alloy,phases of p,μ,M_6C and small amount of a precipitated during sensitization in the tem-perature range from 800℃ to 1200℃ are found, and minimum amount of precipitates in the alloy sensi-tlzed at 900℃。 The larger amount the precipitates and the more severe the richness of Cr and Mo in pre-cipitates,the poorer the resistance of alloy to pitting corrosion and intergranular corrosion. Long sensitiza-tion time can also decrease the resistance to pitting and intergranular corrosion. However,the degree of gen-eral corrosion of alloy is not remarkably affected.