Effect of Sensitization Treatment on Intergranular Corrosion Property of 825 Alloy
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摘要: ,采用50 %硫酸-硫酸铁晶间腐蚀试验及动电位极化曲线分析方法对敏化态825合金抗晶间腐蚀性能异常增强现象进行研究,采用金相(OM)、扫描电镜(SEM)和透射电镜(TEM)观察形貌并分析其原因。结果表明:825合金在750 ℃下保温1 h得到的敏化态试样的腐蚀速率和腐蚀电流密度分别为固溶态试样的57 %和48 %;敏化态和固溶态试样的晶界均无析出物析出,晶界周边无贫铬区,材料无晶间腐蚀敏感性;但晶内析出的TiN及Ti(C,N)粒子与基体电位存在差异,易导致点腐蚀的发生。经过750 ℃保温1 h的敏化处理后,可得到晶粒大小均匀、内部析出的TiN及Ti(C,N)粒子分布更加均匀、材料抗晶间腐蚀性能增强的825合金。Abstract: The influence of sensitisation treatment on the intergranular corrosion properties of 825 alloy is investigated by 50 % sulphuric acid-iron sulphate intergranular corrosion test and polarisation curve analysis, and the causes are observed and analysed by metallography (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that the corrosion rate and corrosion current density of the sensitized specimen of 825 alloy held at 750 ℃ for 1 h are 57 % and 48 % of those of the solid solution specimen, respectively. There are no precipitate precipitation at the grain boundaries of the sensitized and solid solution specimens, and no chromium-poor zones around the grain boundary, therefore, the material has no intergranular corrosion susceptibility. However, there are differences in potentials between the precipitated TiN and Ti(C,N) particles within the grains and the substrate, which can easily lead to the occurrence of pitting corrosion. After sensitisation treatment at 750 ℃ for 1 h, the grain size of the 825 alloy is uniform, the distribution of TiN and Ti(C,N) particles precipitated is uniform, and the corrosion resistance of the material is enchanced.
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