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本文选用五种常用镍基合金在700～850℃的SF_6试验装置中进行对比试验,结果表明:800℃时的腐蚀增重与时间呈直线关系;腐蚀增重随温度升高而加剧;在700℃下这五种合金抗SF_6腐蚀尚可,>750℃则发生较严重的腐蚀,其中GH-49和K-38合金较好。能检查到的腐蚀产物有CrF_3、CrF_2、NiF_2和硫化物等。探针分析表明外层是肿胀疏松的氟化物和硫化物;中间层带有富镍基体碎块、氟化物、硫化物和氧化物的混合层;内层基体中有硫化物带。由于合金表面所形成的氟化物膜无保护性,其腐蚀过程受气体/固体界面反应控制,所以腐蚀速率呈直线变化。在高温SF_6中氟的腐蚀将起主导作用,硫则起先导作用。当基体铬硫化的同时镍亦发生硫化,故能防止形成完整的氟化镍膜。因此可以认为,SF_6比单一氟或硫的腐蚀更严重。
In this paper, five commonly used nickel-based alloys were tested in the SF_6 test device at 700 ~ 850 ℃. The results show that the corrosion weight gain at 800 ℃ is in a linear relationship with the time; the corrosion weight gain increases with the increase of temperature; ℃ corrosion resistance of these five alloys is still SF6,> 750 ℃ occurred more serious corrosion, GH-49 and K-38 alloy which is better. Can check the corrosion products are CrF_3, CrF_2, NiF_2 and sulfide. Probe analysis revealed that the outer layers were loosely swollen fluorides and sulfides; the middle layer had a mixed layer of nickel-rich matrix fragments, fluorides, sulfides, and oxides; and the inner matrix had sulfide bands. Since the fluoride film formed on the alloy surface is unprotected, the corrosion process is controlled by the gas / solid interface reaction, so the corrosion rate changes linearly. The corrosion of fluorine will play a leading role in the high temperature SF_6, while the sulfur will play a leading role. Nickel is also vulcanized while the matrix is being chromium-cured, thus preventing the formation of a complete nickel fluoride film. It is therefore believed that SF6 is more corrosive than either single fluorine or sulfur.