材料期刊网

<正> 高温合金在含硫-氧环境中的行为已开始引起重视。已有的工作表明,单一地研究合金的高温腐蚀不能充分反映合金在使用条件下的行为和破坏倾向,必需了解在高温腐蚀环境和应力复合作用下的特性,才能为使用合金和研制新合金提供可靠的依据。本工作应用自制的可控制环境气氛的高温持久试验装置,以含SO_2的气氛为环境介质,研究了GH33合金在含硫氧化环境和外加应力的复合作用下产生的热腐蚀现象,并对其有关机理作了分析探讨。

Hot corrosion of GH33 Ni-base superalloy was investigated by conducting creep tests in an environmental chamber circulated with SO_2-air mixed gas. Analyses were carried out on the outer surfaces, longitudinal sections and fracture surfaces of the tested specimens, including specimens tested to rupture or interrupted at various extents of creep strain. The results were compared with those tested in air.It was found that both in air and in SO_2/air environment a Cr-riched oxide scale was formed initially, which protected the grain boundaries and matrix from being attacked by SO_2. Therefore, as long as the protective scale was not ruptured by the creep deformation, SO_2/air and air played the same role in corrosion, i. e. oxidation is the principal process. But after the deformation increased to a certain extent, intergranular cracks initiated on the specimen surface and sulfur attack occurred. Molten Ni-Ni_3S_2 eutectics formed at grain boundaries which led to catastrophic corrosion and premature failure of the specimen.The mechanism of such corrosion process is discussed. It is suggested that the interaction of hot corrosion and creep of superalloy greatly accelerated the failure process and attention should be paid to this problem during engineering design or material application.