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采用涂盐热腐蚀试验方法研究了M-38等四种镍基合金(二种铸造:M-38和K_3;二种板材:GH-30和GH-128)在900℃下的热腐蚀。用重量变化和渗透深度评价合金的热腐蚀抗力;用金相、X射线衍射、扫描电镜(配EDS分析)和电子探针分析鉴别腐蚀层结构和产物。结果说明:M-38和GH-30合金热腐蚀过程可分三个阶段—孕育期、扩展期和加速期;GH-128和K_3合金分二个阶段—孕育期和加速期。含有较高铝和钨的GH-128和K_3合金的热腐蚀受到酸性熔融控制,而M-38和GH-30合金受“沿晶界硫化—氧化—开裂—剥落过程”控制。晶粒细、成份均匀的热轧/板材渗透轻微;反之,晶粒粗、成份呈枝晶偏析的铸造合金渗透严重,必须采用失重和渗透深度来评价热腐蚀抗力。
Hot corrosion test of four kinds of Ni-based alloys (two kinds of castings: M-38 and K_3; two kinds of slabs GH-30 and GH-128) of M-38 at 900 ℃ was carried out by hot corrosion test. The hot corrosion resistance of the alloy was evaluated by weight change and penetration depth. The corrosion layer structure and product were identified by metallography, X-ray diffraction, scanning electron microscopy (EDS) and electron probe analysis. The results show that the hot corrosion process of M-38 and GH-30 alloy can be divided into three stages - incubation period, extension period and acceleration period; GH-128 and K_3 alloy are divided into two stages - incubation period and acceleration period. Hot corrosion of GH-128 and K_3 alloys containing higher aluminum and tungsten is controlled by acidic melting while M-38 and GH-30 alloys are controlled by the “grain boundary sulfidation-oxidation-cracking-spalling” process. On the other hand, the coarse grains and the composition alloy with dendritic segregation infiltrate seriously, and the weight loss and penetration depth must be used to evaluate the hot corrosion resistance.