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采用扫描电镜(SME)观测和能谱分析(EDAX)方法研究了改型低膨胀Thermo-Span合金650℃的腐蚀行为,并与标准合金进行了对比。结果表明,合金表面腐蚀产物主要为氧化物和硫化物。合金热腐蚀膜由三层组成,外层主要由Fe、Co和Cr的氧化物组成,改型合金表层还有少量Al和Co的氧化物;次表层为Al、Cr、Ni等元素组成的氧化物;硫化物主要为Ni、Co的硫化物,标准合金硫化物层较厚,而改型合金的硫化物层较薄。改型合金中致密的Al氧化物富积在次表层中,阻止了合金元素的向外扩散和O、S元素的向内扩散,降低了合金的腐蚀速率,提高了合金的耐腐蚀性能。
The corrosion behavior of modified low expansion Thermo-Span alloy at 650 ℃ was investigated by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDAX). The corrosion behavior was compared with that of standard alloys. The results show that the corrosion products of the alloy surface are mainly oxides and sulfides. Alloy hot corrosion film consists of three layers, the outer layer is mainly composed of oxides of Fe, Co and Cr, modified alloy surface layer there is a small amount of Al and Co oxide; sub-surface layer of Al, Cr, Ni and other elements of the composition of oxidation Sulfide is mainly Ni, Co sulfide, the standard alloy sulfide layer is thicker, while the modified alloy sulfide layer is thinner. In the modified alloy, the dense Al oxide accumulates in the subsurface layer, preventing outdiffusion of alloying elements and inward diffusion of O, S elements, reducing the corrosion rate of the alloy and improving the corrosion resistance of the alloy.