晶粒尺寸对耐热钢在高温水蒸汽中的氧化行为的影响

从氧化动力学、氧化膜相组成及微观结构方面，研究了晶粒尺寸对18Cr-8Ni耐热钢在700 ℃下的高温水蒸汽中氧化行为的影响。结果表明：晶粒细化提高了耐热钢的抗水蒸汽氧化性能，降低了其氧化增重，推迟了失稳氧化的发生；晶粒细化改变了耐热钢氧化膜的微观结构，减小了“弹坑”区的尺寸且促进了“弹坑”区与合金界面上富Cr氧化物层的形成；晶粒细化对耐热钢抗水蒸汽氧化性能的改善主要归因于其对氧化物的形核和Cr向氧化膜/合金界面扩散的促进作用。

Effect of Grain Size on Oxidation of Heat-resistant Steels in High Temperature Water Steam

Effect of grain size on oxidation of 18Cr-8Ni heat-resistant steels in high temperature water steam was studied at 700 ℃. Oxidation kinetics was obtained by weighting specimens at intervals. After oxidation, all the samples were investigated using field emission scanning electron microscopy (FE-SEM) in terms of plain and cross section views, the chemical composition was analyzed by X-ray energy dispersive analysis (EDS), and the oxide phases were identified by X-ray diffraction (XRD). The results show that grain refinement improves the oxidation resistance of steels to high temperature water steam by lowering the mass gains and postponing the onset of breakaway oxidation; grain refinement alters the microstructure of oxide scale by reducing the size of “crater” oxide region and promoting the formation of Cr-rich layer at scale/alloy interface; the beneficial effects of grain size on oxidation of steels are ascribed to the promotion of oxide nucleation and Cr transport towards scale/alloy interface.