研究了工业纯铁、Fe-Cr和Fe-Al合金表面有Na_2SO_4沉积时于O_2/SO_2/SO_3气氛中的低温热腐蚀行为。测定腐蚀动力学曲线,研究温度、气体组成及合金元素对腐蚀动力学的影响,并对腐蚀产物的形貌和组成进行观察与分析。结果表明,在工业纯铁、Fe-Cr和Fe-Al合金的低温热腐蚀过程中都发生金属表面致密氧化层的快速成长和疏松的Fe_2O_3在盐膜中的沉积,且前者对腐蚀的贡献居大。以实验结果为依据,初步提出了电化学机理模型,并用以阐述铁基合金低温热腐蚀过程。
Hot corrosion behavior of commercial iron and Fe-Cr,Fe-Al alloys in the presence of a thin Iayer of Na_2SO_4 deposit was studied in O_2/SO_2/SO_3 gas atmospheres at 650～750℃. The reaction kinetics were monitored and found to be dependent upon temperature, gas composition and alloy element content. XRD, SEM, EPMA and chemical analysis were employed to characterize the corrosion products. The results showed that the corrosion product scale for each material tested was composed of a compact oxide plus sulfide layer and a porous Fe_2O_3 plus salt layet. The both layers increased in thickness with the proceeding of corrosion, and the compact layer grew faster than the porous one. On the basis of experimental results, an electrochemical mechanism is preliminarily proposed, and it is used to illustrate low temperature hot corrosion processes of iron base alloys.
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