研究了Fe-20Cr-5Al和Fe-20Cr-5Al-0.5Y合金在1200℃,1atm纯SO_2气氛中的高温腐蚀行为。测定了腐蚀动力学曲线,观察了腐蚀产物表面,横截面和脆断断口的形貌,并分析了元素的分布,确定了腐蚀产物的相组成。结果表明,这两种合金在300小时实验周期内只发生氧化反应,没有遭受硫化腐蚀。无丫合金表面发展出双层结种氧化膜,而钇的添加使合金表面氧化膜呈单层结构,且粘着性显著改善。钇的有益作用在于对Al~(3+)在α-Al_2O_3中扩散的有效抑制作用。
High temperature corrosion behavior of Fe-20Cr-5Al and Fe-20Cr-5Al-0.5Y alloys in pure SO_2 atmosphere at 1200℃ was studied. The corrosion kinetics of these alloys was measured. X-ray diffraction was employed to identify the components in corrosion products. The morphologies of corrosion product surfaces, cross sections and fractures were examined by means of SEM, and the element distribution in corrosion product scales was also analyzed. The experimental results show that the alloys underwent pure oxidation without sulfidation observed in the experimental condition during the period of time of 300 hours. A duplex oxide scale was developed on the surface of the yttrium-free alloy while a single layer oxide scale was produced for the yttrium-containing alloy. The adhesion of the oxide scale was found to be remarkably improved by the addition of yttrium in the alloy. The beneficial effect of yttrium is discussed and attributed to the effective blocking of the bulk diffusion of Al~(3+)in the Al_2O_3 scale in the presence of yttrium.
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