Abnormal phase evolution and degradation behavior of Al-Si coating during 30, 000 h aging. (December 2022)

• Record Type: Journal Article
• Authors: Zhao, Zhiyu; Lu, Jintao; Huang, Jinyang; Zhang, Xingpu; Xu, Hui; Wang, Jiangwei
• Is Part Of: Corrosion science. Volume 209(2022)
• Publication Date: 2022-12
• Subjects: A. Metal coatings -- A. Intermetallics -- B. SEM -- B. TEM -- C. Oxidation; Corrosion and anti-corrosives -- Periodicals; 620.11223
• DOI: 10.1016/j.corsci.2022.110764
• Languages: English
• ISSNs: 0010-938X

Abstract

Abstract: Degradation behavior of silicon-modified aluminide coating over 30, 000 h aging at 650 ℃ was investigated. Significant microstructural evolutions, abnormal elemental distribution and newly-formed secondary internal oxides were observed after prolonged aging. As the aging time extended from 10, 000 h to more than 20, 000 h, interdiffusion induced the formation of α-Fe/AlNi/α-Fe structure, while the AlNi precipitates gradually replaced the Fe-rich matrix by acting as Al source for the formation of surface alumina scale. Based on the microstructural evolutions, a new regime of coating degradation involving both the transitions of diffusion mode and oxidation mechanism is proposed. Highlights: The microstructural evolution of Al-Si coating after 30, 000 h aging is investigated. Interdiffusion within the coating replaces that between the coating and IDZ to dominate the coating degradation. Transitions of oxidation mechanism within the coating are revealed. A new regime of coating degradation, marked by α-Fe/AlNi/α-Fe sandwich structure, is elucidated.