Effect of Shot Peening on the Evolution of Scale on T91 Steel Exposed to Steam

Applied Sciences

Yeonkwan Kang¹  Yinsheng He¹  Keesam Shin²  Liming Xu² 

[1] KEPCO Research Institute, Korea Electric Power Corporation, Munji-ro, Yusung-Gu, Daejeon 34056, Korea;School of Materials Science and Engineering, Changwon National University, Changwon 51140, Korea;

关键词: T91;    shot peening;    steam oxidation;    scale separation;   

DOI  :  10.3390/app11198831

来源: DOAJ

【 摘 要 】

Shot peening can be an effective solution for the prevention or retardation of scale formation, and subsequent exfoliation, upon exposure of the inner tube to steam in coal-fired power plants. In this study, specimens of T91 tubes were shot peened and then exposed to 1-bar steam for 100–1000 h at 650 °C, and were then analyzed using Vickers hardness test and microscopic techniques OM, SEM, TEM, etc. The analysis indicates that the oxide scales are typically Fe₂O₃ on the topmost layer, Fe₃O₄ below, and a FeCr₂O₄ spinel on the bottom in both shot peening treated and untreated specimens. However, the oxide scale thicknesses of shot peened specimens are thinner, indicating that shot peened specimens have better oxidation resistance. In addition, numerous defects, such as voids and micro-cracks, were found in the untreated specimens, which are believed to cause exfoliation of the uppermost Fe₂O₃ layers of the specimens exposed to steam for 800 and 1000 h. By contrast, the shot peened specimens maintained a dense contact oxide scale with fewer defects.

【 授权许可】

Unknown