Effect of Al-Si coating on Thermal Cycling NaCl-induced Hot

• Main Authors: Liu, Hsum-Chou770, 劉勳洲
• Other Authors: Wang Chaur-Jeng
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/61212131450213247403

碩士 === 國立台灣工業技術學院 === 機械工程技術研究所 === 85 === Abstract The NaCl-induced hot corrosion of 310 stainless steel with and without hot dipped Al- Si coating layer was thermal-cycling investigated at 750-850 ℃ in this study. The effects of the supplying NaCl and the cyclic treatment on the formation of the scale morphology as well as the Al-Si coating on improving of corrosion resistance of the steel also explored. The results show that the total depth of attack of the steel increased linearly with increasing cyclic times. The outer scale formed on the steel always spalled after cooling, due presumably to repeating proceses of supplying NaCl, oxychloridation, chloridation, and reoxidation, which leaded to the trend of the total depth of attack increasing with increasing cyclic times. The hot-dipped Al-Si coating layer can provide a good protection for thermal-cyclic tests without NaCl deposit. However, the coating fails to protect the substrate under the condition with NaCl deposits although it is effective at the initial period. The thermal-cyclic process with NaCl deposits causes surface microcracks, which provides a shortcut for NaCl inward diffusion, resulting in the severe spallation at the interface between the coating and the substrate at the later period, leading to a similar corrosion behavior as that without Al-Si coating.