Microstructure, Residual Strain and Stress Corrosion Cracking Behavior in 316L Heat-Affected Zone

• Published in: Acta metallurgica sinica : English letters 2016-09, Vol.29 (9), p.848-858
• Main Authors: Ming, Hong-Liang, Zhang, Zhi-Ming, Xiu, Peng-Yuan, Wang, Jian-Qiu, Han, En-Hou, Ke, Wei, Su, Ming-Xing
• Format: Article
• Language: English
• Subjects: 316L不锈钢; Austenitic stainless steels; Base metal; Characterization and Evaluation of Materials; Chemistry and Materials Science; Corrosion; Corrosion and Coatings; Dissimilar metals; Electron back scatter; Grain boundaries; Hardness tests; Heat affected zone; Materials Science; Metallic Materials; Microhardness; Microstructure; Nanotechnology; Nuclear power plants; Optical microscopes; Organometallic Chemistry; Residual stress; Scanning electron microscopy; SCC敏感性; Spectroscopy/Spectrometry; Stainless steel; Strain; Strain hardening; Stress corrosion cracking; Tribology; Welded joints; 应力和; 显微组织; 残余变形; 焊接热影响区; 焊接过程; 腐蚀行为
• ISSN: 1006-7191; 2194-1289
• DOI: 10.1007/s40195-016-0461-7

Austenitic stainless steels are usually chosen to make many components of nuclear power plants （NPPs）. However, their microstructure in the heat-affected zone （HAZ） will change during the welding process. Some failures of the weld joints, mainly stress corrosion cracking （SCC）, have been found to be located in the HAZ. In this research, the microstructure, micro-hardness, residual strain and SCC behavior at different locations of the 316L HAZ cut from a safeend dissimilar metal weld joint were studied. However, traditional optical microscope observation could not find any microstructural difference between the HAZ and the base metal, higher residual strain and micro-hardness, and higher fraction of random high-angle grain boundaries were found in the HAZ than in the base metal when studied by using electron back-scattering diffraction scanning and micro-hardness test. What＇s more, the residual strain, the microhardness and the fraction of random grain boundaries decreased, while the fraction of coincidence site lattice grain boundaries increased with increasing the distance from the fusion boundary in 316L HAZ. Creviced bent beam test was applied to evaluate the SCC susceptibility at different locations of 316L HAZ and base metal. It was found that the HAZ had higher SCC susceptibility than the base metal and SCC resistance increased when increasing the distance from the fusion boundary in 316L HAZ.