Microstructure, Residual Strain and Stress Corrosion Cracking Behavior in 316L Heat-Affected Zone Hong-Liang Ming 1,2 • Zhi-Ming Zhang 1 • Peng-Yuan Xiu 1 • Jian-Qiu Wang 1 • En-Hou Han 1 • Wei Ke 1 • Ming-Xing Su 3 Received: 23 March 2016 / Revised: 7 June 2016 / Published online: 5 July 2016 Ó The Chinese Society for Metals and Springer-Verlag Berlin Heidelberg 2016 Abstract 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 safe- end 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 micro- hardness 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. KEY WORDS: Austenitic stainless steels; Heat-affected zone; Microstructure; EBSD; Residual strain; Stress corrosion cracking 1 Introduction Austenitic stainless steels are usually chosen to fabricate primary pipes of NPPs because of their proper strength and excellent corrosion resistance. However, low alloy steels are usually selected to make the pressure vessels not only due to their high strength but also due to their low cost [1, 2]. And hence welding process is commonly used to connect these two parts. It has been well known that thermal cycles from the welding process, especially from the multi-pass welding process, can lead to high residual stress/strain and changes of the microstructure and properties in the HAZ of austenitic stainless steels, such as the change of the grain boundary type, higher micro-hardness, the formation of carbides and chromium-depleted zones adjacent to grain boundaries [1–4]. These special microstructures will affect the SCC Available online at http://link.springer.com/journal/40195 & Jian-Qiu Wang wangjianqiu@imr.ac.cn 1 Key Laboratory of Nuclear Materials and Safety Assessment, Liaoning Key Laboratory for Safety and Assessment Technique of Nuclear Materials, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China 2 University of Chinese Academy of Sciences, Beijing 100049, China 3 Shanghai Research Center for Weld and Detection Engineering Technique of Nuclear Equipment, Shanghai 201306, China 123 Acta Metall. Sin. (Engl. Lett.), 2016, 29(9), 848–858 DOI 10.1007/s40195-016-0461-7