PSI - Issue 60

Cyril Reuben Raj et al. / Procedia Structural Integrity 60 (2024) 709–722 Cyril Reuben Raj / Structural Integrity Procedia 00 (2024) 000 – 000

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3) There are no significant differences in macro hardness of as-welded and thermal aged weld specimens. This is because ferrite content (which transforms to hard phases) is lower in the weld thereby making its effect negligible 4) The embrittlement rate which denoted from micro-hardness tests was considerably higher in ferrite phase as compared to austenite phase. This is believed to be due to phase transformation in the δ -ferrite separates into Fe rich α and Cr -rich α′ by spinodal decomposition mechanism together with the formation of G -phase precipitation. The higher ferrite hardness of the thermal aged weld specimens is due to the hardening mechanism based on α – α′ misfit inducing an elastic stress . 5) Effect of thermal aging on weld prepared by SMAW shows significant reduction in ductility i.e. approximately 40% with respect to virgin weld. The microhardness of the thermally aged weld is higher than virgin weld. These results of increased hardness indicate increase in strength and decrease in ductility. This observation is consistent with the tensile results of decrease in ductility. Tensile test results of the heat affected zone shows no significant effect of thermal aging. 6) Although hardness of ferrite phase in the weld has increased significantly but there is no change in hardness of austenite phase after thermal ageing. However, there is no change in strength of the weld because the content of the ferrite phase in weld is very low compared to austenite phase. References Anon. International Organization for Standardization, 2002. Metallic Materials: Instrumented Indentation Test for Hardness and Materials Parameters. Test Method. ISO. Anon. American National Standards Institute, 2007. Standard practice for instrumented indentation testing. American Society for Testing and Materials. Baddoo, N.R., 2008. Stainless steel in construction: A review of research, applications, challenges and opportunities. Journal of constructional steel research, 64(11), pp.1199-1206. Chandra, K., Singhal, R., Kain, V. and Raja, V.S., 2010. Low temperature embrittlement of duplex stainless steel: Correlation between mechanical and electrochemical behavior. Materials Science and Engineering: A, 527(16-17), pp.3904-3912. Chandra, K., Kain, V., Bhutani, V., Raja, V.S., Tewari, R., Dey, G.K. and Chakravartty, J.K., 2012. Low temperature thermal aging of austenitic stainless steel welds: Kinetics and effects on mechanical properties. Materials Science and Engineering: A, 534, pp.163-175. Chen, J., Jang, C., Kong, B.S., Xiao, Q., Subramanian, G.O., Kim, H.S. and Shin, J.H., 2020. Effect of thermal ageing on the corrosion behaviour of austenitic stainless steel welds in the simulated PWR primary water. Corrosion Science, 172, p.108730. Chopra, O.K. and Rao, A.S., 2016. Methodology for estimating thermal and neutron embrittlement of cast austenitic stainless steels during service in light water reactors. Journal of Pressure Vessel Technology, 138(4), p.040801. Dubey, J.S., Chakravartty, J.K., Singh, P.K. and Banerjee, S., 2006, January. Fracture behaviour of type 304LN stainless steel and its welds. In International Conference on Nuclear Engineering (Vol. 42428, pp. 663 672). Hong, S., Kim, H., Kong, B.S., Jang, C., Shin, I.H., Yang, J.S. and Lee, K.S., 2018. Evaluation of the thermal ageing of austenitic stainless steel welds with 10% of δ -ferrites. International Journal of Pressure Vessels and Piping, 167, pp.32-42. Kar, J., Roy, S.K. and Roy, G.G., 2017. Effect of beam oscillation on microstructure and mechanical properties of AISI 316L electron beam welds. Metallurgical and materials transactions A, 48(4), pp.1759-1770. Kim, Y.J., Youn, G.G., Hwang, J.H., Kim, Y.J. and Miura, Y., 2022. Aging constants for efficient fracture toughness prediction of thermally aged GTAW/SMAW of 316L stainless steel. International Journal of Pressure Vessels and Piping, 197, p.104632. Kumar, A., Singh, B. and Sandhu, S.S., 2020. Effect of thermal aging on metallurgical, tensile and impact toughness performance of electron beam welded AISI 316 SS joints. Fusion Engineering and Design, 159, p.111949.