PSI - Issue 60

ScienceDirect Available online at www.sciencedirect.com ^ĐŝĞŶĐĞ ŝƌĞĐƚ StructuralIntegrity Procedia 00 (2024) 000 – 000 Available online at www.sciencedirect.com ^ĐŝĞŶĐĞ ŝƌĞĐƚ StructuralIntegrity Procedia 00 (2024) 000 – 000 Available online at www.sciencedirect.com Procedia Structural Integrity 60 (2024) 709–722

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2452-3216 © 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the ICONS 2023 Organizers 10.1016/j.prostr.2024.05.088 2452-3216© 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the ICONS 2023 Organizers 1. Introduction Stainless steel scopes to find usage in numerous areas of Nuclear Power Plants due to its sustainability to environmental conditions, long term service and corrosion resistance [Was and Ukai (2019)]. In typical light water reactor based nuclear power plants, austenitic stainless steel grade SS 304LN has been used in primary piping system to connect the reactor pressure vessel nozzles. Some physical properties of austenitic stainless steel holds 2452-3216© 2024 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the ICONS 2023 Organizers Abstract A girth austenitic stainless steel (say, SS) weld joints are invariably used for joining piping components in typical light water based nuclear power reactor. To avoid hot cracking during the welding of SS, some 5-8% delta ferrite is required in the filler material, which remains in the metastable phase in weld pool. Under prolonged exposure at operating temperature (300 ℃ ), these delta ferrite which remains in weld metal may get transformed to brittle phases that leads to reduction in its ductility and toughness. Hence, for prolonged safe operation of these piping components in power reactors, it is important to quantify the amount of degradation in toughness and ductility because of thermal aging. Therefore, present work aims at quantifying the reduction in toughness in SS weld joint by carrying out accelerated thermal ageing and thereafter carrying out micro-structural examinations, hardness and tensile tests on specimens machined from different regions of weld joint. Austenitic stainless steel (SA312 Type 304LN) pipe weld joints have been prepared using Gas Tungsten Arc Welding (GTAW) for root passes and Shielded Metal Arc Welding (SMAW) for filling passes. Full-scale pipe weld were subjected to thermally ageing for 10,000 and 20,000 hours at temperature 400 ℃ . The effects of thermal aging on the structural morphology, hardness at macro and micro scale and tensile characteristics of different zones of these joints have been quantified. Micro-structural examination reveals vermicular and lathy morphology in the ferrite and austenite phase. It has been found that, thermal aging leads to significant increase in ferrite hardness and reduction in ductility for the weld specimen from SMAW compared to that of the GTAW and no effect in heat affected zone. Keywords: Austenitic Stainless Steel weld, Thermal Aging, Tensile Property, Toughness and Ductility. 1. Introduction Stainless steel scopes to find usage in numerous areas of Nuclear Power Plants due to its sustainability to environmental conditions, long term service and corrosion resistance [Was and Ukai (2019)]. In typical light water reactor based nuclear power plants, austenitic stainless steel grade SS 304LN has been used in primary piping system to connect the reactor pressure vessel nozzles. Some physical properties of austenitic stainless steel holds © 2024 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the ICONS 2023 Organizers Abstract A girth austenitic stainless steel (say, SS) weld joints are invariably used for joining piping components in typical light water based nuclear power reactor. To avoid hot cracking during the welding of SS, some 5-8% delta ferrite is required in the filler material, which remains in the metastable phase in weld pool. Under prolonged exposure at operating temperature (300 ℃ ), these delta ferrite which remains in weld metal may get transformed to brittle phases that leads to reduction in its ductility and toughness. Hence, for prolonged safe operation of these piping components in power reactors, it is important to quantify the amount of degradation in toughness and ductility because of thermal aging. Therefore, present work aims at quantifying the reduction in toughness in SS weld joint by carrying out accelerated thermal ageing and thereafter carrying out micro-structural examinations, hardness and tensile tests on specimens machined from different regions of weld joint. Austenitic stainless steel (SA312 Type 304LN) pipe weld joints have been prepared using Gas Tungsten Arc Welding (GTAW) for root passes and Shielded Metal Arc Welding (SMAW) for filling passes. Full-scale pipe weld were subjected to thermally ageing for 10,000 and 20,000 hours at temperature 400 ℃ . The effects of thermal aging on the structural morphology, hardness at macro and micro scale and tensile characteristics of different zones of these joints have been quantified. Micro-structural examination reveals vermicular and lathy morphology in the ferrite and austenite phase. It has been found that, thermal aging leads to significant increase in ferrite hardness and reduction in ductility for the weld specimen from SMAW compared to that of the GTAW and no effect in heat affected zone. Third International Conference on Structural Integrity 2023 (ICONS 2023) Thermal aging effects on Tensile and Metallurgical characteristics of Stainless steel weld joint Cyril Reuben Raj a *, Suranjit Kumar a , Kamlesh Chandra b , S. Roychowdhury b , P. K. Singh a . a Reactor Safety Division, Reactor Design & Development Group, Bhabha Atomic Research Centre, Mumbai-400085, India. b Materials Processing and Corrosion Engineering Division, Materials Group, Bhabha Atomic Research Centre, Mumbai-400085, India. Third International Conference on Structural Integrity 2023 (ICONS 2023) Thermal aging effects on Tensile and Metallurgical characteristics of Stainless steel weld joint Cyril Reuben Raj a *, Suranjit Kumar a , Kamlesh Chandra b , S. Roychowdhury b , P. K. Singh a . a Reactor Safety Division, Reactor Design & Development Group, Bhabha Atomic Research Centre, Mumbai-400085, India. b Materials Processing and Corrosion Engineering Division, Materials Group, Bhabha Atomic Research Centre, Mumbai-400085, India. Keywords: Austenitic Stainless Steel weld, Thermal Aging, Tensile Property, Toughness and Ductility.