Effect of Thermal Aging on Fracture Mechanical Properties and Crack Propagation Behavior of Alloy 52 Narrow-Gap Dissimilar Metal Weld
Determination of the fracture toughness properties and thermal aging behavior of dissimilar metal weld (DMW) joints is of utmost importance for successful structural integrity and lifetime analyses. This paper presents results from fracture resistance (J-R), fracture toughness (T0) and Charpy-V impact toughness tests as well as fractography performed for an industrially manufactured narrow-gap DMW mock-up (SA508-Alloy 52-AISI 316L). Tests were performed on post-weld heat treated, 5000 h aged and 10,000 h aged material. The results show that this DMW is tough at the SA 508-Alloy 52 interface, which typically is the weakest zone of a DMW. The DMW joint maintains its high fracture resistance also after thermal aging. Crack propagates for a large part in the carbon-depleted zone (CDZ) of SA 508 but deflects occasionally to the Alloy 52 side due to small weld defects in µm scale. Ductile-to-brittle transition temperature determined from Charpy-V impact toughness tests increases due to thermal aging, but only to a minor extent. No significant change is observed for the T0 transition temperature due to aging.
KeywordsDissimilar metal weld Ni-base alloy Microstructural characterization Aging
This study has been made in collaboration between VTT Technical Research Centre of Finland Ltd and Aalto University School of Engineering within the Nickel-base Alloy Welding Forum (NIWEL) research project funded by TEKES, Finnish (Teollisuuden Voima Oyj and Fortum Oyj) and Swedish (Ringhals AB and OKG AB) energy industry. The authors wish to express their gratitude for the funding and participation of all the participants of the project.
- 1.J.C. Lippold, et al., Welding Metallurgy and Weldability of Stainless Steels (Wiley Hobocken, N.J., USA, 2005). ISBN 0-47147379-0Google Scholar
- 2.S. Kiser, Nickel-alloy consumable selection for severe service conditions. Welding J. 69(1), 30–35 (1990)Google Scholar
- 3.J. Hilkes et al., Electrodes for Welding 9% Nickel Steel. Welding J. 83(1), 30–37 (2004)Google Scholar
- 4.P.L. Andresen, et al., PWSCC of Alloys 690, 52 and 152. in Proceedings of the 13th International Symposium on Environmental Degradation of Materials in Nuclear Power Systems - Water Reactors, Whistler, Canada, CNS-SNC (CD-ROM), Canada, April 19–23, 2007Google Scholar
- 5.D. Buisine, et al., French Steam Generator Tubes: An Overview of Degradations. in: Proceedings of the 7th Fontevraud Conference, Avignon, France, SFEN (CD-ROM), France, September 26–30, 2010Google Scholar
- 6.Hänninen et al., Structural Integrity of Ni-base Alloy Welds. VTT Technology 175. VTT Technical Research Centre of Finland, Espoo, 2014, p. 257. ISBN 978-951-38-8259-4Google Scholar
- 7.M. Ahonen, et al.. Fracture Mechanical and Microstructural Characterization of Narrow-gap Safe-end Dissimilar Metal Weld. in Proceedings of Baltica X—2016—Life Management and Maintenance for Power Plants, Helsinki, Finland, June 7–9, 2016Google Scholar
- 8.P. Joly, et al., Fracture Toughness in the Ductile-brittle Transition and Thermal Ageing Behaviour of Decarburized Heat Affected Zone of Alloy 52 Dissimilar Metal Welds of Nuclear Components. in Proceedings of the ASME-2014 Pressure Vessel and Piping Conference, Anaheim, CA, USA July 20–24, 2014Google Scholar
- 10.G. Gage, et al., Thermal Ageing Embrittlement of the Heat-Affected-Zone in a PWR RPV Steel Weldment. Nuclear Power Plant Life Extension, Snowbird, Utah, USA July 31-August 3, 1988Google Scholar
- 11.T. Sarikka, et al., Microstructural Characterization of Alloy 52 Narrow-Gap Dissimilar Metal Weld after Aging. in Proceedings of the 18th International Symposium on Environmental Degradation of Materials in Nuclear Power Systems—Water Reactors, Portland, Oregon, USA August 13–17, 2017. (Submitted)Google Scholar
- 12.K. Wallin, Fracture Toughness of Engineering Materials: Estimation and Application. (EMAS, UK, Publishing, 2011), p. 543. ISBN 0-9552994-6-2Google Scholar