Effect of Temperature and Ageing on Fracture Toughness of Alloy 617M

• Published in: Procedia Structural Integrity Vol. 60; pp. 298 - 310
• Main Authors: Rakim, Md, Basu, P., Jana, M., Choudhury, S., Mitra, A., Acharyya, S.K., Krishnan, S.A., Moitra, A.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 2024
• Subjects: Ageing; Elastic-plastic fracture toughness (JIC); J-R curve; Monotonic loading; Elastic-plastic fracture toughness (JIC); Ageing; Monotonic loading; J-R curve
• ISSN: 2452-3216; 2452-3216
• DOI: 10.1016/j.prostr.2024.05.051

In recent years, Advanced Ultra Super Critical (AUSC) plants have used Ni-Cr-Co-Mo based alloy 617M for high-temperature components like steam piping and rotors, where material resistance against fracture after prolonged exposure in a hostile environment is a matter of concern to the designers. To this end, fracture toughness characterization of the material in as-received and aged conditions using an elastic-plastic fracture mechanics (J-R curves) approach can provide a significant input towards the component integrity assessments at service conditions. In this study, J-R curves of the alloy 617M have been determined for the as-received and differently aged (up to 20000 h at 710 °C) conditions using compact tension (CT) specimens following ASTM E 1820-13. Repeated tests have been carried out at temperatures 27 °C, 650 °C, 710 °C and 750 °C. The fracture toughness (JIC) thus determined, has shown a declining trend with test temperatures. This attributes to the ease of the crack initiation process owing to the γ′ induced matrix hardening and subsequent ageing-inducing precipitations of M23C6 carbides at the grain boundaries.