PSI - Issue 60

Md Rakim et al. / Procedia Structural Integrity 60 (2024) 136–148

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Md Rakim et al. / Structural Integrity Procedia 00 (2023) 000 – 000

conducted as per ASTM with a constant load ratio ( R = 0.1) and frequency of 15 Hz. From the experimental results, a major trend is observed of decreasing threshold stress intensity factor ( ) with an increase in ageing time and test temperature. The variations in the with test temperature and ageing time have been discussed and the crack growth mechanism has been established through microstructure and fractographic studies validating from existing literatures. © 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 Keywords: Ageing; Alloy 617M; Fatigue crack growth (FCG); Threshold stress intensity factor ( ∆ K TH ).

Nomenclature R load ratio threshold stress intensity factor ⁄ fatigue crack growth rate stress intensity factor range maximum stress intensity factor minimum stress intensity factor W specimen width B specimen thickness maximum force minimum force force range α normalized crack size

1. Introduction Nowadays, super-alloys namely alloy 617M mainly Ni-based have become a well-known name for their operational performance in high-temperature boilers and super heaters used in AUSC power plants [J. Klower et al. (2013)]. Next upcoming power plants focus their operation on more advanced climatic conditions like elevated temperatures (710 °C) also with higher levels of stress (35 MPa) compared to traditional plants in the aspects related to designing and safety management [A.K. Karnati et al. (2019), Ch.V. Rao et al. (2019)]. The plant components are subjected to static and repeatable cyclic thermal gradients along with vibration-induced flowing loads operated while starting up and shutting down of the plant which results in the cause of various types of damage. The literature review verifies that this alloy is very prone to age-induced disintegration, ductility reduction, reduction in strength and fracture resistance degradation [A.N. Singh et al. (2018), Y. Guo et al. (2013)]. Though, several investigations have been carried out regarding the deformation behaviour of alloy 617M based on tensile [Ch.V. Rao et al. (2019),