PSI - Issue 60

Md Rakim et al. / Procedia Structural Integrity 60 (2024) 298–310 Md Rakim et al. / Structural Integrity Procedia 00 (2023) 000 – 000

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temperature of 710 °C at a pressure of 35 MPa [V. Shankar et al. (2017)]. Towards establishing structural compatibility in components during operation, proper knowledge regarding the fracture toughness of this alloy in solution annealed condition is essential for the designers. The subsequent exposure of the material to hostile service conditions leads to ageing-induced microstructural degradation. To this end, the evaluation of fracture toughness at solution annealed and aged conditions provides a fundamental premise to ensure a fail-safe design of the components [T.L. Anderson (2017)]. Though the fracture toughness of this alloy has been evaluated under solution-annealed conditions, studies on aged conditions of alloy 617M are limited. The current investigation aims to determine the trends of the fracture toughness ( J IC ) of alloy 617M for as-received and ageing conditions at 27 °C, 650 °C, 710 °C and 750 °C using elastic plastic fracture mechanics (EPFM) approach. The ageing has been carried out at 710 °C for different time durations maximum up to 20000 hours. Observations have been discussed in coordination with microstructural degradation during ageing.

2. Material and Experimental Description

The super-alloy 617M has been collected from IGCAR situated in Kalpakkam, India having conditions of as received as well as with different ageing conditions consisting of various metallic compositions with its weight percentage that are depicted in Table 1. Full and one-quarter compact tension (CT) specimens have been extracted from forged and tube-based alloy 617M respectively that are fabricated according to ASTM E 1820-13, as shown in Figs. 1 and 2 respectively.

Table 1: Chemical constituents (Weight %) of Alloy 617M. Elements Ni Cr Mo Co

Al

Ti

C

Si

Fe

Weight %

Balance

22.10

8.32

12.28

1.20

0.43

0.07

0.11

0.38

Fig. 1: Schematic diagram of full CT specimen with all the dimensions used in the fracture toughness testing.