PSI - Issue 60

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

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

ageing time. At 27 °C, it has been observed that the values of elastic-plastic fracture toughness are maximum in comparison with results obtained at temperatures 650 °C, 710 °C and 750 °C. Moreover, it has been also observed that the J IC values for all types (base, weld and forged) of alloy 617M at as-received conditions are higher than they are under ageing conditions. In general, alloy 617M shows a decreasing fracture toughness with increasing temperatures. For the base metal from Fig. 9, the result indicates that there is a small decrease of J IC value for the increase in temperature up to 710 °C for material aged up to 5000 hours or less but there has been a drastic decrease in J IC value for 20000 hours aged condition at the same temperatures. At 750 °C, fracture toughness value reduces strongly in case of as-received and also for 1000 hours aged durations compared to prolonged aged conditions. In the case of base material, yield strength has been decreased 25 MPa from 650 °C to 710 °C but again it increases 20 MPa at 750 °C for every ageing time condition. However, this base material has also been shown to possess a higher percentage of elongation at 710 °C temperature compared to the other two temperature ranges. For that reason, at 710 °C, the J IC value does not decrease as sharply compared to the other temperatures. In Fig. 10, the trend indicates that J IC values show a small scatter from room temperature to 750 °C for a particular aged condition. In the case of weld material from Fig. 11, the J IC value shows a small decrement at a particular temperature with an increase in ageing time for all aged conditions. From Fig. 12, the J IC value decreases abruptly from the increasing temperature at 27 °C to 750 °C for all aged conditions prevailing of this material. In the case of a forged material in Fig. 13, with the increase in ageing time, the fracture toughness shows a more decreasing slope compared to the other two materials for all temperature conditions. From Fig. 14, the fracture toughness ( J IC ) value remains constant for all aged conditions at the elevated temperature domain (at 650 °C, 710 °C and 750 °C) but that value has been much lower compared to room temperature.

Fig.9: Variation of J IC with ageing time at different temperature conditions for base material

Fig.10: Variation of J IC with temperature at different ageing times for base material