PSI - Issue 71

Ganesh Nigudage et al. / Procedia Structural Integrity 71 (2025) 218–225

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Fig.8. SEM micrographs of Carbide distribution in – (a), (b) As-fabricated; (b), (c) 1200h thermal aged; (d), (e) 1800h thermal aged.

Fig.9. Number density of carbides in as-fabricated and thermal aged specimens.

4. Conclusions

Acknowledgements The authors would like to thank Shri K.B. Gaonkar, Nirav Kumar for their help in carrying out the experiments. The tensile properties of thermal aged specimens (both 1200 h and 1800 h) at room temperature estimated by validated correlations are within 10% compared to as-fabricated condition which indicate insignificant change in tensile properties for the thermal ageing time studied. This result is in confirmation with no measurable change in size and number density of carbides and grain size. This suggests that hardening mechanism does not contribute to embrittlement of the RPV steel under thermal ageing time studied. In this study effect of thermal ageing on tensile properties of Cr-Mo-V-Ni RPV base steel is evaluated using small punch test. SPT estimates tensile properties using correlations. Thermal ageing of broken half Charpy specimens of base RPV steel was carried out at 500 °C for 1200 h and 1800 h. The validated correlations were used to evaluate tensile properties of thermal aged specimens. Microstructure and carbide distribution of thermal aged specimens were observed under optical and SEM respectively. The fracture surface of SPT tested samples were observed under SEM.