PSI - Issue 71

Pramod Ravindra Kushwaha et al. / Procedia Structural Integrity 71 (2025) 74–81

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Fig. 9. Variation of rupture life with load for Su-263 at 650 °C

Minimum creep rate is a crucial parameter that can be evaluated from small punch creep curve. The plot of minimum creep rate versus load is shown in Fig. 8. The power law relationship (equation 2) (Deshmukh et al. 2016) was used to describe the dependence of minimum creep rate on applied load which is similar to the Norton’s power law used to describe deformation behavior in conventional creep. ̇ = (2) Where, ̇ is minimum creep deflection rate, A is a temperature dependent constant, F is SPC load and n is load exponent. From Fig. 8, the load exponent value was found to be 3.14 which is in accordance with the values discovered by other researchers for different materials like P92 Steel in the same load range ( Choudhary et al. 2011; Deshmukh et al. 2016; Sklenička et al. 2003) . The load dependence and rupture life ( ) also obeys a power law relationship which was also similar Norton’s power law (equation 3). = ′ ′ (3) Where, A’ is a constant, n’ is power law exponent. The load exponent value was found to be 6.25 (Fig.9) which was in agreement with the values of stress exponent reported in the literature for conventional uniaxial creep with other materials (Deshmukh et al. 2016; Ennis et al. 1997; Samuel et al. 2013; Lee et al. 2006). Conclusion In this study, the creep behavior of Su-263 at 650 ºC was evaluated by using SPC technique. The SPC data were analysed and following conclusions were drawn based on the present study: 1. The average creep life of Su-263 at 650 ºC was 88.20 ± 1.50 hrs for 650 N, 50.10 ± 1.50 hrs for 700 N, and 36.15 ± 1.50 hrs for 750 N. This indicated that as the load increased, creep life decreased and the minimum creep rate raised. All the tests showed two slope behavior in the creep curves obtained.