PSI - Issue 14

Ashish Vaidya et al. / Procedia Structural Integrity 14 (2019) 410–415

415

Ashish Vaidya et al. / Structural Integrity Procedia 00 (2018) 000 – 000

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4. Conclusions

Creep tests were carried out on V-notched creep specimens with notch depth of 0.5, 1.0 and 2.0 mm. The net applied stress was 195 MPa and the test temperature was 650 °C. Following conclusions can be drawn from the present study. The notch strengthening effect was observed due to the presence of sharp V-notch. The notch strengthening increased with increase in depth of notch. The degree of strengthening increased two times for creep specimen with 1.0 mm notch as compared to 0.5 mm notch whereas the increase in strengthening was almost four times in 2.0 mm notch depth creep specimen. The minimum creep rate (MCR) decreased by the order of one for creep specimen with 1.0 mm notch and decreased by the order of two for creep specimen with 2.0 mm notch as compared to creep specimen with 0.5 mm notch depth. All the creep fractured samples showed mixed mode of fracture from ductile to brittle at the root of V-notch. Area near the notch root showed brittle mode of fracture due to accumulation of tri-axial state of stresses. The area at the center of creep specimen predominantly showed the ductile fracture due to creep cavitations and micro-void coalescence which can be seen from dimpled surface. Acknowledgements Authors wish to acknowledge the financial support from TEQIP II (133/131016/1L) for facilitating smooth conduct of experiments in this study. Authors also kindly acknowledge the support of TEQIP III for sponsoring this manuscript for presenting in SCIE 2018, Hyderabad. References Masuyama, F., 2001. History of power plants and progress in heat resistant steels. ISIJ International 41(6), 612 – 625. Cerjak, H., Hofer, P., Schaffernak, B., 1999. The influence of microstructural aspects on the service behaviour of advanced power plant steels. ISIJ International 39(9), 874 – 888. Yan, W., Wang, W., Shan, Y.Y., Yang, K., 2013. Microstructural stability of 9-12%Cr ferrite/martensite heat-resistant steels. Frontiers of Materials Science 7(1), 1 – 27. Maddi, L., Deshmukh, G.S., Ballal, A.R., Peshwe, D.R., Paretkar, R.K., Laha, K., Mathew, M.D., 2016. Effect of Laves phase on the creep rupture properties of P92 steel. Materials Science and Engineering A 668, 215 – 223. Hayhurst, D.R., Leckie, F.A., Morrison, C.J., 1978. Creep Rupture of Notched Bars. Proceedings of the Royal Society A 360, 243 – 264. Wu, D., Christian, E.M., Ellison, E.G., 1984. Influence of Constraint on Creep Stress Distribution in Notched Bars. Journal of Strain Analysis 19 (4), 209 – 220. Ni, Y.Z., Lan, X., Xu, H., Mao, X.P., 2014. Finite element analysis and experimental research on notched strengthening effect of P92 steel. Materials at High Temperatures 31(2), 185 – 190. Ni, Y.Z., Lan, X., Xu, H., Mao, X.P., 2015. Study on creep mechanical behaviour of P92 steel under multiaxial stress state. Materials at High Temperatures 32(6), 551 – 556. Chang, Y., Xu, H., Ni, Y., Lan, X., Li, H., 2015. The effect of multiaxial stress state on creep behavior and fracture mechanism of P92 steel. Materials Science & Engineering A 636, 70 – 76. Chang, Y., Xu, H., Ni, Y., Lan, X., Li, H., 2016. Research on representative stress and fracture ductility of P92 steel under multiaxial creep. Engineering Failure Analysis 59, 140 – 150. Ni, Y., Xu, H., Chang, Y., Mao, X., 2018. Research on elastic-plastic creep damage of notched P92 steel specimens. Materials at High Temperatures 35(4), 335 – 342. Naoi, H., Ohgami, M., Araki, S., Ogawa, T., Yasuda, H., Masumoto, H., Fujita, T., 1991. Development of High Strength Ferritic Steel NF616 for Boiler Tubes. Nippon Steel Technical Report 50, 7 – 13. ASTM International, 1999. ASTM E415-99a: Standard Test Method for Optical Emission Vacuum Spectrometric Analysis of Carbon and Low Alloy Steel. In: Annual Book of ASTM Standards. West Conshohocken, PA. Charde, S.R., Ballal, A.R., Peshwe, D.R., Mathew, M.D., Paretkar, R.K., 2013. Effect of Notch on Creep Behavior of 316 L(N) SS. Procedia Engineering 55, 517 – 525. ASTM International, 2011. ASTM E139-11: Standard Test Method for Conducting Creep, Creep-Rupture, and Stress-Rupture Tests of Metallic Materials. In: Annual Book of ASTM Standards. West Conshohocken, PA. ASTM International, 2009. ASTM E292-09: Standard Test Method for Conducting Time-for-Rupture Notch Tension Tests of Materials. In: Annual Book of ASTM Standards. West Conshohocken, PA.