PSI - Issue 13

Vishal Singh et al. / Procedia Structural Integrity 13 (2018) 1427–1432 Author name / Structural Integrity Procedia 00 (2018) 000–000

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Fig.5. Variation of (a) short fatigue crack length ‘ with numbers of cycles ‘ and (b) short crack growth rate ′ with crack length ‘ of X65 and X80 steels at ∆ = 400 MPa. ‘H’ indicates the hydrogen charged sample. 4. Conclusions The experimental framework to investigate the effect of hydrogen on various steels in terms of their short fatigue crack propagation behavior is presented. Hydrogen was found to accelerate the short fatigue crack growth in all type of investigated steels. In 316L steel, localized dislocation activity in the vicinity of the crack tip for hydrogen charged specimen increased the crack propagation rate. However, similar hindrance was offered by the grain boundaries for hydrogen charged and uncharged specimens. In the case of SA508 steel, hindrance to the crack propagation offered by PAGBs were found to diminish under hydrogen environment. Refined microstructure (in X65 and X80 steels) along with hydrogen environment was found to accelerate the fatigue crack growth propagation to greater extent. Presence of M/A islands and stringers specially those aligned with the crack propagation direction were found to facilitate the crack propagation through interface decohesion under both hydrogen charged and uncharged conditions. High resolution microscopy of the propagating short fatigue cracks in steels with refined microstructures demands further investigations. Such work is currently under progress using EBSD and fatigue stage for SEM in our group and shall be reported in future. References Kanezaki, T., Narazaki, C., Mine, Y., Matsuoka, S., Murakami, Y., 2008. Effects of Hydrogen on Fatigue Crack Growth Behavior of Austenitic Stainless Steels. International Journal of Hydrogen Energy 33, 2604 – 2619. Murakami, Y., Matsuoka, S., 2010. Effect of Hydrogen on Fatigue Crack Growth of Metals. Engineering Fracture Mechanics 77, 1926–1940. Chatzidouros, E.V., Papazoglou, V.J., Pantelis, D.I., 2014. Hydrogen Effect on a Low Carbon Ferritic-Bainitic Pipeline Steel. International Journal of Hydrogen Energy 39, 18498–18505. Venezuela, J., Liu, Q., Zhang, M., Zhou, Q., Atrens, A., 2015. The Influence of Hydrogen on the Mechanical and Fracture Properties of Some Martensitic Advanced High Strength Steels Studied Using the Linearly Increasing Stress Test. Corrosion Science 99, 98–117. Tsay, L.W., Chen, J.J., Huang, J.C., 2008. Hydrogen-Assisted Fatigue Crack Growth of AISI 316L Stainless Steel Weld. Corrosion Science 50, 2973–2980. Ogawa, Y., Okazaki, S., Takakuwa, O., Matsunaga, H., 2018. The Roles of Internal and External Hydrogen in the Deformation and Fracture Processes at the Fatigue Crack Tip Zone of Metastable Austenitic Stainless Steels. Scripta Materialia 157, 95–99. Obrtlık, K., Polak, J., Hajek, M., Vasek, A., 1997. Short Fatigue Crack Behaviour in 316L Stainless Steel. International Journal of Fatigue 19, 471– 475. Mikulich, V., Blochwitz, C., Skrotzki, W., Tirschler, W., 2006. Influence of texture on the short fatigue crack growth in austenitic stainless steel. Materials Science 42, 514–526. Mazánová, V., Polák, J., 2018. Initiation and Growth of Short Fatigue Cracks in Austenitic Sanicro 25 Steel, Fatigue & Fracture of Engineering Materials & Structures 41, 1529–1545. Krupp, U., 2007. Fatigue Crack Propagation in Metals and Alloys: Microstructural Aspects and Modelling Concepts. First Edition. Wiley - VCH Singh, R., Singh, A., Arora, A., K., Singh, P.K., Mahajan, D.K., 2018. On the Transition of Short Cracks into Long Fatigue Cracks in Reactor Pressure Vessel Steels. MATEC Web Conf. 165, 13001.