The effect of inclusions on the high‐temperature low‐cycle fatigue performance of cast MarBN: Experimental characterisation and computational modelling

The presence of inclusions is a known source of crack initiation and component failure in cast materials. In this work, the role of inclusions is investigated via a combined program of high-temperature low-cycle fatigue testing and computational modelling of a tempered martensitic steel, MarBN. Microstructural analysis has shown that manufacturing-induced oxide inclusions are a key source of fatigue crack initiation. A fully coupled, critical plane life prediction and damage model is implemented in a unified cyclic viscoplastic user-material subroutine and applied to predict damage and micro-crack initiation for inclusions. It is deduced that more careful control of the development of inclusions in the manufacturing process will provide enhanced material and component performance for highly flexible and ultrasupercritical plant conditions. ; The authors gratefully acknowledge funding from the Irish Research Council and GE Power under the Enterprise Partnership Scheme (EPSPG/2015/55). This publication has also emanated from research conducted with the financial support of Science Foundation Ireland (grant SFI/14/IA/2604). The authors would like to express their gratitude to Mr. Rod Vanstone of GE Power and those in the IMPEL consortium for helpful technical comments and discussions, as well as Dr. Yina Guo, formerly of University of Limerick, for assistance with thin foil TEM analysis. The authors acknowledge the facilities and technical assistance of the Centre for Microscopy & Imaging at the National University of Ireland Galway, in particular Ms. Emma McDermott. The authors wish to acknowledge the DJEI/DES/SFI/HEA Irish Centre for High‐End Computing for the provision of computational facilities and support. ; peer-reviewed