Effect of Manufacturing Process on Defects in Next Generation Power Plant Steel, MarBN: Experimental and Computational Characterisation

Manufacturing defects are a key source of crack initiation and component failure under high temperature cyclic loading. In this work, 3D X-ray micro-computed tomography, in conjunction with microstructural analysis, has been applied to identify the role of manufacturing defects in cracking and failure of a martensitic-ferritic steel, MarBN, under high temperature low cycle fatigue loading. Forging is found to significantly reduce the volume fraction and complexity of manufacturing defects, compared to the cast material, and as a result, increases fatigue life by approximately double. Computational modelling of experimentally identified cast and forged manufacturing defects is performed to predict the role of defects on fatigue crack initiation under high temperature cyclic loading, highlighting the importance of manufacturing process, defect shape and orientation.