Defect analysis and fatigue design basis for Ni-based superalloy 718 manufactured by selective laser melting

Defects of the material investigated in this study were mostly gas porosity and those made by lack of fusion. The successful application of the area parameter model was confirmed. Although the statistics of extremes analysis is useful for the quality control of AM, the particular surface effect on the effective value of defect size must be carefully considered. Since the orientations of defects in AM materials are random, a defect in contact with specimen surface has higher influence on fatigue strength than an internal defect and has the effective larger size termed as areaeff than the real size, area, of the defect from the viewpoint of fracture mechanics. The guide for the fatigue design and development of higher quality Ni-based Superalloy 718 by AM processing based on the combination of the statistics of extremes on defects and the area parameter model is proposed.