Abstract
High-cycle fatigue testing of nickel-based superalloy Inconel 718 made by laser powder-bed fusion was performed on round uniform-gauge or hourglass specimens for various specimen orientations, stress ratios and surface conditions (as-built and machined). Only surface conditions, specifically near-surface process defects, influenced fatigue properties. There was a systematic bias of the azimuthal position of crack initiation sites. Crack initiation in specimens with as-built surfaces occurred at 50 µm diameter near-surface features. These dimensions were used in conjunction with fatigue limits derived from tests suspended at 107 cycles to calculate threshold ΔK values of 2–6 MPa √m due to as-built surface conditions.
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