Influence of surface conditions and specimen orientation on high cycle fatigue properties of Inconel 718 prepared by laser powder bed fusion

•Surface condition was the most important influence on fatigue.•Specimen orientation did not affect fatigue properties for a given surface condition.•Fatigue crack initiation locations were biased due to printing conditions.•Threshold stress intensity for as-built LPBF surfaces was estimated. 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.