Effects of print parameters and heat treatment on fatigue of laser powder bed fused Inconel 718

This paper studies printing parameters and post-printing heat treatment for laser powder bed fused Inconel 718. The printing scanning speeds and energy densities per unit volume were varied, and each print group was subjected to combinations of three different types of heat treatment: homogenization, hot isostatic pressing, and solution heat treating following with aging. The quality of the samples was measured by the porosity present in the samples, hardness, size/quantity of defects, and identification of phases and defects in the microstructure. Both optical and scanning electron microscopy observations showed that a scanning speed of 1250 mm/s and energy density of 54.5 J/mm(3) result in the lowest porosity. Reduction of porosity and precipitation hardening increased material hardness to 470 HV. The Laves phases, normally seen in the as-printed samples, were effectively minimized after these thermal heat treatments. An increment of 550% of fatigue life was seen in axial fatigue testing at 525 MPa on samples after hot isostatic and aging treatment.