Evaluation of microstructure, tensile, and fatigue testing on angled walls of NASA HR-1 using laser powder direct energy deposition

This study investigates the influence of varying deposition angles on the tensile strength and low cycle fatigue (LCF) performance of National Aeronautics and Space Administration (NASA) HR-1 alloy using laser powder-directed energy deposition. This study investigates the influence of varying deposition angles on the tensile strength and LCF performance of NASA HR-1 alloy using laser powder-directed energy deposition. Two sets of build parameters, 1,070 W and 2,620 W, were employed alongside three different build angles to assess their influence on mechanical properties following a uniform heat treatment regimen. This heat treatment encompassed stress relief, homogenization, solution annealing, and double aging. Samples deposited at 1,070 W showed a slightly lower porosity percentage compared to those produced at 2,620 W. All samples displayed similar grain sizes and a homogenized microstructure, indicating the effectiveness of the heat treatment in achieving a uniform microstructure across samples deposited at different build angles and laser power settings. The varying deposition angles did not significantly affect the microstructure or mechanical properties of the alloy. Fractography analysis revealed that all samples fractured through transgranular micro-void coalescence, with fracture initiation predominately occurring at the edges of both tensile and fatigue samples.