Post-treatment selection for tailored fatigue performance of 18Ni300 maraging steel manufactured by laser powder bed fusion

This study investigates the fatigue behaviour of additively manufactured 18Ni300 maraging steel. Specifically, the surface and material parameters impacting fatigue performance are analysed through various post-treatment combinations. Vertically built miniaturised test samples produced by laser powder bed fusion are tested in as-built and age-hardening heat-treated conditions. To utilise the potential of using additive manufacturing for complex-shaped parts in which conventional machining tools could have limited access, vibratory finishing and sand blasting are employed. The fatigue results show that in as-built microstructural condition, both the surface treatments significantly enhanced the fatigue performance, with vibratory finishing outperforming sand blasting owing to better surface finish. After heat treatment, sand-blasted samples performed better than vibratory-finished ones because of higher residual stresses. This competing interaction between post-treatments sheds light on identifying the relative influence of various factors. With systematic postfracture and microstructural analyses highlighting the fatigue influencing factors, recommendations are drawn to select post-treatments to achieve the desired fatigue performance.