Machining and Heat Treatment Effects on the Fatigue Properties of Maraging Steel Produced by DMLS

The present study is focused on the fatigue strength of 15-5 PH stainless steel parts built by DMLS. Four DMLS enables manufacturing of functional parts with complex shapes in a short time. This technology has some drawbacks: high manufacturing cost, residual stresses, and volume and surface imperfections. These problems can be solved by additional post processing (machining, heat treatment and shot peening), which increase manufacturing cost and time. There is an increasing interest towards the mechanical response of parts in the as-fabricated state. Being able to manage these parts, without the need for machining or heat treatment, would strongly increase the great potentials of this technology. The present study deals with the effect of machining and heat treatment (aging at the temperature of 490°C for 6 hours) on the fatigue response of DMLS Maraging steel parts, with vertical build orientation. Specimens have been manufactured according to ISO 1143 for fatigue tests under rotating four-point bending. The experimental campaign has been arranged as a 2-by-2 factorial plane, with a total amount of four treatment combinations. The first results, processed also by tools of analysis of variance, indicate that heat treatment has the greatest beneficial impact on the fatigue response and that even without machining a fatigue limit in the order of 25% of the ultimate tensile strength can be achieved.