Effects of Machining on the Fatigue Strength of Steel Components Produced by DMLS

Abstract

Direct metal laser sintering (DMLS) is the additive manufacturing (AM) technology that allows production of metal machine components with complex geometry. Due to the layer-wise production principle, its products usually require post-processing, predominantly machining, to achieve uniform or requested surface quality. Given the increasing application of DMLS technology in industry and insufficient published data about the effects of machining on the fatigue properties of steel, the focus of this research is put to investigation of the influence of thickness of allowance for machining to fatigue strength of DMLS products. Previous studies revealed significant differences in the mechanical behaviour of samples made of different kinds of steels, both during production and testing. Unlike the samples made from maraging steel, the samples made from stainless steel often deformed during cooling due to the strong residual stresses, and revealed dependence of mechanical properties on orientation during production process. To improve the understanding of the differences, fatigue testing according to ISO 1143 was performed on samples manufactured from two kinds of steel, maraging steel 1.2709 and stainless steel 15-5. Twelve sets of samples were tested with the aim to investigate the effects of machining allowance and build orientation according to an extensive DoE experimental plan.