An Experimental Study on the Fatigue Response of 15-5 PH Stainless Steel Built by DMLS

The present study is focused on the fatigue strength of 15-5 PH stainless steel parts built by DMLS. Four sets of specimens were manufactured, mechanically and thermally treated, and tested under rotating bending fatigue. The samples of the first two sets were built with their longitudinal axis perpendicular or parallel to the vertical stacking direction. In both cases, a 1mm allowance was uniformly distributed. The samples of the third and the fourth sets were similarly generated, with the same orientations. The samples of the last two sets were built with cylindrical shape and with 3mm allowance at gage. The results, processed also by analysis of variance tools, indicate that, considering the first two sets, the fatigue limit, approximately 39% of the ultimate strength, is almost independent of the build orientation. Conversely, the samples with incremented allowance, which required significant machining at gage, exhibit a much higher fatigue limit, very close to the commonly accepted reference value of one-half of the ultimate strength. This is quite an interesting result, as machining seems to be able to remove the process-induced irregularities, thus making it possible to achieve comparable properties to those of wrought material.