Multiaxial fatigue of LB-PBF additive manufactured 17–4 PH stainless steel including the effects of surface roughness and HIP treatment and comparisons with the wrought alloy

Abstract

Additive manufacturing (AM) offers a number of advantages over the traditional subtractive manufacturing techniques. However, there is a little information available on cyclic deformation and fatigue behaviors of some important engineering alloys, such as 17–4 PH stainless steel. This is particularly true with regards to multiaxial fatigue, in spite of the fact that the state of stress at fatigue critical locations is often multiaxial and many of the distinguishing features of AM metals are directional. This study tries to fill some of this gap with considering different stress states by conducting tests under axial, torsion, and in-phase and out-of-phase axial-torsion loads. Similar multiaxial tests were also performed on the wrought material as a benchmark for comparison. Surface roughness effect was studied with considering the as-built surface condition as well as polished and machined surface conditions. Effect of hot isostatic pressing (HIP) in shrinking/closing the internal defects as well as improving the fatigue behavior was also studied. Fatigue failure mechanism of the AM and wrought 17–4 PH stainless steel under different conditions were also evaluated, as well as multiaxial fatigue data correlations.