Tailoring the behaviour of additively manufactured 316L stainless steel by thermomechanical post-processing

Abstract

In the scope of this study, the effects of selected routes of thermomechanical post-processing performed via rotary swaging on the overall performance of additively manufactured AISI 316L stainless steel were evaluated. The acquired results showed that both the swaging ratio and temperature affected the development of microstructure and precipitation, as well as influenced grains morphology, size, and orientations, all of which had effects on the corrosion and mechanical behaviours of the original workpieces. Increasing the swaging ratio and decreasing the processing temperature generally supported grain refinement and increased the strength (UTS), although increasing the processing temperature supported plasticity. The microstructure of the piece processed by cryogenic swaging with the ratio of 1.0 displayed the smallest grains (mean size of 2.4 μm), well-developed substructure, and finest dispersion of precipitates, which increased the mechanical properties (UTS of ∼2100 MPa) and lowered the overall tendency for intergranular corrosion. This piece also exhibited the most favourable corrosion resistance. Nevertheless, swaging under hot conditions already significantly refined the grains, and increased the UTS approximately by 300 % (swaging ratio of 0.7), resp. 400 % (swaging ratio of 1.0) compared to the additively manufactured workpiece (UTS of 283 MPa). The cold swaged pieces also featured refined grains, and exhibited both enhanced strength and increased plasticity.