Influence of scanning strategies on microstructure, residual stress, and corrosion behavior of 17-4 PH stainless steel fabricated by selective laser melting

Abstract

In the present study, the effect of hexagonal (inside out and outside in), rectangular (horizontal, vertical, alternate, and both), and strip (horizontal, vertical, alternate, and both) scan strategies on the microstructure, residual stresses, and the corrosion behavior of 17-4 PH stainless steel samples fabricated by selective laser melting were investigated. The results indicate that through hexagonal inside-out scanning strategy, the sample density and hardness are double than that of wrought and cast alloys. Microstructure consists of small and large molten pools on the side and front surface of each sample generated using a different scan strategy. Austenite phase and ferrite peak at the highest intensity were observed by X-ray diffraction for hexagonal inside-out sample. Electron back scattered diffraction (EBSD) orientation maps showed a high-density of ɣ-austenite phase (43%) in the finer grain size area of the hexagonal inside-out scan strategy sample. Low residual stresses and high corrosion resistance (<0.5 mpy) were obtained for the hexagonal inside-out scan strategy sample compared to other two strategies because of lower defects, lower thermal gradient, and smaller scan tracks.