Heat treatment effects on the corrosion performance of wire arc additively manufactured ER316LSi stainless steel

Abstract

Corrosion performance of a multi-layered ER316LSi wall deposited using wire and arc additive manufacturing was studied in the as-deposited condition and after stress relief heat treatment at 900 °C, in 3.5 wt% NaCl solution. It was found that the heat treatment is not suitable for WAAM ER316LSi components due to the complete transformation of the delta ferrite into sigma decreasing the corrosion performance. The delta ferrite to sigma transformation during heat treatment was facilitated by the cyclic reheating of the part during deposition. The electrochemical response of as-deposited WAAM differed from a wrought alloy with similar composition and linked to microstructural differences: as-deposited WAAM had a higher pitting potential due to the absence of sulfide inclusions and increased metastable-like activity due to the presence of the secondary delta ferrite causing elemental segregation.