Corrosion resistance of 13wt.% Cr martensitic stainless steels: Additively manufactured CX versus wrought Ni-containing AISI 420.

• L-PBF process led to the formation of a hierarchical microstructure in the l -PBF components. • After heat treatment, the microstructure of l -PBF samples is free of sub-grains and austenite. • The microstructure of heat-treated SS 420 is composed of coarse grains, a high fraction of austenite and Cr-rich carbides. • Low corrosion performance of heat-treated wrought sample is attributed to the formation of Cr-rich carbides and austenite phase. • The adverse impact of nano-scale inclusions and β-NiAl precipitates on corrosion performance is lower than carbide precipitates and austenite. The corrosion resistance of heat-treated additively manufactured (AM) precipitation hardening martensitic stainless steel (SS) CX and wrought components of AISI 420-SS with lower Ni content, were compared. The microstructure of heat-treated AM-CX comprised of a martensitic matrix and a few nano-scale particles, while the wrought AISI 420-SS contained approximately 8% of austenite and Cr-rich carbides in a martensitic matrix. Superior corrosion resistance was detected for the AM-CX part as compared to the AISI 420-SS ascribed to nearly absence of Cr-rich carbides and martensite-retained austenite interfaces in the AM-CX SS, while their presence in the AISI 420-SS destabilized the passive film. [ABSTRACT FROM AUTHOR]