Combined XPS / TEM study of the chemical composition and structure of the passive film formed on additive manufactured 17-4PH stainless steel

The structure and chemical composition of the passive film formed on 17-4PH martensitic stainless steel (MSS) manufactured by powder bed laser beam melting (LBM) were investigated combining XPS and TEM analyses, by comparison to a conventional 17-4PH. The structure of the passive film was found similar for both MSSs, with, on the matrix, a duplex layer composed of Fe and Cr oxy-hydroxide followed by an intermediate layer enriched in metallic compounds. A particular Nb oxide film formed on the NbC precipitates merging to the surface for both MSSs. Significant differences in thickness and Cr distribution were observed between both MSSs.