Electrochemical performance of the interfacial region between an AISI 420 and a wire arc additive manufactured PH 13–8Mo martensitic stainless steel

Abstract

In this study, the electrochemical response of the interfacial region between an AISI 420 martensitic stainless-steel (MSS) substrate and a wire arc additive manufactured PH 13-8Mo MSS part was investigated. The complicated thermal cycle through the deposition of the PH 13-8Mo part led to the formation of distinct zones, including far heat-affected zone (FHAZ), close heat-affected zone (CHAZ), partially melted zone (PMZ), and fusion zone (FZ) at the interfacial bonding region. The formation of an austenitic structure with coarse grains was observed in the PMZ and FZ adjacent to the substrate. The corrosion performance of the interface region was degraded significantly, ascribed to the formation of high density of fine chromium-rich carbides. The corrosion onset at the interface region was initiated at the carbide/matrix interface in the CHAZ and PMZ, where chromium depleted regions at the carbides’ periphery intensify the micro-galvanic coupling effect. The corrosion resistance of the as-printed PH 13-8Mo sample was remarkably higher than the 420 MSS and interface samples. The formation of a uniform lath martensitic structure with low energy levels at lath boundaries and the absence of metastable chromium-rich micro-constituents, such as carbides, due to the low carbon content of the PH 13-8Mo MSS alloy, contributed to its superior electrochemical performance.