Influence of microstructure and manganese sulfides on corrosion resistance of selective laser melted 17-4 PH stainless steel in acidic chloride medium

The corrosion resistance of 17-4PH stainless steel obtained by Selective Laser Melting was investigated. It was found that the as-built SLM-ed steel was entirely ferritic, not martensitic as expected. Re-austenitized SLM-ed steel recovered the martensitic microstructure. The two SLM-ed steels (as-built and re-austenitized) had the same general corrosion resistance which was correlated with their similar chemical composition. The martensitic reaustenitized SLM-ed steel had superior general corrosion behavior than the wrought martensitic steel. This was due to the nearly absence of MnS inclusions in the re-austenitized SLM-ed steel, while their presence in the wrought steel destabilized the passive film.