Underlying mechanism for “loss of passivation” effect of a high-carbon martensitic stainless steel coating via laser cladding

Abstract

The microstructure and pitting performance of high-carbon martensitic stainless steel (HMSS) samples, which were produced via laser cladding (LC) and hot isostatic pressing (HIP) were comparatively investigated via electrochemical measurements and electron microscopies. Dendritic and network connected M23C6 carbides are the main precipitates in the HMSS coating, while the M23C6 carbides in HMSS bulk are spherical or elongated in shape. Pitting resistance of the HMSS coating is dramatically deteriorated. The Cr-depleted region induced by the Cr-enriched and dendritic M23C6 carbides are considered as underlying factor for the “LOP” effect of the HMSS coating.