Stellite 6 Cladding on AISI Type 316L Stainless Steel: Microstructure, Nanohardness and Corrosion Resistance

AISI type 316L stainless steel (SS) is used in the manufacturing of components that works in severe aggressive environments. These environments include petrochemical equipments, heat exchangers, power plants, waste water treatments, etc. After prolonged exposure in these environments, corrosion will initiate in these components. The aim of this study is to strengthen the anti-corrosion property of AISI type 316L SS by coating the Stellite 6 alloy via laser cladding. The cladded microstructure was analysed by the optical and FE-SEM micrographs along with the EDS spectra. The nanoindentation was made in the substrate and cladded region to compare the hardness property. In a three-electrode setup, the anti-corrosion behaviour of both AISI type 316L SS and Stellite 6 clad samples was evaluated at 0, 42 and 70 h, followed by the investigation of the corroded morphology and surface roughness (Ra). The results showed that the cladded region contains the Co-rich dendritic structure along with Cr-rich carbides decorated in the dendritic boundaries. These Cr-rich carbides were responsible for enhancing the hardness in the cladded layer. The corrosion test proved the existence of better passive (oxide) film on the cladded samples that provided significant resistance towards corrosion than the AISI type 316L SS samples. Further, the EIS analysis confirmed that the laser cladding of Stellite 6 seems to provide greater Rp values than the AISI type 316L SS. Notably, 70 h clad sample exhibited maximum corrosion resistance in terms of EIS, Tafel and surface roughness.