Effect of in situ tempering on the mechanical, microstructural and corrosion properties of 316L stainless steel laser-cladded coating on mild steel

316L stainless steel coatings were deposited on mild steel substrate using laser cladding technique. The mechanical, microstructural and corrosion properties of the coatings were performed and analysed using axial tensile testing, Vickers micro-hardness testing, optical as well as electron microscopy, energy dispersive spectroscopy, fractography, dye penetrant testing and electrochemical potentiostat testing. Two types of coatings were studied; single-layer (1-L) and multi-layer (3-L). Both these coatings demonstrated good metallurgical bonding with low dilution with the substrate. The tensile strengths of both the 1-L and 3-L specimens were fairly similar; however, the ductility of the 3-L samples was significantly lower (by about 54%) compared to 1-L samples. Moreover, the 3-L specimens were found to be more susceptible to corrosion. This was attributed to the harder regions of the 3-L clad owing to the in situ tempering of the microstructure by the additional heat imparted through two sacrificial layers. In essence, it can be concluded from this study that a single-layer 316L stainless steel clad coating exhibits better corrosion resistance, whereas a multi-layer clad coating with sacrificial layers exhibits better coating hardness. These results are very important in determining the right coating type/strategy for the desired applications.