Development and microstructural characterization of microwave cladding on austenitic stainless steel

In the present work microwave cladding was explored as a new processing method for enhancement of surface properties of austenitic stainless steel (SS-316). Cladding of nickel based powder (EWAC) was developed using microwave radiation as the heating source. This paper explains the possible mechanism of clad formation using microwave hybrid heating with the help of a schematic model. The developed clads were characterized using field emission scanning electron microscope (FE-SEM), energy dispersive X-ray spectroscope (EDS), X-ray diffraction (XRD) and measurement of Vickerʹs microhardness. Typical X-ray diffraction (XRD) pattern of the clad showed the presence of chromium carbide, nickel silicide and nickel iron phases that eventually contribute to enhancement in microhardness of the clads. Clads of approximately 1 mm thickness were developed without any visible interfacial cracking and had significantly less porosity (1.09%). Microstructure of clad transverse section revealed good metallurgical bond with SS-316 substrate by partial mutual diffusion of constituent elements. The microstructure of the clad was found dominantly cellular in nature. Chromium was observed segregated around the cell boundaries while iron and nickel were identified inside the cells. Chromium carbides (Cr23C6, Cr3C2) were formed during the processing and appeared at the cell boundaries. Vickerʹs microhardness study revealed that the hardness profile varies within the clad zone and the average microhardness of the developed clad was observed to be 304 ± 48 Hv.