ELECTRODEPOSITION BASED DEVELOPMENT OF Ni-TiN-AlN AND Ni-SiC-Cr COMPOSITE COATINGS FOR TUNGSTEN CARBIDE CUTTING TOOLS

Metal-based functionally graded coatings have proven effectiveness in improving anti-wear properties and surface integrity of the substrates. The use of electrodeposition coating technique, considering the economics and versatility associated with this method, is a preferred technique of depositing metal-based composite coatings. Further, Ni-based composite coatings are proven for anti-wear applications, and addition of various reinforcement for developing functional coatings need to be evaluated for different applications. This study describes the development, analysis, and performance evaluation of Ni-TiN-AlN and Ni-SiC-Cr electrodeposited composite coatings on tungsten carbide (WC) tool substrates, to impart improved anti-wear properties during machining. The composite coatings were deposited and optimized for current density values of the electrodeposition process, which was identified as the most significant parameter in both the cases. The coatings were characterized using scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) for microstructural analysis. The results were further analyzed for tribological behavior through microhardness and adhesion strength tests of the deposited coatings, which are significant properties imitating anti-wear characteristics of the substrate. A significant increase of 47% and 36% in microhardness was obtained for Ni-SiC-Cr coated specimen and Ni-TiN-AlN coated specimen, respectively, compared to the uncoated WC substrates, accompanied with a good adhesion strength in both the cases. The microstructural analysis in both the cases revealed an increase in the deposited coating constituents with increasing current density, leading to a denser coating deposition up to the saturation point, and then beginning of coating delamination due to over-saturation with further increase in current density.