Pulse Electrodeposition of Co-w and Its Composite Coatings for Hard Chrome Replacements

Abstract

Replacement of hard chromium plating has been of particular interest to many industrial applications, including automotive, aircraft, and machinery parts that require high hardness and wear/corrosion resistance. Electrodeposition is chosen as it is one of the most common, relatively simple, and economical coating technologies capable of depositing metal and alloy coatings with improved surface properties and microstructures. Efforts are directed towards electrodeposition of an amorphous alloy/composite coatings that present the potential for replacing conventional hard chrome coatongs. Co-W alloy coatings, owing to their eco-friendly processing and high hardness/wear resistance, are promising for electrolytic chromium replacement. In this study, pulsed electrodeposition of amorphous and crystalline Co-W coatings is performed. Systematic investigations on the effect of pulse duty cycle and pulse frequency on development of surface microstructure, phases, composition, surface roughness, and micro-hardness are conducted to optimize the parameters of the deposition process. Furthermore, an attempt is made to fabricate composite coatings of Co-W alloys with nano alumina particles as reinforcement. Codeposition of alumina particles in the Co-W alloy matrix has enhanced the mechanical as well as tribological properties of the coating significantly.