Characterisations of Cu-Based Coated Al7075 via Plasma-Spray Technique

Abstract

This work aims to characterise a Cu-based coating material on Al-7075 by using a plasma-spray technique in order to enhance the surface properties of components for automotive applications. Plasma-spray is a process for formation coating on substrates whereby a feedstock is rapidly heated to a molten or near-molten state, and a gas are use to propel the material toward suitably prepared substrate. The most prominent advantages of this method are virtually any coating material can be used and any substrate material can be coated with low thermal stress on substrate parts and high deposition rates [1]. The coating characteristic can be controlled by varying the process variables such as input powers, material feed rates, gas pressures, surface preparation of the substrate and spray distance [2]. The effect of crucial parameters like the electric power input to plasma, spray rate and substrate roughness were studied. The experiments of spraying were design using a 23 fractional factorial plan. The plan allows studying the effect of each factor on the response variables, as well as the effect of interactions between factors on the response variable at the least number of experiment runs. The coating layers have been characterised with respect to the structure by using a scanning electron microscopy (SEM). The result indicates that sprayed particles cool and built up into pancake-like shapes splat, characteristic a plasma spray electric process products. It was found that the optimum parameters were obtained at a power of 24.6 kW, with a powder feed rate of 1 rpm and substrate roughness of 0.5µm.