Wear performance of GGG60 ductile iron rollers coated with WC-Co by electro spark deposition

Abstract

Nodular cast irons are used in many industrial applications such as machine frames and body, rollers and engine blocks due to their higher strengths and ductility with good machinability comparable to grey cast irons. In this study, the outer surface of nodular cast irons (GGG-60) was coated with WC/Co using electro spark deposition (ESD). The aim of the study is to improve both the surface quality and wear behaviour with the coatings formed on the surface of the plastic deformation rollers, whose wear resistance decreases over the time due to high stress working conditions. Heat treatment at 950 ºC for 2 h was applied to the GGG60 specimen rollers and half of the rollers were uncoated and the other half was coated with WC-Co electrodes. The wear behaviour of the heat treated and coated surfaces was measured by ball-on-disc wear method using Al2O3 ball bearing with a diameter of 6 mm for a sliding distance of 250 m at a sliding rate of 6.5 m·s-1 under a dry condition, and using a load of 40 N. WC/Co coatings were successfully applied to rollers. In the SEM/EDS images, the presence of W, Fe, C, Co and Al elements in the coated part of the rollers and Fe, C and Al elements in the uncoated region were detected. It was concluded that Coating and heat treatment increased the wear resistance by nearly 5 times and decreased the friction coefficient by 2.13 times.