Erosion Behaviour of WC–Co–Cr Thermal Spray Coated Grey Cast Iron under Mining Environment

Abstract

Hydraulic machinery components made of grey cast iron (FG 260 grade) are preferred for engineering application because of their excellent damping properties. However when such materials are exposed to mining environments they exhibit poor erosion resistance without meeting their estimated life time. In order to enhance the service life of the material of hydraulic components, WC–Co–Cr thermal spray coating was identified. Grey cast iron samples (FG 260 grade) with and without WC–Co–Cr coating were subjected to slurry jet erosion tests by varying the impingent velocity and angle under two different pH levels at 3 and 7 which pertain to the mining environment. XRD characterization was done to identify and confirm the carbide phases present. Surface morphology studies were carried by SEM on both the substrate and coating, which revealed the erosion of grey cast iron surface, due to ploughing mechanism. In the case of WC–Co–Cr coating, at oblique angle of impact, the degradation is by micro cutting of the matrix and ploughing mechanism. At normal impingement, the fluctuating stress creates the cracks, which interlink each other and thereby causing erosion of the material.