Effect of Spherical Tungsten Carbide Load to the Corrosion Behaviour of Plasma Transfer Arc Hard Facing in Acidic and Alkaline Environment

Abstract

Plasma transfer arc welding (PTAW) has been one of the popular methods for depositing thick hard facing. In this study, this method was used to lay the nickel hard-facing without tungsten carbide and with different compositions which are 35 wt%, 50 wt% and 60 wt% carbides. The hard facing was characterised using a scanning electron microscope with EDS and x-ray diffractometer (XRD). The corrosion behaviour was evaluated using three electrodes electrochemical test with saturated calmonel electrode (SCE) and platinum plate as the reference electrode and counter electrode respectively. The corrosion test shows that the hard facing had higher corrosion resistance in an alkaline environment compared to an acidic environment. The corrosion mechanism was by the dissolution of the nickel matrix, Ni3B dissolution is seen in an acidic environment while in alkaline electrolyte, the dendritic nickel dissolves preferentially.