Electro spark deposition of WC–TiC–Co–Ni cermet coatings on St52 steel

Abstract

The electro spark deposition (ESD) technique has been successfully applied to deposit a cermet layer of WC/TiC/Co/Ni at room temperature on a St52 carbon steel substrate and the electrochemical properties of the bare and coated samples were evaluated. Influence of ESD process parameters on electrochemical properties of coatings were examined by using of potentiodynamic polarization and impedance spectroscopy (EIS) techniques. It has been possible to obtain a dense coating with adjusting the ESD process as the current limit of 15 A, frequency of 11 KHz, duty cycle of 50%, rotating speed of 200 rpm and spark energy of 1.46 mJ. The results confirmed that the sample with these fabrication parameters had higher ESD efficiency with the value of 64% and the dense coating without holes and micro cracks could be fabricated through the process. The electrochemical tests also confirm the good quality of the optimized coated sample. According to the results, the largest corrosion resistance with maximum Rcoat 76.16 Ω cm2 was observed in optimized coating condition.