EFFECT OF WC-Cu COMPOSITE ELECTRODES ON MATERIAL DEPOSITION RATE, MICROHARDNESS AND MICROSTRUCTURE OF ELECTRICAL DISCHARGE COATED MAGNESIUM ALLOY

Nowadays, coated surfaces have been used in the diverse of applications, such as automobile, aerospace and biomedicals. Different surface modification techniques have been used to improve the surface properties. Electrical discharge deposition (EDD) is an electro-thermal process widely used to deposit the hard composite coating on the workpiece with powder metallurgy electrode. To increase the deposition rate, powder composite electrode plays important role in this EDD process. In this work, tungsten carbide-copper composite coating is developed on ZE41A magnesium alloy surface using EDD. Process parameters used in the study are compaction load, current and pulse-on time, and the responses are material deposition rate (MDR) and microhardness (MH). The effects of process parameters on MDR and MH are studied. MDR and MH increased with increasing current and pulse-on time at low compaction loaded WC70-Cu30 electrode. Compaction load was found as the dominating parameter in the study followed by current and pulse-on time. Layer thicknesses of WC70-Cu30 and WC50-Cu50 electrodes are 92.12 and 72.88 mu m, respectively. MH decreased for the low compaction loaded electrode for both types of electrodes. This could be due to the minimum deposition of the tungsten particles. Uniform depositions with large spherical globules were observed at the surface deposited using WC70-Cu30 electrode. Larger craters were observed at WC50-Cu50 electrode. At the intermediate pulse-on time of WC70-Cu30 electrode, voids were formed which diminished the hardness of the surface.