Effect of parameters on microstructure of electrical discharge coated ZE41A magnesium alloy with tungsten carbide-copper composite electrode

Abstract

Electrical discharge coating is a material transfer process of EDM used for fabricating composite coating on the workpiece surface. It is applied in the several applications such as surface texturing, die and mould making industries in order to increase the wear and corrosion resistance. In this investigation, ZE41A magnesium alloy is coated with tungsten carbide- Copper (WC-Cu) powder metallurgy electrode. Electrodes are prepared under three different load conditions (150, 175 and 200 MPa). Effects of process parameters on microstructure of the coated surfaces are studied. EDC experiment is carried out by varying the process parameters viz. compaction load (CL), current (I) and pulse on time (Ton). Response characteristics considered in this study are material migration rate (MMR), layer thickness (LT) and micro hardness (MH). MMR, LT and MH increases with increase in current and pulse on time at low compaction loaded electrode. Conversely, it is decreased with low current and pulse on time at high compaction loaded. Average micro hardness of the deposited surface was 125 HV and average layer thickness was 91.6 μm. Different surface defects were identified in the deposited surface such as cracks, craters and globules. Bigger craters were observed at surface deposited with higher current (4 A) that reduced the hardness of the surface.