Response surface methodology study on electrical discharge deposition of AZ31B magnesium alloy with powder composite electrode

Electrical discharge deposition (EDD) is surface modification method, used to produce thin and thick coating layer on the workpiece materials. Light weight alloys are used to manufacture the components are used in automobile, aircraft and medical applications. Nowadays, Mg alloys surface are modified with desired coating based on the application. However, it cannot be applied in the high load sliding applications due to its poor wear resistance. Hence, it is essential to improve the wear resistance in order to employ in the high load sliding conditions. In this investigation, AZ31B Mg alloy is coated using EDD with WC-Cu powder compacted electrode. Response surface methodology is applied to conduct the experiments and develop the empirical model. Selected factors are compaction load, discharge current and pulse on time while coating thickness (CT) and surface roughness (SR) are measured as responses. Higher discharge current and pulse on time with low loaded electrode increases CT and SR. Conversely, lower setting of current and pulse on time with high loaded electrode reduces the CT and SR. Lump coating with numerous micro cracks were observed at the surface coated using low loaded electrode (150 MPa), resulted increased SR. Maximum layer thickness of 120.55 µm was successfully achieved at compaction load of 150 MPa, current of 4A and pulse on time of 90 µs. Minimum coating thickness of 98.76 µm was observed at compaction load of 200 MPa, current of 2A and pulse on time of 50 µs. Uniform deposition with small sized globules were observed at the surface coated using high loaded electrode (200 MPa) that reduced SR. Energy dispersive spectroscope and scanning electron microscope analysis were carried out to study the quantity of elements and microstructure of the coated surface respectively.