Electrical discharge coating of AA6062 using hBN–Cu powder metallurgy electrodes: Microstructural and tribological characteristics

Electrical discharge coating (EDC) is an electrothermal surface modification technique for improving the functional performance of engineering alloys. In this study, hexagonal boron nitride–copper (hBN–Cu) powder metallurgy electrodes with 70:30, 50:50 and 40:60 compositions were fabricated and used to modify AA6062 aluminum alloy. The effects of electrode composition, compaction pressure, peak current and pulse-on time on material transfer, coating thickness, surface roughness, microhardness and tribological behavior were investigated. Compaction pressure varied from 80 to 160 MPa, while peak current and pulse-on time varied from 5 to 15 A and 100 to 300 μs, respectively. The coatings were characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction and electron backscatter diffraction. Among the investigated conditions, the 50:50 hBN–Cu electrode provided the most favorable surface and tribological characteristics, with a maximum microhardness of approximately 167 HV, minimum coefficient of friction of approximately 0.19 and minimum specific wear rate of approximately 0.00160 mm 3 /N·m. Increasing compaction pressure from 80 to 160 MPa reduced Sa from 4.951 to 4.800 μm and Sz from 56.719 to 50.280 μm, while the maximum coating thickness of 32.45 μm was obtained at 120 MPa. Electron backscatter diffraction (EBSD) analysis indicated 87.6% Cu and 12.4% hBN, with an average misorientation of 35.64° and maximum {001} texture intensity of 3.74 MRD. These results demonstrate that controlled electrode composition and EDC parameters can improve the surface and tribological performance of AA6062.