Altering the surface properties of Al 6061 by depositing tungsten-copper through the spark discharge process

Abstract

This study explores the surface modification of Al 6061 using the electrical discharge coating method with a tungsten-copper (W-Cu) tool (75:25 weight%) fabricated through powder metallurgy. The effect of compact load, peak current and pulse on-time on material deposition rate (MDR), tool wear rate (TWR) and surface roughness (Ra) is evaluated using Taguchi L16 orthogonal design of experiments. Desirability analysis is employed for the simultaneous optimisation of MDR, TWR and Ra, wherein absolute errors of <5% are obtained for all responses at the optimum parametric conditions. The coated surfaces exhibited redeposited layers due to repeated quenching of the workpiece, which is more pronounced at higher energy discharge due to enhanced deposition. Furthermore, globules, voids, pores and cracks are observed by Field Emission Scanning Electron Microscope (FESEM) analysis on the coated surfaces, which are undesirable. Energy dispersive spectroscopy (EDS) analysis confirmed the transfer of W and Cu from the tool and carbon from the dielectric due to pyrolysis. The modified surface exhibited a 381.4% increase in microhardness compared to the base material. Wettability analysis demonstrated enhanced hydrophobic behaviour after coating with a contact angle of 129.4° and 126° for experiments 4 and 16, respectively, compared to 99° of the base material.