Preparation and investigation of diamond-incorporated copper coatings on a brass substrate by composite electrodeposition

Abstract

In the electrical discharge machining (EDM) process, the brass electrode has the benefits of good stability, low cost, and excellent machinability. However, the main drawback is its high discharge wear rate. To reduce the electrode's discharge wear rate and improve its service life, this work investigated an electrode coating technique by using electrodeposition method to deposit multilayers on a brass substrate. The multilayers consisted of a Cu interlayer, a co-deposited Cu/diamond layer, and a Ni outmost layer to fix the protruded diamond particles. The diamond particles of 2–4 μm diameter was used in the study. The surface morphology of the diamond-incorporated multilayers was studied by scanning electron microscopy. The scar shape of the workpiece was investigated by an optical microscope. The coatings' adhesion was evaluated by scratch tests. The anti-corrosion capability was investigated by Tafel curves and electrochemical impedance spectra. The effect of diamond particle content on the discharge wear ratio was studied by considering both workpiece's material removal and electrode's tool wear. The discharge machining quality was evaluated by the ratio of (scar length versus machining length of the electrode) and the alignment of the cutting width on the workpiece. The incorporation of the diamond particles in the Cu coating also significantly enhanced the corrosion resistance and reduced the discharge wear rate of the brass electrode. The implementation of this coated electrode was also beneficial to maintain the cutting width of the EDM workpiece. The optimized deposition process to obtain the mentioned performance was suggested and addressed. In contrast to the high temperature-high pressure methods, the proposed electrodeposition method provides an economical alternative to prepare the composite coatings.