Study on the effect of different electrode forms on the surface modification of Ti–6Al–4V alloy by near-dry electrical discharge machining

Abstract

The surface modification of Ti–6Al–4V alloy was achieved by using an electrical discharge machining (EDM) surface modification technology under the action of pulsed discharge to induce an in-situ synthesis reaction between the molten metallic material and the ionized elements in the atomized medium. In this study, nitrogen and urea solutions are used as the gas-liquid phases of the atomization medium. ANSYS simulation software was used to simulate and analyze the interpolar pressure and flow field of the different electrodes. The effect of different electrode forms on the EDM surface modification layer was investigated by designing comparative trials. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and other detection methods were used to characterize the process indicators, such as surface morphology, roughness, hardness, and wear resistance of the reinforced layer. It was found that a thick and uniform continuous layer can be obtained on the Ti–6Al–4V alloy substrate using multi-channel electrode machining, and the thickness is about 65 μm. XRD analysis indicates that the reinforced layer mainly contains TiN, Ti2N, Ti2AlN, Ti2O, and CuO phases. The samples with reinforced layers were shown to have higher hardness (1578 HV) and better wear resistance than the titanium substrates. The main wear mechanism is spalling wear and light oxidation wear.