Microstructure and wear resistance of Ti6Al4V coating fabricated by electro-spark deposition

Abstract

In this study, a Ti6Al4V coating with a large thickness of more than 550 µm was successfully deposited onto the surface of Ti6Al4V substrate by electro-spark deposition. The microstructure, phase composition, microhardness and wear resistance of the deposited coating were investigated by scanning electron microscope (SEM), X-ray diffraction (XRD), Vickers hardness and wear tester, respectively. The results show that the deposited coating is mainly composed of α’ martensite. The interface between the deposited coating and the underlying substrate is even and consecutive, which implies that a good metallurgical bond was obtained. The average hardness of the deposited coating is ~540 HV, which is about 1.6 times that of the substrate. The wear resistance of deposited coatings is obviously superior to the substrate. Under same conditions, the friction coefficient of the deposited coating decreases by about 0.19. The cumulative mass loss of the coating specimens is only about 1.58 mg in 20 min tests, while the mass loss of the substrate is ~3.6 mg. The analysis indicates that the improvement on wear resistance can be mainly attributed to the high hardness of the deposited coating, i.e., the hardened coating relieves the micro-cutting and adhesive wear in wear processes.