WC/Co composite surface structure and nano graphite precipitate induced by high current pulsed electron beam irradiation

•HCPEB irradiation was conducted on WC-6% Co hard alloy with accelerating voltage 27kV and pulse duration 2.5μs.•The surface phase structure was examined by using GAXRD, SEM and HRTEM methods.•The modified surface was composed of a mixture of nano-grained WC1−x, Co3W9C4, Co3W3C phases and graphite precipitates ∼50nm.•Surface tribological properties were greatly improved with self-lubricating effect. High current pulsed electron beam (HCPEB) irradiation was conducted on a WC-6% Co hard alloy with accelerating voltage of 27kV and pulse duration of 2.5μs. The surface phase structure was examined by using glancing-angle X-ray diffraction (GAXRD), scanning electron microscope (SEM) and high resolution transmission electron microscope (HRTEM) methods. The surface tribological properties were measured. It was found that after 20 pulses of HCPEB irradiation, the surface structure of WC/Co hard alloy was modified dramatically and composed of a mixture of nano-grained WC1−x, Co3W9C4, Co3W3C phases and graphite precipitate domains ∼50nm. The friction coefficient of modified surface decreased to ∼0.38 from 0.6 of the initial state, and the wear rate reduced from 8.4×10−5mm3/min to 6.3×10−6mm3/min, showing a significant self-lubricating effect.