Microstructure and properties of CoCrFeNiMo0.2 high-entropy alloy enhanced by high-current pulsed electron beam

Recently, high-entropy alloys have drawn lots of attention due to their outstanding properties. In this paper, a promising new surface modification technique was acted on CoCrFeNiMo0.2 high-entropy alloy to improve its mechanical and corrosion properties. CoCrFeNiMo0.2 high-entropy alloys were synthesized via vacuum arc melting then, their surfaces were processed by high-current pulsed electron beam (HCPEB). Microstructure, microhardness, wear and corrosion resistance were studied systematically by means of X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Before and after HCPEB irradiation, CoCrFeNiMo0.2 high-entropy alloy had a face-centered cubic (FCC) structure, and the surface of the irradiated samples revealed preferential orientation on the (111) and (200) planes. In addition, a compact and homogenization surface layer formed after irradiation. Also, high-amplitude stress caused high-density dislocations and stacking faults on the surface. After HCPEB irradiation, the properties of the samples were significantly improved, the maximum microhardness (392.9 HV) and lowest wear rate (0.92 × 10−4 mm3·N−1·m−1) was obtained after 35-pulsed irradiation. Furthermore, corrosion resistance was obviously enhanced after 25-pulsed irradiation. [Display omitted] •HCPEB irradiation was conducted on the surface of as-cast CrFeCoNiMo0.2 high entropy alloy.•A 3-8 μm thick compact remelted layer was formed after irradiation and the equiaxed grains along with σ phase were refined with the increase of the pulses.•Abundant structure defects such as subcrystals, high-density dislocations, dislocation cells, and stacking faults were also formed due to thermal stress induced by irradiation, resulting in intense plastic deformation of the material surface.•Surface microhardness, tribological behavior and corrosion resistance were improved due to grain refinement and compositional homogenization.