STRUCTURE AND PROPERTIES OF A HIGH-ENTROPY AlCrFeCoNi ALLOY AFTER ELECTRON-ION-PLASMA TREATMENT

Abstract

With the help of wire arc additive manufacturing, a HEA of AlCrFeCoNi was prepared: of a non-equiatomic composition, on which a B + Cr film with a thickness of ~1 μm was deposited by plasma-assisted RF sputtering. Subsequent processing consisted in electron-beam irradiation of the surface with the following parameters: energy density 20–40 J/cm2, pulse duration 200 μs, frequency 0.3 s–1, number of pulses 3. A quasi-periodic distribution of chemical elements (at. %) 33.4Al; 8.3Cr; 17.1 Fe; 5.4Co; 35.7 Ni is established. It is shown that at the energy density of the electron beam Es = 20 J/cm2, the microhardness increases by a factor of 2, wear resistance by a factor of 5, and the friction coefficient decreases by a factor of 1.3. High-speed crystallization of the surface layer leads to the formation of a subgrain structure with subgrain sizes (150–200 nm). The increase in strength and tribological properties during electron-beam processing is interpreted taking into account the reduction in grain size, the formation of chromium and aluminum oxyborides, and the formation of a solid solution of boron incorporation into the HEA crystal lattice.