Effect of electron-beam treatment on the structure and properties of (B + Cr) film deposited on a high-entropy alloy AlCrFeCoNi

Abstract

The B + Cr film with a thickness of ∼ 1 µm was deposited by plasma-assisted RF sputtering on AlCrFeCoNi HEA of non-equiatomic composition prepared by WAAM. The subsequent treatment included electron beam irradiation of the surface with parameters as follows: energy density Es=(20–40) J/cm2, pulse duration 200 µs, frequency 0.3 s−1, number of pulses 3. It has been proved that microhardness increases by 2 times and wear resistance – by 5 times, whereas friction coefficient decreases by 1.3 times at an energy density Es = 20 J/cm2. High-speed crystallization of the surface layer leads to the formation of a cellular structure with cell sizes (150–200) nm. The increase in strength and tribological properties effected by electron beam treatment has been interpreted with the three factors in view: (1) the decreasing cell size, (2) formation of chromium and aluminum oxyborides, (3) formation of a HEA crystal lattice incorporating solid solution of boron.