Complex Modification of the Surface Layer of a High-Entropy Al-Cr-Fe-Co-Ni Alloy by Electron-Ion-Plasma Treatment

Using the technology of wire-arc additive manufacturing (WAAM), a high-entropy alloy (HEA) of the nonequiatomic composition Al, Cr, Fe, Co, and Ni is manufactured. Using the methods of modern physical materials science, the elemental and phase composition, defective substructure, and mechanical and tribological properties of the HEA surface layer formed as a result of complex modification combining deposition of a film (B + Cr) and irradiation with a pulsed electron beam in an argon medium are analyzed. In the initial state, the alloy has a simple cubic lattice with a lattice parameter of 0.28795 nm; the average grain size of the HEA is 12.3 mu m. Chemical elements (at %) 33.4 Al; 8.3 Cr; 17.1 Fe; 5.4 Co; and 35.7 Ni, which form the HEA, are distributed quasi-periodically. The irradiation regime is revealed (electron beam energy density E-S = 20 J/cm(2), pulse duration 200 mu s, number of pulses 3, and frequency 0.3 s(-1) more than 5 times), allowing one to increase microhardness (almost by 2 times) and wear resistance (by more than 5 times) and reduce the coefficient of friction by 1.3 times. Regardless of the value of Es, the HEA is a single-phase material and has a simple cubic crystal lattice. High-speed crystallization of the surface layer leads to the formation of a subgrain structure (150-200) nm. It is shown that an increase in the strength and tribological properties of the HEA is due to a significant (4.5 times) decrease in the average grain size, the formation of particles of chromium and aluminum oxyborides, and the incorporation of boron atoms into the crystal lattice of the HEA.