Wear and high-temperature oxidation resistance of (AlCrFeTiV)100-xNix high-entropy alloy coatings prepared by laser cladding on Ti6Al4V alloy

A series of novel (AlCrFeTiV)100-xNix (x = 0, 10, 20, and 30) high-entropy alloy (HEA) coatings were prepared via laser cladding on Ti6Al4V. The microstructure evolution, hardness, wear behavior, and high-temperature oxidation resistance were systematically studied. The results indicate that the microstructure of the (AlCrFeTiV)100-xNix HEA coatings gradually transition from BCC1 (enriched Ti, Al) + BCC2 (enriched V, Cr) + Laves phases to BCC + NiAl-type B2 + Laves phases with increasing x content. Ni addition gradually increased the hardness and wear resistance of the HEA; however, the formation of the B2 phase led to a slight decrease in hardness. Among the studied compositions, the Ni30 HEA coating exhibited the best wear resistance, with a wear mass loss of 8 mg & sdot;mm- 2 and a wear mass loss of only 13.6 % for Ti6Al4V. The wear mechanism of the (AlCrFeTiV)70Ni30 HEA coating is a comprehensive effect of abrasive wear, oxidative wear, and adhesive wear. Compared with those of Ti6Al4V, the oxidation rates of the AlCrFeTiV, Ni0, Ni10, Ni20, and Ni30 HEA coatings decreased by 65 %, 62 %, 55 %, and 61 %, respectively. The improved oxidation resistance is attributed to the formation of a dense NiXO4 spinel oxide layer. The Ni20 HEA coating exhibited excellent oxidation resistance at 800 degrees C, and the oxidation mechanism was further investigated via first-principle calculations. The results indicate that there is strong charge transfer between O atoms and Ni and Al, which tends to form NiAlO4-type spinel oxides.