Lightweight refractory high entropy alloy coating by laser cladding on Ti–6Al–4V surface

In order to improve the Ti–6Al–4V (TC4) alloy's defects of low surface hardness and weak high-temperature oxidation resistance, an AlTiVMoNb lightweight refractory high-entropy alloy (RHEA) coating was developed. The AlTiVMoNb coating was successfully deposited on the TC4 substrate by laser cladding. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis showed that the coating and the TC4 substrate are metallurgically bonded, and the coating structure is composed of a single BCC HEA phase, and its lattice constant aXRD = 0.31246 nm, aTEM = 0.31234 nm. Due to the decrease of the d value has a more significant hindering effect on dislocation slip, the decomposition of spinodal in the bcc RHEA coating, the microhardness of the coating is 885.5 HV0.2, which is 2.52 times that of the TC4 substrate, and 1.66 times of the arc-melting alloy. The effect of complex mixed oxides such as Al2O3, TiO2, Al0·2Nb0·2Ti0·6O2, AlMoVO7, and Nb10·7V2·38O32.7 makes the coating continuously oxidized in the air at 800 °C for 120 h, and its oxidation weight is only 10.58% of the TC4 substrate. •AlTiVMoNb high-entropy alloy coating was successfully prepared on the surface of TC4 alloy. The RHEA coating is composed of a single BCC HEA phase with a lattice constant a = 0.31246 nm.•The microhardness of RHEA coating is 2.52 times that of TC4 substrate and 1.66 times that of arc melting alloy.•The oxidation weight of the coating after oxidation at 800 ℃ for 120 h is only 10.58% of that of the TC4 substrate.