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 a(XRD) = 0.31246 nm, a(TEM) = 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 degrees C for 120 h, and its oxidation weight is only 10.58% of the TC4 substrate.