Study on the microstructure and properties of Mo_0.5VNbTiCr_0.25 refractory high-entropy alloy coatings

This study focuses on the preparation of Mo_0.5VNbTiCr_0.25 refractory high-entropy alloy (RHEA) coatings on the surface of Zr-4 alloy using laser cladding technology. The coated samples underwent 24-h aging heat treatment at temperatures of 600 °C, 800 °C, and 1000 °C, as well as laser remelting. The crystal structure, microstructure, microhardness, and wear resistance of each RHEA coating sample were comprehensively analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), electron backscattering diffraction (EBSD), Vickers hardness test, and general-purpose friction and wear test. The different effects of aging heat treatment and laser remelting treatment on the microstructure and properties of Mo_0.5VNbTiCr_0.25 RHEA coatings were investigated. The results showed that each group of RHEA coating samples had good metallurgical bonding with the substrate without obvious defects such as pores and cracks. The coated samples were mainly composed of body-centered cubic (BCC) phases and a small amount of hexagonal close-packed (HCP) phases. The mechanical properties of the laser remelted samples were the best, with a microhardness value of 526 HV_0.2, and the best wear resistance. The wear mechanisms included adhesive wear, oxidative wear, and creep wear.