High-temperature oxidation behavior of laser-cladded refractory NiSi0.5CrCoMoNb0.75 high-entropy coating

Abstract

This study investigated the high-temperature oxidation behavior of a refractory NiSi0.5CrCoMoNb0.75 high-entropy alloy coating prepared via laser cladding technology. X-ray diffraction, scanning electron microscopy, and electron probe microanalysis were used to characterize the microstructure, elemental distribution, and high-temperature oxidation properties of the coating. The results show that the coating was composed of a matrix having the HCP structure, a lumpy σ phase with a rhombohedral structure, and a minor netlike μ phase having the FCC structure. After the coating was oxidized in air at high temperatures, the surface and cross-section of the oxide layer were analyzed. The results show that the oxide scale had a unique layered distribution. The oxide scale was subdivided into six banded layers according to the different alloying elements contained in each layer. The elements in the oxidation reaction were mainly Ni, Co, and Cr. Furthermore, the oxide scale was composed of Ni3(VO4)2, Ni3TiO5, NiCrO3, CoCr2O4, and Nb0.6Cr0.4O2.