Synthesis and Characterization of AlCoCrFeNiNb x High-Entropy Alloy Coatings by Laser Cladding

摘要

AlCoCrFeNiNb x (x in molar ratio x = 0, 0.25, 0.5, 0.75, and 1.0) high-entropy alloy (HEA) coatings were manufactured on 304 stainless steel by laser cladding. The constituent phases, microstructures, chemical composition, micro-hardness and wear resistance of the HEA coatings were investigated respectively by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), a Vickers hardness tester and a friction/wear testing machine. It was found that an AlCoCrFeNi alloy coating without Nb consisted of body-centered-cubic (BCC) and order BCC (B2) phases, while the AlCoCrFeNiNb x (x 0) alloy coatings consisted of BCC, B2 and Laves phases. Microstructures of the AlCoCrFeNiNb x alloy coatings evolved from equiaxed grain (x = 0) to hypoeutectic (0.25 ≤ x 0.75), then to full eutectic (x = 0.75), and finally to hypereutectic (x 0.75). With increasing Nb content, the Vickers hardness values increased. AlCoCrFeNiNb 0.75 alloy coating with a fully eutectic microstructure demonstrated the best wear resistance among the AlCoCrFeNiNb x (x ≥ 0) alloy coatings.