Abstract
AlCoCrFeNiNbx (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 AlCoCrFeNiNbx (x > 0) alloy coatings consisted of BCC, B2 and Laves phases. Microstructures of the AlCoCrFeNiNbx 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. AlCoCrFeNiNb0.75 alloy coating with a fully eutectic microstructure demonstrated the best wear resistance among the AlCoCrFeNiNbx (x ≥ 0) alloy coatings.
Highlights
Traditional alloys consist of one main element, whereas high entropy alloys (HEAs) are usually composed of five or more elements and their concentrations range from 5–35 at. %(atomic percent) [1,2,3]
The AlCoCrFeNiNbx alloys were fabricated using arc melting and the results showed that the alloys exhibited a eutectic microstructure and high strength/hardness
Volume (V)
Summary
Traditional alloys consist of one main element, whereas high entropy alloys (HEAs) are usually composed of five or more elements and their concentrations range from 5–35 at. %(atomic percent) [1,2,3]. The unique component design brings four core effects: high entropy effect, lattice distortion effect, sluggish diffusion and cocktail effect. Due to these effects, HEAs usually consist of simple solid solution structures, nano-structures or can even be amorphous [4,5,6] and they possess excellent properties such as high strength, good thermal stability, good electrical and magnetic performance and excellent corrosion and wear resistance [7,8,9,10,11,12,13,14,15,16,17]. The laser cladding technique will obviously reduce the cost, because the HEA coatings need less raw materials than other techniques such as arc Crystals 2019, 9, 56; doi:10.3390/cryst9010056 www.mdpi.com/journal/crystals
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