Strengthening by Ti, Nb, and Zr doping on microstructure, mechanical, tribological, and corrosion properties of CoCrFeNi high-entropy alloys

Abstract

CoCrFeNi high entropy alloys (HEAs) are renowned for their exceptional ductility and corrosion resistance, positioning them as promising contenders in corrosion-resistant wear applications. Nonetheless, their intrinsic drawback lies in relatively diminished strength and hardness. This study delves deep into elucidating the mechanisms through which the incorporation of dopant elements augments the strength and toughness of CoCrFeNi HEAs. High-speed laser cladding (HLC) was employed to fabricate CoCrFeNi HEAs coatings, and the influence mechanisms of Ti, Nb, and Zr dopants on coating phase structure, microstructure, elemental distribution, microhardness, tensile properties, tribological performance, and electrochemical corrosion resistance were investigated. The results show that Ti boasts the highest affinity for solubility within the CoCrFeNi matrix, preserving its inherent FCC simple solid solution configuration. In contrast, Nb and Zr exhibit diminished solubility, culminating in the emergence of BCC phases and intermetallic compounds. In terms of strengthening mechanisms, the addition of Ti primarily contributes to solid solution strengthening, enhancing the strength, hardness, and wear resistance of CoCrFeNi HEAs coatings, with minimal impact on their ductility, resulting in coatings with optimal corrosion resistance. The introduction of Nb generates an interdendritic eutectic microstructure and shifts the dominant crystallographic plane from (200) to (111) in the FCC phase, leading to superior strength and wear resistance. The incorporation of Zr results in the formation of numerous Ni11Zr9 intermetallic compounds in the interdendritic regions, significantly deteriorating both ductility and corrosion resistance. This comprehensive investigation furnishes pivotal empirical insights and theoretical frameworks, setting the stage for the judicious optimization of HEAs in advanced material applications.