Microstructure and Properties of CoCrFeNiTi High-Entropy Alloy Coating Fabricated by Laser Cladding
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JMEPEG https://doi.org/10.1007/s11665-020-05204-y
Microstructure and Properties of CoCrFeNiTi High-Entropy Alloy Coating Fabricated by Laser Cladding Hao Liu, Wenpeng Gao, Jian Liu, Xiaotong Du, Xiaojia Li, and Haifeng Yang (Submitted July 27, 2020; in revised form September 7, 2020; Accepted October 3, 2020) CoCrFeNiTi high-entropy alloy (HEA) coating with constituent elements of equal molar ratio was fabricated by laser cladding on 40CrNiMoA alloy steel. The microstructure, microhardness, wear resistance, and corrosion resistance of the coating have been investigated. The coating exhibits typical dendritic morphology, composing of solid solution phase with FCC structure, v phase with cubic structure, and Co2Ti phase with HCP structure. The microhardness of the CoCrFeNiTi coating (about 700 HV0.3) is about four times higher than that of the CoCrFeNi. According to the estimated strength increment by the simple rule of mixture, the significant improvement of microhardness of the coating can be mainly attributed to secondphase strengthening rather than solution strengthening. The CoCrFeNiTi HEA coating with the wear rate of 0.84 3 1027 mm3/(N m) has better wear resistance than the substrate and CoCrFeNi HEA. The wear mechanisms of the coating were abrasive wear and low-cycle fatigue wear in the dry sliding process, accompanied by oxidation wear. The CoCrFeNiTi coating with the corrosion rate of 1.41 3 1022 mm/a exhibits poorer corrosion resistance than CoCrFeNi HEA, due to the formation of microanode and microcathode regions. Yet, the sensitivity to localized corrosion of the CoCrFeNiTi coating is reduced, due to the formation of a thicker passivation film. Keywords
corrosion resistance, high-entropy alloy, cladding, microstructure, wear resistance
laser
1. Introduction High-entropy alloys (HEAs) consisting of five or more primary elements are of growing attention as a new type alloy in recent years (Ref 1-3). Generally, the matrix of HEA is highentropy solid solution phase with a FCC lattice or a BCC lattice, in which all the constituent elements act as solvent. The formation of the solid solution phase is attributed to the rise of the configuration entropy caused by the multi-principal components with equal or near-equal molar ratio in the alloy system. The high-entropy effect effectively inhibits the formation of intermetallic compounds and promotes the formation of simple solid solutions (Ref 4, 5). Hence, HEAs present many excellent properties, such as high hardness (Ref 6, 7), outstanding oxidation resistance (Ref 8, 9), good high-temperature stability (Ref 10, 11), superior corrosion resistance, and excellent wear resistance (Ref 12-15). These advantages facilitate HEAs to be a suitable kind of material in the field of surface engineering. Currently, there are many preparation methods of HEA coatings, such as electric spark (Ref 16), Hao Liu and Jian Liu, School of Mechanical and Electrical Engineering, China University of Mining and Technology, Xuzhou, China; and Jiangsu Engineering Technology Research Centre
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