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High-speed laser cladding was introduced to prepare a CoCrFeNiMo high-entropy alloy (HEA) coating. The microstructure, composition distribution, micromechanical properties, and corrosion resistance of the CoCrFeNiMo coating were characterized. As a result, the coating exhibited a dual FCC- and BCC-phase structure, and the grain size of the coating prepared through high-speed laser cladding was only 2~5 μm. The upper and lower parts of the coating were composed of equiaxed cellular crystals and slender columnar crystals, respectively. The interdendritic structure was a Mo-rich phase that was distributed in a network-like pattern. The nanoindentation tests revealed that the interdendritic BCC phase had high hardness and an elastic modulus as well as excellent resistance to deformation, while the intradendritic FCC phase possessed superior crack propagation resistance. In addition, the two phases could generate cooperative elastic deformation during the elastic deformation stage. The electrochemical performance of the coating was tested in 3.5 wt% NaCl solution, and the corrosion potential Ecorr and corrosion current density Icorr of the coating were −0.362 V and 3.69 × 10−6 A/cm2, respectively. The high-speed laser cladding CoCrFeNiMo HEA coating had excellent corrosion resistance thanks to the presence of the easily passivating element Mo and grain refinement. [ABSTRACT FROM AUTHOR]

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Copyright of Steel Pipe is the property of Steel Pipe Magazine and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

High quality 431 steel coatings were prepared on a 27SiMn substrate by extreme-high-speed laser cladding (EHLA) and conventional laser cladding (CLA), respectively. The cladding speed of the EHLA process was 150 m/min, and the surface rate could reach up to 1.14 m2/h, which is four times higher than that of the CLA process. The microstructure of the coatings was investigated in detail. The microstructure of both coatings was dominated by dendrites. Benefitting from the ultrahigh cooling rate, the dendrites of EHLA coatings were more refined than that of CLA coatings. The element distribution between dendrites and interdendritic regions was more uniform. The corrosion resistance was evaluated by electrochemical tests. The results indicated that the EHLA coatings performed better corrosion resistance due to the fine uniform microstructure. [ABSTRACT FROM AUTHOR]