In Situ-Reinforced Phase Evolution and Mechanical Properties of CoCrFeNi High-Entropy Alloy Composite Coating on Q235B by Laser Cladding with Nb Addition.

Abstract

Q235B is widely used in marine engineering materials; however, its wear resistance and corrosion resistance are poor. To improve wear and corrosion resistance, a CoCrFeNi high-entropy alloy (HEA) composite coating was cladded using laser cladding (LC) technology. Different proportions of tungsten carbide (WC) and Nb elements were added to the CoCrFeNi HEA coating, and the microstructure, phase, hardness, wear, and corrosion resistance of three different composite coatings were analyzed. The results show that the in situ synthetic phase is composed of Face central cubic (FCC) (Cr₃C₂) and strengthening phases such as W, WC, and NbC. In the process of LC, Nb will react with WC in situ, which not only reduces the morphology of the CoCrFeNi HEA cladding coating changed by adding WC, but also generates NbC, which leads to the dissolution of WC particles and improves the uniformity of particle distribution of the coating. The hardness of the coating with Nb is increased by 1.40 times, the wear resistance is enhanced, and the peeling of the hard phase is reduced during wear. The corrosion resistance of the coating with only WC particles is the best. Nb reduces the morphology of CoCrFeNi HEA cladding coating changed by WC particles. Although the coating with Nb is not as strong as that with WC particles only, it has outstanding hardness and wear resistance.