Effect of Laser Remelting on the Microstructure and Corrosion Resistance of CoCrFeNiTi-B4C High-Entropy Alloy Composite Coating

In order to reveal the effect of laser remelting on the corrosion resistance of high-entropy alloy (HEA) composite coating, a CoCrFeNiTi-B₄C HEA composite coating was prepared on the surface of AISI 1045 steel by plasma spraying and was remelted by laser technology subsequently. The microstructure and corrosion resistance of the composite coating before and after remelting were comparatively studied. The results showed that the entropy value of CoCrFeNiTi-B₄C composite coating after laser remelting still conformed to the definition of HEA. Moreover, there were almost no defects in the remelted coating, and a metallurgical bonding was formed between the remelted coating and the substrate. The remelted coating was dominated by FCC solid solution, with in-situ generation of TiC phase and (Fe,Cr)₂B phase. Among them, the (Fe,Cr)₂B phase was surrounded by (FCC + BCC) phase, forming a unique eutectic structure. In the electrochemical test, compared with the as-sprayed coating, the self-corrosion potential of the remelted coating increased from − 0.5236 to − 0.4439 V, the corrosion current density decreased from 5.910 × 10⁻⁵ to 9.424 × 10⁻⁶ A cm⁻². In addition, long-term immersion corrosion test also demonstrated that the corrosion resistance of the remelted coating was significantly better than that of the as-sprayed coating. Therefore, laser remelting can significantly improve the microstructure and corrosion resistance of CoCrFeNiTi-B₄C HEA composite coating.