Laser re-melting of modified multimodal Cr3C2–NiCr coatings by HVOF: Effect on the microstructure and anticorrosion properties

Abstract

Abstract Modified multimodal (MMP) Cr3C2–NiCr coatings were fabricated by high-velocity oxy-fuel (HVOF) spraying deposited on a CuCrZr alloy substrate. However, due to the lack of its inevitable porosity, an additional laser re-melting (LRM) approach is highly required to improve the coating performance. Therefore, the LRM technique is employed in this study to improve the microstructure properties of an MMP Cr3C2–NiCr coating by HVOF. Solid-state phase transformation from Cr3C2 to Cr7C3 occurred during the LRM process. After the LRM process, the coating exhibits the presence of Cr3C2 nanoparticles that serve as reinforcement. These nanoparticles demonstrate minimal lattice misfit and exhibit high stability throughout the LRM process. The surface of the coating undergoes modification, resulting in the formation of homogeneous nano (20–130 nm), micron (150 nm to 0.3 μm), and submicron (2–3 μm) Cr3C2 structures, along with high-density microstructures, after the LRM process. Nano-Cr3C2 particle reinforced with high total work function and incredibly increased corrosion rate significantly improves coating corrosion resistance. Overall, porosity decreased from 3.9% of the HVOF coating to 0.3% of the LRM. As a result, the current density of anticorrosion decreased from 33.7 to 4.35 µA·cm−2, and the Vickers microhardness average values ranged from 1,050 to 1,300 HV0.3, indicating improved microstructure development and related properties.