Effect of Laser Remelting on the Microstructural and Mechanical Properties of High-Velocity Oxy-Fuel (HVOF)-Sprayed WC-NiCr Coating

WC-based coatings are found efficient in providing excellent tribological properties to the structures and components subjected to harsh wear and erosion environments. High-velocity oxy-fuel (HVOF) spraying is known as one of the best techniques to deposit such coatings. However, there still exists scope for further microstructural refinement and improvement in the mechanical properties of the as-sprayed HVOF coatings. Laser remelting has proven to be an appropriate process to achieve such improvement in as-sprayed WC-based coatings. In the current investigation, laser remelting at two different power levels was done on the HVOF-sprayed WC-NiCr coating on stainless steel specimens. The post-processed coatings were analyzed using a scanning electron microscope, x-ray diffraction, x-ray photoelectron spectroscopy, and ImageJ software to study the microstructural changes. Microhardness and surface roughness measurements were also performed to study the mechanical changes. The laser remelting resulted in a smoother coating surface, having lower porosity, lower surface roughness, and higher microhardness as compared to the as-sprayed HVOF coatings. The highest reduction in the porosity was found to be around 72%, whereas, an increment of around 21% in the microhardness was witnessed. These two parameters are crucial for the tribological performance of the coatings. The current study also gives direction to further study these remelted coatings in tribological conditions.