The effect of WC-12Co and CrC-NiCr hard coatings applied by HVOF method on the microstructure, mechanical, and surface properties of steel

In today’s world, the use of metals is widespread across various industries, with St37 steel plying a significant role. However, over time, this metal undergoes significant deterioration in its mechanical and physical properties, mainly due to factors such as corrosion and wear. Rather than using expensive methods such as alloying to extend the life of the metal, a more economical and practical approach is to focus on improving the surface properties. Surface engineering techniques, particularly thermal spraying, offer a viable solution. Among thermal spray techniques, High Velocity Oxygen Fuel (HVOF) spraying stands out as an economical and time-saving method for producing materials, equipment or machine components with high resistance to damage mechanisms such as corrosion, erosion and wear. This study investigates the application of tungsten carbide and chromium carbide-nickel chromium coatings to St37 steel surfaces using the HVOF method. Microhardness measurements were carried out after coating to evaluate the mechanical properties, while scratch and wear tests were carried out to determine the tribological properties. In addition, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to assess the structural characteristics of the samples. The results indicate the formation of phases such as Cr 3 C 2 , NiCr and W 2 C on the low-alloy steel surface after the tungsten carbide and chromium carbide-nickel-chromium coating processes. Coating thicknesses of 204 and 239 µm were achieved for tungsten carbide and chromium carbide-nickel-chromium, respectively. These coatings contributed to improved mechanical and tribological properties. The WC-12Co coated sample exhibited the highest hardness value (1304 HV 0.1 ), while the CrC-NiCr coated sample recorded the highest critical load value in the scratch test (48 N). The WC-12Co coated samples showed the best wear resistance.