Cr3C2 is a hard gray powder with metallic luster that is used as a thermal spraying material. It is commonly used in the petrochemical industry as an anti-oxidation coating for wear-resistant parts. The material has excellent oxidation resistance at high temperatures and its crystal structure is orthorhombic. This makes it suitable for use in cemented carbide applications.
In the present study, Cr3C2-NiCr coatings were prepared using High Velocity Oxy Fuel (HVOF) and High Velocity Air Fuel (HVAF). The HVAF and HVOF processes showed comparable microstructures and phase constitutions. However, the hardness of HVOF and HVAF processed coatings varied. These differences can be explained by the porosity content of the sprayed coatings.
For each sprayed coating, the cross-section image was analyzed by SEM. Two distinct phases were observed, a light phase and a dark phase. XRD analyses were also performed on the feedstock powder.
Compared with the HVAF sprayed coating, the HVOF sprayed coating showed more porosity and lower hardness. Moreover, the HVOF sprayed coating underwent inflight melting and showed a defect-free interface with the substrate. Besides, the surface of the HVOF sprayed coating also had a splat-like morphology.
The HVAF and HVOF processed coatings were tested for wear behavior. Ball-on-disc tests at three normal loads were performed. When the wear rates of HVAF and HVOF coatings were compared, the results indicated that the HVAF coating had a higher wear rate than the HVOF coating. But the specific wear rates of HVAF and HVOF sprayed coatings were comparable.