Characterization and High-Temperature Fretting Wear Resistance of HVOF-Sprayed Cr3C2-NiCr, CoCrWC and CoCrWNiC Hardfacing Coatings

In the present study, Cr3C2-25wt%NiCr, CoCrWC (Stellite-6) and CoCrWC (FSX 414) coatings were deposited by the high-velocity oxy-fuel process on Hastelloy X substrates. The microstructure of the coatings was characterized using field emission scanning electron microscopy. X-ray diffraction was employed to identify the phase composition of the coatings. Tensile bond strength, elastic modulus and Vickers microhardness of the coatings were measured. A self-mated fretting wear test was also carried out on the coatings at room temperature and 550 degrees C. The results showed that some carbide dissolution occurred during the formation of Cr3C2-NiCr coating, although the coating displayed the highest bonding strength, Vickers microhardness and elastic modulus. The Stellite-6 coating showed a significant amount of unmelted particles and the most surface roughness. Oxide stringers were the main microstructural defect of the FSX 414 coating. The Stellite-6 and Cr3C2-NiCr coating had the best fretting wear resistance at the temperature of 25 and 550 degrees C, respectively. The wear mechanisms of the hardfacing coatings were discussed in detail.