Tribological and corrosion behaviour of HVOF sprayed Cr3C2-NiCr with nickel cladded graphite and hexagonal boron nitride

High Velocity Oxy Fuel (HVOF) sprayed coatings of Cr₃C₂-NiCr containing solid lubricants such as nickel cladded graphite and hexagonal boron nitride were successfully developed and characterised with the aim of optimizing the frictional and wear behaviour, particularly in the field of industrial valves. Microstructure and composition of these HVOF coatings were characterized and correlated to the results of tribological and corrosion tests. The abrasive wear test in the temperature range of 30 to 650 °C was carried out with the ball-on-disk setup. Self-mated linear contact setup was also utilized to examine the coatings in the practice-oriented tribological system. Corrosion properties were studied through electrochemical measurement in artificial seawater. Through the solid lubricant integration, the friction and wear volume could significantly be reduced at room temperature by minimizing particle pull outs and adhesive wear. Yet, due to the extrinsic property of the solid lubricants, their lubricating effect was highly dependent on the atmosphere and temperature. Cr₃C₂-NiCr with hBN tends to exhibit more stable wear resistance at a broader spectrum of temperatures, and also allows the utilization of the coating at temperatures higher than 450 °C.