The Influence of Particle Temperature, Particle Velocity and Coating Surface Temperature on the Sliding Wear Performance of TiO₂-Cr₂O₃ Coatings

In this work the sliding wear resistance of HVOF and APS-sprayed coatings from two experimental TiO₂-10-20 wt.%Cr₂O₃ fused and crushed feedstock powders was investigated. During the spraying process the particle temperatures and velocities were mapped in the cross section of the spray jet at different spray distances. In addition, the coating surface temperature was monitored. Coating microstructures and phase composition were studied by SEM and XRD, respectively. The elastic modulus (E) and hardness (H) values were measured via in-depth sensing indentation. The unidirectional ball-on-disk sliding wear test was performed at room temperature against a tungsten carbide ball (sliding speed 0.05 m/s, normal force 90 N). The increase of the particle temperature and velocity leads to an increase of hardness and Young’s modulus of the coatings, thereby increasing their sliding wear resistance. The sliding wear resistance can be correlated with the H³/E² ratio better than with the hardness alone. The sliding wear resistance was also sensitive to the coating surface temperature reached during deposition.