Abrasive wear by TiO2 particles on hard and on low friction coatings

The ball cratering test was used to study the abrasive wear resistance of a wide variety of coatings against TiO2 particles. The rutile TiO2, used as white pigment, causes mild abrasive wear in mixers, dyes, injection moulds and other components in the paint and plastic processing. The tests yield a clear ranking of the coatings. The abrasive wear due to the rutile particles is also compared to the wear induced by SiC particles commonly used for ball cratering tests. Differences in the wear mechanism using the latter are demonstrated. Furthermore, the calculation methods to derive the coating and substrate wear coefficients from the wear volume measurements have been critically reviewed. It can be concluded that the methods are especially useful for determining the wear coefficient in the coating. However, the substrate wear coefficient cannot be accurately determined when the wear resistance of the substrate is much lower than that of the coating. It is shown that the ball cratering test is not restricted to polished samples, but remains useful for moderate roughness as applicable to the desired components.