Hydrodynamic lubrication effects in textured PEEK surfaces for friction reduction

The tribology of dimple-shaped textures is investigated within a reciprocating polymeric sliding couple of Invibio poly-ether-ether-ketone (grade 450G). A novel theoretical model was developed for this aim, describing hydrodynamic pressure and frictional force due to surface modifications. Experiments show reduced friction across all textures compared to un-textured surfaces. The parameters of texture depth (5-20 µm) and diameter (50-200 µm) were isolated to analyse the effect of each independently. The diameter showed good agreement with the model; however, depth showed variation at the extremities of the parameters examined. The experimental friction force captured over a single stroke was compared to the instantaneous theoretical friction force, and good agreement was found in the form of the friction trace within the hydrodynamic region of a reciprocating stroke. The texture parameter combination of 50 µm diameter and 20 µm depth showed the most significant reduction in friction at 48.7%.