Effect of surface texturing on friction reduction between ceramic and steel materials under lubricated sliding contact

It has recently been identified that controlled porosity on a tribological surface can contribute to friction reduction at sliding contact interfaces. One of the presumed effects of surface texturing under boundary lubrication conditions is that micro-dimples can act as fluid reservoirs and play a role in promoting the retention of a lubricating film. The present paper verifies the effect of micro-dimples on the frictional properties of a silicon nitride ceramic mated with hardened steel. Pin-on-disk tests modeling the contact between cylindrical and planar faces were carried out for a variety of surface morphologies in which dimples were pattern machined with different size, density, and geometry. Compared to a lapped smooth surface without texturing, some samples successfully realized reductions in friction coefficient from 0.12 to 0.10. It was found that the tribological characteristics depended greatly on the size and density of the micro-dimples, whilst the dimple shape did not significantly affect the friction coefficient regardless of rounded or angular profiles. A dimple size of approximately 100 μm at a density of 5–20% is recommended.