Influence of surface roughness on the tribological properties of HF-CVD diamond coated heat-treatable steel

Standard heat-treatable C35 (1.0501) steel specimens were pre-coated with diffusion chromium carbide interlayer and in second step a crystalline diamond film was applied by Hot-Filament Chemical Vapour Deposition. This study investigates the tribological properties of specimens that were treated mechanically in a different way before the coating in order to achieve a different roughness. The tests were performed in a water lubricated ring-on-disc configuration while the coefficient of friction was measured. Wear analysis was done by light microscope. The wear development was obtained by several stops during testing. The friction and wear developments are compared and discussed for different surface roughness. Pre-treatment of the steel surface has a great influence on the tribological properties of the CVD diamond coating, especially the evenness of the surface determines the real contact area and therefore the wear behavior.

Research highlights▶ Flatness defines the contact area in macroscopic and roughness in microscopic scale. ▶ With crystalline diamond coating the application of sliding rings made out of steel seems to be possible. ▶ For the best tribological performance in planar contact, a low roughness combined with an even surface is essential.