HFCVD nanocrystalline diamond coatings for tribo-applications in the presence of water

Nanocrystalline diamond (NCD) is increasingly popular as engineered surface coatings intended for tribo-mechanical applications. Sliding may occur in the presence of water, or aqueous solutions, for example in mechanical face seals, MEMS, or in preliminary testing bearing surfaces for biotribological applications. NCD coatings of 20 μm thickness were grown by the hot-filament chemical vapour deposition (HFCVD) method on Si3N4 ceramic substrates. The water lubricated NCD/NCD tribosystem was studied in an oscillating ball-on-flat tribometer. For all loading conditions up to the threshold load prior to film delamination (85 N), very low friction coefficient values (μ ∼ 0.02 to 0.05) combined with a high wear resistance (10−  9 to 10−8 mm3N− 1m− 1) were observed.