Experimental study on the effect of surface texture on tribological properties of nanodiamond films under water lubrication

Abstract

The effect of nanoscale surface texture on the frictional and wear performances of nanocrystalline diamond films under water-lubricating conditions were comparatively investigated using a reciprocating ball-on-flat tribometer. Although the untreated nanocrystalline diamond film shows a stable frictional state with an average friction coefficient of 0.26, the subsequent textured films show a beneficial effect on rapidly reducing the friction coefficient, which decreased to a stable value of 0.1. Furthermore, compared with the nanocrystalline diamond coating, the textured films showed a large decreasing rate of the corresponding ball wear rate from 4.16 × 10−3 to 1.15 × 10−3 mm3/N/m. This is due to the fact that the hydrodynamic fluid film composed of water and debris can provide a good lubrication environment, so the entire friction process has reached the state of fluid lubrication. Meanwhile, the surface texture can greatly improve the hydrophilicity of the diamond films, and as the texture density increases, the water contact angle decreases from 94.75° of the nanocrystalline diamond film to 78.5° of the textured films. The proper textured diamond film (NCD90) exhibits superior tribological properties among all tested diamond films, such as short run-in period, low coefficient of friction, and wear rate.

Application of Nano-Crystalline Diamond in Tribology

“…Their frictional wear properties may be significantly altered in an aqueous environment. Yan et al [ 108 ] investigated the effect of surface texture at the nanoscale on the frictional wear performance of NCD films under water-based lubrication conditions. The untreated NCD films showed a stable friction state with an average COF of 0.26.…”

Dry Friction Properties of Diamond-Coated Silicon Carbide

“…They found that there is no obvious wear on the UNCD surfaces after 10 days of operation tests. Meanwhile, other researchers investigated the tribological properties of nanocrystalline diamond (NCD) [ 14 , 15 , 16 , 17 , 18 , 19 , 20 ]. Those results demonstrated the superior tribological performances of NCD and greatly increased the commercial application of diamond coatings in mechanical seals.…”