Low friction in self-mated silicon carbide tribosystem using nanodiamond as lubricating additive in water

Nanodiamond particles(NDPs)have been considered as a potential lubricant additive to various tribological applications,such as water lubrication systems.In this study,the tribological properties of silicon carbide(SiC)lubricated by NDPs dispersed in water are investigated utilizing the ball-on-disk tribometer.It is found that the slight addition of NDP to water(i.e.,0.001 wt%)can distinctly accelerate the running-in process,which is necessary to achieve a friction coefficient(μ)as low as 0.01.This study also discusses two NDP functional terminations—hydroxyl and carboxyl.It is demonstrated that the use of carboxyl-terminated NDP over a wide range of concentration(0.001 wt%-1 wt%)yields a low friction force.In contrast,the ideal effective concentration of hydroxyl-terminated NDP is considerably limited because agglomeration in this material is more probable to occur than in the former.Meanwhile,when utilizing NDPs,the input friction energy(P_(in),defined as the product of sliding speed and applied load)is found to have an essential function.Several sliding tests were implemented at various P_(in) values(50-1,500 mW)using carboxyl-terminated water-dispersed NDPs.It was observed that theμand wear decreased with increasing P_(in) when 200 mW<P_(in)<1,500 mW.However,when P_(in)<200 mW,low friction with high wear occurs compared with the resulting friction and wear when pure water is used.