Abstract: The RCF performances of the steel-to-steel pairs lubricated by two-phase liquid lubricants with additives of nano-grade powders of diamond are studied. The experimental results show that compared with the base oil of N15, the two-phase lubricant with nano-diamond does increase the RCF life, and the more nano-diamond is used, the higher RCF life is increased. When the content of nano-diamond is 0.3% percentage by weight, L10 life is increased only 3.62 times, but when it is 3.0%, the times is 13.85. The anti-fatigue behaviour of nano-diamond particles in the lubricants is investigated by analyses of physical and tribological properties of and physical chemistry properties of lubricant, namely, rolling of nano-diamond particles on the surface and increasing viscosity of the lubricant.

Key words: Contact fatigue life, Nano-diamond particles, Two-phase liquid lubricants