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HEC solutions of varying concentration were used as lubricant, which were introduced into friction pairs of Ti-6Al-4V plates and Si₃N₄ balls. Optical Surface Profiler and 3D Measuring Laser Microscope were used to measure the surface of plates and balls, respectively. The EDS and Raman spectroscopy were used to analysis the chemical composition on the resulting wear scars. The friction tests for the effect of speed and concentration of solution on tribology properties of Ti-6Al-4V were carried out on UMT-2. The results showed that a super-low friction state (μ≈0.005) was ahiceved after a long running-in stage. The COF decreases with the increasing rotational speed (80~630 r/min). The water will evaporate under high speed (> 630 r/min), which is owing to the heat by friction. In addition, the COF decreases with the increasing concentration (0.25%-2.00%). However, the kinematic viscosity of lubricant takes significant negative effect on COF when the concentration is larger than 2.00%. The surfaces of Ti-6Al-4V were worn down with smoothed flats under appropriate speeds and solutions, which was conducive for forming lubrication films. TiO₂ was detected on the scar by Raman spectrum. On the basis of these experimental results, a lubrication model was proposed.