Nanodiamonds (DINNOVARE)Antiwear Additives for Lubricating oil

Advantages of Nanodiamond Antiwear Additives

The recent trends in lubricating oils are the decreasing viscosity and the use in more severe friction conditions due to the demand for next generation energy savings. High frictional sliding materials directly contact with each other under boundary-lubrication conditions, i.e. high load levels and low velocity, causing adhesive and abrasive wear at the real contact area, which will result in higher friction coefficient or seizure. Lubricating oil additives such as extreme pressure agents and antiwear additives are generally applied to address those issues for the severe conditions.

Lubricating oil additives basically have a concept of preventing sliding surfaces from being brought into direct physical contact with each other by tribo-films, which are supersaturated solid solutions formed by reaction with elements from the environment (most often, oxygen). While such additives are effective for suppressing adhesion wear and seizure, however, there is a concern that the wear amount could increase due to the softness of formed tribo-films, degrading the reliability of sliding/frictional parts.

Daicel, as a century-old chemical company, offers detonation-synthesized nanodiamonds, which are nano-sized diamond materials as the splendid antiwear additives for lubricating oils. It has been demonstrated that nanodiamonds prevent direct contact between sliding materials by forming carbon-based tribo-films on the sliding surfaces. Since nanodiamonds do not form chemically-reactive films on the sliding metal surfaces, it is advantageous that the chemical wear (corrosion) is suppressed.

Specific functions of Nanodiamonds
Specific functions of Nanodiamonds

Antiwear Properties of Nanodiamonds

The nanodiamonds as antiwear additives work under wide lubrication conditions ranging from boundary lubrication to mixed lubrication where sliding surfaces are in direct contact with each other. As shown in the figure below, nanodiamonds effectively suppress the wear for the ball-on-disk friction surfaces resulted from the reciprocating sliding friction tester (The basic SRV®5 oscillation system).
A bluish interference film is observed on the wear scars on the ball when the nanodiamond-dispersed mineral oils are used, suggesting that a tribo-film with a thickness of some tens to hundreds nanometers is formed by friction.
This nanodiamond-derived carbon tribo-film contributes to the antiwear function.

Friction set-up and condition
  • Set upThe basic SRV®5 oscillation system
  • BallSUJ2(φ10mm)
  • DiskSUJ2
  • Lubricant100ppm Nanodiamonds in Mineral Oil
  • Load100N
  • Frequency50Hz
  • Stroke length1.5mm
  • Temperature50℃
Friction set-up and condition
  Mineral oil Nanodiamonds
in mineral oil
Wear scar of ball
Wear scar of disk

Wear scar after friction test

In order to maximize the wear suppression function, it is necessary to have know-how to maintain stable and uniform nano-dispersion of nanodiamonds in the lubricating oil. Daicel offers nanodiamonds well-dispersed in lubricating oils that meet various customer needs.

Friction set-up and condition
  • Set upBall on disk tribo meter
  • BallSUJ2(φ8mm)
  • DiskSUJ2
  • Lubricant10~100ppm nanodiamonds in synthetic oils
  • Load30, 50N
  • Velocity2, 25mm/s
  • Temperature25℃
Friction set-up and condition

NDs:Nanodiamonds

Specific wear rate after friction test
Specific wear rate after friction test

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