Restoring friction surfaces of machine parts

Mechanism step by step

3D section of two metal parts and the friction zone between them.

1. Normal operation

   The surfaces slide on the oil film. Revitalizant in the oil: conglomerates of 100–500 nm made of hard nanoparticles in a binding phase; while the film separates the surfaces, the oil only carries them.

   1. The conglomerate as a “pomegranate”

      A revitalizant particle of 100–500 nm: hard nanoparticle “grains” of 2–20 nm separated by a softer binding phase. The oil carries the particle.

2. The oil film breaks

   Load above normal: the oil film breaks and the surfaces come into contact. A conglomerate is caught between asperities; pressure and temperature destroy the binder, and the nanoparticles press on the metal point by point.

   2. Contact spot: pressure and temperature

      The oil film is broken and the particle is caught between asperity tips. The high pressure and temperature in the contact spot break the binding phase.

   3. Crushing down to the “grains”

      The conglomerate falls apart into ever smaller pieces, down to single nanoparticles. The size adjusts itself to the roughness: the initial particle D is larger than the asperities h, after crushing d ≈ h.

   4. “Grains” as pressure concentrators

      The particle is comparable with the surface defects (the grain structure and the micro-roughness), and its “grains” press on the metal point by point: the pressure grows as the inverse square of the size. Special pressure and temperature arise in nanovolumes of the metal.

3. The coating forms

   The modified layer grows: temperature and pressure rise in the contact spots, carbon diffuses into the metal, carbidization and hardening go on; wear debris is caught and sintered onto the surface.

   5. Nanostructuring of the layer

      The metal deforms plastically in nanovolumes: its grains are intensively refined and the density of their boundaries grows, so the surface layer passes into an active nanostructured state.

   6. Carbon diffusion

      Along the many new boundaries carbon goes deep into the surface (vertically) and into the grains (horizontally).

   7. Low-temperature carbidization

      Carbides form readily from the carbon dissolved in iron. The metal-ceramic coating grows: more carbon towards the surface, less iron.

   8. Hardening and smoothing

      The particles work as a non-abrasive “nano-shot”: the asperities are smoothed plastically, and compressive stresses of one sign arise through the whole depth of the layer.

   9. Wear debris into the coating

      Like a “nano-mill”, the revitalizant particles grind the wear debris down to nano size. At the contact spots it is fused in and becomes part of the coating, and there is less metal in the oil.

4. Stabilisation

   The result: a restored surface, the roughness in equilibrium, the particles sized to it, and rolling instead of sliding.

   10. Finish: rolling instead of sliding

       The roughness reaches its equilibrium and the particles a size to match. They roll between the smoothed surfaces: sliding friction turns into rolling friction.