skip to main content

Guide to Scuffing

Scuffing is a severe adhesive failure situation associated with high speed, high load lubricated contacts. It is particularly prevalent with cams, tappets, cylinder bores and gears.

It is characterised by the following sequence of events.

  1. Intermittent surface contact through the lubricating oil film, either due to poor entrainment, localised surface roughness or debris entrapment.
  2. A consequent increase in the friction and, due to the high loads and speeds, an increase in the frictional heating.
  3. A consequent decrease in the oil viscosity, with a corresponding decrease in the oil film thickness and, inevitably, a higher frequency of surface contact events.
  4. As a result of the increased contact, even greater friction, more heating, lower viscosity and decreased separation.
  5. Yet more increase in the contacts and, finally, a runaway situation where the two surfaces suffer sudden, massive adhesive contact and seizure. The event is sufficiently dramatic to produce characteristic heat transformation layers at the surface.

Scuffing is best combated with nitriding or nitrocarburising treatments or by low friction coatings like Diamond-Like Carbon (DLC).