A form of severe adhesive wear on gear teeth, cam followers and piston rings, triggered when the flash temperature in the contact breaks down the lubricant film. The surface shows a matte, torn band running in the sliding direction, often at the tip and root of gear teeth where sliding is highest. It can happen within minutes of an overload or a viscosity mix-up. EP additives, higher viscosity and smoother finishes prevent it.
Tooth tips are scuffed on the first-stage pinion, somebody put a 150 in a box that calls for 320.
Scuffing is a temperature failure, not a fatigue failure, so it tends to show up fast, often at commissioning or right after an oil change.
Also heard as
- scoring
- scuff
Related terms
Adhesive wear
Wear where touching asperities weld together and tear, moving metal from one surface to the other.
EP
Extreme pressure: additives or oils that react with metal under heavy load to prevent welding and scuffing.
Galling
Severe adhesive wear where sliding metals seize and tear, raising lumps of transferred metal.
Four-ball EP test
Four-ball test that raises load in ten-second steps until the balls weld, rating extreme pressure capacity.
Micropitting
Fatigue damage made of tiny pits, about 10 to 20 microns deep, that turns gear and bearing surfaces dull gray.