What are the definitions of wear categories?
- Hard particles or protuberances (e.g., grind marks)
pressed against a surface.
- They only have to be harder than the surface receiving
- Produces cutting or shearing actions.
- Loss of material from a surface to impinging fluid
stream, or a fluid stream with solid particles
- If fluids react with surface, erosion/corrosion
= accelerated process.
- Can be intentional erosion = sand blasting, grit
- Can be unintentional erosion = ash and flue gas exiting
a combustor or passing over heat exchanger tubes.
- Cavitation - imploding bubbles.
- Low stress, high speed particles impinging on a
surface create wear chips.
- Can be minimized by increasing hardness of the
surface through a wear resistant coating.
- Loss of material from surface asperities in
relative motion, started by localized bonding
due to very high local stresses (and possibly
- Transfer of material may be permanent.
- Asperities may fracture, forming wear debris
-- which may oxidize -- changing the wear category
back to abrasion.
- Fracture of material from a surface caused by cyclic
stresses produced by repeated rolling or sliding over
- Examples of surface fatigue would be bearing tracks
and reciprocating shafts in sleeves.