Wear Mechanism Based on Wear Anisotropy

Abstract

Self-mated dry sliding wear experiments were conducted on alumina using a pin-on-disc configuration. Worn alumina surface showed pits and projections in the size and shape of the grains. This paper shows that formation of these pits and projections are due to the wear anisotropy observed in single crystal alumina. Formation of different morphologies within the pits is also shown to be due to the wear anisotropy. Using an independent wear experiment, a model has been proposed that shows that during sliding under load, the pits and projections experience preferential elastic deformation such that their surfaces become co-planar. Based on this model and the observed surface morphological evidence, a new wear mechanism has been proposed. According to this mechanism, during sliding under load, the boundary of such an elastically compressed grain at the grain pits becomes weak due to additional shear, tensile, compressive and thermal stresses. Whenever this combined stress exceeds the grain boundary strength, failure of the boundary occurs resulting in wear transition (severe fracture). It is speculated that this mechanism can be extended to any composite material whose constituent materials have different wear rates and also to single-phase materials with grains having wear anisotropy.

Presented at the 54th Annual Meeting Las Vegas, Nevada May 23–27, 1999

KEY WORDS:

• Ceramics
• Wear and failure
• Wear mechanism
• Wear anisotropy

Notes

Presented at the 54th Annual Meeting Las Vegas, Nevada May 23–27, 1999