Grain‐Size and R‐Curve Effects in the Abrasive Wear of Alumina

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Abstract
Results of sliding wear tests on three alumina ceramics with different grain sizes are discussed in the light of crackresistance (R‐curve, or T‐curve) characteristics. The degree of wear increases abruptly after a critical sliding period, reflecting a transition from deformation‐controlled to fracture‐controlled sulface removal. This transition occurs at earlier sliding times for the aluminas with the coarser‐grained microstructures, indicative of an inherent size effect in the wear process. A simplistic fracture mechanics model, incorporating the role of internal thermal expansion mismatch stresses in the crack‐resistance characteristic, is developed. The results suggest an inverse relation between wear resistance and large‐crack toughness for ceramics with pronounced Rcurve behavior.