Wear-resistant ultra-fine-grained ceramics

We have studied the effect of grain refinement in the sliding-wear resistance of alpha-Al2O3/beta-Al2TiO5 polycrystalline ceramics. In order to obtain dense, ultra-fine-grained ceramics, we start with a single-phase, metastable solid-solution nanopowder (Ti-doped Al2O3), which is subsequently spark-plasma sintered. The resulting 400 nm grain size, fully dense alpha-Al2O3/beta-Al2TiO5 ceramic has significantly improved wear resistance over its 2.2 mum grain size counterpart, and also over a 4 pm grain size pure alpha-Al2O3. A mechanistic model by Lawn and co-workers is used to analyze these wear results, and to provide guidelines for the design and fabrication of highly wear-resistant nanoceramics. This may have important implications because ceramics are being used increasingly in contact-mechanical and tribological applications. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.