ENHANCED WEAR-RESISTANCE OF ALPHA-ALUMINA BY SURFACE MODIFICATION WITH CHROMIA AND TITANIA

Poly crystalline a-alumina surface alloyed with chromia in lubricated sliding contact with 52100 steel was previously shown to have much better wear resistance than unalloyed a-alumina. Surface alloying with titanic had the opposite effect. The present study extended the results to single crystals and to dry contacts. Wear of chromia surface alloyed alumina was three to six times less than unalloyed, alumina, under both dry and lubricated conditions. The wear resistance of titania surface alloyed α-alumina was significantly improved with single crystal samples. Grain pullout and cleavage fracture were the principal wear modes in polycrystalline while single crystal alumina showed mainly cleavage fracture. Subsurface crack propagation, was also observed in both single and polyaystalline samples. The progression of wear in single crystal alumina was recorded Iry observing replicas of the surface taken at increasing sliding distance. © 1990 Taylor & Francis Group, LLC.