TRANSITIONS IN THE MECHANISM OF MATERIAL REMOVAL IN ABRASIVE WEAR OF ALUMINA

The mechanisms of material removal in abrasive wear are investigated b y scratching a fine grain alumina with a diamond indenter. Subsurface damage is examined as a Function of load and number of passes using a bonded-interface sectioning technique together with microscopy. Scratc hing produces classical lateral and median cracks extending from the p lastic zone beneath the contact area. Damage within the plastic zone i s distributed in nature taking the form of intragrain twin/slip bands and intergranular microcracks. Repeated scratching causes damage accum ulation in the material beneath the sliding contact area. After a crit ical number of passes, a transition is observed from a damage accumula tion process to a material removal process that involves mainly grain dislodgement. As the number of passes is increased at large loads, the removal process exhibits a second transition from grain dislodgement to a more severe wear process by lateral crack chipping.