Wear of engineering ceramics by a soft abrasive

The wear behaviour of a number of engineering ceramics sliding against polyethyleneterephthalate (PET) has been examined. Microscopical examination of the worn surfaces has shown a wide distribution of size of grooves, from 50 nm to 1 μm. The smaller grooves seem to be made by anatase particles in the PET sheet. The larger grooves are made by particles ejected from the samples' surfaces by a fatigue mechanism. By relating the hardness of the engineering ceramics at a scale appropriate to the measured wear rates, some degree of agreement found. Further, it was found that the near-surface hardness of all the materials was lower than the macroscopic hardness values: the sole exception was anatase. Although the macroscopic hardness values of anatase were much lower than the alumina-based ceramics, the near-surface hardness values became relatively greater. In this way, what was originally thought to be a "soft" ceramic can now abrade a nominally "harder" one. The wear of the carbides is thought to be by an oxidation-assisted process.