Improved sliding wear-resistance of alumina with sub-micron grain size: A comparison with coarser grained material

Un-lubricated sliding wear behaviour of sub-micron grained (average grain size, G = 0.45 μm), self-mated alumina was studied using conformal-contact with a unidirectional pin-on-disc wear testing machine. The wear characteristics of higher grained alumina samples (G = 0.95 and 4 μm) are also studied under self mating condition for comparative analysis by using similar test parameters and identical test configuration. Sub-micron grained alumina exhibits substantially higher wear resistance compared to the alumina of larger grain size. Scanning electron microscopy of the worn out test samples reveals that in un-lubricated condition, compaction of wear debris on sliding surface governs the wear characteristics of the present set of alumina. In many cases, partly revealed intergranular fracture was noticed. The strength of adhesion of the compacted wear debris with sliding surface increases with decreasing grain size. In case of alumina of larger grain size, the stability of the compacted layer decreases due to cracking. For sub-micron grained alumina, compacted layer of debris with increased adherence efficiently protects the virgin material resulting substantial decrease in wear loss.