The sliding wear behaviour of Al---SiC particulate composites- II. The characterization of subsurface deformation and correlation with wear behaviour

Abstract

The purpose of this paper is to provide a deeper understanding of the wear behaviour of Al---SiC particulate composites through a detailed examination of the subsurface regions beneath the worn surface and the debris. Such an examination indicates that the subsurface deformed layer beneath the worn surfaces of Al-MMC pins is composed of a number of distinct layers like the mechanically mixed layer (MML), the shear deformed and bulk deformed layers. The MML is absent in Al samples. The thickness of each of these layers is dependent on both the volume fraction of SiC and the test load. Within the shear deformed layer, the presence of a soft shear sub-layer wherein the flow stress decreases with increasing shear strain has been established in all the MMC pins and at both the test loads. The hardness of MML is about six times the bulk hardness of Al-MMC. Electron probe microanalysis of both the MML layer and the wear debris indicates the presence of a substantial level of iron, transferred from the disc material. The debris size is of the order of millimetres at higher load while at the lower load, it is of the order of a few hundred micrometres. On the basis of the above experimental observations, the sequence of micromechanical events which lead to the generation of wear debris has been surmised.