Generation of transfer film and its effects on wear mechanisms in alumina conveying pipeline of mild steel

摘要

Pipeline wear is a very complex problem and at present there is limited understanding of the wear mechanisms responsible for the reduction of wall thickness in severe wear regions of alumina conveying pipelines. The ability to determine the wear mechanisms in these areas holds the key in determining the service life of pneumatic conveying pipelines in these industries. In a previous paper it was revealed that delamination and subsequent cracking and spalling of a thin layer plays a major role in material removal in the severe wear regions in the pipeline. The thin surface layer is believed to be the transfer film of alumina generated in the internal pipe surface. In this paper, the transfer film developed in these areas of the pipeline have been analysed to determine its mechanical properties and to correlate the properties with the wear mechanisms observed earlier. In this work, the transfer film formed on mild steel pipes during pneumatic conveying is investigated by using a UMIS nanoindenter. The benefit of using the nanoindenter lies in the very small force that can be applied so that only the properties of the transfer film are measured. The mechanical properties of the film such as the hardness and Young's modulus at different loads are measured. Attempts are also made to measure the fracture behaviour of the film. The elemental analysis of the surface as well as the through depth was conducted using the SEM microanalytical technique EDS (energy dispersive X-ray spectroscopy) and XPS (X-ray photoelectron spectroscopy). The study found that the top layer of the surface is primarily aluminium with hardness value similar to that of sintered alumina.