Some railway managers and practitioners fear that introducing premium rail materials will have a detrimental effect on the wheels of trains that use the line. A review of relevant investigations across all scales in the laboratory, and in the field has been carried out. This showed that, as rail hardness increases, its wear, and overall system wear reduces. Wheel wear does increase with increasing rail hardness, but only for wheels running on rails that are softer than them. Similar trends were observed in all studies, so it seems that the fears were unfounded.While the wear trends appear well characterised some issues have been identified. One relates to the varying work hardening capability of wheel and rail materials. Often only bulk hardness is quoted, but work hardening can increase material surface hardness by up to 2.5 times and make materials that were initially softer, harder than the opposing material. Another related issue is test length. It is essential that enough cycles are applied such that the materials reach steady state wear, i.e., the point at which work hardening has reached its limit. In previous work it is not always clear that steady state wear has been reached. Some gaps have been identified in the current knowledge base, the largest of which is the failure to determine which mechanisms lead to the wear trends seen.Analysis of recent work on different clad layers on rail discs and premium rail materials allowed some of these gaps to be addressed. Results indicated that opposing wheel material hardened to the same level independent of rail hardness. Wheel wear is therefore stress driven under the conditions used, and dictated by the wheel material properties only. At higher slip levels relationships become less clear, but here temperature and therefore hot hardness is most influential and is as yet uncharacterised.

Twin disc tests were carried out to evaluate the wear resistance and Rolling Contact Fatigue (RCF) of premium R400HT rail samples in contact with E8 wheel samples. The wear rate and friction coefficient were correlated with the frictional work expended at the contact interface (the Tgamma approach). Accelerated RCF tests were also carried out on the premium R400HT rail and the results were compared to those obtained for standard R260 rail. The wear rates of rail samples were consistently lower than those reported in the literature for other contacting pairs in which the rail material studied is softer than R400HT. Also, the energy needed for the transition from the moderate to severe wear regime significantly increased for the hardened rail. Fatigue cracks were shallower for R400HT when compared with standard rail material. Hardened rails also showed lower mean spacing between fatigue cracks. This new information can be used to improve wear simulations of wheels and rails by using more realistic wear equations.

In recent years several high profile projects have questioned the repeatability and validity of scientific research in the fields of psychology and medicine. In general, these studies have shown or estimated that less than 50% of published research findings are true or replicable even when no breaches of ethics are made. This high percentage stems from widespread poor study design; either through the use of underpowered studies or designs that allow the introduction of bias into the results. In this work, we have aimed to assess, for the first time, the prevalence of good study design in the field of tribology. A set of simple criteria for factors such as randomisation, blinding, use of control and repeated tests has been made. These criteria have been used in a mass review of the output of five

Railway steel that offers a greater quality and extended life is described by the industry as premium rail. It is mainly used on areas of rail networks where accelerated wear, RCF or other rail related damage phenomena prevail. However, little performance data exists for these materials and where it does it is limited to one set of contact conditions. The aim of this work was therefore to map premium rail performance across a range of Tγ contact conditions to benchmark against standard grade R260 rail. Laboratory tests using a twin disc machine were performed to determine the wear performance of four premium rail grades against R8 wheel material, at various slip conditions of 1-20%. The results are shown in terms of Tγ and cyclic wear rate for both the rail and wheel discs. Material hardness mapping was obtained as a comparison between the full rail and the laboratory small scale specimen materials in order to correlate hardness with their wear behaviour. The purpose of this work is to understand the likelihood of wear in different wheel/rail contact conditions and to produce enough wear information for the premium rail that could be used in prediction tools for comparison with other materials and contact conditions.

Chrome plating is one of many surface engineering techniques used for corrosion resistance, as well as a protective coating against surface damage in load bearing applications, with surface hardness in the region of 1000 Hv. Laser cladding is an alternative hardfacing technique often chosen for corrosion resistance and for increasing the surface hardness of components, through thick clad coatings. The application of chrome plating and other similar surface engineering techniques for thick coatings can be inefficient and costly with practical process limitations. The objective of this case study was to investigate the feasibility of replacing the chrome plated layer of a rod mill pinion, made of forged steel, with a Nickel-based Tungsten-Carbide (Ni-WC) composite layer and an intermediate layer of Inconel 625. Mechanical properties were obtained using microhardness and nanoindentation techniques. Three-point bend tests were performed on test specimens from a pinion sample, in order to observe crack propagation resistance, a challenging task due to the curved geometry of the pinion sample and the difference in thickness between the existing and proposed coating layers. Crack development was captured, and plastic deformation was quantified with the use of Digital Image Correlation (DIC). In bending it was found that the bond between the composite coating, Inconel 625 and the steel substrate provided improved resistance to axial crack propagation, where the composite coating could withstand more than twice the bending tool displacement than the chrome electroplating.