Recycling of Al-Si alloys for high integrity structural components for the automotive industry applications has gained attention in the recent times. In this article, scrap of cylinder heads containing 6.01%Si and 2.62%Cu were recycled by casting into four alloys invariants: base alloy (no alloying elements added), 0.02%Ca, 0.38%Fe and 0.9%Fe+0.45%Mn additions. The structural properties were analysed through optical and SEM/EDS microscopy, X-ray diffraction (XRD). The wear characteristics of the alloys were investigated using a multi-pass ball on the flat reciprocating method under a normal load of 30 N and velocity of 4 mm/s. The results showed delamination and adhesive wear as the predominant wear mechanisms for the recycled Al-Si alloys. The base and 0.02%Ca alloys exhibited the lowest coefficients of friction and rates of wear. A comparison of the wear data to the published data on primary alloys revealed that our secondary alloys have the potential for applications in the automotive industry.

Abstract:Mild steel offers a variety of properties for various applications at lower costs giving the alloy a large application base in industry. However, the increasing complexity and severity of service environments has shifted the focus of many industries to structure modification techniques, like heat treatment, to improve material properties and performance. The focus of this paper was to therefore investigate the effect of heat treatment induced hardness on the sliding wear behaviour of mild steel. The results showed that resistance to dry sliding wear increased with increasing hardness of the mild steel samples. Both abrasive and adhesive wear mechanisms were observed to occur on the samples, however abrasive wear was predominant.

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The demand for efficient railway services has significantly increased in the past years due to an increased demand for the high-speed transportation of goods with high loads. The increase in loads and velocities has resulted in increased problems associated with rolling contact fatigue (RCF), rolling and sliding wear on the wheel and rail materials causing a reduction of service life of wheel/rail systems. Rail operating companies spend significant funds in maintenance and replacing damaged rails and wheels caused by wear. In addition, unscheduled maintenance due to wear and RCF often lead to poor availability of railway networks. For this study, dry sliding wear was investigated on wheel and rail steels using RTEC Multi-Function Tribometer. The results demonstrated that the rig was successful in simulating sliding wear, and that the fractions of the wear components could be varied, and it also provided instrumentation. Information on coefficient of friction against sliding distance and applied force were obtained which were used to compare sliding wear performance of both wheel and rail steels. The wheel was found to perform better than the rail under the same conditions due to its high initial hardness values and smaller interlamellar spacing.

A train experiences different slip ratios at the wheel/rail contact point as it moves along the rail track, which influences the rolling contact fatigue (RCF) and wear properties of wheel and rail materials. This variation in slip ratios is caused by a change in contact area between the wheel and rail head at curves, as the slip ratio increases compared with when a train is moving on a straight track. When the train is moving on a straight track, the wheel is found to be in contact with the rail head; but that changes when moving around curves, as the wheel flange will now be in contact with the gauge corner of the rail, affecting the severity of wear. Therefore, more research needs to be done to understand the role that slip ratio plays in the wear performance of wheel and rail materials in order to be able to develop models or systems that could be used to predict preventive maintenance. The aim of this work was to investigate the effect of the slip ratio on the wear performance of class B wheels against softer R260 rail steels under rolling and sliding conditions, using a twin-disc setup developed at the University of Pretoria. The results showed that the severity of wear was heavily dependent on the slip ratio – i.e., it increased with the slip ratio, with class B wheels performing better than the softer R260 rail.