The effect of top of rail lubricant composition on adhesion has been investigated using a laboratory ball-on-disc tribometer. Rheological properties were analysed using viscosimeter and high pressure torsion device. As a base medium, a biodegradable ester oil with bentonite thickener was selected. Added particles for friction modification were aluminium oxide, zinc oxide, copper sulfide and solid lubricants molybdenum disulfide and graphite. The effect of these components in the base medium on adhesion was evaluated. It was found that the most dominant component was the solid particles for friction modification. Based on the results, top of rail lubricant substances were prepared and tested. The best performing substances provided the optimal level of adhesion. These substances also showed resilience to overdosing, which caused commercial products to provide very low adhesion conditions. The rheological investigation confirmed the very low adhesion is controlled by elastohydrodynamic regime while the stable values are a result of transition to boundary lubrication.
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