Twin-disc tests of iron oxides in dry and wet wheel-rail contacts

The wheel-rail contact system is open to the environment; as a result there are various kinds of contaminants present between railway wheels and rails. In addition to water, oil and sand, which are applied intentionally or unintentionally, iron oxides are constantly present on surfaces. A twin-disc rolling-sliding tribometer has been used to study the influence of iron oxides on the adhesion coefficient and wear rates of wheel and rail materials. Iron oxides were created in a climate chamber and tests were performed under both dry and wet conditions. The adhesion coefficient, wear rates and surface roughness were investigated. Results indicate that an increase in slip ratio increases the adhesion coefficient, and the wear rate also increases in the dry condition. In wet conditions, the effect of iron oxides lasts for a long time and greatly influences adhesion and wear. The adhesion curve peaks at a much larger creep with the presence of thin oxides than for thick oxides.