Role of Oxygen Content and Humidity on Adhesion and Damage Behavior of Wheel-Rail Interface Under Low Temperature

Abstract

The adhesion and damage behavior of the wheel-rail contact is crucial for the safety of railway operations. To investigate the effects of oxygen content and humidity of airflow on the adhesion and damage behavior of the wheel-rail interface, tribological testing of the wheel-rail interface is conducted using a rolling-sliding contact in the laboratory. Results show that the adhesion coefficient of the wheel-rail interface decreases with the increase of relative humidity (RH). The content of Fe²⁺ increases with the increase of humidity of the airflow, which promotes hydration reactions. Specifically, under the condition of RH = 50%, the presence of an appropriate amount of water molecules in the environment, results in a higher degree of oxidation on the worn surface of the wheels and the formation of a large amount of oxides. Furthermore, Fe³⁺ and Fe²⁺ are easily generated on the surface when the oxygen content around the environment is sufficient or insufficient, respectively. In the oxygen enrichment condition, a higher amount of Fe₂O₃ is observed, whereas for the hypoxic condition, the oxide film cannot be quickly formed again after being damaged, resulting in more severe wear on the wheel-rail interface because of the lower oxygen content in the surrounding environment. This work provides critical insights into the friction properties as well as wear mechanism in response to humidity and oxygen content when the wheel-rail interface encounters the humid and warm airflow with different humidity levels in the tunnel, which is crucial for proposing effective measures to improve the adhesion of wheel-rail interface and avoid the occurrence of the low adhesion problems.

Graphical abstract