Pin-on-disc study of the effects of railway friction modifiers on airborne wear particles from wheel–rail contacts

Knowledge of wheel–rail interaction is crucial to wheel and rail maintenance. In this interaction, some of the worn-off material is transformed into airborne particles. Although such wear is well understood, few studies treat the particles generated. We investigated friction modifiersʹ effects on airborne particle characteristics generated in wheel–rail contacts in laboratory conditions. Pin-on-disc machine testing with a round-head pin loaded by a dead weight load 40 N simulated maximum contact pressure over 550 MPa. Airborne particle characteristics were investigated in dry contacts and in ones lubricated with biodegradable rail grease and water- and oil-based friction modifiers. The number of particles declined with the grease; the number of ultrafine particles increased with the water-based friction modifier, mainly due to water vaporization.