Effect of Friction Modifier on Rolling Contact Fatigue and Wear of Wheel and Rail Materials

In this study, the effects of a friction modifier (FM) on wear and rolling contact fatigue were investigated by twin-disc testing under various conditions. It was found that the contact fatigue damage occurred on the rail specimen under the FM condition and the water condition. The test under FM condition was performed under three different spraying times: 0.2, 0.5, and 1.0 s. The progress of contact fatigue damage severely increases at a spraying time of 0.2 s. Contact fatigue damage under the FM condition occurred faster than that under the water condition. Results show that the friction modifier induced a mixed condition that exists at the same time as the wet condition and the dry condition. Cracks were initiated by the traction force due to the friction of the dry condition and the crack growth rate became faster due to the fluid entrapment mechanism under the wet condition. Therefore, the amount of FM should be evaluted to avoid severe contact fatigue damage.