Influence of Lubricating Materials on Wheel-Rail Wear and Rolling Contact Fatigue

With the rapid development of railway towards high speed and heavy load, the wheel-rail wear, rolling contact fatigue and friction noise in the curve section with small radius of freight and urban railways have become the key problems, which need to be urgently solved. Therefore, the purposes of this work was to compare the influence of different lubricating materials on wheel-rail wear and rolling contact fatigue damage through the wheel-rail rolling contact simulation test, and to analyze and discuss the wheel-rail rolling contact fatigue damage mechanism under different lubrication conditions. The wheel-rail lubrication materials selected in this work were oil, grease and friction modifier. The oil was vehicle-used oil, the grease was trackside anti-wear paste used on Houyue Line, and the friction modifier was the water-based friction modifier. In order to simulate the wear and damage behaviors of different lubricating materials in the wheel-rail system under the wear regime, the wheel-rail samples were pre-run 10 000 cycles under the dry condition at the beginning of the test. The simulated wheel-rail samples achieved the stable wear state and the sample surface presented a slight fatigue damage state. Then, the wheel-rail samples continued to run 25 000 cycles under the dry, the friction modifier, and the oil and grease conditions, respectively. Under the friction modifier condition, the friction coefficient between wheel and rail could be adjusted to the range of 0.1~0.3. The wear rates of wheel and rail were reduced by 60.8% and 26%, compared with those under the dry condition. At the same time, the plastic deformation and rolling contact fatigue damage of wheel and rail samples were significantly reduced. Under the oil or grease conditions, the friction coefficient between wheel and rail was reduced to below 0.1 (risk of low adhesion), and the wear rates of wheel and rail were reduced by more than 85%. The surface damage, plastic deformation and rolling contact fatigue damage of wheel samples were slighter than those under the friction modifier condition, but the rolling contact fatigue damage of rail samples was severer. Friction modifier, oil and grease could effectively reduce wheel and rail wear. Oil and grease could aggravate the rolling contact fatigue damage of rail samples. The "oil wedge effect" was the main mechanism that caused the serious rolling contact fatigue damage of rail samples under the oil and grease condition. The solid lubrication characteristics of the friction modifier at the wheel-rail interface made it difficult to enter the crack, thus the "oil wedge effect" was not obvious and the rolling contact fatigue damage was slight.