Friction Modifier Performance in Twin-Disk Tests Using Disks of the Same Microstructure and Hardness

Abstract

Friction management in the wheel-rail interface has received great attention from railway engineering in recent years, mainly due to the possibility of reducing wheel and rail wear. The addition of greases, lubricants and friction modifiers on the track has increased in the main railroads of the world. However, studies demonstrating the effect of applying friction modifiers are mainly carried out by manufacturers. To evaluate the action of the friction modifier, laboratory tests are less expensive tools and can give an indication of the benefit of the application. Thus, in this work, dry and wet twin-disk tests were carried out using disks with the same microstructure and hardness, evaluating only the action of the friction modifier. It was noted that the retentivity of the friction modifier had increased with the distance covered in the test. These results would contribute to increase the distance between applicators on the railway track and promoting a lower volume of product per distance traveled. The addition of a friction modifier also reduced the traction coefficient throughout the test, which contributed to lower wear of the disk. The friction modifier induced rolling contact fatigue cracks with greater depth and length due to hydro pressurization action. However, the addition was still beneficial because the wet condition keeping the friction at smaller values, the crack propagation takes longer to occur.