Rolling-sliding behavior of rail steels

Abstract

A twin disk-rolling-sliding contact machine has been used to investigate the deformation, wear and cracking that occur during rolling-sliding of high-carbon rail and wheel steels. A martensitic wheel steel with initial hardness of 360 HV contacted pearlitic or martensitic rail steels of different initial hardness, 280–360 HV. Other variables included test time, test environment and slip ratio (0%, 5%, 10% and 26%). Tests were run in air, but with different lubrication conditions, e.g. dry, with water, water with inhibitor, silicone oil, and various combinations. Wear was measured by weight loss. Wear surfaces, sample cross-sections and wear debris were observed by optical and scanning electron microscopy. Principal conclusions are as follows. The thickness of the highly deformed layer was very small for pure rolling compared with cases involving slip. Wear debris was generated from near-surface material in which the cementite phase had broken into small particles. Cracks initiated at the surface and propagated along lines of earlier plastic flow, rather than normal to the local direction of maximum tensile stress. The results of rolling-sliding in water or other liquids after dry rolling-sliding indicate that extensive deformation from sliding during the dry stage prepares the material for extensive cracking during subsequent operation with a lubricant.