Complex interaction behavior of rolling contact fatigue/wear of U76CrRE heavy rail steel

The rolling and heat-treated heavy rail steel U76CrRE is taken as the research object, and the wear amount, surface damage, deformation layer, crack initiation and propagation of heavy rail steel with and without precast cracks are measured and observed by using rolling friction and wear tester, laser confocal microscope, scanning electron microscope and backscattering diffractometer. The results show that under the same loading force, loading time and matching with the same wheel steel, when there is no precast crack or the depth of precast crack is less than the wear layer, The deformation layer of rolled heavy rail steel is larger than that of heat treatment. The EBSD results of the deformation layer show that the ferrite in pearlite is refined and mixed with cementite which is also refined into small particles. The ferrite grains are mainly small-angle grain boundaries, and the proportion of large-angle grain boundaries of ferrite grains gradually increases with the increase of the distance from the surface layer. Cracks in rolled heavy rail steel show the characteristics of large angle, deep depth and short length when there is no pre-crack, while cracks in heat-treated heavy rail steel show the characteristics of small angle, shallow depth and long length. Compared with them, the crack propagation trend of heat-treated heavy rail steel is more obvious. The crack angle, depth and length of heavy rail steel in rolled and heat-treated state are more obvious when matched with wheel steel with higher hardness than when matched with wheel steel with lower hardness. When the depth of the prefabricated crack is greater than the wear layer, the crack tends to expand with large angle, deep depth and long length, which leads to the acceleration of fatigue failure, and makes the heavy rail steel in rolled and heat-treated state mainly fatigue failure.