Wear behavior of bainitic and pearlitic microstructures from microalloyed railway wheel steel

Wear and contact fatigue are the main problems that reduce the durability of the rail and wheels. Pearlitic and bainitic microstructures have been studied over the years to obtain steel with higher mechanical properties, minimizing the wear and fatigue defects. However, the studies have not yet consistently confirmed whether bainite is a better alternative than pearlite to reduce the wear and contact fatigue. Therefore, in this paper, the twin-disc test evaluated, under dry conditions, the wear resistance and rolling contact fatigue (RCF) of bainitic and pearlitic microstructures obtained from forged micmalloyed railway wheel steel. The samples were isothermally treated in furnace at 350 and 600 degrees C, respectively, and the tests had controlled load and slip conditions. Thus, the bainitic microstructure presented lower mass loss than the pearlitic one, having higher hardness and greater capacity to absorb plastic deformation in volume. Also, it took the delamination process longer to develop in the bainitic microstructure, and the cracks were closer to the surface than in the pearlitic microstructure. After the wear test, the magnetic Barkhausen noise (MBN) analysis indicated higher levels of stress in the bainitic microstructure surface than in the pearlitic one. These findings suggest that the high concentration of plastic deformation closer to the surface prevented crack nucleation and propagation to greater depths. Thus, this study supports the suggestion that the bainitic microstructure may be a better alternative than pearlitic microstructure concerning railway wheel production.