The impacts of retained austenite on the microstructure and property changes of carbide-free bainite during sliding wear

Abstract

With the rapid development of Chinese railway industry, there is an increased demand for better toughness, wear resistance and fatigue resistance of wheel/rail materials, and the development of carbide-free bainitic wheel/rail materials with stable and outstanding comprehensive properties is of great significance to the acceleration of railway development. This paper conducts sliding wear experiment on the currently developed FCB bainitic wheel steel (abbreviated as FCB in the following content) and AB1 bainitic rail steel (abbreviated as AB1 in the following content), and investigates the impacts of retained austenite (RA) on the microstructure and property changes of carbide-free bainite. During the process of sliding wear, the wear morphology of FCB is chiefly featured by abrasive wear; As wear rotations increase, adhesion wear and fatigue wear gradually appear. Compared with AB1, FCB with similar chemical composition has more RA, which causes it to undergo plastic deformation more easily during sliding wear. The deformation gives rise to higher strain in the surface layer and makes the grains caused by it much smaller, leading to white etching layers (WELs) with higher thickness and hardness more easily. Meanwhile, more RA means that more martensite phase with high thickness will be generated during the wear process, which increases the hardness of FCB. These two factors work together to make wear resistance of FCB better.