Effects Of Hydrogen And Retained Austenite On Wear And Rolling Contact Fatigue Of Bainitic Steel

The purpose of this work is to solve the problem of premature failure of carbide-freebainitic steel crossing in railways and analyze the mechanism of premature failure. Byunderstanding the effects of Hydrogen and the retained austenite (RA) in failure process ofthe railway crossing, we provide theoretical guidance for the railway crossing material.In this paper, the research materials are Al-containing carbide-free bainitic steelcrossing which is designed by us. Electrochemical hydrogen charging, friction and weartest and rolling contact fatigue tests are carried out. The role of hydrogen and RA acted inthe two steels were characterized by scanning electron microscopy, X-ray diffraction, etc.Furthermore, the mechanism is investigated.The results of friction and wear test indicate that hydrogen can significantly improvethe wear resistance of the bainitic steel; and the wear resistance of the bainitic steel wasobviously higher than the high manganese steel. The main wear mechanism of the bainiticsteel at400N is the abrasive wear, and the adhesive wear at1000N. Hydrogen can reducethe stability of retained austenite in the bainitic steel, and promotes RA phase occursstrain-induced martensitic(SIM) transformation in the wear process. The hardness of thewear surfaces was evidently increased. Therefore, the wear resistance of the bainitic steelis enhanced via the combination effects of working hardening and stain.Rolling contact fatigue experimental results show that: the fatigue life of the bainiticsteel reaches5×106cycles; the hydrogen significantly lowers the fatigue life of bainiticsteel; RA affects the fatigue behavior notablely. Under the condition of rolling contactfatigue, the wear rate of bainitic steel is greater than the rate of the micro-cracks’expansion resulting in that the surface micro-cracks are difficult to extend into thesubsurface. Hydrogen promotes of the formation and expansion of the fatigue cracks,accelerating the fatigue failure. Enormous energy can be absorbed by the deformation andtransformation of RA, and more RA ensures a good contact on the surface, delaying theinitiation of fatigue cracks. But, more SIM increased the surface hardness when the cyclesexceeded106, resulting in peeling off and the reducing the fatigue life.