Effect Of Microstructures On Wear Resistance Of Bainitic Rail Steel

In recent years,heavy load has become the main development direction of China Railway,and the wear of curved rail is becoming more and more serious.Compared with the traditional pearlite rail,bainite rail has excellent performance in wear resistance and rolling contact fatigue resistance.Under the same condition,its service life is higher than that of traditional pearlite rail.Bainite rail with high strength and good toughness has been widely concerned by researchers.In this paper,bainitic rail steel was taken as the research object,and different microstructures were obtained by different heat treatment processes.The effect of microstructures on wear resistance of bainitic rail steel were analyzed in terms of weight loss,wear surface morphology and crack initiation and propagation in section.The effect of different cycles on the wear resistance of air cooling and on-line quenched bainitic rail steel were analyzed.Finally,the wear mechanism of bainitic rail steel used in heavy load were analyzed,which provides important theoretical reference for the industrialization of bainite rail.After different isothermal temperatures(including those above and below M_S)of bainitic rail steel,the rolling-silding wear test were carried out.It was found that the morphology characteristics of wear surface were crack and spalling pit.With the constant increase of isothermal temperature,the weight loss increased first and then decreased.When the isothermal temperature was 360?,the weight loss was the largest.At the same time,the rolling-silding wear test on air cooling and on-line quenched bainitic rail steel with different cycles were carried out.It was found that the weight loss of both increased with the increase of cycle times.Under the same cycle times,the weight loss of on-line quenched rail steel was less than that of air cooling rail steel,showing excellent wear resistance.Tempering is one of the main means to control bainitic rail steel.By studying the influence of different tempering temperature on the"on-line quenched"bainitic rail steel,with the increase of tempering temperature,the impact toughness first increases and then decreases;The results showed that the tensile strength and yield strength of the tempered samples are higher than those of the on-line quenched samples,and the best matching of strength and toughness can be obtained after tempering at 280-300?.By comparing the results of ultra high cycle fatigue test between the on-line quenched and tempered at280?,it was found that the fatigue limit of bainitic rail steel is improved after tempering.To sum up,it is an important way to improve the wear resistance of bainite rail to improve the plastic deformation resistance of microstructure through reasonable microstructure control.Compared with the traditional air cooling process,the on-line quenched rail steel has better wear resistance,which has important engineering significance for high wear-resistant bainite rail used in heavy haul railway.