Experimental Investigation The Microstructure And Properties Of U75V Steel During The Wear

With the rapid development of the railway transportation,heavy haul freight transport has become the inevitable trend of modern transportation.Accordingly,it is urgent to study the failure form and propose effective measures of wear resistance.In the study of heavy haul rail,the microstructure evolution and properties transform which it is running is important.The microstructure evolution and properties transform were studied using GPM-40 rolling wear test machine and the MRH Ring-Lump wear tester which simulated the rail and wheel running with the help of optical microscopy,hardness-tester,scanning electron microscopy.The results show that the heavy haul rail material of U75V showed different performances under different operation conditions.In this study,the friction coefficient during the wear process had effected by slip ratio which simulated by GPM-40 rolling wear test machine.It was discovered that the bigger the slip ratio is,the bigger the friction coefficient is.It was discovered that the bigger the slip ratio is,the bigger the friction coefficient is through studying the wear loss curve.Through comparing the change of microstructure under different wear conditions,the microstructure evolution of wear was discovered:Firstly,the direction of pearlite lamellae has been changed;Secondly,the cementite of the pearlite disintegrated gradually to particles,and the sub-grain in the ferrite has deformed;Thirdly,the particulate cementite has dissolve into matrix and the sub-grain in the ferrite has changed to equiaxed.Finally,the perlite which have been occurred by severe plastic deformation or the local temperature rising has become acicular martensites or equiaxial grains.It was investigated both the micro and macro of the worn surface morphology that the wear mechanism of the samples under a pure rolling condition changed from abrasive wear to surface fatigue wear and the wear mechanism of the samples under the rolling-sliding condition was surface fatigue wear;The wear mechanism of the samples which revolution was 300rpm was resulted from abrasive wear and oxidation wear.The wear mechanism of the samples which revolution was 450rpm was mostly resulted from abrasive wear,partially based on fatigue wear.The wear mechanism of the samples which revolution was 600rpm was mostly resulted from fatigue wear,partially based on fatigue wear.