Study On Rolling Contact Fatigue Shelling Performance Of Wheel Materials For High Power Locomotive

With the widespread operation of high power locomotive,the rolling contact fatigue(RCF)shelling on the wheels for locomotives is aggravated,which reduces the service safety of wheels and shortens the service life of wheels.The alloy design of wheel materials is an important measure to alleviate the wear and fatigue of wheel materials.Therefore,it has important theoretical significance and engineering value for improving the service life and reliability of locomotive wheels to study the RCF shelling performance of three kinds of high power locomotive wheel materials with different element contents.In this paper,a field investigation was carried out on the shelling on the wheel tread of HXD2 C high power locomotives to analyze the influence factors and evolution rule of shelling.The difference on RCF crack initiation and propagation rules and shelling performance of three kinds of high power locomotive wheel materials(i.e.1# wheel,2#wheel — with higher Mo content than 1# wheel,3# wheel — with higher C and V contents than 1# wheel)was studied via the MJP-30 A rolling wear and contact fatigue apparatus.The influence mechanism of Mo,C,and V on RCF shelling performance of locomotive wheel materials was clarified.The main conclusions are as follows:(1)The shelling on the tread of HXD2 C high power locomotives in Houma Locomotive Depot was mainly caused by RCF.During the propagation of the transverse cracks at the nominal rolling circle(NRC),the materials fracturing above the cracks and the shallow cracks propagating back to the surface led to the RCF shelling.Route condition(i.e.curve,slope),season,and sanding were the main factors affecting the shelling.Wheels of locomotive running on more curves and slopes,wheels of locomotive running in summer and autumn with more rainy days,and the wheels on No.3 and No.4 axes with sanding all had more serious shelling.(2)Properly increasing Mo content(2# wheel)or C and V contents(3# wheel)in 1#wheel could reduce proeutectoid ferrite content and pearlite lamellar spacing in wheel materials,and improved the hardness and yield strength of materials.(3)With the increase in the number of cycles,the crack size(opening width of surface cracks,the length and depth cracks observed on cross sections)of the three kinds of wheels all gradually increased and then tended to be stable.Compared with 1# wheel,with increasing Mo content(2# wheel)or C and V contents(3# wheel),the maximum opening width of surface cracks decreased from about 600 μm to about 400 μm and 370 μm,respectively.The maximum of cracks length decreased from about 400 μm to about 270 μm and 200 μm,respectively.The maximum cracks depth decreased from 23 μm to about 15μm.(4)Properly increasing Mo content(2# wheel)or C and V contents(3# wheel)in 1#wheel could effectively improve the shelling life of wheel materials.Compared with the 1#wheel,the shelling life of the 2# wheel and 3# wheel were increased by 34% and 185%respectively.(5)RCF shelling was the result of continuous propagation of RCF crack and aggravation of damage.The process of shelling could be divided into three categories:(I)“Crack propagating back to surface”,including branch crack or parallel crack backed to the surface;(II)“Connection of two cracks”,including the connection of a vertical crack and an oblique crack or two oblique cracks,etc.;(III)“Fragments of surface materials”,it was the results of connection of micro-cracks near the surface.