Investigation On The Influence Of Microstructure On Wear And Rolling Contact Fatigue Properties Of Rail Materials

With the rapid development of high-speed and heavy-haul railways,the issues of wear and rolling contact fatigue(RCF)become increasingly prominent.Microstructure is the core factor which affect mechanical properties and wear and damage behavior of metal materials.Therefore,it is of great theoretical significance and engineering value to adjust the microstructure parameters of rail materials and study the influence of microstructure on the wear and RCF properties of rail materials.In this paper,different pearlite interlamellar spacings,pearlite colony sizes and austenite grain sizes were obtained by heat treatment of rail rollers.Rolling wear tests and rolling contact fatigue tests were carried out on rail rollers by using the MJP-30A rolling wear and contact fatigue apparatus.The influence of three microstructure parameters on the wear and RCF performance of rail was analyzed.The mechanism of wear and RCF damage of rail materials with different microstructure was revealed.The quantitative relationship between three microstructure parameters and wear and RCF performance was established.(1)By adjusting heat treatment temperature and holding time,different pearlite interlamellar spacings(0.16μm,0.18μm,0.26μm,0.33μm),pearlite colony sizes(5.4μm,8.6μm,9.7μm,10.6μm)and austenite grain sizes(40μm,69μm,85μm,99μm,135μm)were obtained.(2)The wear rates of rail rollers increased with the increase in pearlite interlamellar spacing,pearlite colony size and austenite grain size.The influential orders of three microstructure parameters on rolling wear performance was:pearlite particle size(0.209)>pearlite particle layer spacing(0.120)>austenite grain size(0.071).(3)After the rolling wear test,the rail crack length decreased but the angle increased with the increase in the pearlite interlamellar spacing,pearlite colony size and austenite grain size.The influence of three microstructure parameters on the degree of relative damage was as follows:pearlite layer spacing(1.075)>pearlite mass size(0.663)>austenite grain size(0.618).(4)After rolling wear of rail rollers with different pearlite interlamellar spacings and pearlite colony sizes,the surface material had serious plastic deformation.When the plastic deformation accumulated to a certain extent,the microcracks initiated and expanded into surface cracks,and the surface cracks was broken into wear debris,leading to wear.For rail rollers with different austenite grain sizes,due to the soft ferrite at the austenite grain boundary,the ferrite flow line was formed during the plastic deformation process,and the crack initiation and propagation along the ferrite flow line were easy.(5)After the RCF tests,the fatigue crack had a"C"shape.The branch cracks would be produced at the front end of the crack,and the RCF cracks would pass through the plastic deformation layer and enter the material matrix.The cracks mostly spread along the direction of crystal,vertical layer and horizontal layer.The depth of the rolling contact fatigue crack and the length of the"C"curve of the crack increased with the increase in the pearlite interlamellar spacing.(6)When the pearlite interlamellar spacing was 0.16μm,the rolling contact fatigue life of the rail rollers were 20.5×10~5 cycles,which was higher than that of the rail roller without heat treatment(17.54×10~5cycles).The fatigue life was increased by 14.4%.