Effect Of Surface Ultrasonic Rolling Treatment On Sliding Wear Performance Of D2/U71Mn Wheel And Rail Material

With the rapid development of high-speed railway,the environment of wheel and rail is changing gradually.The friction and wear phenomenon between wheel and rail is very serious,among which sliding wear is a damage.Surface ultrasonic rolling treatment(SURP)is a new surface strengthening technology,which can improve the surface state and properties of materials.In order to improve the surface properties of wheel steel,the surface ultrasonic rolling treatment of D2 wheel steel was carried out in this paper,and the effect of surface ultrasonic rolling treatment on the pure sliding wear of wheel steel was studied.In this paper,the orthogonal experiment is carried out according to the three parameters of spindle rotation,feed and rolling pressure,which are selected to affect the SURP result.The surface of the wheel steel is subjected to ultrasonic rolling treatment of 9 different processes,and the orthogonal optimization test method is used to determine the optimum process parameters for improving the surface properties of the wheel steel and the optimized parameters are used to treatment on the D2 wheel steel simple.Then,doing the sliding friction and wear tests of the two simples.Finally,using microhardness test and sem to study the performance change and the microstructure evolution of the wheel-rail material under sliding wear.The influence of SURP treatment on the wear properties of D2 wheel steel under sliding wear condition was compared and analyzed,and discuss the wear properties of D2 wheel steel.The results show that after SURP treatment,the depth of plastic deformation layer on the surface of the test ring is about 260?m.In the test of raw materials,U71Mn rail steel is more wear-resistant than D2 wheel steel,and the wear mechanism of U71Mn test block and D2 test ring is similar.With the increasing of rotation,the abrasive wear gradually aggravates,and fatigue cracks appear on the wear surface.With the increase of the rotation,the white layer on the surface will continue to experience the process of formation,growth and exfoliation.The hardness of the white layer can reach 890HV,and it is easy to form a crack source at the junction of the white layer and the plastic deformation layer.And along the white layer of the inner layer continue to expand and spalling.Under the same wear condition,the wear loss of the test ring treated by USRP is obviously lower 57%than the original sample at the initial of sliding wear.SURP treatment can reduce the wear loss at the initial of sliding wear and improves the wear resistance of the material.Compared with the surface wear mechanism of the testring before and after SURP treatment,the original test ring had serious adhesion wear particles.The fatigue crack is easy to appear in the furrow direction of the ridge edge of the worn surface.After SURP treatment,the adhesive wear and abrasive wear of the test ring are very slight,and the worn surface is not easy to produce fatigue crack and almost no spalling.Compared with the surface microstructure changes of the simples in the same sliding wear process before and after SURP treatment,it is not easy to form white layer on the surface of the test ring treated with SURP,and the growth trend of the white layer is slow.Comparison of two simples at 600r,the results show that the hardness of the simples after SURP treatment is lower,the depth of hardened layer is deeper and the grain size of the surface layer is more uniform.The surface ultrasonic rolling treatment can deform,strengthen,improve the hardness of the surface,and reduce the initial wear and retard the evolution of the micro structure in the process of wear,have a better wear resistance.