Influences Of Microstructure On Sliding Wear Performance Of D2 Wheel Steel

Nowadays,the high-speed running of wheel and rail makes the friction and wear problem of wheel and rail more and more serious,putting forward higher and higher requirements for the performance of wheel steel,which is the key component in the railway transportation process.There is not only rolling friction between wheel and rail,but also sliding friction when train starts,brakes or drives to the curve bend.Therefore,it is of great significance to improve the sliding wear performance of wheel steels by changing the original structure of them.Sliding wear tests were conducted on MRH-5 ring-block wear testing machine on D2 steel wheels to study the influence of original structure of D2 wheel steel on sliding wear performance.Using digital camera,OM,SEM,TEM and microhardness tester to analyze the wear surface morphology and surface microstructure changes of D2 steel wheel samples after different revolutions.The results show that under the same test condition,D2 wheel steel with tempered sorbite(TS sample)as the original microstructure has better wear resistance than D2 wheel steel with lamellar pearlite structure(P)+proeutectoid ferrite(F).The surface wear mechanisms of P+F samples and TS samples are both mainly abrasive wear and adhesive wear,while the degree of the surface wear of P+F samples is more serious,accompanied with large peeled debris.After sliding wear,it is earlier and easier for P+F samples to form white etching layer with larger thickness in which it is more likely to initiate surface cracks,leading the spalling of the white etching layer.The plastic deformation of P+F microstructure is more severe.Ferrite is refined into nanocrystalline,the lamellar spacing of pearlite is significantly reduced and great deformation happens on the lamellar Fe3C,leading to its fracture,fragmentation and dissolution.While ferrite of TS microstructure is refined into nanocrystalline.Shear deformation almost doesn’t occur on granular cementite,the size of which becomes smaller and the number of which becomes smaller.And granular cementite gradually dissolved.After plastic deformation,it is the same for both P+F samples and TS samples that with the distance to the topmost surface decreasing,the proportion of large angle grain boundary increases,the proportion of small angle grain boundary decreases and ferrite grains are gradually refined.While the ferrite grain refinement in P+F samples at 5μm from the surface was more serious than that of TS samples and the proportion of large angle grain boundary is larger.After sliding wear,microhardness of P+F samples and TS samples both increase with the increase of revolutions.Microhardness gradually decreases from the surface to the matrix,with the two largest hardness occurred on the topmost surface.After 1200r,the microhardness of P+F samples and TS samples surface rise about 1.9 times and 1.3 times of the matrix microhardness respectively.The hardening effect of P+F samples is more serious than that of TS samples and the hardening depth of TS samples is about half of the hardening depth of P+F samples.