Influence Of Original Microstructure On Rolling Contact Fatigue Properties Of ER9 Wheel Steel

At present,my country’s high-speed railway transportation is developing rapidly,and the running speed of trains is constantly increasing.Wheels,which are important moving parts of trains,are related to the safety of train operation and the safety of passengers’ lives and property.Rolling contact fatigue failure is one of the main failure modes of wheels.Therefore,the surface microstructure of high-speed EMU wheels during operation is studied.Evolution and fatigue performance are of great significance to the development of high-speed railways in my country.Using GPM-40 rolling wear contact fatigue testing machine,the two components are the same,the original structure is proeutectoid ferrite plus lamellar pearlite(P+PF)and tempered sorbite(TS)ER9 wheel steel Perform wear and rolling contact fatigue tests.The effects of different original structures on the rolling contact fatigue performance of ER9 wheel steel were studied by means of light microscope,scanning electron microscope observation,and hardness distribution test.The research results show that under the same wear conditions,the wear resistance of the TS structure is not as good as that of the P+PF structure,and the sample is more prone to multilateralization.The appearance of multilateralization will aggravate the wear of the sample,which is more similar to that of the P+PF structure.Good surface hardening ability is related.The fatigue life of the P+PF sample is about 3 times longer than that of the TS sample,and it has better rolling contact fatigue performance.During the fatigue test,the P+PF sample will preferentially initiate shallow cracks on the surface and grow in the fine-grained layer.Shallow peeling,fatigue cracks initiate in the area where the fine-grained layer peels off.However,the rolling contact fatigue cracks directly initiated in TS specimens after a short cycle of operation.The P+PF sample has better resistance to fatigue crack initiation due to the existence of the fine-grained layer.Under dry friction and pure rolling conditions,when pre-wearing 1×105 cycles,the rolling contact fatigue life of the two specimens will be increased.The fatigue life of the P+PF specimen and the TS specimen are increased by 3 times and 15 times,respectively,and the surface layer is obvious.Microstructure analysis shows that after pre-wearing,the surface layers of the two samples have formed a fine-grained layer of a certain thickness,which is obviously strengthened,and the residual compressive stress on the surface is increased,and the surface of the P+PF sample is removed due to pre-wearing.The machined fine-grained layer of the sample is prone to fatigue wear cracks on the surface of the sample.Some of the fatigue wear cracks become the crack source of the rolling contact fatigue cracks under the subsequent oil lubrication conditions.The TS sample has better resistance to fatigue wear crack formation.Therefore,TS specimens have better rolling contact fatigue performance when they are pre-weared for 1×105 cycles under pure rolling conditions.When pre-wearing for 1.9×105 cycles under the condition of 0.5% Slip ratio,the rolling contact fatigue life of the two specimens is reduced,and the fatigue life of the two specimens is roughly the same.At this time,the original structure affects the fatigue life can be omitted.