Research On Fatigue And Wear Properties Of U75V Steel Based On Ultrasonic Peening Technology

With the increasing development of railway industry,the safe and stable operation is the guarantee of the railway's advancement to be pushed rapidly and orderly.As a commonly used material of railway,the U75V steel is the most basic among all.In this paper,the specimens'surface strengthening mechanism,the improvement mechanism of wear-resisting property,and the improvement mechanism of fatigue behavior of notched specimens via ultrasonic treatment were studied.Meanwhile,the ultrasonic peening treatment in enhancing the economy,applicability and feasibility of U75V steel was analyzed and explored.The study shows that after UPT,the surface of the specimen was formed with a gradient nanostructures of 80-100?m in thickness;the surface of the material underwent obvious plastic deformation and the hardness value increased by 70%;the surface stress changed from tensile residual stress to compressive residual stress.The surface formed peening grooves and peaks that changed the state of microscopic stress concentration;The results show that the friction coefficient of the UPT specimens was small,and decreased with the increase of load.The wear surface was mainly based on the slight oxidation wear mechanism.The work hardened layer was distributed at a depth of 125?m.Analysis of fatigue data showed that the increase in fatigue strength increased significantly with the number of cycles.At 10~7 cycles,the fatigue strength of ultrasonic peening test specimens and ultrasonic peening test specimens increased by 71.9%and 87.8%,respectively.UPTWSL,compared with the UPT specimens increased by 9.2%;Comparing with the fatigue life of specimens not treated by ultrasonic peening,the ultrasonic peening treatment can obviously improve the fatigue life of the specimen,and the ultrasonic peening can be further improved,this was due to surface hardening,the combined effect of compressive residual stress,microscopic stress concentration and grain refinement,the beneficial effects of ultrasonic peening could significantly offset the adverse effects of stacking defects;analysis of fatigue fracture scan images showed that the existence of stacking defects makes the peening in the sample processing,the source of fatigue cracks was significantly increased,and the number of fatigue crack sources in the peening test was further increased.