Study On Wear And Fatigue Properties Of Medium Carbon Cr And Mo Nitriding Bearing Steel

The microstructure and property of 32Cr3 MoVE nitriding bearing steel produced by vacuum induction and the mechanism of alloying elements in steel was investigated under different heat treatment process in this paper.The hardness distribution and microstructure characteristic of nitriding layer of 32Cr3 MoVE were studied.In Point,line,plane contact wear test were carried out the the SRV-4 wear test machine.And the rotating bending fatigue performance and the rolling contact fatigue performance of the test steel were studied.Tempered sorbite and dispersed carbide was obtained after quenching and tempereing.The tensile strength and yield strength of 32Cr3 MoVE were 1357 MPa and 1216 MPa,impact absorption energy at room temperature is 70 J.Strengthening mechanism and the effects of W,Mo in the steel were analyzed through comparing the chemical composition,mechanical properties and microstructure of 30Cr3 WVE nitriding bearing steel.The hardness distribution and microstructure characteristic of nitriding layer of 32Cr3 MoVE were studied.The effective depth of nitriding layer was 400?m and the surface hardness reaches 1000 HV.The nitriding layer was composed of compound layer and diffusion layer.The nitride layer is composed of a compound layer and a diffusion layer,and a large number of VN particles are dispersed on the compound layer.The diffusion layer has a vein structure,and the vein structure is Fe4 N.The wear resistance characteristic of 32Cr3 MoVE nitriding layer was studied under differen contact modes.The wear mechanism of nitrided layer is related to the load and the frequency of oscillating motion.The wear mechanism is abrasive wear and fatigue spalling,the non-metallic inclusions in the material reduce the wear properties.The ultimate rotating bending fatigue strength at room temperature of the 32Cr3 MoVE and 30Cr3 WVE bearing steel was 804 MPa and 732 MP respectivelya.The fatigue limit strength of 32Cr3 MoVE is 947 MPa after nitriding,the increment reaches 143 MPa.The fatigue limit strength of 30Cr3 WVE nitrided bearing steel is 850 MPa after nitriding,the increment is 118 MPa.The surface defects and internal non-metallic inclusions are the main causes of fatigue failure,and the non-metallic inclusions are mainly oxides of Al,Mg,Ca.The size and position of non-metallic inclusions in steel are closely related to the fatigue strength.The rolling contact fatigue life of 32Cr3 MoVE up to 3×107 when the contact stress is 4.5GPa.The contact fatigue damage morphology is a peeling pit,the depth and area of the peeling pit was 84.6 ?m and 0.48mm2.