Study On Rolling Contact Fatigue And Wear Behavior Of G23Cr2Ni2Si1Mo Nanostructured Bainitic Bearing Steel

The nanostructured bainitic carburizing bearing steel is under extensive attention for the spindles of wind turbine generators due to its excellent strength,toughness and rolling contact fatigue(RCF)resistance.It has been used in the manufacture of heavy-duty bearings such as large-scale wind turbine main shaft bearings and rolling mill bearings.The main failure modes of bearings in service are RCF and wear.Therefore,it is crucial to study the relationship between microstructure and wear property,the microstructure evolution and the failure mechanism during RCF process.In this dissertation,the new nanostructured bainitic carburizing bearing steel of G23Cr2Ni2Si1 Mo was reported to study the effects of microstructural evolution on the fatigue and wear behavior.Following conclusions can be drawn:During RCF process,the bainitic ferrite on the top surface of specimen is gradually refined.The block-like retained austenite on the top surface firstly transformed into martensite during the early stage of rolling contact fatigue(RCF)process and then the filmlike retained austenite slowly transformed into martensite after a long time stress/strainaccumulation process.The transformed martensite not only increases the surface hardness but further brings additional residual compressive stress in surface layer.Most of undissolved carbides peel off and some of them dissolve during the RCF process.The dissolve carbide not only increases the carbon content of matrix which contributes to increased hardness of specimen,but further increases the stability of the retained austenite.The micro-voids are prone to be formed at the interface of carbide and matrix.These micro-voids grow up and become micro-cracks.The propagation direction of these cracks is towards the surface and the rolling direction.The crack will stop developing or change its direction when reaches the undissolved spherical carbides.The steel whose microstructure comprised of nanostructured bainitic ferrite,martensite and undissolved spherical carbides has the highest wear resistance.The microstructure of worn surface is refined,and the carbides are redissolved into the matrix during wear process.The subsurface material is tempered under the action of frictional heat,so that the carbides gradually grow and the hardness decreases.The residual austenite in the surface layer below 0.4mm turns into Martensite increases the hardness of the matrix.