| With the development of the aerospace industry,the performance requirements for aviation bearings are becoming increasingly stringent.Improving the surface properties of G13Cr4Mo4Ni4V steel only through conventional surface strengthening processes such as carburizing,nitriding,or carbonitriding has certain limitations,which are mainly reflected in the massive precipitation of nitride or carbides at the grain boundary,weakening the bonding force between grains,and even forming network shaped carbides,seriously reducing the comprehensive mechanical properties of the matrix.Laser shock peening technology is a new type of surface strengthening technology developed in the past two decades,characterized by high power density,short pulses,extremely high strain rates(10~7/s,,precision and controllability,and repeatable processing.In recent years,the use of laser shock peening in ordinary low and medium carbon steels has proven to improve the fatigue and wear resistance of materials.A large number of documents have proven that laser shock peening technology can significantly improve the fatigue and wear resistance of metals.However,there were few reports about the laser shock peening on the microstructure and mechanical properties of aviation grade low carbon high alloy steel(such as G13Cr4Mo4Ni4V steel,.This thesis taked laser shock peening technology and carburized bearing steel G13Cr4Mo4Ni4V as research objects,based on laser shock principle,shock wave propagation theory,and ABAQUS explicit dynamic simulation theory and small light spot of 4 mm×4mm impacted the surface of the carburized bearing steel G13Cr4Mo4Ni4V sample.The effects of laser shock waves with different parameters on the microstructure and mechanical properties of carburized bearing steel G13Cr4Mo4Ni4V were studied through SEM observation,microhardness testing,roughness testing,residual stress testing,reciprocating friction and wear testing,and rotational bending fatigue testing.The effects of laser shock processing parameters on the friction and wear properties and rotational bending fatigue properties of G13Cr4Mo4Ni4V steel were investigated.The results showed that after laser beam with different laser power density shocked G13Cr4Mo4Ni4V steel,primary carbides were broken,and martensite was refined in the surface layer.The surface residual compressive stress increased with the increase of laser power density.The maximum residual stress reached-928 MPa in the range of 1.974GW/cm~2～3.333 GW/cm~2 of laser power density.As the number of shocks increased,the roughness,surface hardness,and wear resistance increased.The optimal number of impacts was 4.The wear resistance of G13Cr4Mo4Ni4V steel was improved after laser impact with different overlap rates,but the optimal spot overlap rate was 50%,which was attributed to the uniform shocks peening effect.The optimal shock path was sequential.Compared with the traditional tempering state of martensite,the rotating bending fatigue property after laser shock peening was increased 30.9%from 870.9 MPa to 1140 MPa,which was related to the microstructure change after laser shock,surface hardening and tensile stress during the resistance test of residual compressive stress.The fracture morphology indicated that laser shock peening inhibited crack initiation and propagation,forming about 5μm hardened layer and about 15μm the toughness layer on the surface layer,which caused the fatigue source moving from the surface to the near surface about 20μm.In summary,after the surface of carburized bearing steel G13Cr4Mo4Ni4V by better laser shock parameters were laser peening treated,the wear mechanism changes from adhesive wear to a composite mechanism of abrasive wear and adhesive wear,and the surface was strengthened and toughened,so then its comprehensive mechanical properties were improved. |
PDF Full Text Request