Effect Of Laser Shock Processing On Microstructure And Friction And Wear Properties Of GCr15 Bearing Steel

Bearings,as one of the important parts in mechanical equipment,are mainly used to bear radial loads,support mechanical rotating shafts or other mechanical components,and reduce the friction coefficient of the connection parts.During the service process of the bearing,there are many phenomena such as spalling,wear,plastic deformation,and cage damage,and most of them occur on the bearing surface,which has a huge impact on mechanical equipment.GCr15 bearing steel is the steel with the highest output among the first-generation bearing steels,accounting for more than 90% of the total bearing steel in China.It is often used in bearing parts with a working temperature of less than 150°C,and is characterized by wear resistance Good,high hardness.Due to the harsh service requirements,the requirements for the mechanical properties of bearings are getting higher and higher,and GCr15 bearing steel cannot adapt to its application conditions.Surface strengthening technology can realize the nanometerization of the material surface,thereby improving the wear resistance,hardness and other properties of the material.The surface strengthening treatment of GCr15 bearing steel can effectively improve the bearing failure situation and prolong the bearing life.Compared with other strengthening technologies,laser shock processingtechnology has the advantages of building a deep and large residual stress layer,precise and controllable strengthening area,and good accessibility of the spot.In order to improve the wear resistance,hardness and other properties of GCr15 bearing steel,this experiment adopts laser shock processing to strengthen the surface of GCr15 bearing steel.The residual stress generated by laser shock processing will be released under the action of temperature.The effect of residual stress release on friction and wear properties was studied by performing low temperature tempering treatment on laser shock processing samples for different times.Using XRD,SEM,TEM,microhardness tester,X-ray residual stress analyzer,friction and wear testing machine to carry out different laser shock processingprocesses and low temperature tempering for different time on the microstructure,mechanical properties and friction of GCr15 bearing steel.The research on the influence of wear performance provides theoretical basis and support for the application of laser shock processing treatment technology in high carbon bearing steel.The results of the study showed that:1.The martensite of GCr15 bearing steel will be fragmented after laser shock peocessing treatment,and the average width of martensite will continue to decrease with the increase of laser shock pulse energy and shock times,and finally a nanocrystalline structure will be formed,The nanocrystal grain size of LSP-7J-6 samples is 52 nm.The retained austenite content of the original sample decreased from 11.82% to 4.12% of the LSP-7J-6 sample after laser shock hardening.The number of carbides increases and the average particle size decreases.2.Laser shock processing can effectively improve the hardness of GCr15 bearing steel,and build a deep and large residual compressive stress layer on the surface and subsurface of GCr15 bearing steel.The hardness value of LSP-7J-6 sample reaches 828 HV,the depth of hardened layer is 1900 μm,the residual compressive stress is 1100 MPa,and the depth of affected layer is 2200 μm.3.The friction coefficient and wear rate of GCr15 bearing steel decreased after laser shock treatment;with the increase of pulse energy and impact times,the wear mechanism of GCr15 bearing steel changed,from the adhesion and oxidation wear of the original sample to the abrasive wear of the LSP-7J-6 sample,and the adhesive wear is the supplement.4.The carbides in the microstructure of GCr15 bearing steel,the depth of the hardened layer,the residual stress and the wear rate are mainly affected by the pulse energy in the laser shock processing.The number of laser shocks has a greater influence on the surface morphology,surface roughness,martensite shape and distribution,hardness value and residual stress on the depth of the layer and the degree of wear scar oxidation than the pulse energy.5.After the LSP-7J-6 sample is tempered at low temperature,the change of structure and hardness is not significant,but the decrease of residual stress is obvious.The friction coefficient and wear rate of LSP-7J-6 samples increased,but the wear resistance decreased,and the wear mechanism was adhesive wear.The laser shock-strengthened samples have good thermal stability,and the release of residual stress will affect the friction and wear properties of GCr15 bearing steel.