Research On Laser Quenching Process Of Automobile Stamping Die Steel Cr12MoV And Wear Mechanism

Cr12MoV steel is widely used in manufacturing automobile stamping die because of its high hardness,strength,wear resistance and little deformation of heat treatment.Laser quenching can effectively improve surface properties of Cr12 MoV automobile stamping die steel.Researches of Cr12 MoV steel is focused on properties for outstanding performance of practical application,but its microstructure and strengthening mechanism are ignored.However,excellent property is dependent on the development of microstructure.For this reason,laser quenching process was used to strengthen the surface of Cr12 MoV steel to improve wear resistance.This study used FL-Dlight-1500 semiconductor laser system to harden the surface of Cr12 MoV steel.The parameters were laser power 1500 W,laser scanning speed 10mm/s and defocusing amount 47 mm.The depth of laser hardened layer is 0.93 mm and surface hardness is 60.1HRC.The nonuniformity of eutectic carbides is reduced effectively by laser quenching.Analysis of microstructure by OM,SEM,TEM and XRD indicates that the main reason of properties development is transformation of twin martensite by laser quenching.Nucleation model is built to confirm secondary carbide(Fe_2.5Cr_4.3Mo_0.1)C₃ nucleated on dislocation.Both the precipitation of(Fe_2.5Cr_4.3Mo_0.1)C₃ and the formation of?Fe,Cr?solid solution improve the properties of matrix.The friction and wear experiments of Cr12 MoV steel after laser quenching were carried out according to actual working environment of die steel.Results show that the wear rate is only 0.36% and the friction coefficient is 0.5272.The width and depth of wear track are 5.1?m and 1.7?m.The phase composition and wear morphology were analysed under different laser power to confirm that wear mechanism was abrasive wear with spalling.Dispersion strengthening of secondary carbide(Fe_2.5Cr_4.3Mo_0.1)C₃ overcame adhesive wear mechanism due to low surface hardness.Partial dissolution of eutectic carbides?Fe,Cr?₇C₃ reduced abrasive wear to a certain extent.The protection between twin martensite and carbides overcame phenomenon of abrasive wear and spalling.