Study On The Correlation Between Laser Surface Strengthening Process Parameters And Residual Stress Of 9310 Alloy Steel

Laser shock peening and laser transformation hardening are new laser surface strengthening processes,which can introduce residual compressive stress on the workpiece surface and improve the fatigue resistance of the workpiece.The difficulty of laser shock peening and laser transformation hardening lies in the reasonable planning of process parameters and the prediction of strengthening effect.In order to realize the wide application of laser shock peening and laser transformation hardening,it is very necessary to study the correlation law between process parameters and residual stress.This paper mainly takes 9310 highperformance aviation gear steel as the research object,and studies the calculation of residual stress strengthened by laser shock peening and laser transformation hardening process in the following aspects:(1)The calculation problem of laser shock peening impact pressure on plane and complex profile of gear is studied and solved.The finite element simulation model of residual stress of gear root strengthened by laser shock considering the actual laser incidence is established.The maximum difference between the residual stress simulation data and the measured data is 2.92%.The effects of initial residual stress,gear root surface and laser lap symmetry on the residual stress distribution of laser shock peening are analyzed quantitatively.The relationship between laser pulse energy,lap rate,laser spot radius,impact times and residual stress distribution in laser shock peening process of gear tooth root is explored.(2)The finite element software is redeveloped,and the moving heat source subroutine is created to calculate the temperature field of the workpiece strengthened by laser transformation hardening.The finite element calculation model of laser transformation strengthened microstructure and residual stress of gear steel is established by DANTE software.The residual stress distribution after laser transformation hardening of plane single point and plane is simulated and calculated,and the evolution process of temperature field,microstructure field,hardness distribution,stress field and deformation field under laser moving scanning is analyzed.To explore the correlation between laser power,laser action time and residual stress in plane single point laser transformation hardening process.(3)The laser transformation hardening experiment was carried out on9310 gear steel samples after tempering grinding to remove the oxide layer.The residual stress,surface roughness and surface morphology of the samples before and after the experiment were measured.The calculated value of residual stress finite element model is compared with the measured value,and they are in good agreement.Through experiments,the correlation law between the process parameters of planar and cylindrical moving scanning laser transformation hardening and residual stress is obtained,and the formulation rules of laser transformation hardening process that can guide practice are summarized.In the research work of this paper,a calculation method of laser shock peening pressure considering the actual laser irradiated gear root surface is proposed,and the finite element simulation model of laser shock peening residual stress of gear root is established,which can be used to predict the laser shock peening residual stress in practical machining.Through the simulation and Experimental Research on the residual stress and phase transformation field of 9310 gear steel material strengthened by laser transformation hardening,the laws and methods that can guide the engineering application are obtained.