Wear And Corrosion Behavior Of 42CrMo Steel Treated By Laser Shock Processing

42CrMo steel is a kind of alloy tool steel commonly used in the field of oil.Because it often works in a complex environment,so it requires a good corrosion and wear resistance.As a new type of surface strengthening technology rapidly developed in recent years,laser shock processing is widely used to improve the corrosion resistance,fatigue and wear property because of its high stability to strengthen the microstructure and residual stress state compared to traditional surface strengthening technology.In this paper,42 CrMo steel was chosen as the research object.Besides,The intensity and distribution of residual stress field,the corrosion resistance and wear resistance of 42 CrMo steel induced by laser shock processing test was carried out by finite element simulation analysis,corrosion electrochemical and friction-wear test.The main research contents are shown as following:(1)The finite element simulation software ABAQUS was utilized to simulate the residual stress field induced by laser shock processing.The intensity and distribution of the residual stress were studied.The results show that the error between the theoretical time and numerical simulation results of the laser shock wave propagation is very small.The maximum residual stress values of the three kinds of laser power densities are found on the surface of the target,which are-172.2MPa,-265.3MPa and-337.7MPa respectively.As the surface and depth direction are away from the impact center,the value of residual compressive stress is correspondingly reduced.The impact radius on the surface caused by laser shock processing is2.0mm,while that in the direction of depth is 0.3mm.The hardness,roughness and residual stress of 42 CrMo steel samples were compared before and after laser shock processing.The results show that the residual compressive stress is produced on the surface of the material after the laser shock processing.And the depth of the residual compressive stress layer is about0.6mm.Compared with the untreated sample,the surface residual compressive stress on the experimental samples is increased by 3 or 4 times.The surface hardness of the experimental samples were increased by 3.9%,8.6% and 16.9% respectively.The surface roughness of 11.32 GW / cm2(the value is 4.02 ?m)was significantly larger than 5.66 GW / cm2 and the untreated samples.(2)The friction and wear test of 42 CrMo steel samples before and after laser shock processing was carried out on the UMT-2 friction and wear tester,and the influence of laser impact parameters on the friction coefficient,wear mass loss and wear morphology was studied.The results show that both the friction coefficient and the wear mass loss decrease with the increase of the laser power density.And the friction coefficient of the 1 impact and the 2 impactis 0.548 and 0.492 respectively.Compared with the untreated specimen,the impact samples were reduced by 14.9% and 39.1% respectively.The wear mechanism of the specimen is contact fatigue wear before laser shock processing,while is mainly abrasive wear after laser shock processing.And the the friction and wear property of 42 CrMo steel were obviously improved by laser shock processing.(3)The electrochemical corrosion test of 42 CrMo steel in 3% NaCl solution of seawater corrosion environment was carried out.The corrosion thermodynamics,corrosion kinetics and corrosion surface morphology of 42 CrMo steel are studied.The results show that the maximum positive displacement of the surface is about 0.069 V after laser shock processing,which shows a low corrosion tendency.The self corrosion current density is shifted.The minimum corrosion current density exists in the power density of 5.66 GW / cm2,2 impacts by the laser shock processing.The corrosion pits are reduced after laser shock processing.It is also indicated that the laser shock processing can significantly improve the electrochemical corrosion resistance of42 CrMo steel.