Study On The Surface Integrity Of GH3039 Superalloy Treated By Laser Shock Treatment

Nickel based superalloys have excellent high temperature mechanical properties,good oxidation resistance and corrosion resistance,which are widely used in the manufacturing of hot components such as guide vane,combustion chamber and turbocharger of aero-engine.With the improvement of the working performance of modern aero-engine,the hot components of the engine bear severe thermal stress and alternating load in the service process,which are prone to wear,fatigue fracture and other failure problems,seriously endangering the operation safety of aerospace equipment.As a new surface modification technology,laser shock peening(LSP)uses laser induced shock wave to induce severe plastic deformation of materials,which can significantly improve the mechanical properties and prolong the service life of materials.In this paper,GH3039 superalloy is taken as the research object.Through the laser shock peening,friction and wear test,tensile test and tensile fatigue test,the influence of laser shock peening on surface integrity,tribological properties,mechanical properties and fatigue resistance of GH3039 superalloy is studied,which provides a theoretical basis for the industrial application of laser shock peening in the field of performance enhancement of engine hot components.The main research work and results are as follows:Laser shock peening was carried out on GH3039 superalloy by procudo(?)200 laser peening system.The effects of different times of laser shock peening on surface properties of GH3039 superalloy,such as surface roughness,microhardness and residual stress,were studied.The results show that laser shock peening improves the surface properties of GH3039 superalloy.The surface roughness of the sample increases from Ra0.0372?m to Ra0.0778?m after three times of laser shock peening.With the increase of laser shock times,the surface roughness of the sample increases;After three times of laser shock peening,the surface microhardness of the sample increases from 252HV to 353HV.With the increase of impact times,the surface microhardness and the depth of deformation hardening layer increase;The residual stress on the surface of the sample without impact is 55 MPa,and the residual compressive stress on the surface of the sample after three times of laser shock reaches-485 MPa;The results show that the phase composition of the alloy is not changed before and after laser shock peening.The grain size in the impact zone is obviously refined,a large number of dislocation tangles are produced near the surface layer,and nano grains appear in some areas.The friction and wear tests of GH3039 superalloy were carried out on UMT-2MT friction and wear tester.The effects of laser shock peening on the friction and wear properties of GH3039 superalloy were studied.The results show that the wear behavior of GH3039superalloy is mainly abrasive wear,accompanied by adhesive wear and oxidation wear.The average wear rate of the sample without impact is 0.852×10^-6 mm³·S^-1·N^-1,while the average wear rate of the third impact sample is 0.182×10^-6 mm³·S^-1·N^-1,and the wear rate of laser shock specimen is lower than that of non impact sample.With the increase of laser shock peening times,the wear rate of the samples decreases gradually.The grain refinement and deformation strengthening induced by laser shock peening are the main reasons for the improvement of wear resistance.Combined with the research results of laser shock peening on GH3039 superalloy surface properties,the laser shock processing parameters were optimized.According to the optimized laser processing parameters,laser shock peening was carried out on GH3039 superalloy.Tensile tests at room temperature and high temperature were carried out to study the effect of laser shock peening on the mechanical properties of GH3039superalloy.The results show that the average tensile strength increases from 817.3MPa to905.8MPa at room temperature,and the elongation decreases from 22.7%to 16.5%;the average tensile strength increases from 642.3MPa to 697.2MPa and the elongation decreases from 53.1%to 31.7%at high temperature.Laser shock peening improves the tensile strength of GH3039 superalloy at room temperature and high temperature,but also reduces its elongation.Fracture analysis shows that high temperature leads to softening of the material,and the dimple size increases and changes greatly.The dimple size on the fracture surface decreases and the distribution is more uniform after laser shock peening.The fatigue test of GH3039 superalloy was carried out by MTS landmark 371.10hydraulic servo fatigue test system.The effect of laser shock peening on fatigue properties of GH3039 superalloy was studied.The results show that the average fatigue life of the original sample is 27633 cycles,and the average fatigue life of the sample treated by laser shock peening reaches 83266 times,an increase of 201.3%.The fatigue properties of GH3039superalloy were significantly improved by laser shock peening.The fracture analysis shows that the fatigue crack spacing in the fatigue crack growth zone of the impact specimen is reduced from 1.16?m to 0.42?m,and the fatigue crack spacing decreases by 63.7%.The results show that the fatigue crack growth rate of GH3039 superalloy is reduced by laser shock peening,and the fatigue life of GH3039 superalloy is increased.The statistical analysis shows that laser shock peening has a significant effect on the fatigue life of GH3039superalloy.The improvement of fatigue resistance of GH3039 superalloy after laser shock peening is attributed to the disappearance of residual tensile stress and the change of surface microstructure.