| Nickel and nickel alloys have good physical and chemical properties,which are widely used in energy development,chemical industry,electronics,automotive,aerospace and other fields.However,with the rapid development of the aviation industry,the anti fatigue,high temperature oxidation resistance and corrosion resistance of Ni-Based superalloys are facing great challenges.Compared with the traditional surface modification technique,pulsed electron beam with high energy utilization,heating and cooling speed,accurate positioning,easy parameter adjustment etc.,the modified material performance can be improved significantly.In this paper,pure nickel and a Ni-Based superalloy(CH3625)were modified by using High Current Pulsed Electron Beam(HCPEB).The changes in microstructure and morphology of the samples before and after the HCPEB treatment was investigated by scanning electron microscope(SEM),optical microscope(OM)and the X-ray diffraction(XRD).The changes in microhardness on the surface and cross section after HCPEB treatment and corrosion resistance of the surface before and after irradiation in 3.5wt%NaCl water solution were carefully measured.Experimental study shows that:(1)The results of XRD shows that the diffraction peaks of samples after HCPEB treatment have shifted,and half width of diffraction peaks high were also changed,indicating the existence of residual stress in the specimen after modification.Through the analysis and calculation of the pure nickel(111)plane and the Ni-Based superalloy(200)plane,the residual stress in the surface becomes larger and the grain size becomes smaller with the increase of the n?mber of pulses.Plastic deformation occurs in the grain,which leads to the formation of dislocation slip bands on the surface of the treated material.(2)Through the observations of SEM and OM,it can be seen in the samples after HCPEB treatment that surface states were changed with different pulse n?mbers.With the increase of the n?mber of pulses,the crater density of the pure nickel decreased and the crater size decreased,while crater density on the nickel base superalloy increased with the increasing n?mber of pulses.It is also found that after repeated pulse treatment the surface roughness reduces,and the composition is becoming more uniform with the smoother surface.Two kinds of materials in pulsed electron beam treatment surface appeared remelting layer with different thickness,and the thickness of the heat affected zone were changed.(3)Based on the test specimen microhardness after modification,the surface hardness increased,the pure N6 sample 5 and 15 pulses treatment under 50 g load respectively.The surface microhardness of original samples increased by 14.8% and 22.5%;Ni-Based superalloy CH3625 sample were 5 and 10 pulses processing in the 50 g load than the original sample increased by about 5%,while the 15 pulse sample is increased by about 15% than the original sample.Show the cross section microhardness specimen of pure nickel N6 specimen microhardness varies with the depth of hardness fluctuation;microhardness of Nickel-based superalloy CH3625 specimen is with the hardness increase the depth values showing a downward trend.(4)The electrochemical test results show that the corrosion resistance of the sample in 3.5wt% NaCl water solution is different from that of the modified before and after modification.The phase angle and polarization resistance of 15-pulsed N6 specimen are maxim?m,the radius of capacitive reactance are also maxim?m,corrosion potential to the right,the corrosion current is relatively small,so the corrosion resistance is the best.After 10 pulses of HCPEB treatment,the Ni-Based superalloy CH3625 has the best corrosion resistance. |
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