| The surface amorphization of Ni-based materials induced by High-current pulsed electron beam?HCPEB?irradiation technology has been investigated in this paper.The sample surface of microstructure was characterized by using optical microscope?OM?,X-ray diffraction?XRD?,transmission electron microscope?TEM?,field emission scanning electron microscope?SEM?and 3D laser scanning microscope?3D LSM?.At the same time,an automatic Vickers microhardness tester,pin-disc friction and wear tester and electrochemical workstation were used to carefully analysis of the changed on surface mrcro-hardness,wear resistance and corrosion resistance of the samples before and after irradiation,the internal relationship between the evolution mechanism of microstructure and the law of performance change was established.After the Ni-Nb powder metallurgy samples were treated by HCPEB,the surface melted to form a remelted layer.SEM results show that the surface after irradiation forms crater morphology,and the crater density decreases with the increase of irradiation times,while more corrugated folds remain.In addition,it is also found that a large number of coarse microcracks are generated on the surface of the sample.What's more,the density decreases with the increase of the number of times,but the crack width slightly increases.After 30 times of irradiation treatment,the thickness of remelting layer reaches about 5?m.XRD and TEM results show that the remelted layer is mainly composed of amorphous phase,?-Ni nanocrystals and second phase particles.The results of performance test show that the microhardness of the sample surface after HCPEB irradiation treatment is significantly improved,reaching 12.1 GPa,which is mainly due to the combined effects of amorphous,nanocrystalline,second phase and solid solution strengthening.However,the corrosion resistance of the irradiated samples has not been significantly improved,mainly due to the generation of surface microcracks,which destroy the integrity of the sample surface,provide corrosion channels for Cl-and accelerate the corrosion rate.After the Ni-Nb coating samples were treated by HCPEB,the surface melted to form a remelted layer,and the thickness increased with the increase of irradiation times.After irradiation treatment,shrinkage cavity occurs on the surface in addition to the morphology of melting pits,and the surface microcracks almost disappear completely.XRD and TEM analysis show that the structure of the remelted layer is mainly composed of amorphous+nanocrystals??-Ni?Nb?,Ni3Nb,etc.?,and the nanocrystals are dispersed in the amorphous matrix.The performance test results show that the surface microhardness and wear resistance of the irradiated samples are obviously improved.It is mainly due to the formation of amorphous and nanocrystalline structure on the surface layer of the irradiated sample,which can effectively improve the hardness and mechanical properties of the sample surface.At the same time,a large number of dispersed nanoparticles??-Ni?Nb?,Ni3Nb,etc.?can be used as hard phase strengthening coatings to reduce wear during friction and wear.In addition,the improvement of the surface hardness of the sample weakens the ploughing effect of the grinding ball on the coating material,thus promoting the improvement of the wear resistance of the coating sample.The corrosion resistance of the coating sample after HCPEB irradiation treatment is also obviously improved.The improvement of corrosion resistance is mainly due to the spontaneous passivation of amorphous phase in the remelting layer to form a stable passivating film.Secondly,the formation of Nb-rich film Nb2O5 can increase the continuous compactness of NiO film and reduce the dissolution rate of passivating film. |
PDF Full Text Request