| In the last decade, high current pulsed electron beam (HCPEB) has been developed as a new technique used for surface modification of materials. In the present paper, the mechanism of Russian-made HCPEB system "Nadezhda-2" was systematically investigated. The energy density of the incident electron beam was correlated with working parameters obtained from experiments. By this way, the difference between duration of electron pulse and the given delay time was clarified, and relationship of the energy density of electron beam and the given delay time was established with respect to the measurement of tension and current waves. It was testified experimentally that there is an optimal matching for these two factor mentioned due to the behavior of anode plasma. In fact, it will take a specific time for anode plasma to fill the drifting space between the cathode and the substrate before it extinguishes. So, incorrect setting of this delay time influences the quality of electron beam significantly, which results in insufficient emissions or even no emission. The optimal delay time of 3.5 us was obtained for this system through technique experiments.Two typical Die steel D2 (Crl2MolVl) and HIS (4Cr5MoSiVl) were studied respectively in terms of surface quenching and surface alloying by HCPEB. The microstructure and mechanical properties of the modified surface layers were characterized by means of optical microscope, SEM, TEM, and micro-hardness testing, etc. It was found that the thickness of melted layers on the treated surface varied markedly with the energy density of the incident electron beam. With our treating parameters, the maximum thickness of melted Layer attained 10|am; moreover, a heat-affected layer of 15um could be formed for un-melted samples. The treated surface with dispersed micro-craters and craters morphology showed a fluctuant shape. For the die steel samples treated with the mode of surface quenching, large carbide particles were melted partially or completely depending on the selected energy of HCPEB, un-melted particles became finer and dispersed with sizes ranging in nanometer scales, the content of residual austenite augmented, compositional segregation decreased, and the structure of the surface layer became more homogenous. Super rapid cooling occurred in and around the heat-affected zone induced microcrystalline and amorphous non-equilibrium structures. A large number of vacancies, vacancy-pairs and dislocation clusters appeared in the modified layers.Micro-hardness was detected along the depth profile. Elevation of hardness in the range of several hundreds micrometers near the treated surface was found for all the samples. For the D2-2 sample treated with 20 pluses at 26.87 kV, the peak value of hardness increased 30%from 955.2 HK to 1250 HK. As to H13, treated with 20 pulsed of 25 kV, the hardness value increased about 17% from 592.1 HK to 691.3 HK. Moreover, with the surface alloying treatment by adding Cr and TiN, the hardness of the D2-Cr2 sample reached 1260 HK, and for D2-TiN4, 1210 HK. The distribution of hardness along the depth direction had a fluctuant shape and exceeded far beyond the heat-affected zone.The wear and corrosion resistance of treated samples increased obviously. The relative wear resistance properties of D2-1, D2-2 and D2-5 augmented 5.63, 7.36 and 7.9, respectively, and those of H13-4, H13-6 and H13-7 augmented by 2.09,11.76 and 9.87 times. The corrosion current of D2-1, D2-3 and D2-4 in a Cl-containing corrosive solution decreased 21%, 28% and 31% respectively.The diffusion effect induced by bombardment of HCPEB was carried out on an aluminum substrate pre-coated with carbon powders. According to simulation results, one electron pulse of 26.8 kV could induce a heating of 109 K/s in the surface layer, melting 1-2 us after the beginning of the bombardment, and a cooling of 108-109 K/s due to the rapid heat conduction. All these processes are finished in 6-7 us only. The solid-liquid interface moves rapidly towards the extreme surface with a speed of...
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