Numerical Simulation Of Surface Alloying By High Current Pulsed Electron Beam

Surface modification techniques can induce changes in phase structure, morphology and composition on substrate surfaces, making them important routes towards improving materials surface performance against wear and corrosion. The recently developed pulsed electron beam surface alloying adopts pulsed energy deposition to modify materials surfaces in an efficient manner and without introducing much substrate piece deformation. The treatment, being carried out in vacuum, prepares quite clean surfaces and in any parts of the substrate workpiece. Through pre-deposition and post pulsed electron beam treatment, the alloyed substrate surface is flexibly modified, leading to much improved surface performance.Previously the electron beam surface alloying has been conducted on stainless steel 316L. Due to the transient nature of such surface modification technique, the working parameters cannot be easily determined by experiments. Therefore, the present attempts to obtain the optimum process parameters via numerical simulation of temperature field, with the objective to guide the practical surface alloying by the pulsed electron beam, specifically surface alloying of Ti on 316L substrate. Our main research has focused on the following three aspects:(1) On the basis of the three-dimensional temperature field model of the electron beam surface modification, a new temperature field theory model is established, considering the interface layer of electron beam surface alloying.(2) According to the coating thickness, the energy distribution function along the depth direction and the total pulse electron beam energy distribution are obtained.(3) Numerical simulation of temperature field on the electron beam surface alloying, processed on the 316L stainless steel considering the electron beam energy density, coating elements and coating thickness.The results showed that, under the energy density of 6 J/cm2, the single pulse electron beam can make 1.1 μm of the Ti coating and substrate surface 1 μm thin layer melt at the same time, and under the condition of 108～109 K/s rapid cooling rate, rapid solidification, finish the substrate surface alloying; Under this energy density, the single pulse electron beam can be realized, including 2μm of the Al coating and substrate surface including 0.5μm thin layer melt at the same time, and under the condition of 107～108 K/s rapid cooling rate, rapid solidification, finish the substrate surface alloying.The results showed that, under the energy density of 6 J/cm2, the single pulse electron beam can make 1.1 μm of the Ti coating and substrate surface 1μm thin layer melt at the same time, and under the condition of 108～109 K/s rapid cooling rate, rapid solidification, finish the substrate surface alloying; Under this energy density, the single pulse electron beam can be realized, including 2μm of the Al coating and substrate surface including 0.5μm thin layer melt at the same time, and under the condition of 107-108 K/s rapid cooling rate, rapid solidification, finish the substrate surface alloying.The results of this paper have guiding value for the optimization of pulsed electron beam surface modification process.