Three Dimension Numerical Simulation Of Materials Modification By High Current Pulsed Electron Beam

Based on the modification materials: 316 L stainless steel, Thermal Barrier Coatings (TBCs), and Fe based - Al coating, this dissertation focus on the thermal effect of the surface modification by High Current Pulsed Electron Beam (HCPEB).The axial symmetric three-dimensional temperature field model is put forward. In the direction of HCPEB, some relative results are obtained: The melt layer (1～2μm), it's quite accordant to the experiment's observation; The temperature gradient is about 10~8 K/m in the heat affected zone, makes the surface of the modification material so strictly plastic deforming, even some microcracks are found; The heating / cooling rate is about 10~8～10~9K/s, is so rapid that grain refinement phenomenon is found near the surface of the modification material. In radial direction, the surface modification is not uniform because ofthe Gauss distribution of the sectional electron energy.The shock thermal stress is generated while the cater being formed. The energy deposition has the maximum value at the sub-layer, so the metastable second phase (or the grain boundary near the second phase) will melt firstly. The gradual expanding drop extrudes the bottom of the cater; the bottom of the cater gets a transient jet power in the depth direction, as the melting drop is expulsed from the sub-layer, so the transient shock stress is generated. The thermal shock stress is the main reason of the deep modification.