| Thermal Barrier Coatings (TBCs) are used as thermal insulation and thermal protection for high-temperature components of aircraft engines and gas turbines due to theirs low thermal conductivity, antioxidation, anticorrosion and wear resistant properties, which enhance efficiency and prolong service lifetime. A typical TBC consist of an ZrO2 ceramic top-coat, NiCoCrAlY bond coat, a thermally grown oxide layer and the superalloy substrate. At present premature spallation-failure of TBCs during service has been the focus of attention. With respect to ceramic coats fabricated by electron beam physical vapor deposition (EB-PVD), numerous studies demonstrated that main factors of premature spallation-failure are (1) gaps between columnar grains provide channels for diffusion of molecular oxygen from the engine environment in combination with the high ionic diffusivity of oxygen in YSZ top-coat; (2) the thermal-expansion mismatch stresses; (3) the oxidation of the metal. Therefore, insulation of ingress of molecular oxygen by surface sealing is an effective measure to improve performance of TBCs. In fact, high-current pulsed electron beam (HCPEB) is an effective surface modification technique. The treated surface of ceramic coatings by HCPEB becomes dense and smooth to initially rough and porous, which insulate effectively ingress of molecular oxygen from the environment and reduce thermal conductivity, improving the performance of TBCs. However, interaction between HCPEB and ceramic materials is quite complicated transient process which involves coupling with both temperature and stress fields. A theoretical research is quite essential to understand physical mechanism of electronic beam and material interactions.In this paper, we have simulated numerically of temperature and stress fields for ceramic coatings sealed by high-current pulsed electron beam. The calculated results demonstrated that the relationship between sealing depths and inputting parameters of energy density and pulse time, obtaining ideal experimental parameter and providing theoretical basis for experiments. Main studies are temperature field simulations based on our established temperature field model using our developed procedure, while stress fields simulations using finite element ANSYS code. The significant results are summarized as following:1. To check reliability and rationality of the temperature field model. Our simulated melting thickness and shapes have in good agreement with experimental observations. For energy density 15 J/cm2 and pulse duration of 120μs, the present simulated melting depth is-4.4μm, in well agreement with the experimental value 4-5μm.2. Under different energy densities or pulse times for HCPEB, the melting depth and temperature distribution of ceramic layer are determined and discussed. The simulated results revealed that the melting layers reach a few micrometers in depth, In order to predict evaporation effect on surface and explore the ideal control parameters, we calculated the effects of energy densities on surface sealing under different pulse times. The simulations shown that:for pulse 80μs, the ideal energy densities are 10-12 J/cm2, sealed thickness is about 3-4μm; while for pulse 200μs, the ideal energy densities are 5-13J/cm2, sealed thickness is 2-6μm. In addition, under same energy density of 12 J/cm2, the melting depth increases with increasing pulse time, while the ablation depths change very small, indicating that relative long pulse time is optimal option for more depth modification on material surface. These results can provide theoretical basis for optimizing of the technological parameters on experiments.3. Simulation of stress distribution by finite element methods. We considered two typical cases of no occurring evaporation and occurring evaporation on ceramic surface, for former maximum temperature exist on surface and maximum thermal stress is 977 MPa; the latter we found that maximum thermal stress is 1540 MPa.
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