Computer Simulation of Sintering in Porous Structures of Thermal Barrier Coating

Monte Carlo simulation was performed to investigate the effect of sintering on the changes in microstructure, porosity, and pore distribution of thermal barrier coating layers synthesized by electron beam physical vapor deposition. First, the simulation well expressed the characteristic porous structures such as columnar and feather-like structures, which were fabricated under the condition of substrate rotation. Secondly, the sintering of such a porous structure by high-temperature annealing could be demonstrated using the simulation. The microstructure of the layer close to the substrate surface shows fine grains and pores, suggesting ease of sintering and grain growth, which is clearly demonstrated from the experimental results of the yttria-stabilized zirconia layer deposited by electron beam physical vapor deposition. The simulation also reveals the sintering behavior of the porous including heterogeneous structure and pore distribution. By introducing a small sintering step to the deposition process during the simulation, the experimental values of the porosity observed in the layers could be successfully explained. The doubled effects of sintering on porosity during both deposition and exposure to high temperature environment enhanced the heterogeneity of the microstructures of the layers.