基于格子波尔兹曼法的热障陶瓷涂层凝固生长过程模拟

Simulation of Thermal Barrier Ceramic Coating Solidification Growth Process Based on Lattice Boltzmann Method

热障涂层(TBCs)在使用过程中表面陶瓷层的脱落是影响其使用寿命的关键,针对以上问题,建立了凝固生长过程流动及传热传质模型,用格子波尔兹曼法(LBM)研究了涂层凝固生长过程。结果显示:不考虑对流影响时,晶体生长的形貌呈现对称十字枝晶形状;在考虑对流的情况下,迎流部分生长快,背流部分生长受到抑制。在大的过冷度影响下,晶界出现波动,出现二次枝晶生长。等离子喷涂涂层在温度梯度下朝向正温度梯度方向呈柱状晶生长。枝晶生长受到对流的影响和侧向温度梯度的影响。迎流方向和大温度梯度方向枝晶形貌发达,背流方向和小温度梯度处枝晶生长受到抑制。

In order to simulate the formation process of coating microstructure accurately, the growth of solidification process and the heat and mass transfer model have been established. The coating solidification growth process is analyzed by means of Lattice Bohzmann Method. The results show that the convection makes an impact on the crystal mor- phology in the process of crystal growth. Specifically, the morphology of crystal growth is symmetric cross dendrite shape if considering no convection. The crystal growth at the incident flow part is accelerated while the growth at the dorsal stream part is restrained if the convection is considered. A variation occurs on the grain boundary, meanwhile, a secondary dendrite growth occurs under large undercooling condition. A plasma spraying coating grows in a shape of columnar crystal under the temperature gradient. The columnar crystal growth direction goes toward the positive temperature gradient direction. The dendrite growth is influenced by convection and the lateral temperature gradient. The dendrite morphology develops quickly at direction of incident flow and large temperature gradient while restrained at direction of dorsal stream and small temperature gradient. The results of numerical calculation are consistent with the parameters of the columnar crystal structure of supersonic plasma spraying coating observed by scanning electron microscope.