高温合金涡轮叶片定向凝固过程数值模拟研究进展

Development of Numerical Simulation in Nickel-Based Superalloy Turbine Blade Directional Solidification

高温合金涡轮叶片被广泛应用于航空发动机与燃气轮机,数值模拟技术能优化和改进涡轮叶片定向凝固工艺,提高成品率。本文总结了国内外高温合金涡轮叶片定向凝固过程宏、微观数值模拟模型,介绍了其发展趋势。对高速凝固(HRS)和液态金属冷却(LMC)2种工艺下高温合金叶片宏观温度场、介观晶粒组织与微观枝晶组织做了模拟仿真,对比分析了2种定向凝固工艺下的传热过程和微观组织演化规律。介绍了变抽拉速率工艺在高温合金定向凝固中的应用,以实际叶片作为算例,对比了常抽拉速率与优化的变抽拉速率对涡轮叶片温度场、晶粒组织的影响。结果表明,优化的变抽拉速率工艺能够改变上凸或者下凹的糊状区形状,得到平直的糊状区与平行的晶粒组织,有利于提升叶片高温力学性能。

Ni-based superalloy turbine blades have been widely used in aerospace and industrial engine. Numerical simulation techniques can optimize the superalloy directional solidification process and enhance the rate of finished products. This paper summarized the existing macroscopic and microscopic numerical models in the superalloy blade directional solidification process. Simulations have been done on the temperature field evolution, grain structure and dendrite morphology in typical HRS and LMC directional solidification conditions, and the resulting microstructure features were investigated. In particular, the application of varying withdrawal rate in directional solidification of the superalloy blade was introduced. And the advantages of the varying withdrawal rate technique were emphasized by comparing it with the constant withdrawal rate method. The simulation results indicate that by applying varying with-drawal rate, the convex or concave shape of the mushy zone can be change to flat shape, so that parallel columnar grains can be obtained with enhanced high-temperature performance of the turbine blade.