辐射涂层对空心涡轮叶片定向凝固组织的影响

为了得到组织细密的定向晶叶片，采用数值模拟和实验相结合的方法，对比研究了铸型表面涂挂具有较高辐射性能的石墨涂层和氧化铬涂层对空心涡轮叶片定向凝固组织的影响。理论分析表明，铸型表面辐射系数提高能够在一定程度上提高铸件顶端的温度梯度。实验结果表明，通过在铸型表面涂挂氧化铬涂层材料，显著提高了铸型表面辐射散热性能，降低了铸件顶端的一次枝晶间距。铸件顶端的一次枝晶平均间距为336 μm，较未涂挂任何涂层减小12.5%，较涂挂石墨涂层减小2.9%，定向晶组织得到显著细化。采用铸型外表面涂挂氧化铬辐射涂层的方法成形的复杂结构空心涡轮叶片定向晶组织形态良好。

Effects of radiation coatings on directional solidification microstructure of hollow turbine blades

To obtain a turbine blade with refined directional crystals, the effects of the graphite coating and the chromium oxide coating on the directional solidification microstructure are studied by numerical simulations and experiments. Numerical simulation results show that the temperature gradient at the top castings is improved by increasing the emissivity of the mold surface. The experimental results show that after the mold surface is coated with the chromium oxide, the heat dissipation performance of the mold surface is remarkably improved, and the primary dendrite spacing at the top of the casting is reduced. The average primary dendrite spacing at the top of the casting is 336 μm, 12.5% less than the one without coating and 2.9% lower than the one coated with graphite, and the directional solidification microstructure is significantly refined. A turbine blade with refined directional crystal is formed by using the integral ceramic mold with the chromium oxide coating.