一种航空发动机密封用镍基合金组织稳定性的实验研究及理论计算

采用显微组织观察和图像分析等方法,结合动力学理论计算,研究了一种航空发动机密封用16Cr-4.5Al镍基高温合金在700℃、750℃下长期时效的组织演化规律。结果表明,试验温度下合金的晶界碳化物具有较好的稳定性,利用DICTRA扩散动力学软件可以较准确地模拟计算出碳化物在不同温度长期时效中的尺寸变化规律。计算结果发现合金晶粒尺寸越大,碳含量越高,晶界碳化物长大越快。合金基体中弥散分布的γ′相在长期时效过程中按Ostwald熟化理论长大速度发生粗化,并会造成硬度明显下降。

Experimental Study and Theoretical Calculation on Structure Stability of a Nickel-based Superalloy for Seals in Aero-engine

Microstructure evolution behavior for 16Cr-4.5Al, a nickel based alloy used for seals, is studied by scanning electron microscope (SEM) observation and image analysis after exposure at 700 ℃ for 24 h, 96 h, 312 h, 960 h, 1 512 h, 2 904 h and at 750 ℃ for 16 h, 96 h, 196 h, 288 h, 528 h respectively. In addition,the size growth of carbide and γ′ phase is also calculated based on the diffusion dynamics theory.Experimental and computational results both show that,the size stability of M23C6 carbide at grain boundary is generally accepted for the investigated alloy at the tested temperatures.Using diffusion modeling software DICTRA and its mobility database,the size changes of M23C6 carbide at different temperatures could be calculated,which have a good approximation with experimental results. The calculated results also show that carbide grows faster with larger grain size or higher C content of alloy.However, the coarsening of γ′ phase is significant, which conforms to the Ostwald ripe formula, and the macro hardness decrease is obvious during its long term exposure at 700 ℃.