Ni-Cr-W基高温合金二次M23C6析出行为

采用差示扫描量热法(DSC)、扫描电镜(SEM)和透射电镜(TEM)系统研究了Ni-Cr-W基高温合金二次M23C6的析出行为。结果表明,合金中二次M23C6的析出温度范围为648～1147℃,当温度高于1160℃时M23C6发生固溶;初生M6C在1349℃发生分解;合金在1400℃时完全熔化。由于时效温度不同,合金中析出两种不同形貌的M23C6。在较低温度时(655～900℃)粗大片层状M23C6在晶界析出;在900℃以上M23C6的形貌由片层状转变为不连续颗粒状。降温速率对M23C6的析出形貌产生一定影响;同时,降温过程中晶界上不连续颗粒状M23C6的析出是导致弯曲晶界形成的主要原因。

Secondary M23C6 Precipitation Behavior in Ni-Cr-W Based Superalloy

The precipitation behavior of the secondary M23C6 carbide in Ni-Cr-W based superalloy was studied by DSC, SEM and TEM systematically. The results show that secondary M23C6 carbide precipitates from 648 to 1147 °C and it dissolves into the matrix when the temperature is above 1160 °C. The primary M6C carbide decomposes at 1349 °C and the alloy melts completely at 1400 °C. There are two morphologies of M23C6 precipitate at the grain boundaries. Coarse lamella M23C6 precipitates from 655 to 900 °C and it changes to discrete particles above 900 °C. The cooling rate has an important effect on M23C6 precipitation behavior. In addition, during the cooling process, the serrated grain boundaries are formed because of the discrete M23C6 carbide particles which precipitate at grain boundaries.