(1. 贵州工程应用技术学院 机械学院，毕节 551700；
2. 沈阳工业大学 材料科学与工程学院，沈阳 110870；
3. 中航工业北京航空材料研究院，材料检测与评价航空科技重点实验室，北京 100095)
摘 要: 通过不同工艺热处理、蠕变性能测试及组织形貌观察，研究了固溶温度对一种定向凝固镍基合金中碳化物形态演化与蠕变性能的影响。结果表明：铸态DZ125合金中存有粗大块状MC型碳化物，热处理期间合金中MC型碳化物可发生分解和形态演化，逐步转变成粒状M23C6型碳化物。随固溶温度提高、时间延长，碳化物发生分解及形态演化的几率增加，并使细小粒状M23C6型碳化物沿晶界不连续析出。与低温固溶处理合金相比，高温固溶处理合金在780 ℃具有良好的蠕变抗力。其中，以共格方式嵌镶在g 基体中的立方γ′相均匀分布在枝晶干和枝晶间区域，并有细小粒状碳化物沿晶界弥散析出，可抑制晶界滑移，是大幅度提高合金蠕变抗力的主要原因。在近780 ℃蠕变后期，与应力轴呈45°角的晶界承受较大的剪切应力。裂纹在沿与应力轴呈45°角的晶界处萌生与扩展，直至断裂是合金的蠕变断裂机制。
关键字: 镍基合金；固溶温度；碳化物；形态；蠕变；裂纹萌生与扩展
（1. School of Mechanical Engineering, Guizhou University of Engineering Science, Bijie 551700, China;
2. School of Materials Science and Engineering, Shenyang University of Technology, Shenyang 110178, China;
3. Aviation Key Laboratory of Science and Technology on Materials Testing and Evaluation, AVIC Beijing Institute of Aeronautical Materials, Beijing 100095, China）
Abstract:By means of heat treatment at different regimes, creep properties measurements and microstructure observations, an investigation has been made into the influence of solution temperature on the carbides configuration evolution and creep properties of a directionally solidified nickel-based superalloy. The results show that the thicker bulk-like MC-type carbide is distributed in the as-cast DZ125 superalloy. And the decomposition and configuration evolution of the MC-type carbide occur gradually, during heat treatment, to transform into the particle-like M23C6-type carbides. As the solution temperature enhances and time prolongs, the probability of the MC-type carbide occurring decomposition and morphology evolution increase, which may promote significant amount of particle-like M23C6-type carbide precipitating along the grain boundary of alloy. Compared with the alloy solution treated by lower temperature, the alloy solution treated at higher temperature displays a better creep resistance at a temperature near 780 ℃. Wherein, the fine γ′ precipitates embedded coherent in the matrix phase are homogeneously distributed in the dendrite/ inter-dendrite regions, and some M23C6-type carbide particles along the grain boundaries may restrain the slipping of boundary, which is thought to be the main reasons of alloy having better creep resistance. At the latter stage of creep at a temperature near 780 ℃, the bigger shearing stress applying in the boundaries at about 45° angles relative to the stress axis results in the initiation and propagation of the micro-cracks along the ones up to fracture, which is thought to be fracture mechanism of the alloy during creep.
Key words: directional solidification nickel-based alloy; solution temperature; microstructure; carbide; creep; initiation and propagation of crack
