(1. 北京科技大学 新金属材料国家重点实验室，北京 100083；
2. 北京科技大学 国家材料服役安全科学中心，北京 100083；
3. 北京航空材料研究院 先进高温结构材料国防科技重点实验室，北京 100095)
摘 要: 通过在不含Mo的基础合金USTB-F7中添加1.5%(质量分数)Mo，形成合金USTB-F9，研究Mo对镍基单晶高温合金组织稳定性和持久寿命的影响。1 100 ℃时效与热处理组织的研究分析表明：合金USTB-F7中γ′相形貌介于球形和立方形之间，属中间态形貌；经长期热处理2 000 h后，其形貌保持稳定，仅发生粗化而未产生筏排现象。Mo的添加使γ相中Re、Mo和Cr等元素含量增加，提高了合金USTB-F9的γ/γ′点阵错配度和γ′相的立方度，从而加速长期热处理过程中的筏排化进程，仅200 h就发生明显的筏排现象。同时，Mo强烈促进富含Re、Mo、W和Cr等元素的P相和σ相的析出，使析出时间由合金USTB-F7的700 h提前到合金USTB-F9的 100 h。在1 100 ℃和140 MPa下的持久性能测试表明，尽管Mo的添加提高了γ′相的体积分数和错配度，并促进筏排组织的形成，有利于合金持久性能的提高；但由于Mo促进TCP相的大量析出，从而使合金的持久寿命降低。
关键字: 高温合金；Mo；错配度；组织稳定性；持久寿命
Ni-based single crystal superalloys
（1. State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing,
Beijing 100083, China;
2. National Center for Materials Service Safety, University of Science and Technology Beijing, Beijing 100083, China;
3. National Key Laboratory of Science and Technology on Advanced High Temperature Structural Materials,
Beijing Institute of Aeronautical Materials, Beijing 100095, China）
Abstract:The effects of Mo on the microstructural stability and stress-rupture property were investigated in two experimental Ni-based single crystal superalloys when adding 1.5% Mo (mass fraction) into the Mo-free baseline alloy. The heat treatment results indicate that the intermediate γ′ precipitates in the dendrite core of the Mo-free alloy do not change in morphology and only become coarsening after (1 100 ℃, 2 000 h) heat treatment. Mo addition increases the content of Re, Mo and Cr in the γ phase. As a result, the lattice misfit is enlarged and γ′ precipitates become more cuboidal, the time of forming the rafting structure is significantly enhanced and occurs at about 200 h. Meanwhile, the TCP phases precipitate after 700 h in the Mo-free alloy while TCP phases are observed only after 100 h in the Mo-containing alloy. Mo addition promotes the formation of TCP phases significantly, which are identified as the σ and P phases and enriched in Re, W, Cr and Mo. The investigation of stress-rupture properties at 1 100 ℃ and 140 MPa indicates that Mo addition shortens the stress-rupture life of the baseline alloy due to the precipitation of large amount of TCP phases, although Mo addition increases the volume fraction of the γ′ phase and enlarges the lattice misfit with a good rafting microstructure.
Key words: superalloys; Mo; lattice misfit; microstructural stability; stress-rupture life
