(1. 北京科技大學(xué) 新金屬材料國(guó)家重點(diǎn)實(shí)驗(yàn)室，北京 100083；
2. 北京科技大學(xué) 國(guó)家材料服役安全科學(xué)中心，北京 100083；
3. 北京航空材料研究院 先進(jìn)高溫結(jié)構(gòu)材料國(guó)防科技重點(diǎn)實(shí)驗(yàn)室，北京 100095)
摘 要: 通過在不含Mo的基礎(chǔ)合金USTB-F7中添加1.5%(質(zhì)量分?jǐn)?shù))Mo，形成合金USTB-F9，研究Mo對(duì)鎳基單晶高溫合金組織穩(wěn)定性和持久壽命的影響。1 100 ℃時(shí)效與熱處理組織的研究分析表明：合金USTB-F7中γ′相形貌介于球形和立方形之間，屬中間態(tài)形貌；經(jīng)長(zhǎng)期熱處理2 000 h后，其形貌保持穩(wěn)定，僅發(fā)生粗化而未產(chǎn)生筏排現(xiàn)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′點(diǎn)陣錯(cuò)配度和γ′相的立方度，從而加速長(zhǎng)期熱處理過程中的筏排化進(jìn)程，僅200 h就發(fā)生明顯的筏排現(xiàn)象。同時(shí)，Mo強(qiáng)烈促進(jìn)富含Re、Mo、W和Cr等元素的P相和σ相的析出，使析出時(shí)間由合金USTB-F7的700 h提前到合金USTB-F9的 100 h。在1 100 ℃和140 MPa下的持久性能測(cè)試表明，盡管Mo的添加提高了γ′相的體積分?jǐn)?shù)和錯(cuò)配度，并促進(jìn)筏排組織的形成，有利于合金持久性能的提高；但由于Mo促進(jìn)TCP相的大量析出，從而使合金的持久壽命降低。
關(guān)鍵字: 高溫合金；Mo；錯(cuò)配度；組織穩(wěn)定性；持久壽命
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
