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对比研究了不含Ru的USTB-F7及添加2.5wt%Ru的USTB-F8两种镍基单晶高温合金的组织稳定性和持久性能。标准热处理与1100℃长期热暴露组织研究表明: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;热暴露2000h后,其形貌仍保持稳定,仅发生粗化而未发生筏排化。Ru的添加使Re元素在γ/γ′中的分配比增大,提高了合金USTB-F8的γ/γ′点阵错配度和γ′相的立方度,从而加速了长期热暴露过程中的筏排化进程,经2000h热暴露发生了明显的筏排化现象。同时,合金USTB-F7热暴露700h后在枝晶干处析出了富集Re、W和Cr元素的TCP相,Ru的加入有效地抑制了TCP相的析出,合金USTB-F8直至2000h仍未析出TCP相。1100℃/140MPa持久性能测试表明,Ru显著提高合金的持久寿命,这与Ru增加合金中的γ′相体积分数和γ/γ′点阵错配度,促进筏排组织的形成,并减小时效组织中的γ通道宽度有关。
The microstructures and ductility of two nickel-based single crystal superalloys, Ru-free USTB-F7 and USTB-F8 with 2.5 wt% Ru, were compared. The results of standard heat treatment and long-term heat exposure at 1100 ℃ showed that the morphology of γ ’phase in alloy USTB-F7 was spherical and cubic, and the morphology was intermediate. After 2000h exposure, the morphology remained stable, only Coarsening occurred without rafting. The addition of Ru increased the distribution ratio of Re element in γ / γ ’, increased the γ / γ’ lattice mismatch degree and the cubic degree of γ ’phase of alloy USTB-F8, and accelerated the long-term heat exposure Of the process of rafting, thermal exposure after 2000h obvious phenomenon of raft. At the same time, the TCP phase enriched in Re, W and Cr elements was precipitated in the dendrites dry after heat exposure of the alloy USTB-F7 for 700h. The addition of Ru effectively restrained the precipitation of the TCP phase. The alloy USTB-F8 did not precipitate until 2000h TCP phase. The long-term performance tests at 1100 ℃ / 140MPa showed that Ru significantly increased the long-term life of the alloy, which was associated with the increase of the γ ’phase volume fraction and γ / γ’ lattice mismatch in the Ru alloy and promoted the formation of raft structure and decreased Aging channel in the γ-channel width.