Rejuvenation Heat Treatment of the Second-Generation Single-Crystal Superalloy DD6
Rejuvenation Heat Treatment of the Second-Generation Single-Crystal Superalloy DD6
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DOI：
10.1007/s40195-015-0323-8
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发表时间：
2015-10
期刊：
影响因子：
--
通讯作者：
Z. Shi;Shi-zhong Liu;Jia-rong Li
中科院分区：
文献类型：
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作者：
Z. Shi;Shi-zhong Liu;Jia-rong Li
在定向凝固炉中，采用螺杆选择法制备了具有[001]取向的第二代单晶高温合金DD6。合金在1100 ° C、400 h条件下进行了完全热处理后的长期时效。然后进行1300 ° C/4h/AC +1120 ° C/4h/AC +870 ° C/24h/AC的复原热处理。在760 ° C/800 MPa、850 ° C/550 MPa、980 ° C/250 MPa和1100 ° C/140 MPa下研究了不同热处理后的应力持久性能。利用扫描电镜研究了不同条件下合金的显微组织。结果表明，合金经1100 ° C × 400 h长期时效后，γ ′相变得非常不规则且尺寸较大。在枝晶核心处有少量针状TCP相析出。经再生热处理后，粗化的γ ′相和TCP相完全溶解。显微组织得到了恢复，与原始组织基本一致。合金经长期时效后，在各种试验条件下的持久寿命均有不同程度的下降。在不同条件下，经复壮热处理后的合金持久寿命均恢复到原始试样的80%以上。合金在长期时效过程中的组织退化包括γ ′相的粗化、P型筏状组织和TCP相的析出，导致持久性能的退化。回复热处理成功地恢复了合金的原始组织和持久性能。
The second-generation single-crystal superalloy DD6 with [001] orientation was prepared by screw selecting method in the directionally solidified furnace. The long-term aging of the alloy after full heat treatment was performed at 1100 °C for 400 h. Then the rejuvenation heat treatment 1300 °C/4 h/AC + 1120 °C/4 h/AC + 870 °C/24 h/AC was carried out. The stress rupture properties were investigated at 760 °C/800 MPa, 850 °C/550 MPa, 980 °C/250 MPa and 1100 °C/140 MPa after different heat treatments. The microstructures of the alloy at different conditions were studied by SEM. The results show thatγ′ phase of the alloy became very irregular and larger after long-term aging at 1100 °C for 400 h. A very small amount of needle-shaped TCP phase precipitated in the dendrite core. The coarsenedγ′ phase and TCP phase dissolved entirely after rejuvenation heat treatment. The microstructure was restored and almost same with the original microstructure. The stress rupture life of the alloy decreased in different degrees at various test conditions after long-term aging. The stress rupture life of the alloy after rejuvenation heat treatment all restores to the original specimen more than 80% at different conditions. The microstructure degradation of the alloy during long-term aging includes coarsening of theγ′ phase, P-type raft and precipitation of TCP phase, which results in the degeneration of stress rupture property. The rejuvenation heat treatment succeeds in restoring the original microstructure and stress rupture properties of the alloy.