钌对一种单晶高温合金980℃和1160℃下TCP相析出影响的两面性

Dual Effects of Ruthenium on the TCP Precipitation of a Single Crystal Superalloy at 980℃ and 1160℃

摘要:

为研究Ru对高代单晶高温合金组织稳定性的影响,制备分别含有6wt.%Ru和4.5wt.%Ru的两种单晶高温合金D1和D2,完全热处理后置于980℃和1160℃下进行200h的长期时效,分析合金长期时效后的显微组织、不稳定相TCP成分及晶体结构。结果表明：980℃时效200h后,含Ru较多的D1合金中TCP析出量显著多于D2合金；1160℃时效200h后,D1合金中未观察到TCP相,而D2合金中观察到少量TCP相；两种合金析出的TCP相为同一种TCP相,Ru为其主要形成元素之一。结合d电子能级计算和热力学计算分析试验结果表明：Ru对单晶高温合金TCP析出的影响具有两面性,一方面Ru含量提高会使合金d电子能级增大,增加合金TCP析出倾向；另一方面Ru含量增加可降低高熔点元素在γ相中的偏析程度,进而减小因高熔点元素在γ相中过饱和而导致的TCP相析出量；在不同温度下,起主要作用的因素会有所不同。

Abstract:

In order to study the effect of Ru on the microstructure stability of high generation single-crystal superalloys, two single-crystal superalloys D1 and D2 containing 6wt.%Ru and 4.5wt.%Ru respectively were prepared. After complete heat treatment, they were long-term aged at 980℃ and 1160℃ for 200h. The alloy microstructure of different scales, compositions of topologically close-packed (TCP) phase and TCP crystal structures were detected. Results show that after long-term aging at 980℃ for 200h, the precipitation of TCP in D1 alloy containing more Ru is significantly higher than that in D2 alloy; after long-term aging at 1160 ℃ for 200h, no TCP phase is observed in D1 alloy, while a small amount of TCP phase is observed in D2 alloy; the TCP phases in both alloys are of the same type, and Ru is one of the main forming elements. The experimental results are analyzed combining with d-electrons concept and thermodynamic calculation. It is shown that the influence of Ru on the TCP precipitation of single crystal superalloys has two sides. On the one hand, adding Ru can increase the d-electron energy level of single crystal superalloys, which increase the TCP precipitation tendency. On the other hand, the increase of Ru content can reduce the segregation of refractory elements in γ phase, thus reducing the amount of TCP phase precipitation caused by the supersaturation of refractory elements. At different temperatures, the main influencing factors are different.