σ and η Phase formation in advanced polycrystalline Ni-base superalloys
σ and η Phase formation in advanced polycrystalline Ni-base superalloys
复制标题
DOI：
10.1016/j.msea.2017.01.064
复制
发表时间：
2017-02-27
期刊：
影响因子：
6.4
通讯作者：
Tin, Sammy
中科院分区：
文献类型：
--
作者：
Antonov, Stoichko;Huo, Jiajie;Tin, Sammy
在多晶镍基高温合金中，第二相的晶界析出可能是显着的，由于它们对机械性能的影响。随着多晶镍基高温合金的新合金化概念的发展，以扩大其温度能力，长期相稳定性和拓扑紧密堆积（TCP）相的形成，需要研究的Nb合金添加量的增加水平的影响。Nb水平升高可导致基体过饱和度增加并促进第二相的沉淀。对两种含有不同Nb含量的实验性粉末处理的Ni基高温合金进行了长期热暴露，以评估TCP相的稳定性和沉淀。发现添加Nb促进了η-Ni 6AlNb沿着粉末处理的多晶Ni基超合金中的晶界沉淀，而减少的Nb水平有利于块状富Cr和Mo的σ相沉淀物沿沿着沉淀。使用Thermo-Calc对这两种合金中这两个相的热力学稳定性进行评估表明，虽然a相预测相当准确，但eta相的预测是有限的。
In polycrystalline Ni-base superalloys, grain boundary precipitation of secondary phases can be significant due to the effects they pose on the mechanical properties. As new alloying concepts for polycrystalline Ni-base superalloys are being developed to extend their temperature capability, the effect of increasing levels of Nb alloying additions on long term phase stability and the formation of topologically close packed (TCP) phases needs to be studied. Elevated levels of Nb can result in increased matrix supersaturation and promote the precipitation of secondary phases. Long term thermal exposures on two experimental powder processed Ni-base superalloys containing various levels of Nb were completed to assess the stability and precipitation of TCP phases. It was found that additions of Nb promoted the precipitation of eta-Ni6AlNb along the grain boundaries in powder processed, polycrystalline Ni-base superalloys, while reduced Nb levels favored the precipitation of blocky Cr and Mo - rich sigma phase precipitates along the grain boundary. Evaluation of the thermodynamic stability of these two phases in both alloys using Thermo-calc showed that while a phase predictions are fairly accurate, predictions of the eta phase are limited.