Microstructural characterization of the M23C6 carbide in a long-term aged Ni-based superalloy
Microstructural characterization of the M23C6 carbide in a long-term aged Ni-based superalloy
复制标题
DOI：
10.1080/09500839.2016.1273554
复制
发表时间：
2017-01
影响因子：
1.2
通讯作者：
Xiaobing Hu;X. Qin;J. Hou;Luchun Zhou;Xinghua Ma
中科院分区：
文献类型：
--
作者：
Xiaobing Hu;X. Qin;J. Hou;Luchun Zhou;Xinghua Ma
摘要利用透射电子显微镜（TEM）对一种长期时效的耐热耐蚀镍基高温合金中M23 C6碳化物的显微组织特征进行了详细的研究。结果表明，TEM衬度始终存在于合金晶粒内部，与晶粒内部的结构和化学不均匀性有关。这些不均匀区域的结构与γ′相和t-M23 C6相的结构相同，其中t-M23 C6表示过渡相和亚稳相。虽然具有与M23 C6相相同的结构，但t-M23 C6的化学组成不同于M23 C6相。与M23 C6相比，t-M23 C6富含Ni、Co、Al和Ti，但贫W、Mo和Cr。这种结构和化学不均匀性的现象表明，在标准热处理样品中沉淀的原始M23 C6碳化物（p-M23 C6）是不稳定的。因此，在长期时效处理后，Ni、Co、Al和Ti可局部富集在p-M23 C6相中，最终形成γ′相，其可通过分解反应p-M23 C6 → M23 C6 + γ′来描述。
Abstract The microstructural features of M23C6 carbide in a long-term aged heat- and corrosion-resistant Ni-based superalloy have been investigated in detail using various kinds of transmission electron microscope (TEM) techniques. It is found that TEM contrast, which is related to structural and chemical inhomogeneities inside the grains, always exists in the interior of grains in the alloy. The structure of these inhomogeneous regions has been determined to be the same as that of the γ′ and t-M23C6 phases, where t-M23C6 indicates a transitional and metastable phase. Although possessing the same structure as the M23C6 phase, the chemical composition of the t-M23C6 is different from that of the M23C6 phase. Compared with M23C6, t-M23C6 is richer in Ni, Co, Al and Ti but poorer in W, Mo and Cr. This phenomenon of structural and chemical inhomogeneity demonstrates that pristine M23C6 carbide (p-M23C6) precipitated in standard heat-treated samples is unstable. Therefore, upon long-term ageing treatment, Ni, Co, Al and Ti may locally enrich inside the p-M23C6 phase, finally forming the γ′ phase, which can be described by the decomposition reaction p-M23C6 → M23C6 + γ′.