Microstructure stability of GH4169 and GH4169C alloys with high content of phosphorus and niobium

To study the microstructural stability of GH4169C alloy with high content of phosphorus and niobium, the microstruc-ture and hardness of GH4169C alloy and GH4169 alloy after long time aging were comparatively analyzed in this paper. These two su-peralloys were subjected to aging treatment at 600, 650, 704 and 720℃ for different times from 30 h to 10000 h. The microstructural evolution of the alloys was characterized by using a field emission scanning electron microscope and a Brinell hardness tester. The re-sults indicate that, at the service temperature of 650℃, GH4169 alloy and GH4169C alloy show excellent structure stability. Howev-er, above the service temperature, GH4169 alloy and GH4169C alloy have poor structure stability. In a short period of time, the two alloys lose stability. In contrast, the microstructure stability of GH4169C alloy is higher than that of GH4169 alloy with aging at 704℃, while GH4169C alloy shows a lower stability compared with GH4169 alloy at 720℃. It is thought that the stability of γ'phase in GH4169C alloy increases with increasing Nb and P contents. GH4169C alloy shows a better microstructure stability than GH4169 alloy at 704℃. However, the content of δphase will also increase with increasing Nb content, leading to the decrease in microstructure sta-bility of GH4169C alloy. At ultrahigh temperature (720℃), the microstructure stability of GH4169C alloy is inferior to GH4169 al-loy. This means that, compared with GH4169 alloy, the modified GH4169C alloy can be used in a higher temperature, whereas the temperature increase is limited, the microstructure stability of GH4169C alloy will decrease at ultrahigh temperature.