Abstract
In this study, we have investigated the possibility of using advanced Co-base superalloys with γ/γ′ microstructures to replace Ni-base superalloys. However, in order to maintain the thermal stability of γ′ phase in the Co-base superalloys, the content of Cr has to be reduced to a low level, but the reduction of Cr will result in a decrease in oxidation resistance. Therefore, we propose to use Si addition in the Co-base superalloys based on Co-Al-W-Ni system to maintain oxidation resistance. The solidification profiles, γ/γ′ microstructure, solid-solid partitioning, room/high temperature hardness, hot corrosion and oxidation behavior of different Si bearing systems have been examined. Our results show that, by the addition of Si: (1) The oxidation weight gains of the alloys are lowed; (2) The hot corrosion resistances of the alloys are improved; and (3) The fraction of γ′ phase increases, leading to an improvement in the degree of hardness in high temperature. These findings indicate that the addition of Si offers a potential to improve the properties of Co-base superalloys in high temperature.