Evolution of precipitates in Ni-Co-Cr-W-Mo superalloys with different tungsten contents  

作　　者：Han-Sheng Bao Zhi-Hua Gong Zheng-Zong Chen Gang Yang 

机构地区：[1]Institute for Special Steels,Central Iron and Steel Research Institute,Beijing 100081,China [2]School of Materials and Metallurgy,Inner Mongolia University of Science and Technology,Baotou 014010,China

出　　处：《Rare Metals》2020年第6期716-724,共9页稀有金属（英文版）

基　　金：financially supported by the National Key Research and Develop Program,China(No.2017YFB0305203)。

摘　　要：The Ni-Co-Cr-W-Mo system is critical for the design of nickel-based superalloys.This system stabilizes different topologically close-packed(TCP)phases in many commercially superalloys with high W and Mo contents.Scanning electron microscopy(SEM),transmission electron microscopy(TEM)and thermodynamic calculations were applied to investigate the thermodynamics of the precipitates in two different W-contained Ni-Co-Cr-WMo superalloys(Alloy 1 and Alloy 2).Computational thermodynamics verifies the experimental observation of theμphase formation as a function of temperature and alloy chemistry,but the kinetics for the precipitation of the M6 C phase do not agree with the experimental findings.The major precipitates of Alloy 1 at temperatures of700℃and 750℃during long-time exposure are M23 C6,γ′phase and MC;for Alloy 2,they are M23 C6,γ′phase,MC,M6 C andμphase.W addition is found to promote the precipitation of M6 C andμphase during exposure.M6 C has higher W and lower Ni content thanμphase,whereas M6 C is an unstable phase that would transform into M12 C after 5000-h exposure at 750℃.A great quantity of needle-likeμphases precipitated after exposure at 750℃for5000 h,which have no effect on the impact properties of Alloy 2.

关 键 词：Nickel-based superalloys M6C μphase Long-time exposure M12C 

分 类 号：TG132.3[一般工业技术—材料科学与工程]