EFFECTS OF Co ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF Fe-Cr-Ni-Co-BASE SUPERALLOY REFRACTOLOY 26
by CHEN Guoliang; ZHUANG Linzhong (Beijing University of Iron and Steel Technology); XU Jialong (Shanghai Iron and Steel Research Institute)
Cite this article:
by CHEN Guoliang; ZHUANG Linzhong (Beijing University of Iron and Steel Technology); XU Jialong (Shanghai Iron and Steel Research Institute). EFFECTS OF Co ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF Fe-Cr-Ni-Co-BASE SUPERALLOY REFRACTOLOY 26. Acta Metall Sin, 1986, 22(6): 5-12.
Abstract An investigation deals with the effects of Co on the microstructure and mechanical properties of Refractoloy 26, an Fe-Cr-Ni-Co-base precipitation hardening superalloy. The experimental results show that as Co is decreased in Refractoloy 26 alloys, the weight fraction of γ′-phase as well as the average diameter of γ′ particles increases, while the γ-γ′ lattice mismatch decreases. Lowering the Co content destabilizes MC carbide in the alloy so that more grain boundary M_23C_6 and M_6 C carbides form during aging treatment, therefore, the total amount of carbides increases. The M_23C_6 carbide disappears but μ-phase forms in the alloys with 14 and 20% Co. The Co content affects both of the amount and morphologies of twin boundaries in alloys. Lowering Co content has a little influence on the tensile properties, but a great influence on the creep resistance at 565℃. In comparison with the creep results of solid solution alloys with the same composition of matrix of Refractoloy 26 alloys, the creep properties for both solid solution alloys and Refractoloy 26 alloys with different Co content depend directly on the values of stacking fault energy in matrices. It seems that a satisfying superalloy could be obtained with low Co content for which the mechanical properties are high enough for practical use and the microstructure stability is even better than that of original Refractoloy 26 alloys.
