Microstructure and Properties of Ni-25Cr-20Co Alloy After Long-term Aging
WEI Limin1,2, YANG Quan1,2, CHENG Yi 1,2, TAN Shuping1,2
1 Material Research Institute of Harbin Boiler Co., Ltd, Harbin 150046; 2 State Key Laboratory of Efficient and Clean Coal-fired Utility Boilers, Harbin 150046
Abstract: Based on Thermo-Calc software, the microstructure and mechanical properties of Ni-25Cr-20Co alloy after long-term aging at 750 ℃ was investigated using OM, SEM, TEM and tensile testing. The relationship between dislocation resistance mechanism and γ′ phase size was calculated. The results show that MC, M23C6 and γ′ phase are the main precipitates, the volume fraction of γ′ phase is 16%. The growth kinetic of γ′ phase follows LSW theory, affecting by the diffusion of solute atoms and interface energy of γ/γ′. The tensile strength increases obviously after aging treatment. The tensile strength decreases with the extending aging time. Deformation mechanism in stretching process is changed with the growth of γ′ phase. When γ′ phase is small, deformation mechanism is climb mechanism→cut mechanism→Orowan mechanism. Deformation mechanism switch to climb mechanism→Orowan mechanism→cut mechanism when γ′ phase exceed critical value.
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2017, Vol. 31 
