Abstract
The microstructure and mechanical properties of two nitrogen (N) modified Ni-Fe base superalloys subjected to long-term thermal exposure were studied. It was found that the M23C6 phase precipitated discretely at the grain boundary even after thermal exposure at 700°C for 7004 h. The inhibition of the continuous precipitation of M23C6 can be attributed to the enhanced formation of intergranular M(C, N) phase due to addition of N. The coarsening of γ' phase during the thermal exposure was found to be gentle in the present Ni-Fe alloys, as compared with those without N. The mechanical properties of the Ni-Fe alloys remained relatively stable after thermal exposure at 700°C for up to 7004 h, which can be related to the suppressed γ' coarsening and discrete precipitation of M23C6 at the grain boundary owning to the addition of N.
Published Version
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