Microstructural Characteristics and Theromdynamic Calculation on Equilibrium Precipitated Phases of a New Fe-Ni-Cr superalloy

Abstract:

The microstructural characteristics of a new-type Fe-Ni-Cr based superalloy was observed by ultra high resolution field emission scanning electron microscopy. The equilibrium precipitated phases and the effects of elements on the melting point and the precipitation behaviors of different phases were calculated by Thermo-Calc software. The results show that a higher C content can lead to higer quantities of MC and M23C6 carbides and higher precipitation temperatures. With the increase of Ti content, the main MC former, there is no obvious change in precipitation amount of MC, but its precipitation temperature range is significantly broadened. With the content of Ti and Al increasing, the precipitation amount and precipitation temperature of γ′ phase can be raised respectively, the effect of Al is particularly remarkable. Lowering Al content or increasing Ti content can dramatically raise the precipitation amount and preciptitation temperatures of η phase. The the formation of MC is not obviously promoted by higher content of W, the MC forming elements. Higer Al, Ti and W content can decrease the initial melting point; especially Al and Ti show more significant effects.

Key words:Fe-Ni-Cr based superalloy; microstructural characteristics; precipitation behavior; thermodynamic calculation