Microstructural Stability and Properties of New Nickel-Base Superalloys with Varying Aluminium: Niobium Ratio

Abstract

New nickel-base superalloys with higher temperature capability are required for future, more efficient gas turbine engines. In designing such alloys, careful consideration is required of the elemental concentrations to ensure a suitable balance of properties is obtained. In this study, the phase equilibria and microstructural stability of new nickel-base superalloys with varying Al:Nb ratio have been assessed via long-term thermal exposures at 700˚C. The alloys have been analysed using scanning & transmission electron microscopy, X-ray diffraction, differential scanning calorimetry and Vickers hardness testing, with the results rationalised through mechanical property predictions based on strong- and weak-pair dislocation coupling mechanisms. The alloys were shown to have greater thermal stability than Inconel 718 and exhibited a pronounced hardening effect after thermal exposure. These results highlight their ability for controlled age hardening and potential ease of processing.