Thermomechanical behaviour of a new low-cost polycrystalline nickel-base superalloy

Abstract

Polycrystalline Ni-base superalloys continue to be widely utilised in the aerospace, petrochemical and power generation sectors, with extensive research significantly improving their performance. Despite this, these alloys require advanced manufacturing methods that result in a high-cost final product. For low-cost alloys to be realised and find widespread industrial application, they must be readily formable by conventional deformation processing routes, with the microstructural changes that occur during these deformation operations understood so that the desired microstructure can be obtained in the final product. In this work, the deformation behaviour of a newly developed, low-cost polycrystalline Ni-base superalloy has been assessed via small-scale compression testing at elevated temperatures, both above and below the γ′ solvus. The microstructural evolution after testing has been characterised using scanning electron microscopy and electron back-scattered diffraction, to elucidate the mechanisms controlling the flow behaviour. Significant differences in the recrystallisation behaviour were observed, both as a function of deformation temperature and the strain rate. Supersolvus deformation produced fully recrystallised microstructures, whilst subsolvus deformation resulted in the presence of unrecrystallised grains. These results will guide future thermomechanical optimisation studies of the newly developed alloy and other related alloys of this type.