A newly developed heavily alloyed polycrystalline nickel-base superalloy containing rhenium and intended as a structural material for turbine discs in gas turbine engines has been studied. Homogenisation and heterogenisation heat treatments were developed for the as-cast superalloy, which led to improving the hot workability as compared to that of as-cast material. electron backscatter diffraction analysis of samples isothermally compressed at temperatures near the solvus temperature showed that continuous dynamic recrystallisation occurred in the superalloy leading to the formation of refined recrystallised structure. These results were used for the development of canned forging processing under quasi-isothermal conditions. The superalloy subjected to canned forging followed by aging exhibited superior high strength and high-temperature capability, while retaining reasonable ductility as compared to known disc superalloys.

The work is devoted to the study of the microstructure and mechanical properties of the nickel base superalloy Inconel 718 manufactured by selective laser melting (SLM).

Severe thermomechanical processing of the Inconel 718 alloy has been shown to cause the formation of a nanocrystalline (NC) structure with an average grain size of 0.08 μm. The processing includes discontinuous thermomechanical treatment by the scheme of multiaxial isothermal forging at low strain rates and stepwise decrease of the treatment temperature to 0.6 T _m. The thermal stability of the NC structure has been studied upon heating and superplastic deformation. It is established that the structure refinement to the NC state decreases the temperature threshold of the low-temperature superplasticity to 0.57 T _m (550°C).

In our previous works, the effects of forging and heat treatment variables on microstructure evolution and mechanical properties have been studied for an ingot-metallurgy Re-bearing nickel base superalloy. To overcome the issues associated with the production of large-scale ingots and fine-grained workpieces, in the present work, the effect of hot forging and heat treatment variables was studied in a Re-bearing nickel base superalloy prepared via powder metallurgy. The purpose of the study was to reach the properly balanced mechanical properties for the potential use of the superalloy as a disc material. The initial as-HIPed workpieces were subjected to different hot forging and post-forging heat treatment or only to heat treatment (no forging). For the processed workpieces, the recrystallization behavior, size, morphology and volume fraction of γ′ precipitates were evaluated by scanning electron microscopy followed by a study of mechanical properties. The most properly balanced mechanical properties (strength, ductility, creep resistance and creep rupture lifetime) were reached for the γ grain size of d_γ ≈ 13.6 µm. A finer and coarser γ grain size (down to d_γ ≈ 2.6 and up to d_γ ≈ 37.5 µm) even when superimposed with a higher volume fraction of dispersed secondary γ′ precipitates (in the case of d_γ = 27–37.5 µm) was associated with worse mechanical properties.