On the Effect of Nb on the Microstructure and Properties of Next Generation Polycrystalline Powder Metallurgy Ni-Based Superalloys

Abstract The effect of Nb on the properties and microstructure of two novel powder metallurgy (P/M) Ni-based superalloys was evaluated, and the results critically compared with the Rolls-Royce alloy RR1000. The Nb-containing alloy was found to exhibit improved tensile and creep properties as well as superior oxidation resistance compared with both RR1000 and the Nb-free variant tested. The beneficial effect of Nb on the tensile and creep properties was due to the microstructures obtained following the post-solution heat treatments, which led to a higher γ′ volume fraction and a finer tertiary γ′ distribution. In addition, an increase in the anti-phase-boundary energy of the γ′ phase is also expected with the addition of Nb, further contributing to the strength of the material. However, these modifications in the γ′ distribution detrimentally affect the dwell fatigue crack-growth behavior of the material, although this behavior can be improved through modified heat treatments. The oxidation resistance of the Nb-containing alloy was also enhanced as Nb is believed to accelerate the formation of a defect-free Cr2O3 scale. Overall, both developmental alloys, with and without the addition of Nb, were found to exhibit superior properties than RR1000.This work was supported by the Rolls-Royce/EPSRC Strategic Partnership under EP/H022309/1, EP/H500375/1 and EP/ M005607/1

Inertia friction welded RR1000 and Inconel718 microstructure

Precipitation hardening Ni based superalloys have been widely used in gas turbine engine components owing to their stable microstructure at high temperature. To assemble these components, joining technology is necessary and friction welding is used for the joints which are suitable for large component welding, taking advantage of its superior mechanical properties compared to fusion welding. Inertia friction welded RR1000 and Inconel718 microstructure was studied. In this study, grain boundaries were intensively characterized to rationalize the intergranular susceptible area from the microstructure point of view

Accompanying data for "On the effect of Nb on the microstructure and properties of next generation polycrystalline powder metallurgy Ni-based superalloys"

The data has been labelled with the same designations as used in the corresponding paper. Raw data is provided from differential scanning calorimetry and scanning electron microscopy following the various heat treatments and oxidation analyses. In addition, data is provided from the tensile, creep and dwell tests performed and the outcomes of the mechanical property modelling are also given.This work was supported by the Rolls-Royce/EPSRC Strategic Partnership under EP/H022309/1, EP/H500375/1 and EP/ M005607/1