Bcc-superalloys: Engineering Resilience to Extreme Environments

Nuclear fusion, Generation IV fission reactors and aerospace gas turbines are critical to our future energy generation and transportation. Their operation at high temperatures necessitates construction from a variety of advanced materials. In order to withstand these extreme environments materials require high melting points, high temperature strength and environmental resistance, and, for nuclear, irradiation resistance. There are strong environmental and economic incentives to yet further increase the temperature capability of the materials used, in order to improve efficiency to reduce fuel use, as well as for improve performance, design life and safety. However, while iterative improvements are being made year on year the temperature gains are becoming ever harder to realise. In this proposal a step change in temperature capability is sought by the realisation of a new class of body-centred-cubic (bcc, an atomic crystal structure) superalloys based on (1) Tungsten, (2) Titanium, and (3) Steel, for the extreme environments of nuclear fusion and gen IV fission reactors as well as aerospace gas turbine engines. I will create a close network of industrial, national and international academic partners, that will enable translation of these advanced materials from concept through to scale-up. The collaborations will be split across the bcc-superalloys Work Packages: (WP1) Tungsten, bringing in Culham Centre for Fusion Energy (CCFE), and ANSTO Sydney, toward nuclear fusion and Gen IV fission; (WP2) Titanium, brining in TIMET and Rolls Royce, for aero-engines, as well as ETH Zurich for thin film based alloy discovery; (WP3) Steel, bringing in Rolls Royce, for gas/steam turbines, and the Max-Planck-Institut für Eisenforschung (Iron Research, MPIE) Dusseldorf for advanced characterisation and steels expertise. Bcc superalloys comprise a metal matrix, where the atoms are arranged in a bcc crystal structure, which are reinforced by forming precipitates of high strength ordered-bcc intermetallic compounds (e.g. TiFe or NiAl). This has parallels to the strategy used in current face-centred-cubic (fcc) nickel-based superalloys. However, changing the base metal's crystal structure, and therefore also the reinforcing intermetallic compound, represents a fundamental redesign and necessitates the development of new understanding. The key advantage of using a bcc refractory-metal-, titanium-, or steel- based superalloy is their increased melting point(s), which give the possibility of increased operating temperatures, as well as greatly reduced cost for the case of steels. However, the change in crystal structure requires a fundamentally new design strategy. While the limited investigations into bcc superalloys have indicated that they have attractive strength, and creep resistance, they have been held back by their low ductility. During this fellowship, I will thoroughly investigate multiple ductilisation strategies on bcc-superalloys to advance their technology readiness level (TRL) and so remove the current barrier to their commercialisation. Investigation of the systems will be undertaken by myself, the 2 Research Fellows (RF), technician, and PhD students allowed for by the programme, as well as staff time from the project partners (CCFE, TIMET, Rolls Royce, ANSTO, ETH Zurich and MPIE). The PhD students will undertake alloy development between: WP1 on Tungsten alloys 50% supported by CCFE, WP2 on Titanium, two students, one 50% by TIMET and a second 50% by Rolls Royce, with a fourth school funded by UoB on WP3 industrially supervised by Rolls Royce. The two 2 RFs and technician would work in alloy development and characterisation alongside these students, but also perform more detailed investigations, with one RF focussed on irradiation damage mechanisms, and the second RF on deformation mechanisms, both using advanced microscopy and micromechanics on which the related students would be progressively trained.