HITNIFO

Development of an advanced design and production process of High Temperature Ni-based Alloy Forgings

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 Obiettivo del progetto (Objective)

'The strong need for higher efficiency, reduced CO2, NOX emissions, weight and noise reduction in aircraft engines leads to a demand of innovative materials with optimized mechanical and physical properties. The special design of new generation geared turbofan aircraft engines with their faster rotating LPT leads to higher temperatures in the turbine, casing and engine mount and thus requires parts with increased high temperature properties. High temperature strength means in most cases bad forgeability and weldability as well as combined with high toughness challenging machinability. Thus, beside of new designs the production processes have to be altered to get high quality parts. The overall goal of this project is an improved understanding of thermomechanical processing and its effect on residual stresses and distortion as well as microstructure and mechanical properties of forgings used for improved temperature exhaust cases. The proposed project consortium has significant experience with regard to nickel base superalloys with higher temperature capability than Inconel718 like Udimet720, Waspaloy, Allvac718Plus, RENE65 and Haynes282. Together with the know-how on residual stress simulation and measurement established in several projects since 2001 a successful realization of this project is possible. Beside project management according IPMA standards six further work packages have been defined. One for radial forging and one for closed die forging will be used to optimise thermomechanical processes based on simulation and to produce demonstrator parts. Open die forgings are used for residual stress and microstructure investigations. Material data for finite element simulation and residual stress modelling will be generated in on work package and verified together with the customer in an other. Residual stress modelling will be verified by neutron diffraction measurements and other methods in the final work package.'

Introduzione (Teaser)

An EU-funded project worked on improving design and processing of jet engine parts. The optimised materials should be able to endure very high temperatures.

Descrizione progetto (Article)

The aviation industry is increasingly looking to geared turbofan engines for more efficient flight. Innovative materials with optimised mechanical and physical properties will allow deep cuts in fuel consumptions and harmful emissions.

Geared turbofan engines may induce very high temperatures in some areas of the turbine and the engine casing and mount. The EU-funded project HITNIFO (Development of an advanced design and production process of high temperature Ni-based alloy forgings) was initiated to produce high-performance materials at low cost by improving processes, overcoming issues related to bad forgeability and weldability.

Project partners selected promising materials for the casing and mount based on nickel alloys for use in high temperatures. Firstly, they performed annealing trials to investigate changes of microstructural properties with time and temperature. The trials also enabled identifying the main impact on mechanical properties such as yield strength, elongation and stress rupture.

After designing and simulating the closed die forging process and producing dies, project partners evaluated the impact of the process on the forging microstructure and mechanical properties. Other activities included flow stress measurements at seven different temperatures and two different strain rates, and measurement of heat capacity and thermal conductivity.

Results provided the basis for finite element simulations of material residual stress. In particular, project partners performed simulations with different mesh densities to estimate the residual stress distributions in components of complex geometry. Simulations were then compared with experimental results.

HITNIFO opens the way to developing engines with higher exhaust temperatures and therefore higher efficiencies. Use of the optimised nickel-based alloys should allow a decrease in the engine weight and hence aircraft, and lead to decreased fuel consumption.