DAFNE

Development of gamma-TiAl forgings in a low-cost near conventional hot-die process and process evaluation

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 Obiettivo del progetto (Objective)

'The strong need for higher efficiency, reduced CO2 emissions and weight reduction in aircraft engines leads to a demand of innovative light-weight high-temperature resistant materials which can partly substitute the materials currently employed. Presently, Ni-base alloys are used for turbine blades in aero-engines which satisfy the high mechanical and thermal requirements. A disadvantage of Ni-base alloys, however, is their high density of about 8 g/cm3. Intermetallic titanium aluminides, which exhibit a low density of about 4 g/cm3, are certainly among the most promising candidates to meet the required thermal and mechanical specifications. During the last decade several “wrought” gamma-TiAl alloys have been developed. These alloys exhibit excellent mechanical properties, but show a narrow processing window. Böhler Schmiedetechnik GmbH & Co KG (BSTG) is specialized on forging processes of materials like Ni-base and Ti-alloys for aero engine applications with a high demand on structure mechanical requirements. In cooperation with the department of physical metallurgy and materials testing at the University of Leoben as well as other project partners a novel Nb and Mo containing gamma-TiAl based alloy (TNM™ alloy) was developed. Due to optimized microstructure the alloy showed good malleability in first forging trials. An innovative approach of near conventional hot-die forging, which means that conventional forging equipment with minor and inexpensive modifications can be used, was made by BSTG. Aim of this project is to develop a robust low-cost near conventional hot-die forging process for low pressure turbine blades which meets on the one hand the requirements of the OEM and gives the right direction for future serial production on other hand.'

Introduzione (Teaser)

Lighter airplanes lead to lower fuel consumption and fewer emissions largely responsible for global climate change. EU-funded scientists demonstrated successful cost-effective forging of a novel low-density alloy for turbine blades.

Descrizione progetto (Article)

Nickel-based alloys commonly used for aeroengine turbine blades meet mechanical and thermal requirements but have relatively high densities. During recent decades, alloys of titanium and aluminium (gamma-TiAl alloys) with half the mass in a given volume have received attention as potential alternatives.

Based on successful preliminary forging trials of a novel gamma-TiAl alloy containing niobium and molybdenum, scientists launched the EU-funded project DAFNE to enable cost-effective production of low-pressure turbine blades. During the present reporting period, scientists conducted hot-die forging trials and mechanical testing of turbine blades demonstrating achievement of customer specifications. The team also advanced the chemical milling process and compared machinability of the selected die materials. Processes and die materials were evaluated for optimisation.

Potential beneficiaries of DAFNE outcomes abound. Successful conventional hot-die forging of low-pressure turbine blades will decrease their cost by more than 75%, opening new markets for DAFNE partners and creating jobs to offset the impact of the current economic crisis. The lower weight of the blades will facilitate faster rotation, increasing efficiency and decreasing fuel consumption and emissions such that what is good for industry is also good for the environment.