Entwicklung eines Herstellprozesses für Turbinenschaufeln aus einer intermetallischen gamma-TiAl Legierung

Translated title of the contribution: Development of a processing route for intermetallic gamma-TiAl turbine blades

Daniel Huber

Research output: ThesisDoctoral Thesis

Abstract

Due to the strong demand for higher efficiency, reduced CO2 and NOx emissions and weight reduction, modern aircraft engines are continuously improved. For in civil aviation widely used turbofan engines this can be achieved by increasing the bypass ratio. A newly developed concept for a bypass ratio higher than ten is the decoupling of fan and low pressure turbine. Therefore, fan as well as low pressure turbine turn at optimum speeds. Rotational speed of the low pressure turbine is almost twice as high as in conventional turbofan engines. This also increases mechanical, thermal and aerodynamic load on the components. A disadvantage of Ni-base superalloys, which are commonly used in this engine section, is their high density of ~8kg/dm³. Intermetallic materials based on gamma-titanium aluminides possess mechanical properties comparable to Ni-base superalloys at a density of ~4kg/dm³. Turbine blades made of a gamma-titanium aluminide alloy in combination with material compatible design lead to reduced centrifugal forces. Increased loads, compared to conventional turbofans, however, necessitate the usage of massive forming processes for turbine blade production. Thermo-mechanical processing of gamma-titanium aluminide based alloys is a complex task due to a small processing window. Isothermal forging, as state of the art process for this material group, results in high production costs and low productivity. Thus, Böhler Schmiedetechnik GmbH & Co KG has developed a highly efficient near conventional hot-die forging process. This process was defined within this work. At first a preforming concept was designed to achieve a material distribution according to the demands of the final product. The preform was subsequently hot-die forged. A design of experiments was performed to establish optimized process parameters for a stable production route. Additionally an assessment of die materials was performed to improve die lifetime. Thermo-mechanical and tribological as well as machining trials provided a basis for the final decision. Finally turbine blades were produced with an optimized parameter set for preforming, hot-die forging and heat treatment. Parts were tested according to customer requirements. Supporting processes to further improve downstream processes were evaluated. Within this work gamma-titanium aluminide low pressure turbine blades were hot-die forged. Process stability was demonstrated. For the first time it was proven, that a modern intermetallic gamma-titanium aluminide alloy can be forged on conventional hydraulic presses in near serial condition.
Translated title of the contributionDevelopment of a processing route for intermetallic gamma-TiAl turbine blades
Original languageGerman
QualificationDr.mont.
Supervisors/Advisors
  • Clemens, Helmut, Assessor A (internal)
  • Kiener, Daniel, Assessor B (internal)
Publication statusPublished - 2016

Bibliographical note

embargoed until null

Keywords

  • forging
  • titanium aluminides
  • turbine blade
  • hot-die
  • process design

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