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Predictive Microstructural Assessment and Micro-Mechanical Modeling of Deformation and Damage Accumulation in Single Crystal Gas Turbine Blading

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Launching the super-alloy; turning up European competitiveness

European gas turbine manufacturers are faced with fierce competition from the US and Japan. To assist in their efforts to maintain and increase their share of the international markets, a European consortium of universities, research institutes, industries and SMEs has launched a four year basic research project on the study, assessment, evaluation and improvement of the materials used in the manufacturing of gas turbine blades.

Industrial Technologies

Advanced engines with increased thermal efficiency such as current gas turbines, work under conditions of high temperatures and stresses. This requires manufacturers to possess advanced knowledge of the properties of the materials they use. Especially for turbine blades that are made from alloys, there is a strong need to predict the deformation and the possible failure of the blades in order to assure that catastrophic failure will not occur, while ensuring at the same time, maximum efficiency of critical components are utilised. Alloys, combination of metals that enhance the properties of the individual metals, have extensive use in critical applications such as jet engines. Gas turbine blades that operate at high temperatures require super alloys. Single crystal super alloys, a recent advanced type of material, if effectively used for the manufacturing of blades, are expected to reduce costs, improve efficiency and performance and make gas turbines much more reliable. Unfortunately, until recently, the full advantage of single crystal super alloys had not been achieved due to the lack of detailed knowledge of their mechanical behaviour. The MICROMOD-SX project was launched in order to provide the knowledge required. The project has achieved an improved understanding of the anisotropic mechanical behaviour of single crystal super alloys under conditions of high temperature. Two models were used for predicting deformation and failure of single crystal gas turbine blades based on uniaxial creep and fatigue tests. Moreover, this was the first attempt to include cast defect structure in the prediction of deformation and failure of the blades. The models that described the creep/fatigue life of anisotropic single crystal super alloys were assessed with appropriate material databases using multiaxial creep and thermal fatigue tests of single crystal specimens. The feedback resulted in a refinement and the models are now commercially available as Finite Element (FE) software packages. Although the current project is a basic research programme in material science, its strong link to industrial applications is evident. It is a step towards the more effective use of super alloys that will aid the gas turbine manufacturing industry considerably.

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