Objectives and content
The aim of this project is to develop new superalloy compositions specifically designed for casting of large single crystal gas turbine blades for power generation. Replacement of conventionally cast blades by single crystal blades would permit an increase of the firing temperature, and consequently a better efficiency of the gas turbine. Other important consequences will be a reduction in fuel consumption and a decrease of the pollutant emission level.
The specific working conditions of industrial gas turbines using low-grade fuels require materials with a high corrosion resistance in severe environment, in addition to a good stress-rupture strength with lives up to 50,000 hours, which is different from the conditions encountered in aeronautical gas turbines. Two sets of objectives will be persued corresponding to alloys satisfying the following requirements :i) corrosion resistance in synthetic ash at 700-800°C comparable to IN738LC and creep strength at 750-950°C comparable to IN792, ii) sulfidation resistance at 900-1000°C comparable to IN738LC and a typical stress-rupture life of 3,500 hours at 950°C and 140 MPa. Moreover, the alloys will have to show: i) a good castability as large single crystal components up to 50 cm height, ii) a good long term microstructural stability, iii) cost effectiveness. Needless to say that none of the currently available materials possess this overall combination of properties and therefore there is a strong need expressed by the European gas turbine industry to develop such new superalloys.
The first phase of the work programme will include the definition of a set of experimental alloys using alloy design procedures, directional casting of single crystal test-pieces and components, corrosion, mechanical and microstructural screening tests. The two most promising alloys will be selected for an extended evaluation. Deformation models and a lifing method developed on the basis of the results of microstructural assessments will be used in order to predict the long-term behaviour of these alloys.
Funding SchemeCSC - Cost-sharing contracts
EX2 7LG Exeter