DESIGN OF SUPERALLOYS FOR SINGLE CRYSTAL BLADE APPLICATIONS: A 20-YEAR EXPERIENCE

摘要

For the past 20 years ONERA has developed several new superalloys for single crystal turbine blade applications in aeronautical, industrial or aerospace gas turbine engines. During the 80's, the effort was made to identify chemistries promoting a good castability, a full solution of the y' strengthening phase, and a good balance between the creep strength and the density. The alloys AM1, AM3 and MC2 are thus used today in SNECMA and TURBOMECA engines. More recently, the development of new generation superalloys MC-NG containing both rhenium and ruthenium was driven by the need for improved temperature capability and increased life of the turbine blades. More specific alloy design programmes also succeeded in developing original chemistries for turbine blade applications in industrial gas turbines for power generation and in rocket engine turbopumps. The use of predictive methods was progressively introduced to estimate some pertinent characteristics such as density, gamma solvus temperature, gamma, fraction, gamma and gamma' phase compositions, gamma/gamma' mismatch and microstructural stability, for a given alloy chemistry. These predictive methodologies were particularly useful for designing appropriate alloy chemistries for tailored applications.