Topic:  Development of superalloys for Gas turbine blades and disks : current status and prospects

Abstract

A considerable amount of work has been performed in Europe and for developing new superalloys for blades and disc materials. In , research on high performance, high temperature materials started in the 1970~s on directionally solidified in-situ composites. In the 1980~s, ONERA was at the forefront of developing new materials to satisfy the requirement of French engine manufacturers, Snecma and Turboméca. This research and development was centered on nickel based superalloys for high temperature powder metallurgy (PM) disks, and for single crystal (SC) turbine blades. The PM N18 alloy developed by the consortium Snecma, ONERA, Centre des Matériaux de l~Ecole des Mines de Paris (CMEMP) and Imphy SA was designed to achieve a high resistance to crack propagation and it is now used as high pressure compressor and turbine disk material in the M88 Snecma engine of the RAFALE fighter. The derivative NR3 and NR6 PM superalloys, designed at ONERA, are suited for higher temperature applications wing to their long-term microstructural stability. The nickel-based SC alloy AM1 was jointly developed by Snecma, ONERA, Imphy SA and the CMEMP. This alloy is now used as high pressure turbine blade and vane material in the M88 engine. The AM3 and MC2 superalloys for SC turbine blades, developed at ONERA to satisfy the specific requirements of Turboméca, are today introduced in commercial helicopter engines. Alloy design procedures based on experimental know-how and theoretical considerations were progressively defined to fulfil specific targets within a limited time and with a maximum reliability. The recent development of the new generation MC-NG single crystal alloy strongly benefited from this experience.

Today, we have reached an upper limit in terms of temperature for the use of single crystal alloy. The next big challenge is to develop the thermal barrier coatings in order to push the temperature limit to about 1200 °C. This lecture will give an overview of the various current development and future prospects for advanced aircraft engines.

Curriculum Vitae -- T. KHAN