New single crystal superalloys – overview and update

Single crystal (SX) superalloys have wide application in the high pressure turbine section of aero and industrial gas turbine engines due to the unique combination of properties and performance. Since introduction of single crystal casting technology, SX alloy development has focused on increased temperature capability, and major improvements in alloy performance have been associated with the introduction of new alloying elements, including rhenium (Re) and ruthenium (Ru). 3% Re-containing second generation alloys have seen the greatest market utilization and have become the benchmark alloys for comparing new alloy developments. However, Re and Ru are rare elements with limited production/availability and corresponding high costs. This has resulted in significant escalation of SX alloy costs, resulting in much interest in the development of improved SX superalloys with lower Re or no Re content compared to second generation alloys. Cannon-Muskegon® has developed two new SX superalloys: 1.5% Re CMSX®-8 alloy and CMSX®-7 alloy, which contains no Re, as alternatives to first and second generation alloys for applications which require slightly less ultra high temperature capability compared to current alloys. This paper provides an overview of development and characterization of these SX alloys, including an update on recent results.