DEVELOPMENT AND TURBINE-ENGINE PERFORMANCE OF 3 ADVANCED RHENIUM CONTAINING SUPERALLOYS FOR SINGLE-CRYSTAL AND DIRECTIONALLY SOLIDIFIED BLADES AND VANES

Turbine inlet temperatures over the next few years will approach 1650 degrees C (3000 degrees F) at maximum power for the latest large comme rcial turbofan engines, resulting in high fuel efficiency and thrust l evels approaching 445 kN (100,000 lbs.). High reliability and durabili ty must be intrinsically designed into these turbine engines to meet o perating economic targets and ETOPS certification requirements. This l evel of performance has been brought about by a combination of advance s in air cooling for turbine blades and vanes, design technology for s tresses and airflow, single crystal and directionally solidified casti ng process improvements, and the development and use of rhenium (Re) c ontaining high gamma' volume fraction nickel-base superalloys with adv anced coatings, including full-airfoil ceramic thermal barrier coating s. Re additions to cast airfoil superalloys not only improves creep an d thermo-mechanical fatigue strength, but also environmental propertie s including coating performance. Re dramatically slows down diffusion in these alloys at high operating temperatures. A team approach has be en used to develop a family of two nickel-base single crystal alloys ( CMSX-4(R) containing 3 percent Re and CMSX(R)-10 containing 6 percent Re) and a directionally solidified columnar grain nickel-base alloy (C M 186 LC(R) containing 3 percent Re) for a variety of turbine engine a pplications. A range of critical properties of these alloys is reviewe d in relation to turbine component engineering performance through eng ine certification resting and service experience. Industrial turbines are now commencing to use this aero developed turbine technology in bo th small and large frame units in addition to aero-derivative industri al engines. These applications are demanding, with high reliability re quired for turbine airfoils out to 25,000 hours, with perhaps greater than 50 percent of the time spent at maximum power. Combined cycle eff iciencies of large frame industrial engines are scheduled to reach 60 percent in the U.S. ATS programme. Application experience to a total 1 .3 million engine hours and 28,000 hours individual blade set service for CMSX-4 first stage turbine blades is reviewed for a small frame in dustrial engine.