Surface Processing for Enhanced Environmental and Creep-Fatigue Resistance

The ongoing drive to increase the performance and efficiency of propulsion systems has led to increasingly severe operating environments, particularly for the components in the hot sections of turbine engines. One potential life-limiting area of future engines is the turbine disk where significant dwell fatigue may occur if engine temperatures are elevated. The mechanism for this reduction is not fully clear but is related to effects of grain boundary creep and surface oxidation / corrosion. The study proposed here will seek to develop advanced surface chemistry and modification techniques for the nickel-base superalloys used for turbine disks to limit dwell fatigue damage and promote higher operating temperatures in the engine. Key factors that will be studied include: (i) computational approaches to designing novel coating compositions that exhibit minimal interdiffusion and hence excellent compatibility with the substrate owing to chemical activity matching; (ii) the manufacture and testing of selected compositions; and (iii) the application of good performing coatings onto selected regions of a turbine disk. A targeted significant outcome of this study is the establishment of novel and cost-effective surface modifications that confer greatly improved component reliability and durability. BENEFIT: This research is anticipated to result in technology that enables higher use temperatures for turbine disk components resulting in improved capability and efficiency for next generation propulsion systems of interest to future turbine, rocket, ramjet and scamjet engines. Specifically, the advanced environmental compositions and application approaches developed in this work will improve the resistance to creep fatigue of high strength superalloys. This will lead to the realization of many advanced gas turbine engine designs while leading to several percent thrust improvement or specific fuel consumption reduction for current turbine engines. These new capabilities will permit improved engine designs and operating levels on a range of Air Force platforms.