Material & Energy Waste during Turbine Blade Replacement

Aircraft propulsion belongs to a critical industrial segment with the blades inside the gas turbines representing one of the most aggressive applications of high-temperature materials. Traditionally, turbine blades are manufactured using conventional methods, such as investment casting. However, investment casting, especially single crystal (SX) casting, is expensive and consumes a high amount of energy. In addition, hot-section components, such as these blades, have a limited operating life due to their rotational motions and high thermal stress which cause material losses from abrasion, oxidation, and corrosion attack through worn protective coatings. Currently, there is no way to repair these blades to their original integrity. Therefore, there is a high amount of material waste and energy use associated with the overhaul of a plane engine due to both the discarding of worn turbine blades as well as the production of new turbine blades to replace the discarded ones. For example, one Boeing 787-9 plane uses a GEnx-1b74/75 engine which contains two high pressure turbines (HPT) with 62 SX blades each. These blades have a life of approximately 25,000 hours. After this time, all 124 SX blades will be discarded and replaced. When blades are discarded, they will either be scraped or reverted. Reverting is a process that seeks to reclaim the superalloy components of the blade. However, this method is imperfect, so there will always be some material lost. Because one of the key components of most turbine blade superalloys, rhenium, has a low crustal abundance, it is important to limit material waste in order to conserve it. By analyzing current and predicting future material waste and energy consumption used in the production of replacement blades, we can quantify the environmental and energy benefits of developing repair processes suitable for turbine blades.