Spall Propagation-Resistant Hybrid Bearings for High-Performance Turbine Engines

The objective of this SBIR project is to develop spall propagation resistant turbine engine mainshaft bearings for improved reliability, safety, and performance margin of aircraft propulsion systems. New case carburized Pyrowear 675 steel has been developed for bearing races that has been shown to resist surface fatigue initiation and therefore improve fatigue life significantly compared to the currently used M50 steel. However, once the initiation occurs, fatigue cracks can propagate rapidly resulting in increased spall rate in Pyrowear 675 races. This aspect of the fatigue properties of Pyrowear 675 has not been studied in great detail.  In this Phase II SBIR project, UES proposes to identify the key properties of Pyrowear 675 such as microstructure, compressive residual stresses and near-surface fracture toughness that control the spall propagation rate by analyzing new and failed bearings.  Also, computer modeling and simulation will be used to understand the role of dynamic operating conditions such as load and speed on the spall propagation. Based on the understanding of the mechanism developed in Phase II, UES will optimize the heat treatment protocol for P675 to achieve the optimum properties for improved bearing life. BENEFITS: Spall propagation-resistant hybrid bearings will improve reliability and safety of high performance aircraft in both military and commercial sectors.