Performance Evaluation of “Duplex Hardened” Bearings for Advanced Turbine Engine Applications

Reliability is one of the most important competitive factors in aeroengines. Engine manufacturers have to provide guarantees for maintenance cost and dispatch reliability. Failures of mainshaft and gearbox bearings can represent a major debit to overall engine reliability. Duplex hardening (conventional hardening followed by special nitriding) has the potential to provide the bearing performance improvements necessary to yield increased engine reliability and reduced cost of ownership. The bearing rig tests performed demonstrate superior performance of duplex hardened M50 and M50NiL bearings over conventional M50 and MSONiL bearings under various operating conditions. Rig tests evaluating a wide range of operating conditions, such as high load, low or boundary lubrication, heavily contaminated lubrication, and oil off were performed. Additional tests were completed to evaluate the spall propagation behavior of duplex hardened bearings in comparison to conventional steel bearings. The results showed that the main benefits of using duplex hardened bearings arise in low or boundary lubrication conditions and contaminated lubrication conditions. The spall propagation tests showed that spall propagation rates are slower for duplex hardened M50 and M50NiL bearing components, hence allowing more time until catastrophic bearing failure in an aeroengine and other applications.