Bearing steel microstructures after aircraft gas turbine engine service

Abstract

The microstructure of aircraft gas turbine engine bearing steel has been characterised after service in Rolls-Royce Trent™ engines, with the focus on surface condition and the consequences of sliding contact. Carbide populations at the surfaces of rolling elements are found depleted by 30% after 30 000 h engine service. A single ball failure occurred after this period, leading to fatigue spalling that initiated below the contact surface. Comparisons between unused bearing raceways and those that have experienced service revealed that the microstructures resulting from secondary hardening remain remarkably stable. Plastic flow along the direction of rolling is confined to a shallow zone <2 μm beneath the contact surfaces. Transmission electron microscopy has revealed a new deformation mechanism in these bearing steels, in the form of mechanical twinning at interfaces and prior austenite grain boundaries. It is demonstrated that workhardening occurs to a depth of 1 mm in the raceway that has experienced 30000 h service.

Critical Assessment 13: Elimination of white etching matter in bearing steels

“…59 Butterflies are known to form at high contact stresses even in the M50/M50NiL alloys, 21 but have not been reported in any study from bearings that have experienced service. 60 Indeed, rolling contact fatigue is not a key feature in the failure of aeroengine bearings: the vast majority of operational failures in M50/M50NiL bearings are due to surface distress; [61][62][63] although such distress can initiate cracks that grow by a fatigue mechanism, leading eventually to spalling, the important Bhadeshia and Solano-Alvarez Elimination of white etching matter in bearing steels Materials Science and Technology 2015 VOL 31 NO 9 distinction is that initiation does not begin below the surface where rolling contact stresses are maximal. A longer term solution is to make tougher bearing steels that have a ductile failure mechanism in the stress affected region.…”

Experiment and simulation analysis of tribological and dynamic characteristics in aeroengine hybrid ceramic bearing

“…The most important difference between aeroengine spindle bearing and conventional rolling bearing lies in the harsh operating conditions, such as long-term working at high speed, heavy load, high temperature, complex stress and strict environmental adaptability, which puts forward strict requirements for the main-shaft bearing as a mechanical support and load transfer (Shi et al , 2016; Nygaard et al , 2014). With the rapid development of computer technology, the finite element analysis (FEA) method is gradually being considered in solving engineering problems (Singh et al , 2018; Zhang et al , 2019; Shankar et al , 2020; Fu et al , 2022; Chen et al , 2023).…”

Simulation of the fatigue-wear coupling mechanism of an aviation gear

“…There is a demand for improved performance, reduced weight, and increased temperature resistance in these aviation applications. Although there are many innovative manufacturing techniques, including surface superfinishing and shot peening that increase the life and reliability of these gears [2], aviation gears can fail or lead to disastrous accidents due to fatigue failures [3]. Gear contact fatigue life is one of the main factors determining the time between overhauls (TBO) of aviation transmissions.…”