Bending fatigue strength of aerospace quality gear steels at ambient and elevated temperatures
Timothy Lisle, Christian P. Little, Chris Aylott, Brian Shaw
Abstract
Gear bending fatigue testing was conducted on six commercial aerospace quality steels, in the carburised, shot-peened and super finished condition, establishing S-N curves at ambient and elevated temperatures, providing evidence of higher than predicted strength established in accordance with ISO 6336:2006. At elevated temperatures, a systematic drop in mean strength was experienced for all candidate steels. Detailed fractography established the fracture initiation site, unique to each steel, illustrating a propensity for surface initiation in the finite life region and subsurface beyond the knee point, whilst certain grades displayed a distinct change in the location of fracture initiation at elevated temperatures.