Abstract
This research presents fatigue life test results for several versions of 208-size (40-mm bore) Pyrowear 675 angular contact bearings. Results with different heat treatments of the Pyrowear 675 materials in a hybrid configuration (silicon nitride rolling elements) are compared to all-metal AISI M50, hybrid AISI M50, and hybrid AISI M50NiL configurations. Bearings were tested for rolling contact fatigue life at an applied thrust load of 22,250 N resulting in maximum Hertzian contact stress values of 3.10 (all metal) and 3.55 (hybrid) GPa. Rolling contact fatigue life testing was conducted at 128°C using a gas turbine engine lubricant conforming to MIL-PRF-23699G. All versions of hybrid Pyrowear 675 bearings showed significant improvement in fatigue life compared to baseline M50 and M50NiL bearing materials. After testing, selected bearings were analyzed for tribofilms using Auger electron spectroscopy. Auger electron spectroscopy showed phosphorus-rich tribofilm formation on the Pyrowear 675 bearing contact zones. The results suggest that the tricresyl phosphate antiwear additive used in current gas turbine lubricant formulations positively reacts with Pyrowear 675 surfaces and shows no detrimental effect on fatigue life at the test conditions studied here.
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