Rolling-element fatigue tests were conducted with 120-mm bore angular-contact ball bearings made of AISI M-50 steel with a synthetic paraffinic oil, a fluorocarbon, and a 5P4E polyphenyl, ether. At 600 deg F under a low-oxygen environment, the synthetic paraffinic oil and the fluorocarbon gave bearing lives approximately 14 and 3 times AFBMA-predicted (catalog) life, respectively. With the polyphenyl ether, bearing life was less than AFBMA-predicted (catalog) life in an air environment at 600 deg F. At temperatures of 400 and 500 deg F with the synthetic paraffinic oil there was no statistical difference in life from those bearings tested with the same fluid at 600 deg F. For the synthetic paraffinic oil and the fluorocarbon, bearing fatigue was subsurface initiated. For the polyphenyl ether, bearing failure was mainly from surface distress, wear, and superficial pitting.

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