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National Advisory Committee for Aeronautics, Technical Notes - Performance of 110-Millimeter-Bore M-1 Tool Steel Ball Bearings at High Speeds, Loads, and Temperatures

Eleven llO-millimeter—bore ball thrust bearings made of Mal tool
steel were operated over a range of DH values product of bearing bore in
mm times speed.in rpm) from 0. 4X106 to 1.54Xlo at mean outer-race tem-
peratures to 678° F. Thrust loads were varied from 1000 to 7000 pounds,
radial loads from 1000 to 4900 pounds, oil flows from 6 to 18 pounds
per minute, and oil inlet temperatures from.lOO° to 5000 F. A synthetic
lubricant of the diester type was used to lubricate the test bearings,
which were equipped with either iron-silicon bronze, silver-plated iron-
silicon bronze, or cast Inconel cages.

Eight of the eleven test bearings failed in fatigue. The life data
for the failed bearings, although not statistically conclusive, indi—
cate that the fatigue life of the M-1 tool steel and diester lubricant
combination may be very much less than the life (based on catalog rat—
ings) for the SAE 52100 steel and mineral oil combination. The fatigue
failures were characterized by deep fissures running perpendicular to
the surface rather than the normally shallow, horizontal pattern. Met—
allurgical examination of four of the failed bearings failed to uncover
any inclusions or structural defects which might have caused the
failures.

Under conditions of continuous oil flow, iron-silicon bronze was
the best of the three cage materials tested. Both iron-silicon bronze
and silver—plated iron-silicon bronze showed negligible wear under con—
ditions of continuous oil flow, but the silver plate blistered on two
of the four silver—plated cages tested, indicating that it may be diffi-
cult to consistentlyo obtain a bond strong enough to withstand tempera-
tures much above 4.500 F. Cast Inconel with a preformed surface film of
nickel oxide is not satisfactory as a cage material for a bearing of
this type operating at high DN values and temperatures below 6000 F.

In several oil-interruption tests no significant differences in the
time to failure were obtained in bearings equipped with iron-silicon
bronze and silver—plated iron-silicon bronze cages.