Forty-millimeter-bore ball bearings with lead and lead-alloy-coated retainers were operated in liquid hydrogen at 30000 rpm under a thrust load of 1780 Newtons (400 lb). Bearing lives were compared using different (1) lead- and lead-alloy coatings, (2) coating thicknesses, (3) substrate materials, (4) retainer locating surfaces, and (5) plating techniques. Longer bearing run times were achieved using retainers with a lead-tin-copper alloy coating electroplated onto a leaded-bronze material (22.5 hr) and an aluminum-bronze alloy (19.3 hr). Thirty percent of the bearings tested achieved the desired objective of 10 hours. All of the lead-alloy coated retainers exceeded this objective. A coating thickness of at least 36 microns (0.0014 in.) was used for all bearings exceeding the 10-hour goal.

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