Some Problems in High-Temperature Bearing Materials

Bearings which are lubricated by process fluids are being considered for application at temperatures exceeding 1000 deg F. Although under static conditions, nickel-base alloys offer an excellent combination of strength and surface stability, these alloys may change dimensions during long-time bearing applications. It is shown that if creep strength is inadequate, high shaft speeds can lead to significant radial growth. Dimensional stability is also affected by precipitation. A detailed study of Hastelloy X heated in the temperature range 1100–1400 deg F reveals that precipitation occurs even after many hundreds of hours exposure, resulting in dimensional changes of up to 3 microin. per hr of exposure. Means of alleviating these problems are discussed.