Experimental Test Program for evaluation of solid lubricant coatings as applied to compliant fuel gas bearings to 315/sup 0/C
An experimental apparatus and test procedure are developed to compare the performance of two solid lubricant coatings for air-lubricated compliant foil gas bearings in the temperature range of 25/sup 0/C to 315/sup 0/C. Polyimide-bonded graphite fluoride (PBGF) and silicate-bonded graphite with cadmium oxide additive (SBGC) are tested extensively for durability and frictional characteristics. A partial arc bearing, constructed of Inconel X-750, is coated on the bore with one of these coatings. The solid lubricant protects the bearing and journal surfaces at times when sliding contact will occur. A journal made from A286 stainless steel is used. The foil is subjected to repeated start/stop cycles under a 14 KPa (2 psi) bearing unit loading. Sliding between the bearing and journal occurs during liftoff and coastdown at surface velocities not exceeding 6 m/sec (3000 rpm). Testing continues until 9000 start/stop cycles are accumulated or high starting torque is present indicating coating failure. Failure is defined as sufficient metal to metal contact to cause surface damage. Performance comparisons reveal that although both coatings survive thousands of start/stop cycles, only the PBGF coated bearing achieves the specified 9000 start/stops. There is enough wear on the SBGC coated bearing to warrant termination of the test prior to 9000 start/stop cycles due to coating failure. The frictional characteristics of the PBGF are better at the elevated temperatures than at lower temperatures: a marked increase in sliding friction occurs as the temperature decreases. The SBGC maintains relatively constant frictional characteristics independent of operating temperature.
- Research Organization:
- Case Western Reserve Univ., Cleveland, OH (USA)
- DOE Contract Number:
- AI01-80CS50194
- OSTI ID:
- 6063194
- Report Number(s):
- DOE/NASA-0030-1; NASA-CR-174837; ON: DE85006579
- Country of Publication:
- United States
- Language:
- English
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