SLIDING CONTACT PM212 BEARINGS FOR SERVICE TO 700-DEGREES-C

Cylindrical, sliding contact bearings made entirely of the self-lubric ating powder metallurgy composite (PM212) or of superalloy shells line d with clad PM212 were tested in an oscillating mode at temperatures f i-om 25 degrees to 700 degrees C. Tests of 100-hour duration or longer were conducted with the journal oscillating +/- 15 degrees at a frequ ency of 42 cycles/min and at a bearing unit load of 3.45 MPa (500 psi) . Shorter duration tests at various unit loads up to 24.2 MPa (3500 ps i) were also conducted. In comparison tests, bearings lubricated with PM212 had lower friction and superior antiwear characteristics compare d to the baseline unlubricated, superalloy bearings. No galling of PM2 12-lubricated bearings occurred, while severe surface damage including galling occurred, especially at high loads, during the baseline tests . A heat treatment procedure, which dimensionally stabilizes PM212 and thereby minimizes clearance changes during high temperature bearing o peration, is described.