Evaluation of several space lubricants using a vacuum four-ball tribometer

The friction and wear behavior of seven space lubricants was investigated u nder boundary lubrication conditions using a vacuum four-ball tribometer. T hree of the lubricants were perfluoropolyethers (143AC, S-200, and Z-25). T hree were synthetic hydrocarbons (a multiply alkylated cyclopentane, 2001a) , and a formulated version with an antiwear and an antioxidant additive (20 01). The third hydrocarbon was an unformulated polyalphaolefin (PAO-100). A n unformulated silahydrocarbon (SiHC) was also evaluated. Test conditions i ncluded: a pressure <6.7 x 10(-4) Pa, a 200N load, a sliding velocity of 28 .8 mm/sec (100 rpm), and room temperature (similar to 23 degrees C). The we ar rate for each lubricant was determined from the slope of wear volume as a function of sliding distance. The lowest wear rate (0.033 x 10(-9) mm(3)/ mm) was obtained with the silahydrocarbon. The formulated synthetic hydroca rbon had a wear rate of 0.037 x 10(-9) mm(3)/mm, which was a 36 percent red uction compared to the unformulated fluid. The polyalphaolefin had the high est wear rate of the non-PFPE fluids. Of the perfluoropolyethers (PFPEs), w ear rates decreased by about 50 percent from Z-25 (1.7 x 10(-9) mm(3)/mm) t o S-200 (0. 70 x 10(-9) mm(3)/mm) to 143AC (0.21 x 10(-9) mm(3)/mm).