Tribological performance of a 3-D carbon-carbon composite Part II: Vacuum eEnvironment
- Lockheed Martin Astronautics Co., Denver, CO (United States); and others
The tribological performance of a carbon-carbon (C-C) composite tested under ambient-vacuum (6.7 x 10{sup {minus}7} Pa) and elevated-temperature (1000{degrees}C) vacuum (67 x 10{sup {minus}7}Pa) conditions was determined using a reciprocating flat-on-pin test technique. The coefficient of friction was observed to decrease with increased applied load, conforming to solid lubrications theory. Environment had a pronounced effect on the tribological performance of C-C. Vacuum tests at room temperature resulted in reduced coefficients of friction compared to ambient air tests. This behavior is presumably due to condensation of vacuum system impurities and outgassed intercalants from the graphite (Gr) in the C-C onto the cold wear surface, which acted as solid lubricants at the wear interface. In contrast, 1000{degrees}C vacuum tests resulted in dramatic increases in coefficients of friction. This was attributed to outgassing of intercalants within the Gr and condensation onto cold vacuum system components away from the wear surface. The latter test conditions also resulted in much greater wear damage to the stationary pin with removal of carbon matrix material exposing Gr fibers, which were subsequently fractured. Thus, elevated temperature vacuum conditions provide a harsh tribological environment for C-C composites. 12 refs., 5 figs., 1 tab.
- OSTI ID:
- 518232
- Journal Information:
- Lubrication Engineering, Journal Name: Lubrication Engineering Journal Issue: 2 Vol. 52; ISSN LUENAG; ISSN 0024-7154
- Country of Publication:
- United States
- Language:
- English
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