Tribological properties of polytetrafluoroethylene at cryogenic temperatures

Many cryogenic applications like bearings, pumps, valves, seals etc cannot be lubricated by conventional means with oils and grease because the cryogenic temperature range is far below the pour points of these lubricants. For these applications, solid lubricants like poly tetra fluoro ethylene (PTFE), molybdenum disulphide (MoS2), amorphous carbon, polymers, etc. are used. In this study, experiments are carried on plain and carbon filled PTFE materials to study their tribological properties at cryogenic temperature. A cryotribometer has been designed and developed which works on the principle of pin on disc wear type tribometer according to ASTM standard (ASTM G 99–95). Both plain and carbon filled PTFE pins were made to slide for 10 minutes over an abrasive surface rotating at 400 rpm under the applied load of 10N. Experiments were carried both at room and cryogenic temperatures. The effect of cryogenic temperature on the wear, frictional force and coefficient of friction are presented.