Tribological properties of polytetrafluoroethylene-based composite in different lubricant media

A kind of polytetrafluoroethylene (PTFE) based multilayer self-lubricating composite material, made of a steel backing, a sintered porous bronze middle layer and a surface layer consisting of a mixture of PTFE and Pb powders, was prepared. The friction and wear properties as well as the limiting PV (pressure times velocity) values of the PTFE composite sliding against stainless steel with lubrication of 10* gasoline engine lubricant oil, glycerol and triethanolamine were studied. An MPV-1500 friction tester with a steel axis rotating on a sliding bearing was used. The friction coefficient was determined by measuring the friction torque during testing, while the wear was detected by the weight loss of the PTFE composite bearing after each test. The worn surfaces of PTFE composite and the steel counterface were then examined by using electron probe microanalysis (EPMA). Experimental results show that the friction and wear properties as well as the limiting PV value of PTFE composite can be greatly improved using the above lubricant media. The limiting PV value of this PTFE composite is above 120 MPa m s^-1 under lubrication of these kinds of lubricant media, which is about 100 times that of pure PTFE in dry friction conditions. EPMA investigations show that the wear and the transfer of PTFE composite onto the steel counterface were significantly reduced, but still took place.