Study on friction and wear properties of metal sulfides and graphite filled PTEE composites

The friction and wear properties of polytetrafluoroethylene (PTFE) composites filled with MoS₂, CuS, PbS, and graphite (addition quantity is 30 vol% in volume fraction) sliding against GCr15 bearing steel under dry friction conditions were studied by using an MHK-500 ring-block wear tester (Timken wear tester), then the wear debris and the frictional surfaces of these PTFE composites were examined by using a scanning electron microscope (SEM) and an optical microscope. Experimental results show that graphite reduces the friction coefficient of the PTFE, but MoS₂, CuS and PbS increase the friction coefficient of the PTFE. Meanwhile, filling PTFE with MoS₂, CuS, PbS, or graphite can reduce the wear of PTFE by 2 orders of magnitude, but the wear-reducing action of PbS is the most effective, while that of MoS₂ is the worst. SEM and optical microscope investigations show that the MoS₂, CuS, PbS, and graphite not only prevent the banded structure of PTFE from destruction, but also enhance the adhesion of the transfer films to the counterfaces, so they greatly reduce the wear of the PTFE.