Friction and wear characteristics of metal sulfides and graphite-filled PTFE composites under dry and oil-lubricated conditions

Abstract

Five kinds of polytetrafluoroethylene (PTFE)-based composites, pure PTFE, PTFE ϩ 30(v)% MoS 2 , PTFE ϩ 30(v)% PbS, PTFE ϩ 30(v)% CuS, and PTFE ϩ 30(v)% graphite (GR) composites, were first prepared. Then the friction and wear properties of these PTFE composites, sliding against GCr15-bearing steel under both dry and liquid paraffin-lubricated conditions, were studied by using an MHK-500 ring-on-block wear tester. Finally, the worn surfaces and the transfer films of the PTFE composites formed on the surface of GCr15 bearing steel were investigated by using a scanning electron microscope (SEM) and an optical microscope, respectively. Experimental results show that filling with MoS 2 , PbS, CuS, or graphite to PTFE can reduce the wear of the PTFE composites by two orders of magnitude compared to that of pure PTFE under dry friction conditions. However, the friction and wear-reducing properties of these PTFE composites can be greatly improved by lubrication with liquid paraffin. Investigations of transfer films show that MoS 2 , PbS, CuS, and graphite promote the transfer of the PTFE composites onto the surface of GCr15-bearing steel under dry friction conditions, but the transfer of the PTFE composites onto the surface of GCr15-bearing steel can be greatly reduced by lubrication with liquid paraffin. SEM examinations of worn surfaces show that with lubrication of liquid paraffin, the creation and development of the cracks occurred on the worn surfaces of the PTFE composites under load, which reduces the load-supporting capacity of the PTFE composites. This would lead to the deterioration of the friction and wear properties of the PTFE composites under higher loads (Ͼ600N).

Tribofilm Formation and Run-In Behavior in Ultra-Low-Wearing Polytetrafluoroethylene (PTFE) and Alumina Nanocomposites

“…However, PTFE has been excluded from many tribological applications due to its high wear rate (∼10 −4 mm 3 /Nm) under engineering sliding conditions (Gong,et al (5), (6); Blanchet and Kennedy (7). A variety of filler compositions, shapes, and sizes have been added to PTFE, resulting in wear reductions ranging from a few percent to up to five orders of magnitude (Gong,et al (5), (6); Blanchet and Kennedy (7); Sawyer, et al (8); Tanaka and Kawakami (9); Bahadur and Tabor (10); Zhang, et al (11); Li, et al (12), (13); Khedkar,et al (14); Chen, et al (15); Klaas,et al (16); Burris and Sawyer (17); Lai, et al…”

Tribological and thermal properties of hexagonal boron nitride filled high‐performance polymer nanocomposites

“…This increases the contact area between the asperities and the pin surface, causing more dragging or lateral force during sliding wear resulting in higher COF . Similar increasing trend in coefficient of friction was found for the polyetheretherketone (PEEK)/CuO, PTFE/Al 2 O 3 , PTFE/graphite, which was attributed to the increased contribution to the deformation component of friction by the hard CuO particles acting as third body abrasion during sliding against the composites. Sometimes, coefficient of friction of the composites might decrease, if these hard particles help in smoothing the countersurface.…”

Wear reduction mechanism of graphite and MoS2 in epoxy composites

“…One of the main results is that graphite can be used in polymer materials as friction-reducing phase to increase the wear resistance and to decrease the friction coefficient of the polymers [5][6][7]14]. In this study, a similar conclusion can be drawn, as shown in Fig.…”

“…Gong et al [5] and Zhang et al [6] found that both graphite powder and MoS 2 powder have the effect on reducing the wear loss of PTFE material when they being added in PTFE. These researchers also discovered that graphite powder can effectively lower the friction coefficient of PTFE while MoS 2 powder cannot.…”