Effect of rare earth compounds as fillers on friction and wear behaviors of PTFE-based composites

Abstract

ABSTRACT:The friction and wear behaviors of polytetrafluoroethylene (PTFE)-based composites filled with rare earth compounds CeO 2 , CeF 3 , and La 2 O 3 in volume content from 5 to 30% sliding against GCr15 bearing steel under dry friction conditions were evaluated by using an MHK-500 ring-block wear tester. The wear debris and the worn surfaces of the PTFE composites were investigated by using a scanning electron microscope (SEM), whereas the transfer films of the PTFE composites formed on the surface of GCr15 bearing steel were examined by using an optical microscope. Experimental results show that the antiwear properties of the PTFE composites can be improved greatly by filling PTFE with different contents of CeO 2 , CeF 3 , and La 2 O 3 , and that the wear of the PTFE composites can be decreased by one to two orders of magnitude compared with that of pure PTFE. The wear of the CeF 3 -filled PTFE composite decreases with the increase of the content of CeF 3 from 5 to 30 vol %, but its friction coefficient increases with the increase of the content of CeF 3 in PTFE. When the content of CeO 2 in PTFE is 15 vol %, the friction and wear properties of CeO 2 -filled PTFE composite are the best. But when the content of La 2 O 3 in PTFE is between 15 and 20 vol %, the PTFE composite filled with La 2 O 3 exhibits excellent friction and wearreducing properties. Microscope investigations show that rare earth compounds CeO 2 , CeF 3 , and La 2 O 3 in PTFE not only inhibit the large-scale destruction of the banded structure of PTFE but also enhance the adhesion of the transfer films of the PTFE composites to the surface of GCr15 bearing steel, so they greatly reduce the wear of the PTFE composites. With the increase of the content of CeO 2 , CeF 3 , and La 2 O 3 in PTFE, the actions with which the rare earth compounds inhibit the large-scale destruction of the banded structure of PTFE are enhanced; so the wear of the PTFE composites decreases. Meanwhile, because CeO 2 -and La 2 O 3 -filled PTFE composites can easily form uniform transfer films on the surface of GCr15 bearing steel, the friction and wear-reducing properties of CeO 2 -and La 2 O 3 -filled PTFE composites are better than those of CeF 3 -filled PTFE composites under dry friction conditions.

A Review of Surface Treatments for Sliding Bearings Used at Different Temperature

“…Fabrics were treated with rare earths CeO 2 , LaCl 3 , La 2 O 3 and CeF 3 by Shen, Zhan and some scholars, and their friction, wear properties and bonding properties of the joint bearings with the modified rare earths were studied. The results shown that the bonding strength was higher under the action of rare earths, the film formation is faster, and the coefficient of friction is generally less than 0.1 [13][14][15][16]. Liners and adhesive glue as the main component cannot be used at medium and high temperatures, and the bonding liner method is generally applicable to small thick-walled sliding bearings, which has certain limitations for medium and large sliding bearings.…”

Friction and wear of rare earths modified carbon fibers filled PTFE composite under dry sliding condition

“…It is suggested that, in friction process, La Oxide (La 2 O 3 ) and La Fluoride (LaF 3 ) will be produced in tribochemical reaction because the element La exists on the frictional interface. La Oxide and La Fluoride both have low hardness and excellent lubrication properties [17]. Under dry sliding condition, these two La compounds can act as lubrication to CF/PTFE composites; therefore, the tribological properties of the composite are improved.…”

Synthesis and Characterization of Novel NiW–CeO2 Composite Coating with Enhanced Corrosion and Wear Resistance

“…Among the various metal-oxide reinforcement particles, CeO 2 can be attractive due to its special physical and chemical characteristics. CeO 2 particles have been used as fillers for fabricating polytetrafluoroethylene-based composites where the tribological properties of the fabricated composites were improved significantly at high temperatures [21][22][23]. The co-deposition of CeO 2 particles with Ni has been reported in a few articles.…”