Effect of Counter Surface Roughness on the Wear Mechanism of PTFE and PTFE Based Composites Liners in Aqueous Medium

Abstract: For the past years bearings that use a self-lubricating PTFE-based liner material which replace standard metal-to-metal greased bearings in many aerospace, marine, and hydroelectric applications. When designing a bearing all of the operating parameters including radial and axial loads/pressures, rotational velocity, frequency, operational cycles, and environmental conditions are evaluated and taken into account Polytetrafluoroethylene (PTFE) is an important engineering material. When rubbed or slid against a hard surface, PTFE exhibits a low coefficient of friction but a high rate of wear. These unique properties of the polymer have encouraged many mechanistic and physical examinations of the processes involved in the friction and wear of this polymer. When rubbed against a hard surface, the PTFE chain undergoes scission, creating active groups which chemically react with the counterface. This results in strong adhesion and a coherent transfer film. Experimental work has been carried out considering loads varying at a constant velocity against mirror finish and polished surface. The test has been carried out for four materials of PTFE and its composites in water lubricated condition against EN-24 Steel plates. Duration of each test conducted is one hour. To improve resistance to wear property of PTFE, Glass Fiber is added as a filler material by varying its percentage. Tests were carried out for investigation of tribological properties such as wear rate and coefficient of friction against different surface roughness of counter surface. The results are used to generate friction and wear maps of different value of roughness of counterface of different loads and a relationship between a loads, Surface texture and behavior of PTFE and its composites. Keywords: Surface Texturing, Tribology, Dimples, Polyamide, HDPE, Wear, Friction, Aqueous medium.