Chapter 20 - Surface engineering with micro- and nanosized solid lubricants for enhanced performance of polymer composites and bearings

Abstract

This chapter elaborates on the need for surface tailoring of tribocomposites with solid lubricants rather than their inclusion in the bulk. The first part presents the details of fabrication of surface-engineered composites based on commingled yarns of carbon and polyether-ether-ketone (PEEK), which is a novel method to eliminate some existing limitations in manufacturing bidirectionally reinforced composites. The details of the process of developing surfaces containing various powdery lubricants such as polytetrafluoroethylene (PTFE), MoS2, graphite, etc. are discussed. Since PTFE on the top surface proved as the most promising lubricant in preliminary studies, it was explored in various forms such as wool, short fibers of various lengths, long fibers, etc. to investigate the benefits endowed by surface tailoring for further studies. Since the maximum performance enhancement (both mechanical and tribological) was observed due to the long PTFE fibers, bearing was fabricated by proper placement of PTFE fibers in commingled yarn composite of PEEK and carbon fabric (CF). Two bearings with and without surface modification were evaluated under different operating parameters. It was observed that CF at an angle of 45° led to the best combination of friction and wear performance. PTFE fiber inclusion removed the stick-slip problem associated with PEEK apart from reducing the coefficient of friction from 0.6 to 0.12 and enhancing wear resistance approximately by 70 times. The bearing thus proved very effective for dry situations with a very good combination of friction, wear and mechanical properties.