A complex interdependence of thermal conductivity and lubricity of two solid lubricants to control the tribo-performance of PAEK based composites

Abstract

In this work, a series of four composites was developed by incorporation of two solid lubricants (SLs) (total amount 20 wt % and added in a complementary manner) viz. graphite (well known for thermal conductivity as well as good lubricity) and PTFE (Poly tetra fluoroethylene) (well known for excellent lubricity, but poor thermal conductivity) into PAEK (Poly aryl ether ketone) reinforced with short glass fibres. It was of interest to investigate how these two SLs work together, especially when with increasing contents of PTFE, thermal conductivity (TC) of the composites would decrease and lubricity should increase. The composites were characterized for density, TC and mechanical properties. Tribo-testing was done by varying load, velocity and against mild steel counterface. The composites showed very low wear rates (K0 ≈ 10−16 m3/Nm) and ultra-low coefficient of friction (μ ≈ 0.03). With increase in PTFE contents, wear resistance and also TC decreased indicating TC was a dominating parameter to control the wear of composites. Worn surfaces were studied with scanning electron microscopy (SEM), energy dispersive X ray analysis (EDAX), Raman spectroscopy, XPS (X-ray photoelectron spectroscopy) and wettability analysis to understand the wear mechanisms.