Role of micro and nano-particles of hBN as a secondary solid lubricant for improving tribo-potential of PAEK composite

Abstract

Hexagonal boron nitride (hBN), also called as white graphite is known to exhibit excellent combination of thermal, thermo-physical, mechanical and tribological properties as a filler (solid lubricant). Not much reported on its potential as nano-particles. In this study, micro and nanocomposites of hBN were prepared with the combination of polyaryl ether ketone (PAEK) as a matrix (50%), short glass fibers (GF) (30%) as a reinforcement and natural graphite (10%) as a primary solid lubricant (SL) apart from hBN particles (10%) as a secondary SL. The micro-composite (MC) and nano-composite (NC) contained hBN particles in micron size and combination of micron and nano size (7 and 3%) respectively. The NC exhibited enhanced mechanical and tribological performance compared to the MC. Tribological tests were performed on a pin-on-disc tribometer under dry sliding regime to evaluate PVlimit (pressure x velocity) values. Influence of load and sliding speed on the friction coefficient (μ) and specific wear rate (K0) on the composites was investigated. The composites showed PVlimit of 100 MPa m/s along with μ in the range of 0.04–0.08 and K0 in the range of 2.5–7 × 10− 16 m 3/Nm. It was also found that the superior performance of NC was due to more efficient, thin and coherent film transferred on the disc. Moreover, structural and morphological changes were studied with Raman spectroscopy and scanning electron microscopy (SEM). Wear mechanism of the worn surfaces were discussed using XPS (X-ray photoelectron spectroscopy).