In this research work, fabrication, tribological and icrostructural characterization of polyether ether ketone (PEEK)/SiO 2 polymer nanocomposite coatings were investigated. In this order, the amorphous and semi-crystalline PEEK and PEEK/10 vol% SiO 2 coatings were deposited on the plain carbon steel (st37) substrate by means of the electrostatic powder spray technique. The nanocomposite powder was prepared by high energy ball milling. Before milling, to achieve a good dispersion and strong interface, silica nanoparticles were surface modified using a silane coupling agent, (3-glycidoxypropyltrimethoxysilane) and characterized by means of furrier transformed infrared spectrophotometer (FTIR), transmission electron microscope (TEM) and Light transmittance (LT) measurement. The morphological and particle size distribution changes, crystalline structure and thermal behavior of the obtained nanocomposite during milling process were evaluated by scanning electron microscope (SEM), laser particle size analyzer (LPSA), X-ray diffractometer (XRD) and differential scanning calorimeter (DSC), respectively. The electrostatic spray parameters and processing time and temperature to obtain a uniform coating were determined. The coatings were studied in the terms of surface and cross-section quality, crystalline structure, dispersion and distribution of nanoparticles in the polymer matrix and molecular bond structure using the optical and scanning/transmission electron microscopes (OM and SEM/TEM), XRD and FTIR, respectively. The coatings hardness and their adhesion strength were evaluated by Vickers microhardness and pull-off tests. The tribological behaviors of the coatings were investigated using pin-on-disk test. The results indicated that dispersion and distribution of the surface modified nanoparticles were more uniform and homogeneous in PEEK matrix than the unmodified ones. The hardness of the semi-crystalline pure PEEK coatings was higher than the amorphous one but their adhesion strength was lower. However, the hardness and adhesion strength of the nanocomposite coatings improved significantly than the pure PEEK coatings and also, their sensitivity to the crystallinity of the coating decreased remarkably. It was also found that the wear and frictional behavior of the semi-crystalline coatings were better than the amorphous ones. However, the presence of the surface modified silica nanoparticles caused the improvement of wear rate but increase in the friction coefficient. The wear mechanisms of each crystalline and amorphous PEEK and nanocomposite coatings were studied using the SEM observations of wear tracks.
