Development of hydrophobic PTFE coatings by electrophoretic deposition and heat treatment for low-friction applications

Abstract This study investigated the possibility of obtaining polytetrafluoroethylene (PTFE) coatings on Ti–6Al–4V titanium alloy substrates using electrophoretic deposition (EPD) and heat treatment. Different polyelectrolytes involving chitosan (CS), sodium alginate (SA), and PAZO were used, which enabled the deposition of PTFE particles of different sizes. Heat treatment changed the morphology of PTFE from particles to continuous coatings with high open porosity. In some of them, a network of micro-cracks was observed. PTFE coatings including a mixture of nanoparticles and submicroparticles deposited without mixing with CS or SA showed very high adhesion to the substrate and relatively high scratch resistance. The coatings were characterized by a high water contact angle, i.e., 145.4 ± 1.1° and 133.4 ± 4.0° for those deposited with CS and SA, respectively. Until the continuity of the coating was ensured at the friction contact point, the coatings showed very good sliding properties and a thin tribofilm was formed on the Al 2 O 3 ball surface. The friction coefficient was 0.09 and 0.11 for the coatings obtained with CS and SA, respectively. However, the wear resistance of the coatings was poor and they were subject to significant deformation and intense abrasion. This work contributes to the understanding of PTFE coating fabrication processes based on EPD and heat treatment and shows that it is possible to obtain highly hydrophobic coatings exhibiting low-friction properties at low loads.