Development of Tribologically Optimized Surface Coatings with Micro and Nano Particles

Abstract

This paper is focused on the tribological behaviour of epoxybased coatings applied to metal substrates. Aramid particles, nanometer-sized Titanium dioxide (TiO 2 ), graphite and Polytetrafluoroethylene (PTFE) served as filler materials. Under sliding conditions, incorporation of Aramid particles to the graphite and TiO 2 filled composites improved the wear resistance significantly, but it slightly increased the coefficient of friction (cof). Under fretting wear conditions, 10 vol.% Aramid particles filled composite showed the lowest wear rate and cof. To further improve the wear performance, PTFE (2 -6 vol.%) was introduced to the above-optimized composition (10 vol.% Aramid particles, graphite and TiO 2 ). However, both the sliding and fretting wear resistance was impaired, and cof was increased. Deterioration of the mechanical properties and the friction films were attributed to the unusual trend. Finally, the optimal composition for epoxy-based coatings was determined as 10 vol.% Aramid particles together with graphite and nano-TiO 2 filled composite.Keywords: Aramid, epoxy, nanocomposite, wear and friction, sliding, fretting Im Rahmen dieser Arbeit wird das tribologische Verhalten von polymeren Gleitschichten auf Epoxidharzbasis, welche mit Aramidpartikeln, nanoskaligem Titandioxid (TiO 2 ), Graphit und Polytetrafluorethylen (PTFE) gefüllt sind, näher betrachtet. Unter Gleitverschleißbedingungen wird die Verschleißfestigkeit von graphitund TiO 2 -gefüllten Verbunden durch die Zugabe von Aramidpartikeln weiter verbessert, während sich allerdings der Reibungskoeffizient leicht erhöht. Unter Schwingverschleißbedingungen zeigte der mit 10 vol.% Aramid gefüllte Verbund den günstigsten Reibungskoeffizienten und die niedrigste Verschleißrate. Um die tribologischen Eigenschaften weiter zu verbessern, wurde diesem Verbund dann nochmals 2-6 vol.% PTFE zugemischt. In diesem Falle kam es jedoch zu einer Verschlechterung, sowohl des Gleitverschleiß-als auch des Schwingverschleißverhaltens. Der Grund hierfür lag in der Herabsetzung der mechanischen Werkstoffeigenschaften. Die im Rahmen dieser Arbeit optimale Zusammensetzung der Gleitschicht war, in Kombination mit Graphit und nanoskaligem TiO 2 , ein mit 10 vol.% aramidpartikelgefüllter Epoxydharz.

A synergistic effect of nano‐Tio2 and graphite on the tribological performance of epoxy matrix composites

“…8(b)] in agreement with a previous investigation. 5 The formation of the transfer film on the steel counterpart at high sliding velocity can be assigned to the increased temperature in the contact surfaces, which enhances the plastic deformation of the epoxy resin and thus the adhesion of the resin to the counterpart. 21 The transfer film, serving as a stress reducer, 12 is believed to contribute to the wear reduction at higher sliding velocities for the neat epoxy (>1 m/s) [ Fig.…”

“…The compositions were cured in an oven for 8 h at 808C, followed by 8 h at 1408C. This mixing process proved to be effectively in distributing nanoparticles in the matrix, 5 which is the prerequisite for the unique features of a nanocomposite. For graphite/epoxy, the mixing process was done without high disc rotation speed.…”

“…8,11 The lubricants help to form transfer films between the subsurfaces during sliding, thus decreasing the frictional forces and lowering the mechanical stress and wear of the polymer surface. 5,12 The combination of reinforcements and lubricants commonly endows a polymeric material with an improved wear characteristics, which cannot be realized with one component only. 1,2,5,13 In recent years, nanometer-sized mineral particles have been widely introduced to the polymer matrix composites for tribological studies.…”

“…1,2,5,13 In recent years, nanometer-sized mineral particles have been widely introduced to the polymer matrix composites for tribological studies. 1,2,4,5,9,13 In comparison with the conventional microscale particles, nanoparticles proved to have some special advantages for tribological applications 1,2,4,9,14 : (1) lower abrasiveness due to its reduced angularity; (2) a remarkable reinforcing effect, i.e., the enhanced modulus, strength, and toughness simultaneously; (3) better adhesion between the nanoparticles and the matrix due to its higher specific areas; and (4) a lower content of filler needed.…”

Grafting of nano-TiO2 onto flax fibers and the enhancement of the mechanical properties of the flax fiber and flax fiber/epoxy composite

“…Unfortunately, no more information regarding the distribution and content of the nano-particles on the natural fibers or the working mechanisms and effects of nano-particles on the properties of the PMCs were reported in that paper. Nanometer-sized TiO 2 is a typical nanoparticle used for polymer based nano-composites, and a low content of nano-TiO 2 could lead to pronounced enhancement in strain, strength and modulus of an epoxy resin system [26]. In addition, abundant hydroxyl groups on the nano-TiO 2 surfaces [27,28] are expected to facilitate the grafting to the flax fiber when assisted with a silane coupling agent.…”