C. Becker-Willinger, P. Kalmes, D. Bentz
INM - Leibniz Institute for New Materials, Germany
pp. 484 - 487
Keywords: solid lubricant, boron nitride, corrosion protection, polyimide, composite
A new class of multifunctional low friction coatings combining a low coefficient of friction of µ < 0.1 over 1 km sliding distance with high corrosion protection ability > 1000 h in the neutral salt spray test on mild steel have been developed. The coatings possess a fine textured composite morphology achieved during the spray application and thermal curing process. Flake type hexagonal boron nitride as solid lubricant with appropriate surface modification and a particle size in the submicrometer range has been dispersed in a polyimide matrix together with high aspect ratio platelet shaped SiO2 particles having a thickness in the range of 200-400 nm in order to improve the barrier properties against diffusion of corrosive substances. The fine textured morphology has been proven by means of scanning electron microscopy on polished cross sections. The tribological properties of the resulting fine structured coatings have been investigated in dependence on the boron nitride flake and the SiO2 platelet content. It could be shown that at certain concentrations the combination of the different platelet additives provide a synergistic effect with respect to minimum achievable coefficient of friction and maximum achievable corrosion protection effect.