Improving Tribological Performance of Flame-Sprayed Polyamide Coatings via Incorporation of Oil-Containing Microcapsules

Abstract

In order to improve the tribological performance of polyamide 11 (PA11) coatings, oil-containing microcapsules, consisting of the heat-resistant polysulfone (PSF) as the wall material and the polyalphaolefin 40 (PAO40) oil as the core material, were fabricated by the solvent evaporation method and then incorporated into PA11 coatings via the flame spray process. The microstructure and tribological performance of PA11 coatings were investigated before and after the incorporation of PAO40@PSF microcapsules. Results show that the synthesized PAO40@PSF microcapsules had an average diameter of 70 μm and exhibited good heat stability up to 380°C. Surface and cross-sectional observations of coatings reveal that PAO40@PSF microcapsules were uniformly embedded in the PA11 coating. The incorporation of PAO40@PSF microcapsules had remarkable influence on the tribological performance of PA11 coatings. Specifically, comparing the PA11/PAO40@PSF composite coating containing 10 wt.% microcapsules to the pure PA11 coating, the friction coefficient and the wear rate were reduced by 67% and 45%, respectively, under the normal load of 370 N and at the rotational speed of 100 r/min. However, further increase in the content of PAO40@PSF microcapsules up to 15 wt.% resulted in a spike in the wear rate due to the decreased coating hardness and bonding strength.