Solid Lubricant Properties of Carbon Nanomaterials and Their Polymeric Composite Coatings

Co-continuous alumina/aluminum based composites with excellent physical and mechanical properties offer great potentials for lightweight, wear resistant, and high temperature applications. The development of suitable coating materials will provide low coefficient of friction to extend life under different environments for aerospace applications. In this study, carbon powders containing diamond clusters or fullerene were burnished on to the surface of alumina/aluminum substrates. These powders and c-nanofiber materials were also incorporated in polymer matrices and were spin coated onto the alumina/aluminum composites. Performance of a newly developed aerospace thermoplastic material and two currently used aircraft canopy materials were chosen as the matrix materials for comparison. Tribological evaluation of alumina/aluminum composites with and without coatings was performed against 440C stainless steel balls using pin-on-disc wear tests at 0.2 m/s sliding velocity, 0.25 N, and 0.75 N normal load. The morphology and wear tracks on the composite discs and material transfer to the steel balls were examined using a scanning electron microscope. Raman analysis was performed to determine the chemical bonding of the as-burnished materials and the changes after wear tests. The effects of reinforcement or lubricant material, polymer matrix material and test environment on the friction behavior will be presented.