Long-Term Lubricity of Carbon Nanoparticle Coatings on Periodically Laser-Patterned Metallic Surfaces

The lubricity of coatings made from diferent types of carbon nanoparticles such as carbon onions, carbon nanohorns and carbon nanotubes is investigated on line-patterned AISI 304 stainless-steel substrates using ball-on-disc tribometry over 200,000 sliding cycles. Picosecond direct laser interference patterning is used to create line-patterns on the substrate surfaces which are subsequently coated by electrophoretic deposition. Friction testing is conducted on as-processed surfaces in linear reciprocal mode at a normal load of 100 mN with alumina and 100Cr6 as counter body materials. The resulting wear tracks on the substrates as well as wear scars on the counter bodies are characterized by scanning electron microscopy as well as energy-dispersive X-ray spectroscopy. Tribometry shows that CNTs have the ability to maintain lubricity against both counter body materials. CO and CNH coatings sustain their lubricity against 100Cr6 over the full test duration but fail against alumina. In contrast to alumina, substantial carbon transfer from the substrate surface to 100Cr6 counter body is observed