Methods: NiTi substrate coating with IF WS2 nanoparticles, which are known for their superior lubricant qualities, was carried out in electroplating procedure. Cobalt solution with dispersed WS2 nanoparticles was used for electroplating of the NiTi archwires which served as the negative electrode. Scanning electron microscopy (SEM) was used for the analysis of the coating morphology. Elemental composition of the plating was determined using energy dispersive x-ray spectroscopy (EDS). Friction evaluation was done using tribological tests, atomic force microscope (AFM) lateral force analysis and a new in-situ SEM analyzing method.
Results: A significant reduction of the friction force of the coated NiTi was detected in all three methods. Tribological tests presented a significant reduction of the friction coefficient (from a value of 0.25 in the case of the pristine wire to 0.09 for the Co-IF coated wire). AFM analysis showed 4 to 7 times less friction of the coated NiTi in relation to the uncoated substrate.
Conclusion: The unique property of superplasticity of NiTi alloys provides remarkable advantages in orthodontics and other medical disciplines. Co-IF-WS2 nanoparticles coating of Nickel-Titanium alloy demonstrated a significant friction reduction and thus offers low friction NiTi archwires and could also be applied to other medical devices.