Friction reduction and wear resistance of electro-co-deposited inorganic fullerene-like WS₂ coating for improved stainless steel orthodontic wires

Abstract

A new type of composite metal–nanoparticle coating that significantly reduces the friction force of various surfaces, particularly archwires in orthodontic applications, is demonstrated. The coating is based on electrodeposited Ni film impregnated with inorganic fullerene-like nanospheres of tungsten disulphide. The first encouraging tests have shown reduction of up to 60% of the friction force between coated rectangular archwires and self-ligating brackets in comparison with uncoated archwires. The coating not only significantly reduces friction of commercial archwires but also maintains this low value of friction for the duration of the tests in comparison to archwires coated with nickel film without the nanoparticles. The coated surfaces of the wires were examined by scanning electron microscopy equipped with energy dispersive analyzer and by x-ray powder diffraction methods before and after the friction tests. Using these analyses, it was possible to qualitatively estimate the state of the Ni+IF-WS2 coating before and after the friction test compared to Ni coated wires without IF-WS2.

Metallic Films with Fullerene-Like WS2 (MoS2) Nanoparticles: Self-Lubricating Coatings with Potential Applications

“…The W to S ratio is found to be 1:1.7 in the electrodeposited fi lm, which is in accordance with previous studies [ 2,12 ] . The W/Cr ratio was found to be about 1/30 confi rming that IF-WS 2 nanoparticles made some 3-4% of the fi lm content.…”

“…In the case of the IF nanoparticles impregnated into metal [ 2,12 ] or polymer fi lms [ 13 ] , the nanoparticles are gradually released by the wear and are therefore initially confi ned to the relevant tribological interface. This release is possibly accompanied by damage and exfoliation of the nanoparticles.…”

“…In previous studies [ 2,12 ] , nickel and cobalt fi lms containing ca. 5% of IF-WS 2 nanoparticles were shown to exhibit strong a self-lubricating effect.…”

“…The friction coeffi cient of the softer Ni-P fi lms is somewhat smaller (ca. 0.06-0.07) [ 12 ] . Nonetheless, the IF impregnation in the chromium rich coating provides satisfactory tribological behavior which is uncommon for such hard coatings.…”

Coating and Surface Treatments on Orthodontic Metallic Materials

“…Investigations carried out in this area are in vitro in nature, but results are promising enough to incorporate some of these treatments into orthodontic practice. Redlich et al [75] used electrodeposition to coat orthodontic archwires to reduce friction. The coating is based on a Ni film impregnated with inorganic fullerene-like nanospheres of tungsten disulphide.…”