Adhesiveness of TiO2 PVD coating on electropolished stainless steel 17–4 PH orthodontic bracket

Abstract

Performance of stainless steel 17-4 PH as the orthodontic bracket can be improved by titanium dioxide (TiO _2 ) coating. In order to produce a good quality of the coating layer, the substrate had to be smooth and free from any contaminants. The electropolishing method was used to clean bracket’s surface from oxides substances which formed during sintering by reducing its surface roughness. Bath temperature and electropolishing time were varied to 30 °C and 70 °C, for 15 and 25 min, respectively. Those differences in electropolishing condition would affect the final surface’s roughness of the substrate. The atmosphere during PVD was controlled using oxygen and argon gases with the flowing rate ratio of 10:90 sccm and 50:50 sccm, and these gases would affect TiO _2 coating mechanical properties. The lowest roughness of 0.99 μ m and the highest roughness of 2.85 μ m were obtained after electropolishing. The coating quality on the substrates with different roughness was assessed through coating adhesivity on the substrate by micro Vickers qualitatively. The results showed that the TiO _2 coating layer on the substrate with a lower roughness had better adhesivity rather than on the substrate with higher roughness.

Keywords

• SS 17–4 PH
• orthodontic bracket
• electropolish
• PVD
• TiO2
• coating