Corrosion performance and mechanical stability of 316L/DLC coating system: Role of interlayers

• Published in: Surface & coatings technology Vol. 204; no. 24; pp. 3986 - 3994
• Main Authors: Azzi, M., Amirault, P., Paquette, M., Klemberg-Sapieha, J.E., Martinu, L.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-09-2010; Elsevier
• Subjects: Adhesion; Adhesive strength; Applied sciences; Austenitic stainless steels; Chemical vapor deposition; Coating; Corrosion; Corrosion environments; Cross-disciplinary physics: materials science; rheology; Diamond-like carbon DLC; Diamond-like carbon films; EIS; Electrochemical impedance spectroscopy; Exact sciences and technology; Interlayers; Materials science; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; Physics; Production techniques; Silicon nitride; Stability; Stainless steel 316L; Surface treatment; Surface treatments; Stainless steel 316L; Corrosion; Adhesion; EIS; Diamond-like carbon DLC; Silicon nitride; Interfacial layer; Austenitic stainless steel; Stability; Synthetic diamond; Mechanical properties; Surface treatments; Coatings; Diamond structure; Carbon; Stainless steels; Impedance; Stainless steel-316L
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2010.05.004

In the present work, the corrosion performance and mechanical stability of diamond-like carbon (DLC) coatings were investigated in the context of their biomedical applications. DLC was prepared by radio-frequency (RF) plasma-enhanced chemical vapor deposition (PECVD) onto medical grade 316L stainless steel. Interlayers of amorphous hydrogenated silicon-based materials such as a-Si, a-SiN
x
, a-SiC
x
, and a-SiC
x
N
y
, and a nitrided interlayer, were studied in order to optimize its adhesion strength. Potentiodynamic polarization tests were performed to evaluate the corrosion performance of the 316L/DLC coating system. Electrochemical impedance spectroscopy (EIS) was used to determine the stability of the coating system during long-term tests of exposure to a simulated body fluid solution. The evolution of EIS spectra was monitored during two years of immersion in Ringer's solution. In addition to providing the best adhesion, the a-SiN
x
interlayer was found to significantly improve the corrosion resistance of the DLC system since it is highly impervious to the liquid. This is demonstrated by a two-order of magnitude improvement in the corrosion current density compared to the DLC with the nitrided interlayer. The a-SiN
x
interlayer substantially enhances the mechanical stability of the DLC coating system in the simulated body fluid environment, indicated by a slight reduction (less than 20%) in the adhesion strength and fivefold increase in the charge transfer resistance after two years of immersion. Moreover, Si-doped DLC coatings show improved corrosion barrier properties, due to the formation of a passive silicon oxide film at the electrode/electrolyte interface.