Effect of duplex treatments by plasma nitriding and triode sputtering on corrosion behaviour of 32CDV13 low alloy steel

• Published in: Surface & coatings technology 2006-06, Vol.200 (22), p.6568-6571
• Main Authors: Chala, A., Nouveau, C., Djouadi, M.A., Steyer, P., Millet, J.P., Saied, C., Aïda, M.S., Lambertin, M.
• Format: Article
• Language: English
• Subjects: Applied sciences; Condensed Matter; Corrosion; Corrosion environments; Cross-disciplinary physics: materials science; rheology; Duplex; Exact sciences and technology; Heat treatment; Materials Science; Metals. Metallurgy; Other topics in materials science; Physics; Plasma nitriding; Production techniques; Thermochemical treatment and diffusion treatment; Triode sputtering
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2005.11.036

This paper presents corrosion behaviour of duplex treated low alloy steel. Different kinds of samples were tested: non-treated, plasma nitrided, ZrBN-triode sputtered and ZrBN-duplex treated samples. The corrosion behaviour was evaluated by electrochemical techniques (corrosion potential and polarisation resistance evolutions versus immersion time, potentiodynamic curves). The corrosion tests were carried out in neutral aqueous saline solution (NaCl 30 g L − 1 ), naturally aerated. The composition and the structure of layers were determined by EDS and XRD, respectively, while the morphology was observed by SEM. Experimental results showed that the corrosion current density I corr increased with decreasing white layer thickness in plasma nitrided specimens. The nitrides ε-Fe 2 − 3 N and γ′-Fe 4N present in the white layer are nobler than the substrate but may promote, by galvanic effect, a localised corrosion through open porosity. The duplex treated specimens (nitriding + ZrBN coating) present better corrosion protection and enable to overcome the drawbacks of both techniques, mainly the porosity of the deposited films.