Reduction of corrosion current of CoCr alloys by post-PIII oxidation

Nitriding of biomedical CoCr alloys at elevated temperatures leads to a marked increase in the hardness and wear resistance. However, a compromised corrosion resistance is encountered even at relatively low temperatures, not correlated with the appearance of CrN in the XRD spectra. A duplex treatmen...

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Bibliographic Details
Published in:Surface & coatings technology 2014-10, Vol.256, p.59-63
Main Authors: Díaz, C., Gerlach, J.W., Mändl, S., García, J.A.
Format: Article
Language:English
Subjects:
Alloys
Applied sciences
CoCr
Correlation
Corrosion
Corrosion environments
Corrosion resistance
Cross-disciplinary physics: materials science
rheology
Exact sciences and technology
Materials science
Metals. Metallurgy
Oxidation
Oxides
Physics
PIII
Post-oxidation
Protective coatings
Surface treatments
X-ray photoelectron spectroscopy
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Summary:Nitriding of biomedical CoCr alloys at elevated temperatures leads to a marked increase in the hardness and wear resistance. However, a compromised corrosion resistance is encountered even at relatively low temperatures, not correlated with the appearance of CrN in the XRD spectra. A duplex treatment of initial nitrogen and subsequent oxygen PIII at 350°C was already shown to partially reduce the corrosion current. Here, it is investigated whether restoring the oxide passivation layer by PIII is necessary, a simple annealing is sufficient or an intermediate processing is more suitable. GDOES, XRD, XPS and corrosion investigations in bovine serum are performed to obtain information on the underlying mechanisms of the improved corrosion resistance. It is shown that post-oxidation by PIII leads to a more favourable corrosion protection with lower corrosion current and more positive corrosion potential compared to thermal oxidation or plasma oxidation. As the XPS and GDOES data show no differences, the cause of this behaviour should be correlated with the microstructure of the oxide. •Combination of nitrogen and oxygen PIII processes improved tribocorrosion effects.•The oxygen content itself and the chemical surface are not influenced by the oxidation process.•Momentum transfer, stress formation and sputtering are apparently beneficial for the corrosion protection in CoCrMo.•PIII is the best alternative for forming a small surface modification of oxygen into CoCr alloys.
ISSN:0257-8972
1879-3347
DOI:10.1016/j.surfcoat.2014.03.027