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Proust G.,University of Sydney | Retraint D.,University of Technology of Troyes | Chemkhi M.,University of Technology of Troyes | Roos A.,University of Technology of Troyes | Demangel C.,CRITT MDTS
Microscopy and Microanalysis | Year: 2015

Austenitic 316L stainless steel can be used for orthopedic implants due to its biocompatibility and high corrosion resistance. Its range of applications in this field could be broadened by improving its wear and friction properties. Surface properties can be modified through surface hardening treatments. The effects of such treatments on the microstructure of the alloy were investigated here. Surface Mechanical Attrition Treatment (SMAT) is a surface treatment that enhances mechanical properties of the material surface by creating a thin nanocrystalline layer. After SMAT, some specimens underwent a plasma nitriding process to further enhance their surface properties. Using electron backscatter diffraction, transmission Kikuchi diffraction, energy dispersive spectroscopy, and transmission electron microscopy, the microstructural evolution of the stainless steel after these different surface treatments was characterized. Microstructural features investigated include thickness of the nanocrystalline layer, size of the grains within the nanocrystalline layer, and depth of diffusion of nitrogen atoms within the material. © © Microscopy Society of America 2015.

Jelliti S.,Compiegne University of Technology | Jelliti S.,CNRS Risk Management Science and Technology | Richard C.,University of Tours | Retraint D.,CNRS Risk Management Science and Technology | And 3 more authors.
Surface and Coatings Technology | Year: 2013

By means of surface mechanical attrition treatment (SMAT), a nanocrystalline surface layer was formed on a Ti-6Al-4V alloy. The corrosion behavior of Ti-6Al-4V in a Ringer's solution was investigated by potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) measurements. Overall results of all studies identified beneficial impacts of SMAT on corrosion behavior of Ti-6Al-4V alloy. The surface oxide film formed on Ti-6Al-4V and its stability in biological environments play a decisive role for the biocompatibility of implants. In this study, passive oxide films formed on Ti-6Al-4V surfaces and their natural growth in a Ringer's solution have been investigated by microhardness and X-ray photoelectron spectroscopy (XPS). © 2013 Elsevier B.V.

Chemkhi M.,CNRS Risk Management Science and Technology | Retraint D.,CNRS Risk Management Science and Technology | Roos A.,CNRS Risk Management Science and Technology | Garnier C.,CNRS Risk Management Science and Technology | And 3 more authors.
Surface and Coatings Technology | Year: 2013

The combined effect of superficial nanocrystallisation by SMAT (Surface Mechanical Attrition Treatment) followed by plasma nitriding on the mechanical properties of a medical grade austenitic stainless steel was studied. SMAT conditions were optimised to enhance nitrogen diffusion. Experimental observations (energy dispersive X-ray spectroscopy profiles, cross-sectional optical micrographs, phase analysis by X-ray diffraction and micro-hardness profiles) show that polishing away a very thin layer after SMAT and before nitriding significantly improves nitrogen diffusion into the substrate, yielding a 50% thicker nitrided layer. Possible causes for this improvement are discussed. © 2013 Elsevier B.V.

Pi Y.,LISM URCA | Agoda-Tandjawa G.,LISM URCA | Potiron S.,LISM URCA | Demangel C.,CRITT MDTS | And 2 more authors.
Journal of Nanoscience and Nanotechnology | Year: 2012

In this study, microstructural and mechanical properties of Ti-6Al-4V alloy, before and after the SMA treatment (SMAT) as well as the duplex SMAT/Nitriding process at different treatment conditions, were investigated in order to deepen the knowledge of these properties for biomedical devices. For that purpose, tribological (wear resistance, coefficient of friction) and mechanical (Vickers microhardness) tests were performed. To carry out the microstructural and surface topographical characterization of the samples, the scanning electron microscopy (SEM) and the 3D-SEM reconstruction from stereoscopic images have been used. By means of profiles deduced from the 3D images, the surface roughness has been calculated. The obtained results allowed to find an interesting SMAT condition which, followed by nitriding at low temperature, can greatly improve tribological and mechanical properties of Ti-6Al-4V alloy. It was also shown from SEM characterization and the original method of 3D-SEM reconstruction, that SMAT can reduce the machined grooves and consequently the roughness of the samples decreases. Moreover, we demonstrated, for the first time, that instead of usual etching method, the ionic polishing allowed to reveal the grains, the grain boundaries and the twins as well as the surface nanocrystalline layer generated by SMAT. Thus, the thickness of the SMATed layer decreases with the nitriding temperature, whereas the surface grain size increases. Copyright © 2012 American Scientific Publishers All rights reserved.

Ben Jaber N.,CNRS Laboratory of Engineering and Materials Science | Ben Jaber N.,University of Tunis | Drevet R.,CNRS Laboratory of Engineering and Materials Science | Faure J.,CNRS Laboratory of Engineering and Materials Science | And 5 more authors.
Advanced Engineering Materials | Year: 2015

This work presents a new experimental process for the thermal treatment of prosthetic coatings obtained by electrodeposition on titanium alloy Ti6Al4V. This thermal treatment is required to evaporate the solvent from the coating and to improve its cohesion and its adhesion to the titanium alloy substrate. When such treatment is carried out in air, the temperature is limited to 550 °C due to the high oxidation of the titanium substrate. To overcome this limitation, we introduce a new thermal treatment process using a controlled atmosphere obtained by Argon injection under vacuum. In these conditions, the temperature can be increased up to 1 000 °C. This process prevents the formation of the oxide layer onto the titanium alloy surface without noticeable modification of its mechanical properties. It also allows to obtain a fully crystallized biphasic coating made of hydroxyapatite and β-tricalcium phosphate. Consequently, this work resulted in obtaining an implant (calcium phosphate coating on Ti6Al4V) with improved mechanical properties. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

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