Caractérisation nano-mécanique et tribologique des revêtements TiO

Dans ce travail, nous avons développé des couches nanométriques biocompatibles à base de titane (TiN et TiO2) sur acier inoxydable 316L, par CAE-PVD (Cathodic Arc Evaporation), qui est un procédé efficace pour la synthèse de revêtements de haute qualité. Nous avons axé notre étude sur une caractérisation mécanique et tribologique des revêtements par des tests d’indentation et des rayures. Les résultats obtenus montrent une morphologie dense et uniforme couplée à des propriétés mécaniques et interfaciales importantes. Les revêtements TiN et TiO2 ont montré une dureté comprise entre 5,9 GPa et 8,23 GPa. La mesure de l’adhérence par des tests de rayure a montré que les deux revêtements ont une qualité d’adhérence légèrement différente. Les couches développées en TiN et TiO2 ont montré des charges de cohésion critiques comprises entre 1,8 N et 3,3 N avec une charge d’adhérence critique de 13,1 N. Les propriétés tribologiques ont été étudiées, en utilisant un test de Scratch multi-passes à charge constante, ce qui a permis de déterminer le coefficient de frottement et le taux d’usure énergétique. Les coefficients de frottement des deux couches étudiées sont du même ordre de grandeur (0,1), mais on peut dire que la résistance au frottement varie d’une couche à l’autre. L’énergie spécifique d’usure était comprise entre 3,09 × 10−5 J/μm3 et 8,36 × 10−5 J/μm3, et elle n’a pas changé après immersion de la couche de TiN pendant 48 h dans une solution de NaCl à 3 %. Le film mince de TiN, connu pour sa biocompatibilité et ses performances biologiques, a montré des propriétés mécaniques et tribologiques qui lui permettent d’être utilisé dans les implants de hanche et de genou

Fluorinated Ethylene Propylene Coatings Deposited by a Spray Process: Mechanical Properties, Scratch and Wear Behavior

International audienceTo increase the lifetime of metallic molds and protect their surface from wear, a fluorinated ethylene propylene (FEP) polymer was coated onto a stainless-steel (SS304) substrate, using an air spray process followed by a heat treatment. The microstructural properties of the coating were studied using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) as well as X-ray diffraction. The mechanical properties and adhesion behavior were analyzed via a nanoindentation test and progressive scratching. According to the results, the FEP coating had a smooth and dense microstructure. The mechanical properties of the coatings, i.e., the hardness and Young’s modulus, were 57 ± 2.35 and 1.56 ± 0.07 GPa, respectively. During scratching, successive delamination stages (initiation, expansion, and propagation) were noticed, and the measured critical loads LC1 (3.36 N), LC2 (6.2 N), and LC3 (7.6 N) indicated a high adhesion of the FEP coating to SS304. The detailed wear behavior and related damage mechanisms of the FEP coating were investigated employing a multi-pass scratch test and SEM in various sliding conditions. It was found that the wear volume increased with an increase in applied load and sliding velocity. Moreover, the FEP coating revealed a low friction coefficient (around 0.13) and a low wear coefficient (3.1 × 10−4 mm3 N m−1). The investigation of the damage mechanisms of the FEP coating showed a viscoelastic plastic deformation related to FEP ductility. Finally, the coating’s resistance to corrosion was examined using electrochemical measurements in a 3.5 wt% NaCl solution. The coating was found to provide satisfactory corrosion protection to the SS304 substrate, as no corrosion was observed after 60 days of immersion

Electrophoretic Deposition of 45S5 Bioglass® Coatings on the Ti6Al4V Prosthetic Alloy with Improved Mechanical Properties

In this paper, 45S5 Bioglass® coatings were elaborated by electrophoretic deposition (EPD) on the titanium alloy Ti6Al4V. An adequate grinding protocol was developed to obtain a stable suspension of submicrometric particles in isopropanol. The voltage and the deposition time of EPD were optimized. An optimal voltage of 30 V and two deposition times (30 and 90 s) were chosen to obtain two different coatings with thicknesses of 21 and 85 µm, respectively. The as-deposited coatings were thermally treated following a two-step protocol: one hour at 120 °C followed by one hour at 450 °C. The surface morphology and the chemical analysis of the 45S5 Bioglass® coatings were assessed, before and after heat treatment, by scanning electron microscopy associated to X-ray microanalysis (SEM-EDXS). Their structural analysis was performed by X-ray diffraction (XRD). A scratch test study was developed for mechanical properties analysis. The obtained results revealed that the obtained coatings were homogeneous, weakly crystallized with an important compactness. An increase in the critical load LC associated with the cohesive limit of the film (from Lc = 3.39 N to Lc = 5.18 N) was observed when the coating thickness was decreased from 85 to 21 µm. After the thermal treatment, the chemical composition of the coatings was not altered, and their mechanical properties were improved