Ce travail a été réalisé dans le cadre d’une collaboration entre le laboratoire de Chimie-Métallurgie de l’INSA de Rennes et le laboratoire de biomatériaux en site osseux (LBSO) de la Faculté de Chirurgie Dentaire de l’Université de Rennes1. L’alliage de titane de type β Ti-27Nb (% at.) a été nitruré pour des applications en implantologie orale parce qu'il possède un bas module d'élasticité, proche de celui de l’os et qu’il est composé uniquement d'éléments biocompatibles. Dans un premier temps l’alliage Ti-27Nb a été synthétisé grâce à un four à induction magnétique selon la technique de fusion en lévitation en creuset froid sectorisé. Un traitement de surface par nitruration en phase gazeuse a ensuite été effectué pour augmenter sa résistance à la corrosion et à l’usure. L’analyse structurale a été réalisée par DRX et par des observations en microscopies optique et électronique à balayage. L’analyse chimique a été effectuée par spectrométrie à dispersion d’énergie. La topographie et la dureté superficielle ont été caractérisées par AFM et par nano-indentation. Des essais tribologiques ont permis d’évaluer le coefficient de frottement et la résistance à l’usure. Pour la caractérisation mécanique des essais de traction conventionnels et cycliques ont été effectués. La biocompatibilité a été évaluée in vitro par des cultures bidimensionnelles de plusieurs populations cellulaires en contact des implants métalliques : ostéoblastes, fibroblastes et cellules épithéliales. Elle a été déclinée en termes de cytotoxicité, de prolifération cellulaire, d’expression génique et de morphologie cellulaire. Les propriétés de l’alliage Ti-27Nb nitruré sont particulièrement intéressantes pour une implantation durable en site osseux. / This work was performed in collaboration with the Metallurgical Chemistry team of the Institute of Chemical Sciences of Rennes and the Biomaterials Laboratory of the Faculty of Dentistry of Université de Rennes1. The low modulus Ti-27Nb (at. %) alloy with non-toxic elements was nitrided for the first time in this study for dental implant applications. The alloy was firstly synthetized by cold crucible levitation melting technique. A high temperature gas nitriding treatment was then carried out in order to improve the wear and corrosion resistance. The structural analysis was performed by X-ray diffraction and the microstructure was observed by optical microscopy and by scanning electron microscopy. The chemical analysis was performed by Energy Dispersion Spectrometry. Superficial mechanical properties were then studied by nano-indentation and ball-on-disc tribological tests. Conventional and tensile tests were realized. The biocompatibility was evaluated by in vitro tests performed on human osteoblasts, fibroblastic cells and epithelial cells. Cell proliferation and differentiation were studied as well as cell morphology. All of the observed properties make the nitrided Ti-27Nb alloy particularly suitable for enhanced longevity of dental implants.

<p>Proučavane su koroziona postojanost i tendencija lepljenja različitih<br />materijala u kontaktu sa tečnom Al&ndash;Si&ndash;Cu legurom. Ispitivanjem su<br />obuhvaćeni čelik za rad na toplo, plazma nitrirani čelik i dupleks<br />slojevi sa CrN, TiAlN, TiAlSiN i CrAlN prevlakama, različitog nivoa<br />površinske hrapavosti. Za ispitivanja pomenutih fenomena<br />primenjena je metoda izvlačenja, koja je unapređena kako bi se povećale<br />njena tačnost i verodostojnost simulacije procesa livenja. Korozioni<br />efekti su pojačani tako što su uzorci osim kratkog kontakta sa odlivkom<br />zadržavani i u dužim periodima u kontaktu sa tečnom legurom (5 i 20<br />min). Uprkos opštim stavovima, za ispitivane materijale je<br />ustanovljeno da su sile izvlačenja uzoraka iz Al&ndash;Si&ndash;Cu odlivaka<br />nezavisne od njihovog hemijskog sastava. Uticaj hrapavosti je izražen<br />kod uzoraka sa prevlakama kod kojih pri smanjenju hrapavosti dolazi do<br />povećanja sile izvlačenja. Sve ispitane prevlake su sklone mehaničkom<br />lepljenju Al&ndash;Si&ndash;Cu legure za svoje površine, ali sa aspekta korozije u<br />tečnom metalu značajno prevazilaze performanse čelika i plazma<br />nitriranog sloja. Duži kontakt livene legure sa površinama prevlaka<br />uzrokovao je niže vrednosti sila izvlačenja, što je posledica<br />oksidacije površina prevlaka. Ustanovljeno je da su ispitivane<br />prevlake inertne ka tečnoj leguri aluminijuma. Međutim, dolazi do<br />oksidacije i korozije materijala podloge kroz greške rasta koje su<br />prisutne u prevlakama. Stečena znanja o identifikovanim<br />mehanizmima habanja i propadanja zaštitnih slojeva prevlaka<br />poslužiće daljem razvoju dupleks slojeva namenjenih za zaštitu alata<br />za livenje pod pritiskom.</p> / <p>Corrosion resistance and soldering tendency of different materials in molten<br />Al&ndash;Si&ndash;Cu alloy were studied. Hot-working tool steel, plasma nitrided steel and<br />duplex layers with CrN, TiAlN, TiAlSiN and CrAlN top coatings, which were<br />produced to various degree of surface roughness, were covered by the study.<br />An ejection test was employed for investigation of the concerned phenomena.<br />The ejection test was improved in order to increase its accuracy and the<br />reliability of process simulation. Samples were examined in both short and<br />extended periods of contact (5 and 20 min) with liquid casting. Casting<br />solidification was extended in order to intensify the corrosion effects. Contrary<br />to common findings, it was found that the ejection force of the investigated<br />materials does not depend on their chemical composition. For the coated<br />samples, a pronounced dependence of the ejection force on the surface<br />roughness was found. The ejection force increases with decrease in surface<br />roughness. All investigated coatings are prone to mechanical soldering by Al&ndash;<br />Si&ndash;Cu alloy. Still, their corrosion resistance substantially exceeds the corrosion<br />resistance of steel and plasma nitrided layer. Longer exposure of coated<br />samples to cast alloy induced lower ejection forces, which is a consequence<br />of coatings oxidation. It was found that the investigated coatings are inert to<br />liquid aluminium. However, the underlying material undergoes oxidation and<br />corrosion through coating growth defects. The findings concerning the wear<br />mechanisms of protective layers support further development of duplex layers<br />intended for die casting tools protection.</p>