Tribological performance and corrosion behavior of CoCrMo alloy

The present work focuses on the Tribological properties and corrosion behavior evaluation of sintered CoCrMo alloy. The CoCrMo alloy was elaborated by Powder metallurgy process at various sintering temperatures (1200°C, 1250°C and 1300°C). The structural properties were characterized by X-ray diffraction and scanning electron microscopy. The tribological characteristics were measured using a dry disc-ball tribometer. The corrosion behavior of the samples was studied using different electrochemical tests in a simulated physiological environment (Hank’s solution). The obtained results show that higher sintering temperatures have a positive impact on the tribological behavior as well as the corrosion resistance of CoCrMo alloys. The sintered samples at 1300°C showed a better resistance to friction wear and a lower corrosion rate

Performances tribologique et électrochimique de l’alliage TiNi poreux

Ce travail vise l’étude de l’effet de la porosité sur le comportement tribologique et électrochimique de l’alliage TiNi poreux pour des applications biomédicales. L’alliage TiNi poreux a été élaboré par le procédé de frittage en phase solide à la température de 850°C. En effet, l’analyse microstructurale par MEB et EDS confirme bien que lorsque la pression de compactage varie il se produit un changement de la morphologie des pores et des fractions des phases formées. L’étude du glissement à sec de notre matériau a permis de mettre en évidence que la présence de la porosité interconnectée améliore leur comportement tribologique. Cependant l’étude électrochimique a révélé que quelque soit le taux de porosité les échantillons présentent un caractère passif. Les paramètres électrochimiques dépendent dans une large mesure du pourcentage de pore, leur morphologie et leur distribution.Mots-clés: biomatériaux, porosité, tribologie, résistance à la corrosion, impédanceEnglish Title: Tribological and electrochemical performances of porous TiNi alloyEnglish AbstractThis work aims to study the effect of porosity on the tribological and electrochemical behavior of the porous TiNi alloy for biomedical applications. The porous TiNi alloy was developed by the solid phase sintering process at the temperature of 850°C. Indeed, the microstructural analysis by SEM and EDS confirms that when the compaction pressure varies there is a change in the morphology of the pores and fractions of the phases formed. The study of the dry sliding of our material made it possible to highlight that the presence of the interconnected porosity improves their tribological behavior. However, the electrochemical study revealed that whatever the porosity rate, the samples have a passive character. The electrochemical parameters depend to a large extent on the percentage of pore, their morphology and their distribution.Keywords: biomaterials, porosity, tribology, corrosion resistance, impedanc

Comportement à la corrosion des alliages TiNi et TA6V4 dans la salive artificielle et performance d’usure

Ce travail porte sur l’étude du comportement tribologique sans lubrification et électrochimique dans la salive artificielle des alliages TiNi (50/50) et TA6V4 pour les applications en orthodontie (implants dentaires). L'alliage TiNi (50/50) a été préparé dans un four à induction sous vide alors que l'alliage commercial TA6V4 sera utilisé comme matériau de référence. L’analyse microstructurale et la composition chimique des deux alliages TiNi et TA6V4 a été réalisée par microscopie électronique à balayage (MEB) couplée à l’EDS. Les résultats montrent que l'alliage TiNi présente une meilleure résistance à l'usure par glissement à sec (1,327x10-4 mm3 /Nm) par comparaison avec l'alliage TA6V4 (9,506x10-4 mm3 /Nm). Les mécanismes  d’usure ont été clairement identifiés pour les deux alliages et sont principalement basés sur une usure abrasive et adhésive pour l'alliage TiNi, et une usure abrasive associée à une oxydation, pour l’alliage TA6V4. L'étude électrochimique a révélé que les deux alliages présentent un caractère passif avec une résistance élevée à la corrosion.Mots clés: Alliages de titane- Microstructure- Comportement à l'usure- Résistance à la corrosion- Impédance.Corrosion Behavior of TiNi and TA6V4 Alloys in Artificial Saliva and Wear PerformanceThis work aims to study the tribological performance in dry conditions and electrochemical behavior, in the artificial saliva of TiNi (50/50) alloys in comparison with TA6V4 alloys in the focus to use them for dental applications. The TiNi alloy was prepared in a vacuum induction melting furnace whileTA6V4 commercial alloy should be used as a reference material. The TiNi alloy (50/50) was prepared in a vacuum induction melting furnace while the TA6V4 commercial alloy will be used as a reference material. The microstructural analysis and chemical composition of the two TiNi and TA6V4 alloys was determined by scanning electron microscopy(SEM) coupled to EDS. Results showed that TiNi alloy exhibits a better wear resistance in dry sliding mode (1.327x10-4 mm3 / Nm) when compared to the alloy TA6V4 (9,506x10-4 mm3 / Nm). The wear mechanisms of both alloys have been clearly established. It can be retained that NiTi alloy degradation is governed by an adhesive and abrasive wear mechanism, but for the TA6V4 alloy, abrasive and oxidative wear mechanisms are determined. Electrochemical studies reveal a passive behavior character and higher resistance against corrosion.Key words: Titanium alloys- Microstructure- Wear behavior- Corrosion resistance- Impedance

The Corrosion Protection Behaviour of Zinc Rich Epoxy Paint in 3% NaCl Solution

Electrochemical impedance spectroscopy (EIS) in the l00 kHz-10 mHz frequency range was employed as the main electrochemical technique to study the corrosion protection behaviour of zinc rich epoxy paint in 3% NaCl solution. The EIS results obtained at the open-circuit corrosion potential have been interpreted using a model involving the impedance of particle to particle contact to account for the increasing resistance between zinc particles with immersion period, in addition to the impedance due to the zinc surface oxide layer and the electrical resistivity of the binder. Galvanic current and dc potential measurements allowed us to conclude that the cathodic protection effect of the paint takes some time to be achieved. The loss of cathodic protection is due to a double effect: the decrease of the Zn/Fe area ratio due to Zn corrosion and the loss of electric contact between Zn to Zn particles. Even when the cathodic protection effect by Zn dust become weak, the substrate steel is still protected against corrosion due to the barrier nature of the ZRP film reinforced by Zn