A scanning electrochemical microscopy characterization of the localized corrosion reactions occurring on nitinol in saline solution after anodic polarization

Sensors and Actuators B: Chemical 321 (2020) 128610. https://doi.org/10.1016/j.snb.2020.12861

A vasút felelőssége a fuvarozásra átvett árukért

INST: L_08

Fretting corrosion de matériaux utilisés comme implants orthopédiques

This work aims at understanding hip total joint cemented prostheses degradation by fretting corrosion. 316L stainless steel degradation, the femoral stem is made of this alloy, according to fretting against polymethylmethacrylate (PMMA), model component of bone cement, has been particularly investigated. Two tests types have been carried out: in dry conditions and in Ringer solution close to, from its chlorides concentration, the physiological liquid composition. In a first time, from experimental conditions of displacement and normal load, the fretting map has been drawn for 316L/PMMA contact. This work allows, for sinusoidal displacement with a half amplitude equal to 40 μm and normal loads within the range from 42.5 N to 170 N, to fix gross slip conditions. Then, the fretting study, in dry conditions, between stainless steel and PMMA, exhibits the PMMA wear volume measurements according to dissipated energy. This material is worn contrary to stainless steel that is not worn. Stick slip phenomenon exists during fretting and increases according to the normal load. Due to the PMMA transparency, debris production and transport have been described during fretting experiments. Moreover, PMMA debris infrared analysis, on stainless steel surface, provides interesting findings on PMMA behaviour, i.e. configurations changes. In Ringer solution, a corrosive medium, stainless steel suffers significant degradation during fretting against PMMA and bone cement. During dissolution process at free corrosion potential, protons reduction seems to be added to the oxygen reduction. 316L exhibits a particular ‘W' wear shape. A crevice effect assisted by fretting could explain this particular dissolution. Moreover, dissipated energy changes according to the applied potential. Finally, current analysis shows that cathodic reaction exists inside the contact. Lastly, tests, made in dry and wet conditions, provide wear volumes measurements for PMMA and 316L to expect materials wear.Ce travail s'inscrit dans la problématique de la dégradation des prothèses de hanche cimentées par fretting corrosion. L'endommagement de l'acier inoxydable 316L, alliage constituant la tige fémorale, par frottement contre du polyméthacrylate de méthyle (PMMA), composé modèle du ciment chirurgical, a été particulièrement étudié. Deux types d'expériences ont été envisagées : à sec et en solution de Ringer voisine, par sa teneur en chlorures, de la composition du liquide physiologique. Dans un premier temps, à partir des conditions expérimentales choisies de déplacement et de force normale, la carte de fretting a été tracée pour le contact 316L/PMMA permettant de fixer des conditions reproductibles de glissement total pour un déplacement sinusoïdal de demi-amplitude égale à 40 μm et des forces normales comprises entre 42,5 N et 170 N. Ensuite, l'étude, à sec, du fretting entre l'acier inoxydable et du PMMA a permis de quantifier le volume d'usure du PMMA, seul matériau à se dégrader, en fonction de l'énergie dissipée. Le phénomène de stick-slip a été nettement mis en évidence lors du glissement et augmente en fonction de la force normale de contact. Grâce à la transparence du PMMA, la production et l'évolution des débris ont pu être isolées et commentées en cours de fretting. De plus, les analyses infrarouges des débris de PMMA, à la surface de l'acier inoxydable, ont amené des informations sur le changement de configuration au cours du processus de dégradation. En solution de Ringer, milieu corrosif, l'acier inoxydable se dégrade d'une manière très significative pendant le fretting contre du PMMA et du ciment chirurgical. Au cours du processus de dissolution à potentiel libre, la réaction de réduction des ions oxoniums semble s'ajouter à la réduction du dioxygène. L'acier inoxydable 316L présente une forme particulière d'usure en ‘W'. Un effet de crevasse permet de proposer un mécanisme d'endommagement assisté par le fretting. De plus, l'énergie dissipée varie en fonction du potentiel imposé. Une analyse des courants a montré l'existence d'une réaction cathodique supplémentaire. Enfin, les expériences effectuées à l'air ambiant et en solution de Ringer ont fourni des données quantitatives d'usure du PMMA et du 316L

Predicting the steady state thickness of passive films with the point defect model in fretting corrosion experiments

International audienceThe Point Defect model (PDM), was developed in early 1980s to provide an atomic scale account of passivity. Understanding and predicting the passivity of metals is a fundamental challenge to maintaining our 'metals-based civilization'. Three generations of this model have been devised and a fourth is under development. The third generation is currently being applied to fretting corrosion, which is corrosion in the presence of friction under small displacements. The parameters of the point defect model can be extracted through the interpretation of the Faradaic impedance measured via electrochemical impedance spectroscopy (EIS). These parameters can then be used to explain and predict behavior of the film. The experimental apparatus was designed specifically for this type of investigation in a previous paper. This work employs the Point Defect Model to account for enhanced fretting corrosion of 316L stainless steel wearing against poly methyl methacrylate

Tribocorrosion

National audienceLe terme de "tribocorrosion" désigne le processus conduisant à l'endommagement (fissuration, écrouissage) et à l'usure de la surface d'un matériau métallique sous les effets conjugués d'une sollicitation mécanique de contact (frottement, impact) et de la corrosion par un milieu environnant. Cette définition, très générale, entre l'usure mécanique et (électro)chimique englobe une grande variété de configuration de contact. Nous présenterons uniquement les contacts à grands (slidding) et petits (fretting) débattement sans aborder les processus d'abrasion-corrosion (rolling) et d'érosion-corrosion (impingement) qui mettent en jeu des mécanismes de dégradations similaires. La tribocorrosion affecte donc un grand nombre de tribosystèmes constitués de dispositifs mécaniques comportant des pièces généralement métalliques en contact et en mouvement relatif (mécanismes de pompes, paliers, engrenages, roulements, charnières, implants orthopédiques, ...). Les conséquences du couplage entre le frottement et la corrosion sont complexes à maîtriser compte-tenu du nombre élevé et de la variété des paramètres qui déterminent le comportement du système tribologique

Predicting the steady state thickness of passive films with the point defect model in fretting corrosion experiments

International audienceThe Point Defect model (PDM), was developed in early 1980s to provide an atomic scale account of passivity. Understanding and predicting the passivity of metals is a fundamental challenge to maintaining our 'metals-based civilization'. Three generations of this model have been devised and a fourth is under development. The third generation is currently being applied to fretting corrosion, which is corrosion in the presence of friction under small displacements. The parameters of the point defect model can be extracted through the interpretation of the Faradaic impedance measured via electrochemical impedance spectroscopy (EIS). These parameters can then be used to explain and predict behavior of the film. The experimental apparatus was designed specifically for this type of investigation in a previous paper. This work employs the Point Defect Model to account for enhanced fretting corrosion of 316L stainless steel wearing against poly methyl methacrylate

Shock machine for the mechanical behaviour of hip prostheses: a description of performance capabilities

International audienceThe aim of this study was to describe the behaviour of a shock machine designed for testing hip prostheses. A microseparation between head and cup occurs inducing a shock of several times the body weight, leading to fracture of ceramic femoral components. Femoral heads and cups of diameter 32 mm manufactured from alumina were tested in dry and wet conditions. Implants were subjected to shocks with a load profile of 9 kN load at 2 Hz and various microseparations. Position is monitored and force is measured with two acquisition systems. The working range and the device capabilities were investigated. Only cups tested in dry conditions failed. Observations by scanning electron microscopy revealed intergranular and transgranular fractures. Two wear stripes were observed on the heads. Three-dimensional roughness of wear stripes was measured. Since experimental results are in good agreement with retrieved femoral heads, the shocks machine reproduces the in vivo degradations

Fretting corrosion in biomedical implants

International audienceFretting corrosion is a phenomenon which occurs when two materials are submitted to friction under a slight relative motion. This chapter will focus on fretting corrosion degradations in the field of implants. After describing the most significant implants submitted to fretting, fretting corrosion is defined. Laboratory investigations highlight particular degradation mechanisms such as the key role of passive film stability, crevice corrosion, etc. Free corrosion and applied potentials conditions are investigated for understanding tribocorrosion. Finally, the role of proteins in tribological behavior is investigated, since the fretting corrosion degradations of biomaterials such as implants occur in a biological environment and proteins play a role in the tribocorrosion processes

Electrochemical impedance spectroscopy insights for fretting corrosion experiments

International audiencePas de résum

Understanding Dual Mobility-Multi scale analysis

International audiencePas de résum