4 research outputs found
DiffĂ©rentes approches dâingĂ©nierie de surface pour des applications biomĂ©dicales
AISI 316L stainless steel is commonly used as biomaterial because of its desirable properties such as high corrosion resistance. They have, however, the problem of releasing metal ions upon corrosion that may cause allergies to both humans and animals. In addition, implant failures have been reported due to their limited resistance to localised corrosion. There is thus a need to find ways to improve their corrosion resistance. This thesis aims to evaluate different approaches intending to improve the corrosion resistance of AISI 316L stainless steel for biomedical applications using two strategies: (1) modification of the bulk composition and (2) surface modification.The bulk composition of 316L-type stainless steel was modified by adding nitrogen. Laboratory grades with controlled compositions were tested in chloride conditions at a wide range of pH and in simulated physiological conditions. The combination of Mo and N on the pitting potential was found to be beyond the sum of their individual effects, indicating synergy. The effect, however, was found to be pH-dependent, being largely present in acid to neutral chloride conditions and in physiological solutions, while diminishing in high pH. When tested in physiological conditions, this effect was even more beneficial with ageing. Nitrogen was found to enhance the repassivation of the Mo-containing stainless steel grade, driving the potential for passive film breakdown to higher values.The surface of AISI 316L was coated with Fe-based metallic glasses using laser cladding. The resulting coatings had different results depending on the alloy. The coatings of Fe43.2Co28.8B19.2Si4.8Nb4 and Fe60Cr8Nb8B24 showed a matrix with segregations, particularly of Nb, thereby lowering their corrosion resistance. On the other hand, the Fe48.6Mo13.9Cr15.2C14.4Y1.8B6 coating was found to be amorphous but with lower corrosion resistance than the substrate, due to the presence of defects.Ti and TiN were also coated on AISI 316L wires using a prototype for magnetron sputtering in moving deposition mode. In this study, static and semi-continuous modes of motion were used. Overall, the corrosion resistance of the coatings were lower than the substrate, increasing further with coating thickness. The presence of coating heterogeneity allowed for substrate-electrolyte interaction, driving forward corrosion and delamination with further immersion. Deposits of calcium phosphate were found on the coating surface after 14 days of immersion, indicating the possible favourability of bone material growth.AISI 316L est un acier inoxydable couramment utilisĂ© comme biomatĂ©riau grĂące Ă des propriĂ©tĂ©s telles qu'une rĂ©sistance Ă la corrosion Ă©levĂ©e. Cependant, en cas d'attaque corrosive, ils sont susceptibles de libĂ©rer des ions mĂ©talliques qui peuvent provoquer des allergies. En outre, plusieurs dĂ©faillances d'implants ont Ă©tĂ© rapportĂ©es et reliĂ©es au fait que leur rĂ©sistance Ă la corrosion localisĂ©e est nĂ©anmoins limitĂ©e. Dans ce sens, cette thĂšse vise Ă Ă©valuer diffĂ©rentes approches visant Ă amĂ©liorer la rĂ©sistance Ă la corrosion de l'acier inoxydable 316L pour des applications biomĂ©dicales Ă l'aide de deux stratĂ©gies: (1) la modification de la composition au sein de l'alliage et (2) la modification de la surface.La composition globale de l'acier inoxydable 316L a Ă©tĂ© modifiĂ©e avec l'addition d'azote. Des coulĂ©es âlaboratoire' avec des compositions contrĂŽlĂ©es ont Ă©tĂ© testĂ©es dans des milieux chlorurĂ© ainsi que dans des solutions physiologiques. L'effet de la combinaison de Mo et N sur le potentiel de piqĂ»re s'est avĂ©rĂ© supĂ©rieur Ă la somme de leurs effets individuels, ce qui indique une synergie. Cet effet, cependant, s'est montrĂ© dĂ©pendent du pH, Ă©tant fortement prĂ©sent pour des milieux acides et neutres, tout en diminuant de façon importante avec l'augmentation du pH. Lors des essais dans des conditions physiologiques, cet effet Ă©tait encore plus bĂ©nĂ©fique avec le vieillissement. L'azote semble avoir amĂ©liorĂ© la tendance Ă la rĂ©passivation de l'acier inoxydable avec Mo, dĂ©plaçant ainsi le potentiel de rupture du film passif vers des valeurs plus Ă©levĂ©es.La surface de AISI 316L a aussi Ă©tĂ© revĂȘtue avec de verres mĂ©talliques Ă basede fer Ă l'aide de laser cladding. Les revĂȘtements ont donnĂ© des rĂ©sultats diffĂ©rents en fonction de l'alliage. Les revĂȘtements de Fe43.2Co28.8B19.2Si4.8Nb4 et Fe60Cr8Nb8B24 ont montrĂ© une matrice avec des sĂ©grĂ©gations, en particulier de Nb, ce qui rĂ©duit leur rĂ©sistance Ă la corrosion. D'autre part, le revĂȘtement de Fe48.6Mo13.9Cr15.2C14.4Y1.8B6 s'est avĂ©rĂ© ĂȘtre effectivement amorphe mais avec une rĂ©sistance Ă la corrosion infĂ©rieure Ă celle du substrat, en raison de la prĂ©sence de dĂ©fauts.Ti et TiN ont Ă©galement Ă©tĂ© revĂȘtus sur les fils AISI 316L en utilisant un prototype de pulvĂ©risation magnĂ©tron en mode dĂ©filĂ©. Dans cette Ă©tude, les modesstatiques et semi-continus ont Ă©tĂ© utilisĂ©s. Globalement, la rĂ©sistance Ă la corrosion des revĂȘtements Ă©taient plus faibles que celle du substrat, ce surtout avec l'augmentation de l'Ă©paisseur du revĂȘtement. La prĂ©sence d'hĂ©tĂ©rogĂ©nĂ©itĂ©s de revĂȘtement a permis l'interaction substrat-Ă©lectrolyte, diminuant la rĂ©sistance Ă la corrosion la corrosion et entrainant la dĂ©lamination des revĂȘtements avec le vieillissement. Des dĂ©pĂŽts de phosphate de calcium ont Ă©tĂ© trouvĂ©s sur la surface du revĂȘtement aprĂšs 14 jours d'immersion, ce qui semble indiquer la possibilitĂ© de la croissance favorable de la matiĂšre osseuse
Some insights on different approaches of surface engineering for biomedical applications
AISI 316L est un acier inoxydable couramment utilisĂ© comme biomatĂ©riau grĂące Ă des propriĂ©tĂ©s telles qu'une rĂ©sistance Ă la corrosion Ă©levĂ©e. Cependant, en cas d'attaque corrosive, ils sont susceptibles de libĂ©rer des ions mĂ©talliques qui peuvent provoquer des allergies. En outre, plusieurs dĂ©faillances d'implants ont Ă©tĂ© rapportĂ©es et reliĂ©es au fait que leur rĂ©sistance Ă la corrosion localisĂ©e est nĂ©anmoins limitĂ©e. Dans ce sens, cette thĂšse vise Ă Ă©valuer diffĂ©rentes approches visant Ă amĂ©liorer la rĂ©sistance Ă la corrosion de l'acier inoxydable 316L pour des applications biomĂ©dicales Ă l'aide de deux stratĂ©gies: (1) la modification de la composition au sein de l'alliage et (2) la modification de la surface.La composition globale de l'acier inoxydable 316L a Ă©tĂ© modifiĂ©e avec l'addition d'azote. Des coulĂ©es âlaboratoire' avec des compositions contrĂŽlĂ©es ont Ă©tĂ© testĂ©es dans des milieux chlorurĂ© ainsi que dans des solutions physiologiques. L'effet de la combinaison de Mo et N sur le potentiel de piqĂ»re s'est avĂ©rĂ© supĂ©rieur Ă la somme de leurs effets individuels, ce qui indique une synergie. Cet effet, cependant, s'est montrĂ© dĂ©pendent du pH, Ă©tant fortement prĂ©sent pour des milieux acides et neutres, tout en diminuant de façon importante avec l'augmentation du pH. Lors des essais dans des conditions physiologiques, cet effet Ă©tait encore plus bĂ©nĂ©fique avec le vieillissement. L'azote semble avoir amĂ©liorĂ© la tendance Ă la rĂ©passivation de l'acier inoxydable avec Mo, dĂ©plaçant ainsi le potentiel de rupture du film passif vers des valeurs plus Ă©levĂ©es.La surface de AISI 316L a aussi Ă©tĂ© revĂȘtue avec de verres mĂ©talliques Ă basede fer Ă l'aide de laser cladding. Les revĂȘtements ont donnĂ© des rĂ©sultats diffĂ©rents en fonction de l'alliage. Les revĂȘtements de Fe43.2Co28.8B19.2Si4.8Nb4 et Fe60Cr8Nb8B24 ont montrĂ© une matrice avec des sĂ©grĂ©gations, en particulier de Nb, ce qui rĂ©duit leur rĂ©sistance Ă la corrosion. D'autre part, le revĂȘtement de Fe48.6Mo13.9Cr15.2C14.4Y1.8B6 s'est avĂ©rĂ© ĂȘtre effectivement amorphe mais avec une rĂ©sistance Ă la corrosion infĂ©rieure Ă celle du substrat, en raison de la prĂ©sence de dĂ©fauts.Ti et TiN ont Ă©galement Ă©tĂ© revĂȘtus sur les fils AISI 316L en utilisant un prototype de pulvĂ©risation magnĂ©tron en mode dĂ©filĂ©. Dans cette Ă©tude, les modesstatiques et semi-continus ont Ă©tĂ© utilisĂ©s. Globalement, la rĂ©sistance Ă la corrosion des revĂȘtements Ă©taient plus faibles que celle du substrat, ce surtout avec l'augmentation de l'Ă©paisseur du revĂȘtement. La prĂ©sence d'hĂ©tĂ©rogĂ©nĂ©itĂ©s de revĂȘtement a permis l'interaction substrat-Ă©lectrolyte, diminuant la rĂ©sistance Ă la corrosion la corrosion et entrainant la dĂ©lamination des revĂȘtements avec le vieillissement. Des dĂ©pĂŽts de phosphate de calcium ont Ă©tĂ© trouvĂ©s sur la surface du revĂȘtement aprĂšs 14 jours d'immersion, ce qui semble indiquer la possibilitĂ© de la croissance favorable de la matiĂšre osseuse.AISI 316L stainless steel is commonly used as biomaterial because of its desirable properties such as high corrosion resistance. They have, however, the problem of releasing metal ions upon corrosion that may cause allergies to both humans and animals. In addition, implant failures have been reported due to their limited resistance to localised corrosion. There is thus a need to find ways to improve their corrosion resistance. This thesis aims to evaluate different approaches intending to improve the corrosion resistance of AISI 316L stainless steel for biomedical applications using two strategies: (1) modification of the bulk composition and (2) surface modification.The bulk composition of 316L-type stainless steel was modified by adding nitrogen. Laboratory grades with controlled compositions were tested in chloride conditions at a wide range of pH and in simulated physiological conditions. The combination of Mo and N on the pitting potential was found to be beyond the sum of their individual effects, indicating synergy. The effect, however, was found to be pH-dependent, being largely present in acid to neutral chloride conditions and in physiological solutions, while diminishing in high pH. When tested in physiological conditions, this effect was even more beneficial with ageing. Nitrogen was found to enhance the repassivation of the Mo-containing stainless steel grade, driving the potential for passive film breakdown to higher values.The surface of AISI 316L was coated with Fe-based metallic glasses using laser cladding. The resulting coatings had different results depending on the alloy. The coatings of Fe43.2Co28.8B19.2Si4.8Nb4 and Fe60Cr8Nb8B24 showed a matrix with segregations, particularly of Nb, thereby lowering their corrosion resistance. On the other hand, the Fe48.6Mo13.9Cr15.2C14.4Y1.8B6 coating was found to be amorphous but with lower corrosion resistance than the substrate, due to the presence of defects.Ti and TiN were also coated on AISI 316L wires using a prototype for magnetron sputtering in moving deposition mode. In this study, static and semi-continuous modes of motion were used. Overall, the corrosion resistance of the coatings were lower than the substrate, increasing further with coating thickness. The presence of coating heterogeneity allowed for substrate-electrolyte interaction, driving forward corrosion and delamination with further immersion. Deposits of calcium phosphate were found on the coating surface after 14 days of immersion, indicating the possible favourability of bone material growth
Synergy between molybdenum and nitrogen on the pitting corrosion and passive film resistance of austenitic stainless steels as a pH-dependent effect
International audienceThis paper brings up some insights upon the pH dependence of the synergistic effect of Mo and N on the localized corrosion resistance of austenitic stainless steels. The objective of this work is to study the synergetic effect of Mo and N additions on corrosion and passive film properties of austenitic grades. A comparison between Mo containing (3 wt% Mo); Mo and N containing (3 wt% Mo and 0.1% N) and free Mo or free Mo and N grades of highly controlled laboratory heats was done considering their localized corrosion resistance and oxide film formation in different aggressive conditions, from neutral to alkaline pH. The passive layer was characterized by EIS and XPS analyses. The combined effect of Mo and N on the pitting potential was confirmed to be synergistic, and not just the addition of their individual effects. Moreover, this effect was found to be pH-dependent, being very positive in acid to neutral conditions whereas it was almost inexistent in high pH