Caracterización y estudio del comportamiento electroquímico de aleaciones biomédicas de titanio

[ES] Se investiga el comportamiento frente a la corrosión de nuevas aleaciones de titanio mediante técnicas electroquímicas en condiciones similares al cuerpo humano empleando una disolución de fosfatos (PBS) y trabajando a 37 ºC y a pH=7.4. Se estudia la influencia del proceso de fabricación y de la composición química (al añadir niobio y estaño).[EN] It is investigated the corrosion behavior of new titanium alloys by electrochemical techniques in similar conditions to the human body using a solution of phosphate (PBS) and working at 37 ° C and pH = 7.4. It is studied the influence of the manufacturing process and the chemical composition (by adding niobium and tin).Dalmau Borrás, A. (2012). Caracterización y estudio del comportamiento electroquímico de aleaciones biomédicas de titanio. http://hdl.handle.net/10251/27283Archivo delegad

Degradation mechanisms in martensitic stainless steels: wear, corrosion and tribocorrosion appraisal

[EN] A deep understanding of degradation mechanisms of metals is crucial for developing new materials with high performance. Within the different families of stainless steels, martensitic stainless steels are widely used in a great variety of industrial applications where mechanical properties, such as strength, wear resistance and fatigue behavior, need to be high. In many of those applications, such as bearings or gears, martensitic stainless steels may be subject to tribological conditions leading to wear. Furthermore, when a contact operates in a corrosive environment its deterioration can be significantly affected by surface chemical phenomena, leading to a tribocorrosion degradation mechanism. Indeed, martensitic stainless steels degrade through a great variety of wear and corrosion mechanisms. This paper aims to review the published data from 2005 to present related to wear, corrosion and tribocorrosion of martensitic stainless steels. Individual studies of tribological and corrosion behavior of martensitic stainless steels have been widely published since 2005. From the wear point of view, ploughing or abrasive wear in dry contacts involving martensitic stainless steel has been reported, while pitting corrosion is the most common mechanism for those steels. However, only nine papers were found since 2005 related to tribocorrosion of martensitic stainless steels, although most authors concluded that this joint action is the most important material degradation in martensitic stainless steels.Dalmau-Borrás, A.; Richard, C.; Igual Muñoz, AN. (2018). Degradation mechanisms in martensitic stainless steels: wear, corrosion and tribocorrosion appraisal. Tribology International. 121:167-179. https://doi.org/10.1016/j.triboint.2018.01.036S16717912

Wear model for describing the time dependence of the material degradation mechanisms of the AISI 316L in a NaCl solution

[EN] The tribo-electrochemical behavior of AISI 316L has been investigated under tribocorrosion conditions in a 3% NaCl solution and the material damage evolution with time has been analyzed. A numerical contact model based on a Boundary Element Method (BEM) has been developed in order to determine the contact pressure distribution and to quantify the worn material as a function of time. The time dependence of the tribological behavior of the material has been described. At the initial state, the high contact pressures generate a material flow causing an increase in the worn area. After around 300 cycles, the Archard wear model linearly describes the wear evolution with time. The proposed model describes the evolution with time of the wear profiles of the tested material and takes into account the plastic behavior of the material during the first cycles.This work has been funded by the Spanish Ministry of Economy and Competitiveness under the Ref. MAT2014-53764-C3-3-R and the Generalitat Valenciana under the PROMETEO program Ref. 2016/040.Dalmau-Borrás, A.; Roda Buch, A.; Rovira, A.; Navarro-Laboulais, J.; Igual Muñoz, AN. (2018). Wear model for describing the time dependence of the material degradation mechanisms of the AISI 316L in a NaCl solution. Wear. 394-395:166-175. https://doi.org/10.1016/j.wear.2017.10.015S166175394-39

Chemo-mechanical effects on the tribocorrosion behavior of titanium/ceramic dental implant pairs in artificial saliva

[EN] In this paper, the degradation mechanisms of the ceramic and the metal in Titanium/Zirconia pairs for biomedical applications were analyzed. To do that, an experimental set-up with well-controlled mechanical and chemical conditions was used based on a unidirectional ball-on-disk tribometer coupled to a potentiostat. Tribocorrosion tests were carried out in artificial saliva at different applied potentials, this is, different chemical conditions of the surface. Wear damage of the titanium/zirconia pair was influenced by the properties and the behavior of wear debris in the contact. Under passive conditions metallic and oxidized titanium particles (formed by the cyclic removal of the passive film and subsequent repassivation) were smeared and mechanically mixed within the contact forming compacted wear debris through which the loading was carried out. Properties and amount of oxidized titanium lead to low wear at low passive conditions (OCP) and higher wear at high passive conditions. Zirconia did not suffer any damage under all the studied conditions and oxidized titanium was transferred to the ball at anodic applied potentials.Authors would like to acknowledge the Generalitat Valenciana for the financial support under the PROMETEO/2016/040 and GV/2017/042 projects. A. Dalmau acknowledges the Generalitat Valenciana for her contract (APOSTD/2017/051).Dalmau-Borrás, A.; Roda Buch, A.; Rovira, A.; Navarro-Laboulais, J.; Igual Muñoz, AN. (2019). Chemo-mechanical effects on the tribocorrosion behavior of titanium/ceramic dental implant pairs in artificial saliva. Wear. 426-427:162-170. https://doi.org/10.1016/j.wear.2018.12.052162170426-42

Tribocorrosion behavior of new martensitic stainless steels in sodium chloride solution

The tribo-electrochemical behavior of two new martensitic stainless steels in a 3% NaCI solution has been investigated. Different electrochemical and surface analysis techniques (Scanning Electron Microscopy, Focused Ion Beam) were discussed to analyze the influence of the effect of the electrochemical conditions on friction and wear, and to elucidate involved wear mechanisms (plastic deformation, plastic shakedown and low-cycle fatigue). The selected stainless steels degrade through a delamination type of wear mechanism. The effects of the applied potential on wear are related to the formation of a passive film which alters the mechanical behavior of the surface and subsurface of the materials to promote wear. A coefficient of friction below 0.6 promotes nanowear, and a transition was observed when the coefficient of friction exceeded that value. (C) 2016 Elsevier B.V. All rights reserved.The authors would like to thank to BPI, Region Centre and Tours Plus for support of this research. This work is done under the project FUI 11 Mekinox.Dalmau Borrás, A.; Rmili, W.; Richard, C.; Igual Muñoz, AN. (2016). Tribocorrosion behavior of new martensitic stainless steels in sodium chloride solution. Wear. 368:146-155. doi:10.1016/j.wear.2016.09.002S14615536

Study of tribological, corrosion and tribocorrosion behavior of new martensitic stainless steels for aeronautical applications

Tesis por compendio[EN] The present study is part of the work carried out in the MEKINOX project (Mécanique Inoxydable - FUI n° 11) conducted by aeronautical industry with the main goal of developing new stainless steels for manufacturing high mechanical performance parts. Martensitic stainless steels are widely used in a great variety of industrial applications (i.e. valves, pumps, turbines, compressor components) where high mechanical properties as strength, wear resistance and fatigue behavior are needed. In many of those applications, such as bearings or gears, martensitic stainless steels may be subject to tribological conditions leading to wear. Furthermore, when a contact operates in a corrosive environment its deterioration can be significantly affected by the surface chemical phenomena, leading to a tribocorrosion degradation mechanism. Under this framework, the present Doctoral Thesis aims to evaluate the tribological, corrosion and tribocorrosion behavior of new martensitic stainless steels and their degradation mechanisms for aeronautical applications. For this, electrochemical, tribo-electrochemical and ex-situ surface analysis techniques were used. Wear damage was found to be critically affected by the hardness of the material and its hardening during sliding. Martensitic stainless steels showed higher scratch wear resistance but higher wear material loss when compared to the austenitic stainless steel. Corrosion resistance of martensitic stainless steels is driven by their passivity, whose kinetics can be described through a high field conduction model. Passive dissolution rate depends on the surface chemistry of the material, thus decreasing with the Cr content in the passive film. Degradation mechanisms involved in tribocorrosion of martensitic stainless steels included plastic deformation, shakedown and low-cycle fatigue. The consequences of those involved mechanisms depended on the prevailing electrochemical conditions.[ES] El presente estudio es parte del trabajo realizado en el proyecto MEKINOX (Mécanique Inoxydable - FUI n° 11) llevado a cabo por la industria aeronáutica, con el objetivo principal de desarrollar nuevos aceros inoxidables para la fabricación de piezas con altas prestaciones mecánicas. Los aceros inoxidables martensíticos son ampliamente utilizados en una gran variedad de aplicaciones industriales (p.e. válvulas, bombas, turbinas, componentes de compresores...) donde altas propiedades mecánicas, como la resistencia al desgaste y a la fatiga son requeridos. En muchas de estas aplicaciones, tales como rodamientos o engranajes, los aceros inoxidables martensíticos pueden estar sujetos a condiciones tribológicas que conducen al desgaste. Además, cuando un contacto opera en un ambiente corrosivo su deterioro puede verse afectado de manera significativa por los fenómenos químicos de superficie, lo que conduce a un mecanismo de degradación de tribocorrosión. Bajo este contexto, la presente Tesis Doctoral tiene como objetivo evaluar el comportamiento tribológico, frente a la corrosión y a la tribocorrosión de nuevos aceros inoxidables martensíticos y sus mecanismos de degradación en aplicaciones aeronáuticas. Para ello, se han utilizado técnicas electroquímicas, tribo-electroquímicas y de análisis de superficie ex situ. El desgaste depende de la dureza del material y de su endurecimiento durante el deslizamiento. Los aceros inoxidables martensíticos tienen una mayor resistencia al rallado pero una mayor pérdida de material en el ensayo tribológico de desgaste si se compara con el acero inoxidable austenítico. La resistencia a la corrosión de los aceros inoxidables martensíticos es promovida por su pasividad, cuya cinética puede ser descrita a través de un modelo tipo high field. La velocidad de disolución pasiva depende de la química de la superficie del material, disminuyendo por lo tanto con el contenido de Cr en la película pasiva. Los mecanismos de degradación de tribocorrosión de los aceros inoxidables martensíticos incluyen deformación plástica, shakedown y fatiga de bajo ciclo. Las consecuencias de esos mecanismos dependen de las condiciones electroquímicas del sistema.[CA] El present estudi és part del treball realitzat al projecte MEKINOX (Mécanique Inoxydable - FUI n° 11) dut a terme per la indústria aeronàutica, amb l'objectiu principal de desenvolupar nous acers inoxidables per a la fabricació de peces amb altes prestacions mecàniques. Els acers inoxidables martensítics són utilitzats en una gran varietat d'aplicacions industrials (vàlvules, bombes, turbines, components de compressors...) on altes propietats mecàniques, com la resistència al desgast i a la fatiga són requerits. En moltes d'aquestes aplicacions, com rodaments o engranatges, els acers inoxidables martensítics poden estar subjectes a condicions tribològiques que condueixen al desgast. Ademés, quan un contacte opera dins un ambient corrosiu el seu deteriorament es pot veure afectat de manera significativa pels fenòmens químics de superfície, el que condueix a un mecanisme de degradació de tribocorrosió. Sota aquest context, la present Tesi Doctoral té com a objectiu evaluar el comportament tribològic, front a la corrosió i a la tribocorrosió de nous acers inoxidables martensítics i els seus mecanismes de degradació en aplicacions aeronàutiques. Per tot això, es van utilitzar tècniques electroquímiques, tribo-electroquímiques i d'anàlisi de superfície ex-situ. El desgast depen de la duresa del material i del seu enduriment durant el lliscament. Els acers inoxidables martensítics van mostrar una major resistència al ratllat però una major pèrdua de material en l'assaig tribològic de desgast si es compara amb l'acer inoxidable austenític. La resistència a la corrosió dels acers inoxidables martensítics és promoguda per la seva passivitat, i la seua la cinètica pot ser descrita a través d'un model de tipus high field. La velocitat de dissolució passiva depen de la química de la superfície del material, disminuint per tant amb el contingut de Cr a la pel.lícula passiva. Els mecanismes de degradació en tribocorrosió dels acers inoxidables martensítics inclouen deformació plàstica, shakedown i fatiga de baix cicle. Les conseqüències d'aquests mecanismes implicats depenen de les condicions electroquímiques del sistema.Dalmau Borrás, A. (2015). Study of tribological, corrosion and tribocorrosion behavior of new martensitic stainless steels for aeronautical applications [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/57188TESISCompendi

Influence of fabrication process on electrochemical and surface properties of Ti-6Al-4V alloy for medical applications

The electrochemical behavior of rolled and sintered Ti-6Al-4V alloy has been investigated by different electrochemical techniques in order to study the influence of the fabrication process on the corrosion mechanisms of those titanium alloys. Before performing the electrochemical tests, an activation of the electrode surface is carried out to minimize the effect of the spontaneous formation of titanium oxides and to quantify the electrochemical active area of the alloys. The results show that the rolled and the sintered alloy have similar electrochemical behavior, but the sintered alloy presents higher corrosion resistance than the rolled one. Roughness factor associated to the powder metallurgy fabrication process is determined by Electrochemical Impedance Spectroscopy (EIS) and an active area 1.54 times higher than the rolled Ti-6Al-4V is obtained. The higher active area of the sintered alloys generate higher amount of metallic cations but also lower passive dissolution through the oxide film, then enhancing the passive film formation. Powder metallurgy is a promising fabrication technique to obtaining titanium biomedical alloys according to the optimal corrosion resistance. (c) 2013 Elsevier Ltd. All rights reservedThe authors would like to thank the Ministerio de Ciencia e Innovacion of the Spanish Government for the financial support under the project MAT2011-22481. They would also like to thank the Universidad Politecnica de Valencia for the specialization grant.Dalmau Borrás, A.; Guiñon Pina, V.; Devesa Albeza, F.; Amigó Borrás, V.; Igual Muñoz, AN. (2013). Influence of fabrication process on electrochemical and surface properties of Ti-6Al-4V alloy for medical applications. Electrochimica Acta. 95:102-111. doi:10.1016/j.electacta.2013.01.155S1021119

Degradation mechanisms and future challenges of titanium and its alloys for dental implant applications in oral environment

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