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  • Effect of sandblasting and residual stress on strength of zirconia for restorative dentistry applications

     Kiran Chintapalli, Ravi; Mestra Rodríguez, Alvaro Miguel; Garcia Marro, Fernando; Anglada Gomila, Marc
    Journal of the mechanical behavior of biomedical materials
    Date of publication: 2014-01
    Journal article

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    Sandblasting is a commonly used surface treatment technique for dental crowns to improve the adhesion of the mating parts of a restoration. The goal of this work is to study the effect of different sandblasting conditions on the mechanical properties of 3 mol % yttria stabilized tetragonal zirconia (3Y-TZP), such as biaxial strength, surface elastic modulus, contact hardness and residual stresses induced by sandblasting. The specimens were sandblasted considering two different particle sizes (110, 250 pm), two pressures (2 and 4 bar) and two impact angles (30 and 90). Biaxial strength of 3Y-TZP increases when sandblasted with 110 mu m particles while its decreases with 250 mu m particles for impact angle of 90. Strength increases slightly when sandblasting with 30' impact angle regardless of the size of the particle. Elastic modulus and contact hardness were not affected by sandblasting with 110 mu m particles, and compressive residual stresses are produced down to a depth of similar to 10 mu m. (C) 2013 Elsevier Ltd. All rights reserved.

  • Mechanical properties and resistance to low temperature degradation of surface nitrided 3Y-TZP

     Valle Chiro, Jorge Antonio; Mestra Rodríguez, Alvaro Miguel; Garcia Marro, Fernando; Anglada Gomila, Marcos Juan
    Journal of the european ceramic society
    Date of publication: 2013-12
    Journal article

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    3Y-TZP has been one of the most applied ceramics in the biomedical field, specifically for hip, knee and dental implants, given its high strength, moderate fracture toughness and excellent biocompatibility. However, hydrothermal degradation has meant an important disadvantage, as surface t-m transformation, followed by microcracking, can lead to the premature failure of the implant. In this work, surface nitriding at 1600, 1500 and 1400°C for 1, 2 and 4h with N2 gas and ZrN powder was applied and optimised to avoid hydrothermal degradation. Nitriding at 1600 and 1500°C produces a harder low-toughness surface, not adequate for structural implants. It is shown that the most favourable condition is nitriding at 1400°C for 1h, since the mechanical properties of the original 3Y-TZP are not affected with the advantage of retarding hydrothermal degradation by a factor close to 10.

    3Y-TZP has been one of the most applied ceramics in the biomedical field, specifically for hip, knee and dental implants, given its high strength, moderate fracture toughness and excellent biocompatibility. However, hydrothermal degradation has meant an important disadvantage, as surface t–m transformation, followed by microcracking, can lead to the premature failure of the implant. In this work, surface nitriding at 1600, 1500 and 1400 °C for 1, 2 and 4 h with N2 gas and ZrN powder was applied and optimised to avoid hydrothermal degradation. Nitriding at 1600 and 1500 °C produces a harder low-toughness surface, not adequate for structural implants. It is shown that the most favourable condition is nitriding at 1400 °C for 1 h, since the mechanical properties of the original 3Y-TZP are not affected with the advantage of retarding hydrothermal degradation by a factor close to 10.

  • Effect of sigma phase on the wear behavior of a super duplex stainless steel

     Fargas Ribas, Gemma; Mestra Rodríguez, Alvaro Miguel; Mateo Garcia, Antonio Manuel
    Wear
    Date of publication: 2013-06-15
    Journal article

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  • Fatigue performance improvement of electrical discharge machined hardmetals by means of combined thermal annealing and surface modification routes

     Llanes Pitarch, Luis Miguel; Salán Ballesteros, Mª Núria; Casas Aguirregomezcorta, Begoña; Mestra Rodríguez, Alvaro Miguel; Torres Hernandez, Yadir
    International journal of refractory metals and hard materials
    Date of publication: 2013-01
    Journal article

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    Electrical discharge machining (EDM) provides an effective means of shaping hardmetals. However, it is also known that surface integrity of these materials may be affected by EDM, degrading their tribomechanical characteristics. This work focuses on assessing the use of two different surface modification routes: thermomechanical treatments (shot blasting, polishing and final high temperature annealing) and/or physical vapor deposition of hard coatings, for improving the fracture and fatigue strength of an EDM-shaped fine-grained hardmetal grade. In doing so, an optimal EDM's surface finish variant and a diamond ground and polished one are used. Mechanical behavior is evaluated under four-point bending and fatigue characterization is given in terms of fatigue limit following the staircase method. Experimental results indicate that both approaches markedly decrease the lessening effect of EDM on the mechanical strength of hardmetals, although a complete fracture and fatigue strength retention is only achieved by combining both of them. The improved mechanical behavior is rationalized on the basis of the beneficial changes induced by surface modification on the effective residual stress field at the surface of EDM-shaped hardmetals, as assessed by a linear elastic fracture mechanics analysis combined with fractographic examination.

    Electrical discharge machining (EDM) provides an effective means of shaping hardmetals. However, it is also known that surface integrity of these materials may be affected by EDM, degrading their tribomechanical characteristics. This work focuses on assessing the use of two different surface modification routes: thermomechanical treatments (shot blasting, polishing and final high temperature annealing) and/or physical vapor deposition of hard coatings, for improving the fracture and fatigue strength of an EDM-shaped fine-grained hardmetal grade. In doing so, an optimal EDM's surface finish variant and a diamond ground and polished one are used. Mechanical behavior is evaluated under four-point bending and fatigue characterization is given in terms of fatigue limit following the staircase method. Experimental results indicate that both approaches markedly decrease the lessening effect of EDM on the mechanical strength of hardmetals, although a complete fracture and fatigue strength retention is only achieved by combining both of them. The improved mechanical behavior is rationalized on the basis of the beneficial changes induced by surface modification on the effective residual stress field at the surface of EDM-shaped hardmetals, as assessed by a linear elastic fracture mechanics analysis combined with fractographic examination.

  • Tratamientos post-mecanizado para la mejora de la integridad mecánica de metales duros electroerosionados

     Llanes Pitarch, Luis Miguel; Casas Aguirregomezcorta, Begoña; Torres Hernandez, Yadir; Mestra Rodríguez, Alvaro Miguel
    Congreso Nacional de Tratamientos Térmicos y de Superficie
    Presentation's date: 2013
    Presentation of work at congresses

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  • Micromecanismos de daño sub-superficiales inducidos por indentación esférica en aceros herramientas recubiertos

     Ramírez Sandoval, Giselle; Jimenez Pique, Emilio; Mestra Rodríguez, Alvaro Miguel; Vilaseca, Montse; Casellas, Daniel; Llanes Pitarch, Luis Miguel
    Congreso Nacional de Tratamientos Térmicos y de Superficie
    Presentation's date: 2013
    Presentation of work at congresses

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  • Notch effects on the fatigue endurance of cemented carbides

     Coureaux Mustelier, David; Reig, Begoña; Rimbau, Victor; D'Armas, Heber; Mestra Rodríguez, Alvaro Miguel; Llanes Pitarch, Luis Miguel
    Euro PM Congress & Exhibition
    Presentation's date: 2013
    Presentation of work at congresses

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  • Mechanical response under contact loads of AlCrN-coated tool materials

     Yang, Jing; Botero Vega, Carlos Alberto; Cornu, Nicolas; Ramírez Sandoval, Giselle; Mestra Rodríguez, Alvaro Miguel; Llanes Pitarch, Luis Miguel
    EEIGM International Conference on Advanced Materials Research
    Presentation's date: 2013-03-21
    Presentation of work at congresses

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    The mechanical behavior under contact loading of systems consisting of PVD AlCrN film deposited onto two distinct hard substrates - cemented carbides and tool steel is studied by means of indentation testing techniques, under monotonic and cyclic condition. Experimental work includes assessment of critical applied loads for emergence of circular cracks at the coating surface, as well as evaluation of both surface and subsurface damage evolution. Results indicate that both coated systems are susceptible to mechanical degradation associated with repetitive contact load. Furthermore, significant differences on contact fatigue behavior between the two studied coated systems are evidenced under consideration of cracking evolution at top surface and penetration towards the substrate. In this regard, the intrinsic mechanical properties of the substrate are pointed out as key feature for rationalizing the experimental findings.

  • Decoration of indentation cracks in 3Y-TZP by hydrothermal ageing

     Garcia Marro, Fernando; Camposilvan, Erik; Mestra Rodríguez, Alvaro Miguel; Anglada Gomila, Marcos Juan
    Encuentro del Grupo Español de Fractura
    Presentation's date: 2012-03-21
    Presentation of work at congresses

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    Las grietas de indentación en cerámicas son frecuentemente utilizadas no sólo para estimar semi-empíricamente la tenacidad a fractura KIC, sino también cómo método para crear grietas agudas superficiales y semielípticas a partir de las cuales analizar la tenacidad de fractura. Para ello es necesario conocer la forma exacta de la grieta inicial, así como en el momento de fractura inestable. A menudo dicha identificación no es obvia debido a un pobre contraste visual de las superficies fracturadas. La circona estabilizada con 3% molar de itria (3Y-TZP) es una cerámica biocompatible con buenas propiedades mecánicas que la hacen interesante para su utilización en prótesis dentales y cabezas femorales. Adicionalmente, la 3Y-TZP es susceptible a un fenómeno de degradación a baja temperatura por el cual un ambiente acuoso produce una transformación de fase en la superficie expuesta. En este trabajo se ha aprovechado la susceptibilidad a degradación hidrotérmica de la 3Y-TZP para revelar grietas de indentación en probetas que son ensayadas a flexión posteriormente. Se muestra como grietas de indentación en 3Y-TZP afectadas por vapor de agua son claramente reveladas en la posterior caracterización fractográfica. Se consideraron diferentes tipos de 3Y-TZP con diferentes grados de susceptibilidad a degradación hidrotérmica. Se observó que una exposición en autoclave de unas pocas horas es suficiente para revelar las grietas en la superficie de fractura sin llegar a afectar la carga de rotura de las probetas. Por consiguiente, la técnica puede utilizarse para obtener un conocimiento preciso de la geometría de las grietas de indentación utilizadas para determinar la tenacidad de fractura. // Indentation cracks on ceramics are frequently used not only for the semi-empirical determination of the fracture toughness KIC but also as a method for generating semielliptical surface cracks to be used in as starting cracks in fracture and fatigue studies. Tetragonal zirconia stabilized with 3 % mol of yttria (3Y-TZP) is a biocompatible ceramic with good mechanical properties which is used in dental and femoral prostheses applications. Additionally, 3Y-TZP is susceptible to low temperature degradation in which a hydrothermal environment induces a phase transformation of the exposed surface. In the present work, this degradation susceptibility of 3Y-TZP has been used to reveal indentation crack profiles on specimens which were tested by flexural bending afterwards. Different types of 3Y-TZP were considered which presented different degrees of susceptibility to hydrothermal degradation. It is shown that these cracks are clearly decorated by the water vapour which make them easily revealed on the fracture surfaces. An exposition of few hours in autoclave is sufficient for revealing the indentation cracks on the fracture surface without affecting the fracture load of the specimens. Therefore, the method can be applied to visualize with precision the geometry of indentation cracks which are used to determine the fracture toughness.

  • Aging resistance and fracture toughness of ceria¿infiltrated zirconia

     Camposilvan, Erik; Garcia Marro, Fernando; Mestra Rodríguez, Alvaro Miguel; Anglada Gomila, Marcos Juan
    Congreso Nacional de Materiales
    Presentation's date: 2012-05-30
    Presentation of work at congresses

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    The main drawback of yttria stabilized zirconia (3Y-TZP) is represented by the Low Temperature Degradation (LTD), which consists in the progressive transformation of the tetragonal phase, metastable at room temperature, to the stable monoclinic phase, when the material is exposed to humid environment and moderate temperatures. LTD is responsible for a decrease in superficial mechanical properties for relatively short exposure times, while bulk properties are affected for longer exposures. These effects have limited the use of 3Y-TZP in biomedical devices during the last years. A process based on the addition of ceria, a stabilizer of tetragonal phase less susceptible to LTD, has been recently developed. A solution of Cerium salts is infiltrated into the ceramic piece at the porous pre-sintered state. After sintering, ceria diffuses into zirconia lattice. In a first stage, the process was optimized in terms of LTD resistance, maintaining the microstructure, strength and hardness of 3Y-TZP. Nevertheless, a slight decrease in indentation fracture toughness was recorded. In a second stage, the research has been focused on the possibility of compensating the toughness decrease by sintering at higher temperature, obtaining a moderate increase in grain size without prejudicial effects on the LTD resistance achieved with ceria addition.

  • Influencia de la degradación hidrotérmica en la resistencia mecánica y en el comportamiento al desgaste de 3Y-TZP

     Mestra Rodríguez, Alvaro Miguel; Garcia Marro, Fernando; Kiran Chitapalli, Ravi; de Armas Sancho, Zamir; Anglada Gomila, Marcos Juan
    Encuentro del Grupo Español de Fractura
    Presentation's date: 2012-03-21
    Presentation of work at congresses

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    En este trabajo se realiza un estudio comparativo de la influencia de la degradación hidrotérmica a baja temperatura de circona tetragonal estabilizada con el 3% molar de Itria (3Y-TZP) en la resistencia mecánica a flexión y en el comportamiento bajo cargas de indentación esférica. Se presentan resultados de resistencia mecánica a flexión y de indentación esférica monotónica así como de ensayos de rayado en probetas artificialmente degradadas durante diferentes períodos de tiempo. Se pone de manifiesto que la resistencia mecánica a flexión es poco sensible a la degradación; por el contrario, los ensayos superficiales ponen claramente de manifiesto la presencia de degradación en sus etapas iniciales. Se constata la fuerte sensibilidad de la resistencia al desgaste y de la fatiga por contacto a la presencia de degradación hidrotérmica a baja temperatura. Los resultados se analizan en términos de la capa degradada de estructura monoclínica que se forma durante la degradación. // In the present work a comparative study is carried out of the influence of low hydrothermal degradation on the bend strength and in the behaviour under contact loading of zirconia polycrystals stabilised with 3% molar of yttria (3YTZP). Results of bend strength by four point loading and monotonic spherical indentation and scratch testing are compared in specimen degraded for different times. It is shown that bending tests are very insensitive to degradation; on the contrary the surface testing methods show clearly the influence of degradation in their initial stages. This has important consequences in their behaviour in contact fatigue and wear behaviour, which it is shown are strongly affected by low temperature degradation. The results are analysed in terms of the monoclinic degraded layer that forms during degradation.

  • Microstructural effects on damage induced under monotonic and cyclic contact loading in cemented carbides

     Coureaux Mustelier, David; Ingebrand, A.; Góez Úsuga, Alexey; Tarres, Elena; Mestra Rodríguez, Alvaro Miguel; Jimenez Pique, Emilio; Llanes Pitarch, Luis Miguel
    European Inter-Regional Conference on Ceramics
    Presentation's date: 2012
    Presentation of work at congresses

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  • Proceedings of the 13th European Inter-Regional Conference on Ceramics

     Anglada Gomila, Marcos Juan; Jimenez Pique, Emilio; Garcia Marro, Fernando; Mestra Rodríguez, Alvaro Miguel
    European Inter-Regional Conference on Ceramics
    Presentation's date: 2012
    Presentation of work at congresses

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  • Surface damage on PVD TiN and CrN coatings under monotonic and cyclic spherical indentation

     Tarrago Cifre, Jose Maria; Mir, Jordi; Mestra Rodríguez, Alvaro Miguel; Heredero Alari, Francisco; Llanes Pitarch, Luis Miguel
    European Inter-Regional Conference on Ceramics
    Presentation's date: 2012-09-12
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  • Effect of MWCNT addition on the friction coefficient and the electrical properties of 3Y-TZP

     Melk, Latifa; Garcia Marro, Fernando; Mestra Rodríguez, Alvaro Miguel; Jimenez Pique, Emilio; Anglada Gomila, Marcos Juan
    European Inter-Regional Conference on Ceramics
    Presentation's date: 2012-09-12
    Presentation of work at congresses

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  • Determination of the intrinsic fracture toughness from the COD analysis of indentation cracks in Spark Plasma Sintered 3Y-TZP reinforced with MWCNT

     Garcia Marro, Fernando; Kiran Chitapalli, Ravi; Mestra Rodríguez, Alvaro Miguel; Anglada Gomila, Marcos Juan
    Encuentro del Grupo Español de Fractura
    Presentation's date: 2012-03-21
    Presentation of work at congresses

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    El método de la indentación para medir la tenacidad de fractura ha sido ampliamente utilizado en materiales frágiles debido a su sencillez y a que puede realizarse en volúmenes pequeños de material. Especialmente en estos casos, las tenacidades de fractura obtenidas mediante el método de indentación pueden llegar a ser muy distintas de los valores reales obtenidos mediante métodos rigurosos basados en un conocimiento preciso de todos los parámetros que intervienen en la fractura. Esto ha llevado a desarrollar métodos que relacionan el perfil de la abertura de la grieta de indentación con la tenacidad intrínseca de fractura KI0. En este trabajo se ha estudiado la cerámica 3Y-TZP y el material compuesto formado por 3Y-TZP y 2% en volumen de nanotubos de carbono con paredes multicapa (MWCNT) ambos producidos por Spark Plasma Sintering (SPS). El método de análisis del COD permitió comprobar que la adición de este contenido de MWCNT no afecta prácticamente al COD medido experimentalmente y que la tenacidad intrínseca KI0 es por tanto muy similar para ambos materiales. Estas observaciones en principio no justifican las diferencias en tenacidad de fractura determinadas por el método clásico de tenacidad de fractura por indentación en los materiales estudiados. // The indentation method has been widely used to measure the fracture toughness in fragile materials due to its simplicity and that only needs of a small sample. However, it is well known that the fracture toughness values obtained by indentation methods can be substantially different from the values obtained from more rigorous methods which are based on a precise knowledge of all parameters involved in fracture. This situation has lead to the development of new methods that investigate the crack opening displacement (COD) and relate it to the intrinsic fracture toughness KI0. In the present work, a 3Y-TZP ceramic has been studied together with a composite containing 2% vol. of multiwall carbon nanotubes (MWCNT); both of which were produced by Spark Plasma Sintering (SPS). The COD method showed that the addition of MWCNTs did not effectively affect the COD and the intrinsic fracture toughness KI0 was thus very similar in both materials. These observations in principle do not justify the differences determined by the classical indentation fracture toughness method on the present materials.

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    Influencia de la degradación hidrotérmica en la resistencia mecánica y comportamiento al desgaste de 3Y-TZP  Open access

     Mestra Rodríguez, Alvaro Miguel; Garcia Marro, Fernando; Kiran Chitapalli, Ravi; de Armas Sancho, Zamir; Anglada Gomila, Marcos Juan
    Encuentro del Grupo Español de Fractura
    Presentation's date: 2012
    Presentation of work at congresses

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    En este trabajo se realiza un estudio comparativo de la influencia de la degradación hidrotérmica a baja temperatura de circona tetragonal estabilizada con el 3% molar de Itria (3Y-TZP) en la resistencia mecánica a flexión y en el comportamiento bajo cargas de indentación esférica. Se presentan resultados de resistencia mecánica a flexión y de indentación esférica monotónica así como de ensayos de rayado en probetas artificialmente degradadas durante diferentes períodos de tiempo. Se pone de manifiesto que la resistencia mecánica a flexión es poco sensible a la degradación; por el contrario, los ensayos superficiales ponen claramente de manifiesto la presencia de degradación en sus etapas iniciales. Se constata la fuerte sensibilidad de la resistencia al desgaste y de la fatiga por contacto a la presencia de degradación hidrotérmica a baja temperatura. Los resultados se analizan en términos de la capa degradada de estructura monoclínica que se forma durante la degradación.

  • Structural and microstructural characterization of the max-phase Ti3SiC2

     Hernandez Edo, Eric; Mir Carbonell, Jordi; Heredero Alari, Francisco; Mestra Rodríguez, Alvaro Miguel; Jimenez Pique, Emilio; Anglada Gomila, Marcos Juan
    European Inter-Regional Conference on Ceramics
    Presentation's date: 2012
    Presentation of work at congresses

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  • Increasing low temperature degradation resistance by a thin diffussion layer of cerium in 3Y-TZP

     Garcia Marro, Fernando; Camposilvan, Erik; Jimenez Pique, Emilio; Mestra Rodríguez, Alvaro Miguel; Anglada Gomila, Marcos Juan
    European Inter-Regional Conference on Ceramics
    Presentation's date: 2012-09-12
    Presentation of work at congresses

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  • Determination of the intrinsic fracture toughness from COD analysis of indentation cracks in spark plasma sintered 3Y-TZP reinforced with MWCNT

     Garcia Marro, Fernando; Chintapalli, Ravi Kiran; Mestra Rodríguez, Alvaro Miguel; Anglada Gomila, Marcos Juan
    Anales de mecánica de la fractura
    Date of publication: 2012
    Journal article

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    Influencia de la degradación hidrotérmica en la resistencia mecánica y comportamiento al desgaste de 3Y-TZP  Open access

     Mestra Rodríguez, Alvaro Miguel; Garcia Marro, Fernando; Kiran Chitapalli, Ravi; de Armas Sancho, Zamir; Anglada Gomila, Marcos Juan
    Anales de mecánica de la fractura
    Date of publication: 2012
    Journal article

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    En este trabajo se realiza un estudio comparativo de la influencia de la degradación hidrotérmica a baja temperatura de circona tetragonal estabilizada con el 3% molar de Itria (3Y-TZP) en la resistencia mecánica a flexión y en el comportamiento bajo cargas de indentación esférica. Se presentan resultados de resistencia mecánica a flexión y de indentación esférica monotónica así como de ensayos de rayado en probetas artificialmente degradadas durante diferentes períodos de tiempo. Se pone de manifiesto que la resistencia mecánica a flexión es poco sensible a la degradación; por el contrario, los ensayos superficiales ponen claramente de manifiesto la presencia de degradación en sus etapas iniciales. Se constata la fuerte sensibilidad de la resistencia al desgaste y de la fatiga por contacto a la presencia de degradación hidrotérmica a baja temperatura. Los resultados se analizan en términos de la capa degradada de estructura monoclínica que se forma durante la degradación.

  • Influence of substrate microstructure on the contact fatigue strength of coated cold-work tool steels

     Ramírez Sandoval, Giselle; Mestra Rodríguez, Alvaro Miguel; Casas, B.; Valls, Isaac; Martinez, R.; Bueno, R.; Góez Úsuga, Alexey; Mateo Garcia, Antonio Manuel; Llanes Pitarch, Luis Miguel
    Surface and coatings technology
    Date of publication: 2012-02-25
    Journal article

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    The contact fatigue behavior of three microstructurally distinct tool steels coated with a physical vapor deposited TiN film is studied. Substrate microstructural differences come from variations in either chemical composition or processing route. Experimental procedure is based on determining critical applied loads and pressures, under both monotonic and cyclic spherical indentation loading conditions, for emergence and evolution of distinct damage modes at the coating surface: circumferential cracking, cohesive spallation and interfacial decohesion. Experimental results indicate that all coating/substrate systems evaluated are susceptible to mechanical degradation associated with repetitive contact loading. This is clearly discerned from the fact that some damage mechanisms, such as cohesive spallation at the coating and adhesion failure at the interface, are exclusively observed under cyclic loading. Substrate microstructure effects are evidenced by consideration of coating detachment as the critical damage mechanism. In this regard, crack nucleation resistance of primary carbides is pointed out as the main reason for the distinct response against decohesion observed under cyclic contact loads. Hence, finer and tougher, as well as less irregular and more homogeneously distributed primary carbides are pointed out as key microstructural features for enhancing contact fatigue strength of coated cold-work tool steels.

  • Decoration of indentation cracks in 3Y-TZP by hydrothermal ageing

     Garcia Marro, Fernando; Camposilvan, Erik; Mestra Rodríguez, Alvaro Miguel; Anglada Gomila, Marcos Juan
    Anales de mecánica de la fractura
    Date of publication: 2012
    Journal article

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    Las grietas de indentación en cerámicas son frecuen temente utilizadas no sólo para estimar semi-empíri camente la tenacidad a fractura K IC , sino también cómo método para crear grietas aguda s superficiales y semielípticas a partir de las cuales analizar la tenacidad de fractura. Para ello es necesario conocer la forma exacta de la grieta inicial, así como en el momento de fractura inestable. A menudo dicha ident ificación no es obvia debido a un pobre contraste v isual de las superficies fracturadas. La circona estabilizada co n 3% molar de itria (3Y-TZP) es una cerámica biocom patible con buenas propiedades mecánicas que la hacen interesan te para su utilización en prótesis dentales y cabez as femorales. Adicionalmente, la 3Y-TZP es susceptible a un fenóm eno de degradación a baja temperatura por el cual u n ambiente acuoso produce una transformación de fase en la sup erficie expuesta. En este trabajo se ha aprovechado la susceptibilidad a degradación hidrotérmica de la 3Y -TZP para revelar grietas de indentación en probeta s que son ensayadas a flexión posteriormente. Se muestra como grietas de indentación en 3Y-TZP afectadas por vap or de agua son claramente reveladas en la posterior caracterizació n fractográfica. Se consideraron diferentes tipos d e 3Y-TZP con diferentes grados de susceptibilidad a degradación hidrotérmica. Se observó que una exposición en auto clave de unas pocas horas es suficiente para revelar las grietas en la superficie de fractura sin llegar a afectar l a carga de rotura de las probetas. Por consiguiente, la técnica puede utiliz arse para obtener un conocimiento preciso de la geo metría de las grietas de indentación utilizadas para determinar l a tenacidad de fractura.

  • BIOCERAMICS FOR BONE REPAIR

     Jimenez Pique, Emilio; Mestra Rodríguez, Alvaro Miguel; Garcia Marro, Fernando; Anglada Gomila, Marcos Juan
    Participation in a competitive project

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    Propiedades mecánicas a flexión a temperatura ambiente y a 150 ºC para un material compuesto denominado FERROTEX  Open access

     Mestra Rodríguez, Alvaro Miguel; Mateo Garcia, Antonio Manuel
    Date: 2012
    Report

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    Determinar las propiedades mecánicas a flexión a temperatura ambiente y a 150 ºC para un material compuesto denominado FERROTEX.

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    Propiedades mecánicas a tracción  Open access

     Mestra Rodríguez, Alvaro Miguel; Mateo Garcia, Antonio Manuel
    Date: 2012
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    Propiedades mecánicas a tracción a 450ºC  Open access

     Mestra Rodríguez, Alvaro Miguel; Mateo Garcia, Antonio Manuel
    Date: 2012
    Report

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    Propiedades mecánicas a tracción de DIUs  Open access

     Mestra Rodríguez, Alvaro Miguel; Fargas Ribas, Gemma
    Date: 2012
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  • Estudio rotura eje aerogenerador

     Mateo Garcia, Antonio Manuel; Heredero Alari, Francisco; Mestra Rodríguez, Alvaro Miguel
    Date: 2012
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  • Nuevos materiales nanocompuestos de circona con mayor tenacidad de fractura y resistencia a la degradación hidrotérmica

     Jimenez Pique, Emilio; Garcia Marro, Fernando; Mestra Rodríguez, Alvaro Miguel; Anglada Gomila, Marcos Juan
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  • Reparaciones con composites en tuberías

     Mateo Garcia, Antonio Manuel; Mestra Rodríguez, Alvaro Miguel
    Date: 2012
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  • Contact damage and residual strength in hardmetals

     Góez Úsuga, Alexey; Coureaux Mustelier, David; Ingebrand, A.; Reig, B.; Tarres, Elena; Mestra Rodríguez, Alvaro Miguel; Mateo Garcia, Antonio Manuel; Jimenez Pique, Emilio; Llanes Pitarch, Luis Miguel
    International journal of refractory metals and hard materials
    Date of publication: 2012-01
    Journal article

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    Daño por contacto hertziano en un nanocompuesto Ce-TZP/Al2O3  Open access

     Garcia Marro, Fernando; Mestra Rodríguez, Alvaro Miguel; Anglada Gomila, Marcos Juan
    Encuentro del Grupo Español de Fractura
    Presentation of work at congresses

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    El material compuesto Ce-TZP/Al2O3 es una cerámica nanoestructurada con granos de alúmina y circona tetragonal estabilizada con ceria. Actualmente, este tipo de compuestos están siendo desarrollados con el objetivo de sustituir a la circona dopada con 3% molar de itria de grado biomédico. En este trabajo, se ha estudiado el comportamiento de este compuesto bajo contacto monotónico aplicado mediante indentación esférica. Mediante espectroscopia micro-Raman se ha puesto en evidencia el cambio de fase local inducido por acción de las tensiones en la huella residual. Esto indica que el mecanismo de transformación de fase es máximo en los bordes de la huella, que corresponde a la zona donde el campo de tensiones de tracción es máximo de acuerdo con la teoría hertziana de la indentación esférica. Las conclusiones son que a pesar de que las grietas anillo aparecen para cargas de indentación esférica similares a las correspondientes a la circona dopada con itria, en el presente nanocompuesto su penetración hacia el interior del material es mucho menor, lo cual pone de manifiesto una mayor tolerancia al daño. Esta mayor tolerancia se relaciona a una mayor a tenacidad de fractura. // The composite material Ce-TZP/Al2O3 is a nanostructured ceramic with alumina grains and tetragonal zirconia stabilized with ceria. Currently, this type of composites is being developed with the objective to substitute biomedical grade tetragonal zirconia polycrystals doped with 3% molar yttria. In the present work, the microstructure and mechanical properties of such a composite have been studied. Additionally, the behaviour under monotonic contact loading has also been studied by spherical indentation at different load ranges. Raman spectroscopy revealed the local phase transformation induced by the locally applied stresses on the residual imprint. This indicates that the phase transformation mechanism is maximal at the border imprints, which corresponds to the zone where the traction stresses are maximal according to classical Hertzian theory. The conclusions are that while the crack rings appear at similar indentation loads as 3Y-TZP, the penetration of these cracks in the interior of the composite is much smaller, which means a higher tolerance to contact damage. This higher tolerance is related to its higher fracture toughness.

  • Resistencia a fractura y fatiga de materiales compuestos wc-co: influencia de la microestructura y sensibilidad a la presencia de entallas

     Coureaux Mustelier, David; Góez Úsuga, Alexey; Mestra Rodríguez, Alvaro Miguel; Mateo Garcia, Antonio Manuel; Llanes Pitarch, Luis Miguel
    Congreso Nacional de Materiales Compuestos
    Presentation's date: 2011-07-05
    Presentation of work at congresses

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  • Influence of substrate microstructure on the contact fatigue

     Llanes Pitarch, Luis Miguel; Ramírez Sandoval, Giselle; Mestra Rodríguez, Alvaro Miguel; Casas, B.; Valls, I.; Martínez, R.; Bueno, R.; Góez Úsuga, Alexey; Mateo Garcia, Antonio Manuel
    International Conference on Advanced Materials Research EEIGM / AMASE / FORGEMAT
    Presentation's date: 2011-11-07
    Presentation of work at congresses

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    Anodic oxidation of titanium for implants and prothesis: processing characterization and potential improvement of osteointegration  Open access

     Pavon, Juan José; Galvis, Oscar; Echevarria, F; Castaño, J; Echeverry, M; Robledo, S; Jimenez Pique, Emilio; Mestra Rodríguez, Alvaro Miguel; Anglada Gomila, Marcos Juan
    Congreso Latinoamericano de Ingeniería Biomédica
    Presentation's date: 2011
    Presentation of work at congresses

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    Among all biomaterials used for bone replacement, it is recognized that both commercially pure titanium (Ti c.p.) and Ti6Al4V alloy are the materials that show the best in vivo performance due to their excellent balance between mechanical, physical-chemical and biofunctional properties. However, one of its main drawbacks, which compromise the service reliability of the implants and its osteointegration capacity, is the thin film of fibrous tissue around the implant due to the bioinert behaviour of titanium. One of the alternatives more studied to improve the titanium osteointegration is the surface modification through the control of the roughness parameters within a specific range which is recognized that improve the osteoblasts adhesion. In this work is investigated the influence of different electrochemical processing conditions for surface modification of c.p. Ti, in their microstructural, morphological, topographical and mechanical properties, as well as in their biological behaviour. The electrochemical anodizing treatment was performed by using different electrolytes based on phosphoric acid (H3PO4), sulphuric acid (H2SO4) with a fluoride salt; and the Focused Ion Beam (FIB) technique, normally named as Nanolab, was used for the microstructural, chemical and morphological characterization, as well as the confocal laser microscopy technique which also served for roughness measurements. The mechanical response of the anodic layers was evaluated through the using of a scratch tester which showed the critical loads for the coating damages. The characterization results showed that both, concentrations and electrolyte species, clearly influenced the morphological and topographical features, as well as the chemical composition of the anodic layer. By using the FIB was possible to detect nanopores within both the surface and the bulk of the coating. Some of the conditions generated a very special coating morphology which promoted a better osteoblasts adhesion. Contrary to what it was a priory expected, all anodic coatings showed high critical loads for damages during scratch test, despite their high porosity, which could be related with some defects coalescence mechanism that allows dissipating the high stress concentration applied during the test.

  • Sliding wear behaviour of surface nitrided zirconia

     Valle Chiro, Jorge Antonio; Mestra Rodríguez, Alvaro Miguel; Garcia Marro, Fernando; Anglada Gomila, Marcos Juan
    Congreso Ibérico de Tribología
    Presentation's date: 2011-06-16
    Presentation of work at congresses

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    Tetragonal polycrystalline zirconia stabilised with 3% molar yttria (3Y-TZP) has found wide applications in orthopaedics and dentistry because of its excellent mechanical properties (flexural strength above 1000 MPa, fracture toughness about 5 MPa·m1/2, hardness above 12 GPa) and biocompatibility. However, 3Y-TZP has a strong drawback: poor resistance to hydrothermal ageing also referred to as low temperature degradation (LTD). Nitriding of 3Y-TZP can make the surface resistance to LTD, but surface mechanical properties are also affected. In this work, the sliding wear resistances of as sintered and nitrided 3Y-TZP have been studied and compared. Nitriding has been carried out by embedding 3Y-TZP in a powder of ZrN and posterior heat treatment at 1400, 1500 and 1600 °C in a nitrogen atmosphere. The sliding wear behaviour of as sintered and nitrided surfaces was studied by means of ball on disc tests. The results show that by nitriding at 1400 °C the nitrided surface is resistance to LTD without any significant drop in the surface mechanical properties, so that it has similar sliding wear behaviour and surface mechanical properties as those of the starting 3Y-TZP. The results are discussed in terms of the change in the microstructure induced by nitriding.

  • Comportamiento a fatiga de un nanocompuesto Ce-TZP/Al2O3

     Mestra Rodríguez, Alvaro Miguel; Garcia Marro, Fernando; de Armas Sancho, Zamir; Anglada Gomila, Marcos Juan
    Congreso Nacional de Materiales Compuestos
    Presentation's date: 2011-07-08
    Presentation of work at congresses

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    Se ha evaluado la resistencia a flexión biaxial y el comportamiento a fatiga de un nanocompuesto cerámico basado en Ce-TZP y Al2O3. Los ensayos se realizaron en flexión biaxial y se ha determinado la resistencia y el módulo de Weibull, así como el límite de fatiga para 106 ciclos con R=0.1 en aire. Los resultados se comparan con el comportamiento de 3Y-TZP bajo condiciones similares.

  • Hydrothermal ageing of smooth and cracked 3Y-TZP

     Garcia Marro, Fernando; Mestra Rodríguez, Alvaro Miguel; Anglada Gomila, Marcos Juan
    Conference of the European Ceramic Society
    Presentation's date: 2011
    Presentation of work at congresses

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    The effect of hydrothermal degradation on the flexural strength of smooth and indented specimens of tetragonal polycrystalline zirconia doped with 3% mol yttria (3Y-TZP) has been investigated. The specimens were exposed for several periods of time to water vapour at 131 ºC in autoclave. The t-m transformation was studied by micro-Raman spectroscopy and SEM on the specimen’s surface and on Palmqvist crack faces after fracture. It is shown here that the Weibull modulus of the flexure strength of smooth degraded specimens increases, while the flexural strength decreases in the ageing interval studied. On the contrary, specimens with indentation cracks larger than the size of crack-like natural defects, increase strongly their flexural strength after an incubation ageing time. It is shown here that the Weibull modulus of the flexure strength of smooth degraded specimens increases, while the flexural strength decreases in the ageing interval studied. On the contrary, specimens with indentation cracks larger than the size of crack-like natural defects, increase strongly their flexural strength after an incubation ageing time. It is proposed that crack tip blunting by water vapour is responsible for this effect, which has not been previously reported. It is also shown that exposure to water vapour can be an excellent tool to reveal cracks in 3Y-TZP.

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    Hydrothermal ageing of cracked 3Y-TZP  Open access

     Garcia Marro, Fernando; Mestra Rodríguez, Alvaro Miguel; Anglada Gomila, Marcos Juan
    Encuentro del Grupo Español de Fractura
    Presentation of work at congresses

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    En la circona dopada con 3% molar de itria, el vapor de agua puede inducir la transformación de la fase tetragonal a monoclínica en la superficie. Dicha transformación se extiende hacia el interior acompañada por la aparición de microfisuras, lo que induce una pérdida de la integridad estructural. Este fenómeno de degradación a baja temperatura (LTD) es una clara desventaja para la utilización del material en atmósferas húmedas. Sin embargo, el efecto del agua sobre grietas de indentación no ha sido estudiado. Este trabajo estudia la influencia de LTD en la resistencia mecánica de dichas grietas. Los resultados muestran sorprendentemente un incremento de la resistencia mecánica en probetas indentadas sometidas a largos tiempos de degradación; al contrario del comportamiento en probetas sin indentar. Para explicar este comportamiento, se ha evaluado también la influencia de las tensiones residuales y el tratamiento de recocido adecuado para eliminarlas. Finalmente, se plantean los mecanismos que explican el aumento de la resistencia mecánica observado. // In zirconia stabilised with 3% molar of yttria, the water vapour can induce the transformation from tetragonal to monoclinic phase at the surface. This transformation propagates to the bulk with the apparition of microcracks; which induce a loss in the structural integrity. This low temperature degradation (LTD) is a clear disadvantage for the application of the material in humid environments. On the other hand, the effect of the water on indentation-induced cracks has not been previously studied. This work studies the change in mechanical strength of indentation cracks submitted to water vapour. The results show how, after long degradation times, there is surprisingly an increase in mechanical strength. This is the opposite behaviour as the one expected in normal specimens which are not indented. To explain the observed behaviour here, the influence of the residual tensions was evaluated included annealing treatments. Finally, the mechanisms explaining the observed increase in strength are discussed.

  • Daño por contacto hertziano en un nanocompuesto Ce-TZP/Al2O3

     Garcia Marro, Fernando; Mestra Rodríguez, Alvaro Miguel; Anglada Gomila, Marcos Juan
    Anales de mecánica de la fractura
    Date of publication: 2011
    Journal article

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    El material compuesto Ce-TZP/Al 2 O 3 es una cerámica nanoestructurada con granos de alúmina y circona tetragonal estabilizada con ceria. Actualmente, este tipo de compuestos están siendo desarrollados con el objetivo de sustituir a la circona dopada con 3% molar de itria de grado biomédico. En este trabajo, se ha estudiado el comportamiento de este compuesto bajo contacto monotónico apli cado mediante indentación esférica. Me diante espectroscopia micro-Raman se ha puesto en evidencia el cambio de fase local inducido por acción de las tensiones en la huella residual. Esto indica que el mecanismo de transformación de fase es máximo en los bordes de la huella, que corresponde a la zona donde el campo de tensiones de tracción es máximo de acuerdo con la teoría hertziana de la indentación esférica. Las conclusiones son que a pesar de que las grietas anillo aparecen para cargas de indentación esférica similares a las correspondientes a la circona dopada con itria, en el prese nte nanocompuesto su penetración hacia el interior del material es mucho menor, lo cual pone de manifiesto una mayor tolerancia al daño. Esta mayor tolerancia se relaciona a una mayor a tenacidad de fractura

  • Hydrothermal ageing of cracked of 3Y-TZP

     Garcia Marro, Fernando; Mestra Rodríguez, Alvaro Miguel; Anglada Gomila, Marcos Juan
    Anales de mecánica de la fractura
    Date of publication: 2011
    Journal article

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    En la circona dopada con 3% molar de itria, el vapor de agua puede inducir la transformación de la fase tetragonal a monoclínica en la superficie. Dicha transformación se ex tiende hacia el interior acompañada por la aparición de microfisuras, lo que induce una pérdida de la integridad es tructural. Este fenómeno de degradación a baja temperatura (LTD) es una clara desventaja para la utilización del material en atmósferas húmedas. Sin embargo, el efecto del agua sobre grietas de indentación no ha sido estudiado. Este trabajo estudia la influencia de LTD en la resistencia mecánica de dichas grietas. Los resultados muestran sorprendentemente un incremento de la resistencia mecánica en probetas indentadas sometidas a largos tiempos de degradación; al contrario del comportamiento en probetas sin indentar. Para explicar este comportamiento, se ha evaluado también la infl uencia de las tensiones residuales y el tratamiento de recocido adecuado para eliminarlas. Finalmente, se plantean los mecanismos que explican el aumento de la resistencia mecánica observado.

  • Incremento de la eficiencia y competitividad de procesos pulvimetalúrgicos mediante optimización y prediccción del rendimiento de

     Jimenez Pique, Emilio; Mateo Garcia, Antonio Manuel; Mestra Rodríguez, Alvaro Miguel; Llanes Pitarch, Luis Miguel
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  • Micro i ultrafiltració targento-axial per macromembranes

     Mestra Rodríguez, Alvaro Miguel; Cremades Oliver, Lazaro Vicente; Cusido Fabregas, Juan Antonio; Anglada Gomila, Marcos Juan
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  • Caracterización mecánica de dos productos de PRFV elaborados a partir de procesos de laminación manual e inyección

     Mestra Rodríguez, Alvaro Miguel; Mir Carbonell, Jordi; Mateo Garcia, Antonio Manuel
    Date: 2011
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  • Ensayos de durabilidad en cables BLF con mango actual

     Mestra Rodríguez, Alvaro Miguel; Anglada Gomila, Marcos Juan
    Date: 2011
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  • Ensayos de larga duración en cables BLF con mango de nuevo diseño

     Mestra Rodríguez, Alvaro Miguel; Anglada Gomila, Marcos Juan
    Date: 2011
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  • Estudio de fallo de una rueda de ferrocarril ligero

     Heredero Alari, Francisco; Mestra Rodríguez, Alvaro Miguel; Mateo Garcia, Antonio Manuel
    Date: 2011
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