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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.

    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 μm), two pressures (2 and 4 bar) and two impact angles (30° and 90°). Biaxial strength of 3Y-TZP increases when sandblasted with 110 µm particles while its decreases with 250 µm 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 µm particles, and compressive residual stresses are produced down to a depth of ~10 µm.

  • Enhanced contact fatigue behavior of coated tool steel by using W-C:H thin film

     Ramirez, Giselle; Jimenez Pique, Emilio; Mestra Rodríguez, Alvaro Miguel; Vilaseca, Montserrat; Casellas, Daniel; Llanes Pitarch, Luis Miguel
    Nordic Symposium on Tribology
    Presentation's date: 2014
    Presentation of work at congresses

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  • Contact mechanical response of PCD: microstructural effects on induced damage

     Garcia Marro, Fernando; Jimenez Pique, Emilio; Mestra Rodríguez, Alvaro Miguel; Ozbayraktar, S; Llanes Pitarch, Luis Miguel
    International Conference on the Science of Hard Materials
    Presentation's date: 2014
    Presentation of work at congresses

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  • 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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  • 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.

  • 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.

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    Mechanical response under contact loads of AlCrN-coated tool materials  Open access

     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.

    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.

  • Bio-based composites with different moisture contents under static and dynamic loading

     Doroudgarian, Newsha; Anglada Gomila, Marcos Juan; Mestra Rodríguez, Alvaro Miguel; Joffe, Roberts
    International Conference on Composites Testing and Model Identification
    Presentation's date: 2013
    Presentation of work at congresses

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    Notch effects on the fatigue endurance of cemented carbides  Open access

     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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  • Contact fatigue of ceramic-coated hardmetals

     Yang, Jing; Botero Vega, Carlos Alberto; Cornu, Nicolas; Ramírez Sandoval, Giselle; Mestra Rodríguez, Alvaro Miguel; Llanes Pitarch, Luis Miguel
    International Conference on Advanced Materials Research EEIGM/AMASE/FORGEMAT
    Presentation's date: 2013
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    In this investigation spherical indentation tests are used for assessing the contact fatigue behavior of a fine-grained WC-Co cemented carbide coated with two distinct ceramic films: AlCrN and WC/C, either as monolayers or bilayers. Emphasis is placed on determining the indentation stress affiliated to the emergence of circular cracks at the coating, event found to be critical for the coated systems under consideration. Results indicate that coated cemented carbides are found to be fatigue susceptible under contact loading, although effective fatigue sensitivity and failure scenario are discerned to be dependent on ceramic nature (crystalline/amorphous) and assemblage (mono- or bilayer) of the coatings

  • 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
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  • 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
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  • ATZ via infiltration method: mechanical properties, aging resistance and wear behaviour

     Camposilvan, Erik; Garcia Marro, Fernando; Mestra Rodríguez, Alvaro Miguel; Anglada Gomila, Marcos Juan
    International Conference on Advanced Materials Research EEIGM/AMASE/FORGEMAT
    Presentation's date: 2013
    Presentation of work at congresses

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  • Ensayos de extracción en núcleos de metal duro

     Mestra Rodríguez, Alvaro Miguel; Llanes Pitarch, Luis Miguel
    Date: 2013
    Report

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  • Basic characterization of zirconia components

     Garcia Marro, Fernando; Mestra Rodríguez, Alvaro Miguel; Llanes Pitarch, Luis Miguel
    Date: 2013
    Report

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  • Análisis de fallo en hileras de trefilado

     Mestra Rodríguez, Alvaro Miguel; Llanes Pitarch, Luis Miguel
    Date: 2013
    Report

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  • Evaluación de la rugosidad superficial en probetas de fatiga axial tipo T

     Mestra Rodríguez, Alvaro Miguel; Mateo Garcia, Antonio Manuel
    Date: 2013
    Report

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

     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.

    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.

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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.

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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  Open access

     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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  • 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.

  • 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.

  • 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.

  • 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
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  • 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
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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
    Presentation of work at congresses

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  • Influence of sandblasting on bi-axial strength of 3Y-TZP

     Chintapalli, Ravi Kiran; Garcia Marro, Fernando; Mestra Rodríguez, Alvaro Miguel; Anglada Gomila, Marcos Juan
    Congreso Nacional de Propiedades Mecánicas de Sólidos
    Presentation's date: 2012-09-26
    Presentation of work at congresses

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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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  • 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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  • 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
    Participation in a competitive project

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  • Reparaciones con composites en tuberías

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

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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
    Report

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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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  • Revista latinoamericana de metalurgia y materiales

     Mestra Rodríguez, Alvaro Miguel
    Collaboration in journals

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  • Thermal stability in air of surface nitrided 3Y-TZP

     Valle Chiro, Jorge Antonio; Mestra Rodríguez, Alvaro Miguel; Anglada Gomila, Marcos Juan
    Journal of the european ceramic society
    Date of publication: 2011-06
    Journal article

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    Surface nitriding can be optimised to protect 3Y-TZP against hydrothermal degradation and at the same time to keep the mechanical properties of the surface and the bulk unchanged. However, thermal stability is a concern that can limit its use above room temperature. In this work, surface nitrided 3Y-TZP was heat treated in air at 200, 400, 600 and 800◦C for 8 h. Treatments up to 600◦C did not change microstructure and Vickers hardness, but heating at 800◦C produced surface defects, inner cracks and grain decohesion, conducing to a dramatic decrease in mechanical strength. Heat treatments above 400◦C led to an increase of indentation fracture toughness and to a complete loss of the hydrothermal degradation resistance achieved by nitriding.

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    Hydrothermal ageing of cracked of 3Y-TZP  Open access

     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.

    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.

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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
    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

    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

  • Contact damage in a Ce-TZP/Al2O3 nanocomposite

     Garcia Marro, Fernando; Mestra Rodríguez, Alvaro Miguel; Anglada Gomila, Marcos Juan
    Journal of the european ceramic society
    Date of publication: 2011-11
    Journal article

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    The damage tolerance of a nanocomposite based on Ce-TZP and 30 vol% Al2O3 has been studied un der monotonic contact with a spherical indenter. The results are compared with those previously known for commercial 3Y-TZP zirconia. It is concluded that the minimum load for ring crack appearance is similar in both ceramics. However, in the nanocomposite the ring cracks penetrate much less into the bulk, because of its higher fracture toughness. Finally, the stress-induced phase transformation of the zirconia component was quantified and mapped by micro-Raman spectroscopy.

  • Anodic oxidation of titanium for implants and prosthesis: Processing, characterization and potential improvement of osteointegration

     Pavon, Juan José; Galvis, Oscar; Echeverria, F.; Castaño, J; Echeverry, M; Robledo, S; Jimenez Pique, Emilio; Mestra Rodríguez, Alvaro Miguel; Anglada Gomila, Marcos Juan
    Latin American Congress on Biomedical Engineering
    Presentation's date: 2011-05
    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...

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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.