Elena Gordo | University of Carlos III Madrid (original) (raw)
Papers by Elena Gordo
Metals
High production costs of Ti alloys usually hinders their use in industry sectors like the automot... more High production costs of Ti alloys usually hinders their use in industry sectors like the automotive and hence, low-cost titanium alloys could broaden titanium alloy usage. This work presents the study of three alloys— Ti-Fe, Ti-Fe-Al, and Ti-Fe-Cr—produced by powder metallurgy methods. The design of the compositions was aimed at reducing cost and enhance the oxidation and corrosion resistance while not decreasing the mechanical performance. The use of titanium hydride as raw material instead of Ti powder is highlighted as a key feature in the design and manufacturing procedure of the alloys. Introducing a dehydrogenation process during sintering favors the densification process while reducing the oxygen contamination and the production cost. There is a lack of studies focused on the implementation of affordable PM Ti alloys in high demanding environments. Therefore, a study of high temperature oxidation resistance and electrochemical behavior was performed.
International Journal of Refractory Metals and Hard Materials, 2017
In a wide sense, the term "cermet" refers to ceramic-metal composites including cemented carbides... more In a wide sense, the term "cermet" refers to ceramic-metal composites including cemented carbides and hardmetals, which use Co and Ni as main constituents of the metal binder, being WC the hard phase. The Co-WC combination is the most successful to the moment to fulfil the high demands of the cutting and wear tools. However, economics and health concerns are motivating an intense research activity and high interest of hardmetals industry on the searching of alternative materials. In Europe the REACH programme, Registration, Evaluation, Authorisation and Restriction of Chemical substances (http://ec.europa. eu/environment/chemicals/reach/reach_intro.htm), has classified cobalt as very toxic for the human health. Also, the U.S. National Toxicology Program, NTP (http://ntp-server.niehs.nih.gov/), included WC-Co in the 12th Report on Carcinogens (2011) as one of 240 substances that may increase risk for cancer both as a powder and as a sintered material; the report states that the tungsten carbide-cobalt hard metal dust has been shown to be more toxic in combination than both pure cobalt and tungsten carbide by themselves in vitro studies. On the other hand, Co and W were included in the list of Critical Raw Materials by the European Commission in the basis of economic importance and supply risks (https://ec.europa.eu/growth/sectors/raw-materials/specificinterest/critical_es), as Europe presents a total dependence of third countries for the supply of these materials.
Materials Characterization, 2016
Materials Science Forum, 2016
Key Engineering Materials, 2016
Key Engineering Materials, 2016
Advanced Engineering Materials, 2016
Materials Letters, May 13, 2013
The colloid-chemistry control of metallic powders in aqueous slurries is proposed as a way to pro... more The colloid-chemistry control of metallic powders in aqueous slurries is proposed as a way to produce spherical granules of fine titanium particles able to be processed by powder metallurgy (PM) techniques. Significant improvement of sintering behavior is achieved, leading to high dense parts at reduced sintering temperature and time. Consequently the control of grain growth during sintering was achieved, as well as the oxygen content. This approach can be extended to other strategies for Ti design, such as the homogeneous dispersion of second phases for further control of grain size and modification of properties.
International Journal of Refractory Metals and Hard Materials, 2015
The aim of this work is the design, processing and characterization of a metal-ceramic composite ... more The aim of this work is the design, processing and characterization of a metal-ceramic composite (cermet) with an iron-aluminum alloy as metallic matrix and NbC as ceramic phase. The cermet is obtained from a composite powder containing in situ formed NbC-rich precipitates on an iron rich metal matrix. The starting powder was supplied by CBMM (Brazil), and it was produced by a synthesis process under development which introduces other metals such as Al, Si and Ti to the composition. Due to the in situ process, good bonding is expected between the carbide and the matrix. However it is necessary to study the processability of those complex particles and the transformations occurring during sintering to get the final microstructure. Thermodynamic studies by means of ThermoCalc® software were performed to predict phases stable with the starting composition and also the influence of Fe and C additions. Samples were produced by uniaxial pressing and vacuum sintering (PS), and also by Field Assisted Hot Pressing (FAHP). The processing parameters for PS processing, that is, sintering temperature and time were based on thermodynamic simulations by ThermoCalc® software together with thermal analysis. The powders were characterized by measuring density, particle size, carbon content and chemical composition; and consolidated samples by density and Vickers hardness. The microstructure and morphology of the powder and consolidated samples were analyzed by SEM. The addition of Fe and both C and Fe to the starting cermet composition provided good results as the final microstructure consisted essentially of NbC and Fe matrix.
Key Engineering Materials, 2013
The Ti-6Al-7Nb alloy was specially developed to replace the well-known Ti-6Al-4V alloy in biomedi... more The Ti-6Al-7Nb alloy was specially developed to replace the well-known Ti-6Al-4V alloy in biomedical applications due to supposed cytotoxicity of vanadium in the human body. This alloy is normally fabricated by conventional ingot metallurgy by forging bulk material. Nevertheless, powder metallurgy techniques could be used to obtain this alloy with specific properties. This is because by changing the processing parameters, such as the sintering temperature, it is possible to vary the porosity level and to tailor the final properties. This work deals with the production of the Ti-6Al-7Nb alloy by means of the master alloy addition variant of the blending elemental approach. The powder is processed by means of different powder metallurgy routes considering diverse processing conditions for each method. The materials are characterised in terms of microstructural features, relative density and hardness. Homogeneous microstructures as well as properties comparable to those of the wrought alloy are generally obtained.
Materials Science Forum, 2007
Materials Science Forum, 2013
ABSTRACT Titanium is characterised by an outstanding combination of properties like high strength... more ABSTRACT Titanium is characterised by an outstanding combination of properties like high strength, low density, good corrosion resistance and biocompatibility. Nonetheless, widespread employment of titanium at the industrial level, especially in the automotive industry, has not been achieved yet because of its high extraction and production costs. Consequently, titanium finds applications mainly in high demanding sectors, such as the aerospace industry or to produce biomedical devices, where the final high cost is not the principal issue. The processing of titanium and its alloys by means of powder metallurgy (PM) techniques is claimed to be a suitable way to reduce the fabrication cost of titanium products as well as offering the possibility to design new alloys which are difficult to obtain using the conventional metallurgical route, for example due to segregation of heavy alloying elements. This work deals with the processing of hydride-dehydride elemental titanium powder by means of different PM methods and aims at investigating the processing of near net-shape, chemically-homogeneous and fine-grained titanium-based components. In particular, properties achievable (i.e. relative density, microstructure and mechanical properties) and problems related to the processing of elemental titanium, by both the conventional PM route of pressing and sintering and the advanced PM method of hot-pressing, are presented.
Key Engineering Materials, 2012
Powder metallurgy (PM) permits to obtain titanium alloys with properties and microstructures clos... more Powder metallurgy (PM) permits to obtain titanium alloys with properties and microstructures close to ingot metallurgy products. However, residual porosity is normally present in the products produced by the PM route of powder pressing and sintering (P&S)\, and this needs to be reduced by using post-sintering process step such as hot isostatic pressing (HIP) and forging. In this study, the microstructural and mechanical property changes caused by HIP of samples of two alloys, near-α Ti-3Al-2.5V alloy and α+β Ti-6Al-4V, produced by P&S route were investigated. Two types of powders were utilised: prealloyed powders and blend of elemental titanium powder and master alloy powder. Four conditions defined by HIP temperature, pressure and time were used to HIP the sintered samples with two geometries. The results show that, independent of the HIP conditions used, HIP increased the relative density of the samples to approximately 97.5% and their hardness by 30-50 HV depending on the HIP condition. However, HIP at 1000ºC changes the fracture mode of the sintered samples from ductile to brittle.
Materials Science Forum, 2007
Key Engineering Materials, 2012
The colloid-chemistry control of metallic powders in aqueous slurries is proposed as a way to pre... more The colloid-chemistry control of metallic powders in aqueous slurries is proposed as a way to prepare Ti powders with small particle size for a better pressing behavior through the spray dry process. The chemical-physic behavior of titanium powders with two different particle size distributions dispersed in water has been studied by measuring the zeta potential as a function of pH, and dispersant concentration. The employment of poly-acrylic dispersants allowed the fabrication of stable slurries with solid contents up to 50 vol% that have been sprayed under different conditions to form agglomerates ranging between 50 and 200 µm. Conditions were selected to achieve spherical agglomerates formed by a broad distribution of particle sizes that shown excellent flowability. Agglomerates were pressed in a uniaxial die to measure the compressibility, showing an improvement in pressing behavior with respect to powders with bigger particle size. The sintering behavior is also improved, as values of 96 % of the theoretical density were obtained for compacts sintered in vacuum at 1100 ºC for 30 minutes.
Revista de Metalurgia, 2005
El acero pulvimetalúrgico HCx ha sido desarrollado para combinar la resistencia a corrosión de lo... more El acero pulvimetalúrgico HCx ha sido desarrollado para combinar la resistencia a corrosión de los aceros inoxidables con la resistencia al desgaste de los aceros de herramientas. Aparece así como un material adecuado para componentes sometidos a desgaste en un ambiente agresivo, como los asientos de válvulas en motores de automóviles. En este trabajo se estudia la dilución del HCx con dos aceros inoxidables, uno ferrítico (430) y otro austenítico (316L), en porcentajes hasta 15 % en masa, para mejorar las condiciones de procesado, especialmente la compresibilidad. La sinterabilidad de los materiales diluidos se ha estudiado mediante sinterización en vacío, a temperaturas entre 1.200 °C y 1.260 °C, y se han determinado las propiedades de los materiales sinterizados. Los resultados se discuten en relación a la evolución microestructural.
Materials Research-ibero-american Journal of Materials, 2005
The user has requested enhancement of the downloaded file.
Surface and Coatings Technology, 2010
Wear resistance of Ti alloys needs to be improved, and an effective way to achieve this is throug... more Wear resistance of Ti alloys needs to be improved, and an effective way to achieve this is through surface treatment. Boronizing is a surface treatment in which boron diffuses into the surface of Ti leading to the formation of hard and wear-resistant Ti borides. Boronizing of wrought and/or cast Ti alloys by pack cementation has been studied, while similar coatings
Materials Research, 2005
The user has requested enhancement of the downloaded file.
Metals
High production costs of Ti alloys usually hinders their use in industry sectors like the automot... more High production costs of Ti alloys usually hinders their use in industry sectors like the automotive and hence, low-cost titanium alloys could broaden titanium alloy usage. This work presents the study of three alloys— Ti-Fe, Ti-Fe-Al, and Ti-Fe-Cr—produced by powder metallurgy methods. The design of the compositions was aimed at reducing cost and enhance the oxidation and corrosion resistance while not decreasing the mechanical performance. The use of titanium hydride as raw material instead of Ti powder is highlighted as a key feature in the design and manufacturing procedure of the alloys. Introducing a dehydrogenation process during sintering favors the densification process while reducing the oxygen contamination and the production cost. There is a lack of studies focused on the implementation of affordable PM Ti alloys in high demanding environments. Therefore, a study of high temperature oxidation resistance and electrochemical behavior was performed.
International Journal of Refractory Metals and Hard Materials, 2017
In a wide sense, the term "cermet" refers to ceramic-metal composites including cemented carbides... more In a wide sense, the term "cermet" refers to ceramic-metal composites including cemented carbides and hardmetals, which use Co and Ni as main constituents of the metal binder, being WC the hard phase. The Co-WC combination is the most successful to the moment to fulfil the high demands of the cutting and wear tools. However, economics and health concerns are motivating an intense research activity and high interest of hardmetals industry on the searching of alternative materials. In Europe the REACH programme, Registration, Evaluation, Authorisation and Restriction of Chemical substances (http://ec.europa. eu/environment/chemicals/reach/reach_intro.htm), has classified cobalt as very toxic for the human health. Also, the U.S. National Toxicology Program, NTP (http://ntp-server.niehs.nih.gov/), included WC-Co in the 12th Report on Carcinogens (2011) as one of 240 substances that may increase risk for cancer both as a powder and as a sintered material; the report states that the tungsten carbide-cobalt hard metal dust has been shown to be more toxic in combination than both pure cobalt and tungsten carbide by themselves in vitro studies. On the other hand, Co and W were included in the list of Critical Raw Materials by the European Commission in the basis of economic importance and supply risks (https://ec.europa.eu/growth/sectors/raw-materials/specificinterest/critical_es), as Europe presents a total dependence of third countries for the supply of these materials.
Materials Characterization, 2016
Materials Science Forum, 2016
Key Engineering Materials, 2016
Key Engineering Materials, 2016
Advanced Engineering Materials, 2016
Materials Letters, May 13, 2013
The colloid-chemistry control of metallic powders in aqueous slurries is proposed as a way to pro... more The colloid-chemistry control of metallic powders in aqueous slurries is proposed as a way to produce spherical granules of fine titanium particles able to be processed by powder metallurgy (PM) techniques. Significant improvement of sintering behavior is achieved, leading to high dense parts at reduced sintering temperature and time. Consequently the control of grain growth during sintering was achieved, as well as the oxygen content. This approach can be extended to other strategies for Ti design, such as the homogeneous dispersion of second phases for further control of grain size and modification of properties.
International Journal of Refractory Metals and Hard Materials, 2015
The aim of this work is the design, processing and characterization of a metal-ceramic composite ... more The aim of this work is the design, processing and characterization of a metal-ceramic composite (cermet) with an iron-aluminum alloy as metallic matrix and NbC as ceramic phase. The cermet is obtained from a composite powder containing in situ formed NbC-rich precipitates on an iron rich metal matrix. The starting powder was supplied by CBMM (Brazil), and it was produced by a synthesis process under development which introduces other metals such as Al, Si and Ti to the composition. Due to the in situ process, good bonding is expected between the carbide and the matrix. However it is necessary to study the processability of those complex particles and the transformations occurring during sintering to get the final microstructure. Thermodynamic studies by means of ThermoCalc® software were performed to predict phases stable with the starting composition and also the influence of Fe and C additions. Samples were produced by uniaxial pressing and vacuum sintering (PS), and also by Field Assisted Hot Pressing (FAHP). The processing parameters for PS processing, that is, sintering temperature and time were based on thermodynamic simulations by ThermoCalc® software together with thermal analysis. The powders were characterized by measuring density, particle size, carbon content and chemical composition; and consolidated samples by density and Vickers hardness. The microstructure and morphology of the powder and consolidated samples were analyzed by SEM. The addition of Fe and both C and Fe to the starting cermet composition provided good results as the final microstructure consisted essentially of NbC and Fe matrix.
Key Engineering Materials, 2013
The Ti-6Al-7Nb alloy was specially developed to replace the well-known Ti-6Al-4V alloy in biomedi... more The Ti-6Al-7Nb alloy was specially developed to replace the well-known Ti-6Al-4V alloy in biomedical applications due to supposed cytotoxicity of vanadium in the human body. This alloy is normally fabricated by conventional ingot metallurgy by forging bulk material. Nevertheless, powder metallurgy techniques could be used to obtain this alloy with specific properties. This is because by changing the processing parameters, such as the sintering temperature, it is possible to vary the porosity level and to tailor the final properties. This work deals with the production of the Ti-6Al-7Nb alloy by means of the master alloy addition variant of the blending elemental approach. The powder is processed by means of different powder metallurgy routes considering diverse processing conditions for each method. The materials are characterised in terms of microstructural features, relative density and hardness. Homogeneous microstructures as well as properties comparable to those of the wrought alloy are generally obtained.
Materials Science Forum, 2007
Materials Science Forum, 2013
ABSTRACT Titanium is characterised by an outstanding combination of properties like high strength... more ABSTRACT Titanium is characterised by an outstanding combination of properties like high strength, low density, good corrosion resistance and biocompatibility. Nonetheless, widespread employment of titanium at the industrial level, especially in the automotive industry, has not been achieved yet because of its high extraction and production costs. Consequently, titanium finds applications mainly in high demanding sectors, such as the aerospace industry or to produce biomedical devices, where the final high cost is not the principal issue. The processing of titanium and its alloys by means of powder metallurgy (PM) techniques is claimed to be a suitable way to reduce the fabrication cost of titanium products as well as offering the possibility to design new alloys which are difficult to obtain using the conventional metallurgical route, for example due to segregation of heavy alloying elements. This work deals with the processing of hydride-dehydride elemental titanium powder by means of different PM methods and aims at investigating the processing of near net-shape, chemically-homogeneous and fine-grained titanium-based components. In particular, properties achievable (i.e. relative density, microstructure and mechanical properties) and problems related to the processing of elemental titanium, by both the conventional PM route of pressing and sintering and the advanced PM method of hot-pressing, are presented.
Key Engineering Materials, 2012
Powder metallurgy (PM) permits to obtain titanium alloys with properties and microstructures clos... more Powder metallurgy (PM) permits to obtain titanium alloys with properties and microstructures close to ingot metallurgy products. However, residual porosity is normally present in the products produced by the PM route of powder pressing and sintering (P&S)\, and this needs to be reduced by using post-sintering process step such as hot isostatic pressing (HIP) and forging. In this study, the microstructural and mechanical property changes caused by HIP of samples of two alloys, near-α Ti-3Al-2.5V alloy and α+β Ti-6Al-4V, produced by P&S route were investigated. Two types of powders were utilised: prealloyed powders and blend of elemental titanium powder and master alloy powder. Four conditions defined by HIP temperature, pressure and time were used to HIP the sintered samples with two geometries. The results show that, independent of the HIP conditions used, HIP increased the relative density of the samples to approximately 97.5% and their hardness by 30-50 HV depending on the HIP condition. However, HIP at 1000ºC changes the fracture mode of the sintered samples from ductile to brittle.
Materials Science Forum, 2007
Key Engineering Materials, 2012
The colloid-chemistry control of metallic powders in aqueous slurries is proposed as a way to pre... more The colloid-chemistry control of metallic powders in aqueous slurries is proposed as a way to prepare Ti powders with small particle size for a better pressing behavior through the spray dry process. The chemical-physic behavior of titanium powders with two different particle size distributions dispersed in water has been studied by measuring the zeta potential as a function of pH, and dispersant concentration. The employment of poly-acrylic dispersants allowed the fabrication of stable slurries with solid contents up to 50 vol% that have been sprayed under different conditions to form agglomerates ranging between 50 and 200 µm. Conditions were selected to achieve spherical agglomerates formed by a broad distribution of particle sizes that shown excellent flowability. Agglomerates were pressed in a uniaxial die to measure the compressibility, showing an improvement in pressing behavior with respect to powders with bigger particle size. The sintering behavior is also improved, as values of 96 % of the theoretical density were obtained for compacts sintered in vacuum at 1100 ºC for 30 minutes.
Revista de Metalurgia, 2005
El acero pulvimetalúrgico HCx ha sido desarrollado para combinar la resistencia a corrosión de lo... more El acero pulvimetalúrgico HCx ha sido desarrollado para combinar la resistencia a corrosión de los aceros inoxidables con la resistencia al desgaste de los aceros de herramientas. Aparece así como un material adecuado para componentes sometidos a desgaste en un ambiente agresivo, como los asientos de válvulas en motores de automóviles. En este trabajo se estudia la dilución del HCx con dos aceros inoxidables, uno ferrítico (430) y otro austenítico (316L), en porcentajes hasta 15 % en masa, para mejorar las condiciones de procesado, especialmente la compresibilidad. La sinterabilidad de los materiales diluidos se ha estudiado mediante sinterización en vacío, a temperaturas entre 1.200 °C y 1.260 °C, y se han determinado las propiedades de los materiales sinterizados. Los resultados se discuten en relación a la evolución microestructural.
Materials Research-ibero-american Journal of Materials, 2005
The user has requested enhancement of the downloaded file.
Surface and Coatings Technology, 2010
Wear resistance of Ti alloys needs to be improved, and an effective way to achieve this is throug... more Wear resistance of Ti alloys needs to be improved, and an effective way to achieve this is through surface treatment. Boronizing is a surface treatment in which boron diffuses into the surface of Ti leading to the formation of hard and wear-resistant Ti borides. Boronizing of wrought and/or cast Ti alloys by pack cementation has been studied, while similar coatings
Materials Research, 2005
The user has requested enhancement of the downloaded file.