Publication: Procesamiento por polvos de TI mediante asociación de técnicas coloidales y pulvimetalúrgicas
Loading...
Identifiers
Publication date
2014-09
Defense date
2014-09-11
Authors
Advisors
Tutors
Journal Title
Journal ISSN
Volume Title
Publisher
Impact
Export
Abstract
En los últimos años ha aumentado el interés en el estudio de la pulvimetalurgia (PM) como técnica
de procesamiento para la reducción del coste de componentes de titanio frente a la metalurgia
convencional. El interés en la reducción del coste del titanio radica, no sólo para las aplicaciones
habituales (aeronáutica, biomédica), sino además en la posibilidad de diversificar su uso a otras
industrias como la del transporte terrestre (automóviles y camiones ligeros). El procesamiento de Ti
mediante prensado en frío y sinterización (PS) (que es la vía de bajo coste dentro de PM) es un
proceso complejo que requiere elevadas temperaturas y tiempos de sinterización lo que provoca
contaminación y crecimiento del tamaño de grano, limitando las propiedades finales de los
componentes.
En este trabajo se propone una alternativa de procesamiento para obtener microestructuras
optimizadas gracias al empleo de polvo de tamaño de partícula fino y la introducción de partículas
cerámicas. Para ello se ha recurrido a técnicas coloidales, que han permitido la preparación de
suspensiones acuosas de polvos de titanio y la correcta dispersión de partículas submicrónicas o
nanométricas, sin introducir contaminación adicional. Las suspensiones obtenidas, estables y con
elevado contenido de sólidos, se han consolidado por distintas vías: (1) Atomización o “Spray-Dry”,
para la obtención de gránulos esféricos de alta compresibilidad, seguido de prensado uniaxial en
frío y, (2) Moldeo de barbotina o “Slip casting” tanto con presión como sin presión (SLCP Y SLSP).
Las piezas en verde se han sinterizado en vacío a temperaturas y tiempos considerablemente
inferiores a las habituales (1100ºC, 30 min). Los gránulos esféricos de Ti y Ti con partículas
cerámicas se han consolidado también mediante “spark plasma sintering” (SPS), obteniendo
materiales de Ti densos utilizando menores tiempos y temperaturas de sinterización, lo cual
conlleva a un mayor control del tamaño de grano. Mediante SLCP y SLSP ha sido posible obtener piezas con porosidad controlada que pueden tener aplicaciones potenciales para la industria
biomédica.
Por tanto, esta tesis abarca todo el proceso desde la adecuación y preparación de los polvos de
partida de Ti y cerámicos, control coloide-químico de los polvos, formulación de suspensiones
estables, consolidación de las suspensiones Ti y Ti con partículas cerámicas mediante la
granulación o colaje, y posterior procesado por técnicas PM hasta la caracterización de los
componentes de Ti obtenidos.
In the last years, a strong interest has been dedicated to study powder metallurgy (PM) as a processing technique for reducing the cost of titanium components versus conventional metallurgy. The interest of reducing the cost of titanium appears, not only for the usual applications (aeronautics, biomedical), but also in the possibility of expand its use to other industries such as ground transportation (cars and light trucks). Ti processing by cold pressing and sintering (PS) (which is the low cost route within PM) is a complex process which requires high temperatures and sintering times that causes contamination and growth of the grain size, limiting the final properties of the components. In this work, an alternative processing is proposed to obtain optimized microstructures through the use of powder of fine particle size and the introduction of ceramic particles. Thus, colloidal techniques have been used due to allow the preparation of aqueous suspensions of powders of titanium and suitable dispersion of submicron or nanometric particles, without the introduction of additional contamination. The obtained suspensions stable and with high solids content, have been consolidated by two ways: (1) Spray Dry, for obtaining spherical granules of high compressibility, followed by uniaxial cold pressing and, (2) Pressure and pressureless slip casting (PSC and PLSC). The green pieces were sintered in vacuum at temperatures and times considerably lower than those of usual (1100 °C, 30 min). The spherical granules of Ti and Ti with ceramic particles have been consolidated by Spark Plasma Sintering (SPS), obtaining dense Ti materials using lower sintering times and temperatures, which leads to a higher grain size control. Through PSC and PLSC, it has been possible to obtain pieces with controlled porosity which can have potential applications for the biomedical industry. Therefore, the PhD Thesis covers the all process from the adequacy and preparation of the starting powders of Ti and ceramics, colloid-chemical control of powders, formulation of stable suspensions, consolidation of suspensions of Ti and Ti with ceramic particles by granulation or slip casting, and then processed by PM techniques to the characterization of the components of Ti obtained.
In the last years, a strong interest has been dedicated to study powder metallurgy (PM) as a processing technique for reducing the cost of titanium components versus conventional metallurgy. The interest of reducing the cost of titanium appears, not only for the usual applications (aeronautics, biomedical), but also in the possibility of expand its use to other industries such as ground transportation (cars and light trucks). Ti processing by cold pressing and sintering (PS) (which is the low cost route within PM) is a complex process which requires high temperatures and sintering times that causes contamination and growth of the grain size, limiting the final properties of the components. In this work, an alternative processing is proposed to obtain optimized microstructures through the use of powder of fine particle size and the introduction of ceramic particles. Thus, colloidal techniques have been used due to allow the preparation of aqueous suspensions of powders of titanium and suitable dispersion of submicron or nanometric particles, without the introduction of additional contamination. The obtained suspensions stable and with high solids content, have been consolidated by two ways: (1) Spray Dry, for obtaining spherical granules of high compressibility, followed by uniaxial cold pressing and, (2) Pressure and pressureless slip casting (PSC and PLSC). The green pieces were sintered in vacuum at temperatures and times considerably lower than those of usual (1100 °C, 30 min). The spherical granules of Ti and Ti with ceramic particles have been consolidated by Spark Plasma Sintering (SPS), obtaining dense Ti materials using lower sintering times and temperatures, which leads to a higher grain size control. Through PSC and PLSC, it has been possible to obtain pieces with controlled porosity which can have potential applications for the biomedical industry. Therefore, the PhD Thesis covers the all process from the adequacy and preparation of the starting powders of Ti and ceramics, colloid-chemical control of powders, formulation of stable suspensions, consolidation of suspensions of Ti and Ti with ceramic particles by granulation or slip casting, and then processed by PM techniques to the characterization of the components of Ti obtained.
Description
Mención Internacional en el título de doctor
Keywords
Ensayo de materiales, Procesado del Titanio, Procesado coloidal, Pulvimetalurgia