Resistencia al desgaste y adherencia de recubrimientos de óxido de titanio sobre Ti 6Al 4V
Cargando...
Archivos
Fecha
Autores
Título de la revista
ISSN de la revista
Título del volumen
Editor
Comisión Nacional de Energía Atómica. Instituto de Tecnología Sabato
Resumen
Los recubrimiento de óxido de titanio poseen excelentes propiedades hemocompatibles, esto hace que sean de interés para el desarrollo de prótesis de válvulas cardíacas. Este trabajo de tesis tiene como objetivo estudiar la resistencia al desgaste y la adherencia de recubrimientos de óxido de titanio, sintetizados por sol gel dip-coating obre la aleación de titanio grado 5 (ASTM). Las variables del proceso de síntesis analizadas son: el envejecimiento del sol, velocidad de extracción y el tratamiento térmico. Además, se fabricaron recubrimientos monocapa y multicapas donde se estudió la influencia de las condiciones de síntesis del recubrimiento con respecto a la formación e fisuras. Se obtuvieron recubrimientos de diversos colores según las condiciones de proceso empleadas. Para poder calificar la resistencia al desgaste de los recubrimientos se fabricó un equipo hall on flat, donde la geometría de contacto implica una contraparte esférica rotante. El desgaste del recubrimiento se califica a través del cambio de olor de la superficie de la probeta. La adherencia se midió a partir de ensayos de Scratch Test, por observaciones al microscopio se obtuvieron valores de carga crítica para los recubrimientos. Las condiciones para recubrir sin formación de fisuras son: con bajo tiempo de envejecimiento del sol, a bajas velocidades de extracción y la temperatura e tratamiento térmico debe ser menor que 650 grados C, de manera de no acelerar la oxidación térmica del sustrato. Los resultados muestran que la mejor resistencia al desgaste se obtiene con recubrimientos de mayor espesor (tricapas) y tratamientos térmicos entre capas (en cuanto a temperatura-tiempo); la adherencia también fue superior para este tipo de recubrimientos.|The titanium dioxide coating has excellent haemocompatibility which is required in many applications such as the fabrication of prosthetic Herat valves. This thesis has the objective of studying the wear resistance and the adherence of the titanium dioxide coating deposited on a Grade 5 (ASTM) titanium alloy. The synthesis of the coating is performed by the sol-gel dip-coating process. The process variables that have been analyzed are: the heat treatment, the sol aging and the withdrawing velocity. Also, mono and multilayer coatings were made and the influence of the process variables on the superficial cracks is studied. In all cases, colorful coatings were obtained and the color was related with the process conditions and film thickness. A ball-on-flat wear machine was build to measure the wear resistance of the coatings. This machine has a rotating sphere that press on the sample. The wear was measured by the change of color of the sample surface which is related with the change in thickness and therefore the amount of wear of the coating. The coating adherence was measured by the scratch tests technique determining the critical load on the sample surface at which morphological changes such as: cracks, debonding are observed by microscopy. The results show that a better wear resistance is obtained with coatings of larger thickness (trilayers) and with heat treatment between each layer deposition: in addition it was determined that a better layer wear property is also associated with a better film adherence. The optimum conditions found for coating the titanium alloy without superficial cracks were: short aging time, low withdraw velocity and a temperature lower than 650 C degrees during the heat treatment, which reduces the thermal oxidation of the substrate.
The titanium dioxide coating has excellent haemocompatibility which is required in many applications such as the fabrication of prosthetic Herat valves. This thesis has the objective of studying the wear resistance and the adherence of the titanium dioxide coating deposited on a Grade 5 (ASTM) titanium alloy. The synthesis of the coating is performed by the sol-gel dip-coating process. The process variables that have been analyzed are: the heat treatment, the sol aging and the withdrawing velocity. Also, mono and multilayer coatings were made and the influence of the process variables on the superficial cracks is studied. In all cases, colorful coatings were obtained and the color was related with the process conditions and film thickness. A ball-on-flat wear machine was build to measure the wear resistance of the coatings. This machine has a rotating sphere that press on the sample. The wear was measured by the change of color of the sample surface which is related with the change in thickness and therefore the amount of wear of the coating. The coating adherence was measured by the scratch tests technique determining the critical load on the sample surface at which morphological changes such as: cracks, debonding are observed by microscopy. The results show that a better wear resistance is obtained with coatings of larger thickness (trilayers) and with heat treatment between each layer deposition: in addition it was determined that a better layer wear property is also associated with a better film adherence. The optimum conditions found for coating the titanium alloy without superficial cracks were: short aging time, low withdraw velocity and a temperature lower than 650 C degrees during the heat treatment, which reduces the thermal oxidation of the substrate.
The titanium dioxide coating has excellent haemocompatibility which is required in many applications such as the fabrication of prosthetic Herat valves. This thesis has the objective of studying the wear resistance and the adherence of the titanium dioxide coating deposited on a Grade 5 (ASTM) titanium alloy. The synthesis of the coating is performed by the sol-gel dip-coating process. The process variables that have been analyzed are: the heat treatment, the sol aging and the withdrawing velocity. Also, mono and multilayer coatings were made and the influence of the process variables on the superficial cracks is studied. In all cases, colorful coatings were obtained and the color was related with the process conditions and film thickness. A ball-on-flat wear machine was build to measure the wear resistance of the coatings. This machine has a rotating sphere that press on the sample. The wear was measured by the change of color of the sample surface which is related with the change in thickness and therefore the amount of wear of the coating. The coating adherence was measured by the scratch tests technique determining the critical load on the sample surface at which morphological changes such as: cracks, debonding are observed by microscopy. The results show that a better wear resistance is obtained with coatings of larger thickness (trilayers) and with heat treatment between each layer deposition: in addition it was determined that a better layer wear property is also associated with a better film adherence. The optimum conditions found for coating the titanium alloy without superficial cracks were: short aging time, low withdraw velocity and a temperature lower than 650 C degrees during the heat treatment, which reduces the thermal oxidation of the substrate.