Caracterización de nuevos recubrimientos biocompatibles de hidroxiapatita-TiO₂ obtenidos mediante Proyección Térmica de Alta Velocidad

Abstract

(HAp: Ca 10 (PO 4 ) 6 OH 2 ), es un material cerámico biocompatible y bioactivo muy empleado como recubrimiento sobre superficies metálicas (implantes dentales, prótesis de cadera…); sin embargo, la baja adherencia entre la HAp y el sustrato, debida a las diferencias entre los coeficientes de expansión térmica de ambos (a tener en cuenta en recubrimientos por proyección térmica ya que el enfriamiento posterior a la proyección puede producir una pérdida de adherencia o incluso la descohesión del recubrimiento) y a la degradación de la HAp, se está intentado mejorar mediante la incorporación de TiO 2 , para obtener una buena combinación de propiedades mecánicas y biológicas. Por tanto, el objetivo de este trabajo es la obtención de recubrimientos de 80% de HAp y 20% de TiO 2 (en peso) sobre Ti6Al4V mediante Proyección Térmica de Alta Velocidad (HVOF -High-Velocity Oxy-Fuel-). El estudio de la microestructura se ha llevado a cabo mediante microscopía electrónica de barrido y la caracterización de las fases presentes a través de difracción de rayos X y espectrometría Raman. La adherencia de los recubrimientos ha sido medida mediante ensayos de tracción, según la norma ASTM C633-01 (2008); asimismo, se ha evaluado su bioactividad a través de su inmersión en Fluido Fisiológico Simulado (SBF), midiendo así la capacidad que presentan para formar una capa de apatita en superficie. Palabras clave: recubrimientos, bioactividad, adherencia, caracterización Characterization of new bioactive coatings of hydroxyapatite and TiO 2 obtained by High-Velocity Oxy-FuelHydroxyapatite (HAp: Ca 10 (PO 4 ) 6 OH 2 ) is a biocompatible and bioactive ceramic material widely used as a coating on metal surfaces (dental implants, hip replacements ...), but the low adhesion between HAp and the substrate, due to differences in thermal expansion coefficients of both (very important in thermal spraying because of the fast cooling of the coating, which can produce a lost of adherence), and the degradation of HAp, have been tried to be improved through the incorporation of TiO 2 to get a good combination of mechanical properties. Therefore, the objective of this project is to produce coatings of HAp 80% TiO 2 and 20% (by weight) on Ti6Al4V by High-Speed Thermal Spray (HVOF). The study of the microstructure has been carried out using scanning electron microscopy and characterization of the crystalline phases by X-ray diffraction and Raman spectrometry. The coatings adhesion has been measured by tensile tests according to ASTM C633-01 (2008), and their bioactivity also has been evaluated through its immersion in simulated body fluid (SBF), in order to measure their capacity to form an apatite layer on their surface. Key-words: Coatings, Bioactivity, Adhesion, Characterization InTrOduCCIónDebido al envejecimiento de la población que viene dado por el desarrollo de las sociedades occidentales, determinados trastornos ligados a la edad, como pueden ser los problemas articulares, son cada día más comunes. El número de prótesis de este tipo aumenta cada...

Corrosion Resistance Evaluation of HVOF Produced Hydroxyapatite and TiO2-hydroxyapatite Coatings in Hanks' Solution

“…It would be expected that HA, an inert material, when applied on the substrate surface will move the E OCP to nobler values 7,14,[16][17][18]25,39,40 . This behavior can be explained because of the dissolution of the amorphous phase that occurred in these coatings during the first 24 hours and produced an increase of the porosity as time goes by 41 . The electrolyte may then achieve the substrate across the coating, forming a local cell, according to Lavos-Valereto and co-workers 36 , that induced the latter corrosion.…”

In vitro performance of ceramic coatings obtained by high velocity oxy-fuel spray

“…Four conditions have been considered: T0V0, T0V1, T1V0 and T1V1, where T is the theoretical temperature of the beam where the particle travels and V its velocity; and where 0 corresponds to a lower level and 1 to a higher one (of temperature or velocity), at distances where the maximum coating adherence is obtained [15].…”

Adhesion improvement and in vitro characterisation of 45S5 bioactive glass coatings obtained by atmospheric plasma spraying

“…Plasma-sprayed HA coatings have been used as surface coatings on metallic implants since the 1980s [18]. Moreover, it is possible to find in the literature several studies of ceramics or glass coatings produced by different thermal spray techniques such as a coating of a HA and TiO2 mix (80-20% by weight) on Ti6Al4V by High-Speed Thermal Spray (HVOF) [19], biomimetic nanocrystalline apatites deposited by low pressure cold sprayed (LP-CS) on Ti6Al4V [20], apatite and wollastonite coatings by APS on Ti6Al4V [21], 45S5 bioactive glass by APS on AISI 304 metallic substrate [22], etc.…”