Cambios microestructurales en 3Y-TZP desbastada y su influencia en la degradación hidrotérmica
- Autores: José Alejandro Muñoz Tabares
- Directores de la Tesis: Marc Joan Anglada Gomila (dir. tes.)
- Lectura: En la Universitat Politècnica de Catalunya (UPC) ( España ) en 2010
- Idioma: español
- Tribunal Calificador de la Tesis: Luis Llanes Pitarch (presid.), Yves Gaillard (secret.), Eduardo Sáiz Gutiérrez (voc.)
- Materias:
- Enlaces
- Tesis en acceso abierto en: TDX
- Resumen
The use of zirconia ceramics (ZrO2) as advanced structural materials is based on toughness increasing by tetragonal to monoclinic (tm) phase transformation. Of these, the 3Y-TZP (tetragonal polycrystalline zirconia doped with 3 mol% yttria) has a good combination of mechanical properties, so it has found a wide range of applications. However, the phase transformation can also be induced on material surface by interaction with water. This phenomenon is known as hydrothermal degradation, because it produces progressive microcracking and thus the loss of mechanical properties. In recent years has been developed a renewed interest in this material because of its use in the manufacture of dental restorations (crowns, bridges), mainly due to its mechanical properties and aesthetics can be achieved. However, conformation of those devices requires different types of machining processes in order to achieve, both piece’s shape and an specific surface finish. These processes include: cutting, grinding, polishing, diamond-tipped drilling, sandblasting, CAD/CAM machining, etc. That in turn produces different types of damage that can affect the material structural integrity and reliability. Thus, the aim of this thesis was to study the microstructurals changes produced by grinding in 3Y-TZP and its effect in the resistance to hydrothermal degradation. The work was divided into five sections: I) Introduction, II) experimental techniques and material, III) hydrothermal degradation, IV) grinding and V) conclusions and future work. The results showed that mechanical properties increasing (strength and fracture toughness) is due to the presence of compressive residual stress by phase transformation. The characterization of the subsurface microstructure showed severe changes, some of them none reported to date, such as plastic deformation, recovery and recrystallization. Moreover, microstructural changes were studied under indentation and scratch imprints, which are used to simulate the contact events produced during grinding. The results indicated that the monoclinic phase distribution and deformation in both cases were significantly different. Finding that, the scratch test is more suitable to simulate the grinding, while the indentation test is closer to processes such as sandblasting. Finally, we analyzed the hydrothermal degradation behaviour of ground zirconia. The results showed that this surface treatment completely inhibited the t-m phase transformation induced by water. This resistance was discussed in terms of microstructural changes.
