Hydroxyapatite coatings (HACs) are synthesized on Ti-6Al-4V substrates using the plasma spraying process followed by autoclaving hydrothermal treatment at 125 and 150 °C. The quantitative analysis of X-ray diffraction indicates that the hydrothermal treatment is available to promote HA crystallization and further eliminate the amorphous and impurity phases of the HACs. The microstructural self-healing effect of hydrothermally treated HA coatings (HT-HACs) can be recognized as a nucleation and grain growth of nano-crystalline HA which tends to diminish the spraying defects through the hydrothermal crystallization. The significant hydroxy ion (OH-) peak in XPS spectra detected from HT-HAC specimens represents that the hydroxyl-deficient state of plasma-sprayed HACs is significantly improved with the abundant replenished OH- groups during the hydrothermal treatment. XPS analysis also demonstrates that the hydrothermal crystallization helps to promote the interfacial Ti-OH chemical reaction. The bonding strength of HA coatings is significantly improved from 32.4 MPa for the as-sprayed HACs to 38.9 MPa after 150 °C hydrothermal treatment. Through the statistical analysis of Weibull distribution function, the strengthening HT-HACs are generally reliable materials with a wear-out failure model. The failure morphologies of HT-HACs represent homogeneity with a larger area fraction of cohesive failure and a decreased adhesive failure area. The phenomena were resulted from the microstructural self-healing effect and the enhanced interfacial adhesion of HT-HACs to Ti-6Al-4V substrate.
|Number of pages||9|
|Journal||Journal of the European Ceramic Society|
|Publication status||Published - 2008|
All Science Journal Classification (ASJC) codes
- Ceramics and Composites
- Materials Chemistry