Enhanced Macro and Micro Stress Evaluation Diffraction Techniques Applied to Biomedical Materials

Residual stress has large effect to the service life of biomedical ceramic coatings. It is therefore important to characterize it precisely. Since in-service damage of the prostheses is generally characterized by cracking of the substrate layers located close to the metal / ceramic interface, our study was focused on these particular zones of the parts. High energy synchrotron radiation diffraction techniques were therefore developed to evaluate the residual stress profiles of the metal / ceramic interfaces. The method requires, however, defining precisely the true position of the X-ray probe inside the materials. A complete modeling of the instrument, using a ray tracing Monte Carlo simulation method, was developed for that purpose. Fourier analysis of the diffraction peaks was also implemented to evaluate the micro stresses of second and third kind. These diffraction techniques were tested on a glassy ceramic coating used for the manufacturing of dental prostheses.