Micro-Structural Characterization and Stress-Corrosion Cracking Behavior of a FGM Glass-Based Coating on Ti6Al4V for Biomedical Applications

Abstract

Microstructural and stress-corrosion cracking characterization of two glass-based coatings on Ti6Al4V with different SiO2 content (61% and 64% of SiO2) have been investigated in this work. These coatings belong to the SiO2-CaO-MgO-Na2O-K2O-P2O5 system and were obtained using a simple enamelling technique. They will be used as the first layer of the bioactive FGM coating. Microstructural characterization performed in the coatings by SEM shows the separation of the sintered glass particles after acid etching. The XRD integration method shows that the percentage of the crystalline phase (2.4CaO•0.6Na2O•P2O5) due to the partial devitrification is between 3-16 % vol. Mechanical characterization was made using Vickers and Hertzian indentation. Both coatings were sensitive to Vickers indentation subcritical crack growth with longer crack lengths for the smaller SiO2 content. This coating was also more sensitive to stress-corrosion “ring” cracking by Hertzian indentation. These two results are related with the larger residual stresses due to the thermal expansion mismatch.