Effect of Titanium Surface Oxidation on the Bonding Strength of Ti-Porcelain

Effects of titanium surface oxidation on titanium-ceramic adhesion were investigated. Cast pure titanium was subjected to pre-oxidation and introduction of an intermediate layer of SnOx by sol-gel process. Specimen surfaces were characterized by XRD and SEM/EDS. The adhesion between the titanium and porcelain was evaluated by three-point flexure bond test. A rutile layer is formed on the titanium surface after pre-oxidation. Failure of the titanium-porcelain with pre-oxidation treatment predominantly occurs at the titanium-oxide interface. Pre-oxidation treatment does not affect the fracture mode of the titanium-porcelain system. The rutile layer is more strongly bonded to the porcelain than titanium. The poor adhesion of the rutile with substrate is due to the thermal stress arising from the large lattice mismatch and difference in coefficient of thermal expansion between Ti and rutile during cooling. However, a thin and coherent SnOx film with small spherical pores obtained after heat-treated at 300 erves as an effective oxygen diffusion barrier to improve titanium-ceramic adhesion. The SnOx films change the fracture mode of the titanium-porcelain system and improve the mechanical and chemical bonding between porcelain and titanium, resulting in the increased bonding strength of titanium-porcelain.