Improving The Interfacial Bonding Strength Between Ti6Al4V Alloy And Bioceramic By Laser Gas Nitriding

The key of success in metal-ceramic implants is to obtain an excellent interface bonding, to ensure it can support any force from every aspects without glass-coating fell off in the exercise after implants into human body. A TiN surface layer was fabricated on Ti6Al4V alloy by laser gas nitriding and etched to expose a dendritic TiN on its suface by escharotic, and then a bioactive glass-ceramic layer was sintered on this dendritic surface. The surface morphology, chemical composition and phase's presence of the nitrided-layer were investigated by Scan electron-microscope (SEM), X-ray diffraction (XRD) and Atomic force microscope (AFM). The bonding strength between metal and ceramic was measured by longitudinal pull-off test, tensile shearing test and indentation test after sintered a glass-coating on Ti6Al4V alloy and LGN-Ti6Al4V alloy in this paper. The efficient methods and influencing factors to enhance the bonding strength between metal and ceramics are also discussed. Electrochemical test and Inductance coupling plasma launch spectrum (ICP) were introduced to demonstrate the corrosion behavior and the deleterious dissolved ions behavior.The results of the dense TiN after laser gas nitrided on Ti6Al4V specimens exhibited good wear resistance and corrosion resistance.The results of bonding strength after sintered a ceramic coating on the substrate shown that the bonding strength of metal and ceramic after nitrided by laser beam was higher than that of metal and ceramic without nitrided. The reasons were: 1.A TiN layer was obtained after nitrided while a rough surface was created after acid etching, 2. The purpose of preserve several minutes during the sintering was to enhance the wetting effect and the bonding strength, 3. TiN layer prevent thick oxidation layer from forming which lead to the poor bonding strength, 4. The redox reaction was happened between TiN and SiO2 that lead to Ti5Si3, which result in a inter diffusion and a continuous composition transition, 5. TiN was joined as a transition layer into substrate and ceramic-coating lead to a gradual change on thermal expansion coefficients of metal-transition layer-ceramic glass-coating.