Study On The Improvement In Surface Properties Of Metal And Bonding Of Metal-Bioceramic By Laser Gas Nitriding

A TiN surface layer was fabricated on pure titanium and Ti6Al4V alloy by lasergas nitriding. This TiN layer can improve the corrosion resistance and wear resistanceof pure titanium and Ti6Al4V. A bioactive ceramic layer was in turn sintered on thisTiN surface layer. The surface morphology, chemical composition and phases presence of thenitrided-layer were investigated using Optical Microscopy(OM), EnvironmentScanning Electron Microscopy(ESEM) and X-ray Diffraction(XRD).Electrochemistry test and Block-on-ring sliding wear test were carried to measure thecorrosion resistance and wear resistance of the nitrided layer. Longitudinal pull-offtest was carried to examine the bondingstrength between the coating and substrate. The results of wear and electrochemistry test showed that the nitrided Ti andTi6Al4V specimens exhibited good wear resistance and corrosion resistance. The results of Longitudinal pull-off test showed that the adhesion between thebioactive ceramic coating and substrate was excellent. Following mechanisms wereintroduced by laser gas nitriding: 1. A rough surface was created after acid etching. 2.Chemical bonds was created due to the chemical reaction between TiN and Oxide inbioceramic. 3. TiN layer hinderd the formation of TiO and TiO2, these oxide maydecrease the bonding strength between coating and substrate. 4. Thermal expansioncoefficients of TiN are close match for that of bioceramic coating.