Investigations On Improving Tribological Properties Of Zr-2.5Nb Alloy By Plasma Nitriding/laser Texturing Technology

Zr-Nb alloy has been widely used in biomedical application due to its good mechanical properties,excellent biocompatibility,excellent corrosion resistance and lower modulus of elasticity.However,the lower microhardness and bad abrasion resistance are main factors influencing the lifetime of Zr-Nb implants.Hence,one of the key problems to promote the clinical application is to improve the wear resistance of Zr-Nb alloy.With this purpose,plasma nitriding technology(PN)combined with laser texturing technology(LT)were used to improve the surface hardness and in turn improve the wear resistance of the Zr-2.5Nb alloy.XRD results showed that.ZrN and Zr3N4 were formed on the surface of Zr-2.5Nb substrate after PN,LT/PN and PN/LT treatment.The results from EDS analysis also confirmed the XRD results.A textured morphology was achieved after LT,LT/PN and PN/LT treatment.The surfaces processed with different technology presented different surface roughness.A uniform and compact nitride layer was observed after PN and LT/PN treatment.The surface energy of Zr-2.5Nb substrate increased significantly,while the contact angles in SBF fluid decreased significantly after the four treatments.Such results indicated that the wettability of Zr-2.5Nb substrate was significantly improved.Compared to LT and PN/LT treatment.PN and LT/PN technology presented more excellent effect in improving wettability of Zr-2.5Nb alloy.The microhardness of Zr-2.5Nb substrate was improved after the four treatments Especially,LT/PN and PN/LT presented more interesting effects.The coefficient of friction of Zr-2.5Nb substrate decreased distinctly after modifying treatments,meanwhile,the anti-wear resistance property was improved significantly,especially the combination of LT/PN technology.Wear mechanism of Zr-2.5Nb control can be characterized as adhesive wear.abrasive wear,and oxidative wear.However,the sample processed with LT/PN presented typical abrasive wear characterization.The corrosion electric current density and corrosion rate of the samples processed with PN.PN/LT.and LT/PN decreased obviously compared to that of the Zr-2.5Nb substrate,indicating that the corrosion resistance of Zr-2.5Nb substrate was improved significantly by PN,PN/LT and LT/PN treatments.