Construction And Investigations Of Bifunctional Surface With Excellent Antibacterial Property And Corrosion Resistant Property

Aseptic loosening due to wear and corrosion,together with the loosening caused by BCI have been regarded as two main factors result in the failure of titanium implants.This in turn leads to the additional financial burden and enormous pain to the patients.Meanwhile,the application and development of titanium alloys as a biomaterials was limited to some extent.Hence,it is very urgent and essential to prolong the service life and improve the service safety and reliability of titanium implants by improving the wear and corrosion resistance of titanium alloys.It is of great economic and social significance.For this purpose,two technologies,coating technology and construction surface microstructure technology via laser cladding and laser shock peening were used to construct a bifunctional surface with excellent antibacterial property and corrosion resistant property of Ti-6A1-4V alloy and Ti-Cu alloy,respectively.The wear and corrosion resistance,and antibacterial property were significantly improved.It can be concluded as following:A bifunctional ZnO/HA coating was generated on the surface of Ti-6Al-4V alloy via laser cladding technology,and got the following results.(1)No significant effect on content of ZnO on the phase type was observed.However,the content of ZnO has a great influence on grain refinement.The main phases in the coatings can be characterized as CaTiO3,Ca3(PO4)2,ZnTiO3 and CaO.The increasing of surface free energy results from the grain refinement improved the wettability and in vitro bioactivity of the coatings.The grain size decreased with increasing of the content of ZnO in the coatings,which in turn results in the better wettability and more excellent in vitro bioactivity.(2)The bio-corrosion resistance of Ti-6Al-4V alloy was significantly improved by laser cladding ZnO-HA coatings.Moreover,the corrosion resistance depends on the content of ZnO in the coatings.The coatings with higher content of ZnO present a more excellent bio-corrosion resistance.(3)The antibacterial property of the coatings depend on the content of ZnO addition.The antibacterial ratio of pure HA coating is 20.8%.However,that of the coatings with ZnO addition is approximately 100%,whatever the content of ZnO is 5 wt.%,10 wt.%,or 15 wt.%.This indicates that ZnO-HA coatings presents excellent antibacterial property.A bifunctional structure was constructed on the surface of Ti-3Cu alloy via laser shock peening technology.It can be concluded as following:(1)The main phases of Ti-3Cu alloy composed of α-Ti and Ti2Cu phase.The microstructure can be characterized as net-like and needle-like structure.An obvious plastic deformation was observed in the zone near the top of the Ti-3Cu surface after laser shock peening treatment.The stripe crystals in the area fractured leading to the increased number of grain boundaries and the grain refinement.The LSP treatment promoted the precipitation of Ti2Cu phase and the preferred orientation of a phase.The grain size decreased with increasing of laser pulse energy and impact times.Meanwhile,the intensity of the copper-rich phase precipitation increased with increasing of laser pulse energy and impact times.(2)The surface roughness of Ti-3Cu alloy increased after LSP treatment.The grain refinement and the increasing of surface roughness play an important role in improving the surface free energy.As a result,the wettability and the corrosion resistance of Ti-3Cu alloy were significantly improved.The corrosion resistance property depend on the impact times and pulse energy of laser.With the same impact times,a higher pulse energy is beneficial to get more excellent corrosion resistance.On the contrary,the corrosion resistance of the Ti-3Cu alloy decreased when the impact time is more than 3.(3)The microhardness of the Ti-3Cu surface was significantly improved by LSP treatment.The microhardness present a soft-hard(S-H)alternation distribution character after LSP treatment.The improvement together with the S-H distribution of the hardness are main factors of the improvement of wear resistance of Ti-3Cu alloy.However,it is found that the LSP with more impact times(more than 3)is bad for improving the wear resistance.The wear mechanism of Ti-3Cu control and the shocked Ti-3Cu alloy with lower pulse energy can be characterized as abrasive wear,adhesive wear and slight oxidation wear.The Ti-3Cu shocked once with higher pulse energy present the character of abrasive wear and adhesive wear.With increasing of impact times to 3 and 5,fatigue wear characteristics together with abrasive wear and adhesive wear was observed.(4)The improvement of the antibacterial property of Ti-3Cu after LSP can be attributed to the precipitation of copper-rich phases at the grain boundaries.When the Ti-3Cu alloy was shocked with lower pulse energy(5J),no significant effect of impact times on the antibacterial ratio was observed.The antibacterial ratio for the samples shocked once,3 times and 5 times changes between 32.6%and 40.9%,that for the Ti-3Cu control is about 14.4%.However,when the pulse energy is 7J,the antibacterial ratio increased significantly from 64.6%to 90.3%and 92.1%with variation of impact time from once to 3 times and 5 times due to the increasing of the intensity of precipitation of copper-rich phases.This indicates that a higher pulse energy is better than a lower energy to improve the antibacterial property of Ti-3Cu alloy.