Structure And Properties Of TiNi Modified Layer By Laser Alloying Using Antibacterial Metal

Equi-atomic TiNi compounds are widely used in medical and engineering application, due to its unique shape memory effect and pseudoelasticity, good mechanical properties and biocompatibility. However, high Ni content and lack of antibacterial properties have limited its application. In this paper, to solve these problems, two surface modification method have been presented, in order to improve its corrosion resistant and give its antibacterial properties: one is laser alloying on a layer of copper created by vacuum evaporation on TiNi; the other is femtosecond laser alloying doping silver on the surface of TiNi with the layer of silver preparation by vacuum evaporation. Modified layer’s morphology, composition, structure, corrosion resistance and antibacterial properties are analyzed by scanning electron microscope, energy spectrometer, X-ray diffraction, electrochemical workstation and antibacterial experiment.Results show that the laser alloying can obviously improve surface properties such as surface morphology and reduction of porosity and precipitated phase. Laser power, scanning speed and scanning interval have different influences on the modified layer, especially scanning speed. After optimization, the best modified layer can be obtained, when the parameter is laser power 120 W, scanning speed 100mm/s and scanning interval 0.06 mm. In addition, the Cu content of modified layer is uniform and can be controlled by deposition time.The corrosion resistance of laser copper alloying layer was improved, compared with TiNi. The antibacterial property for S.aureus has been got, while for E.coli has not been observed. Laser power, scanning speed and scanning interval show various effects on the corrosion behavior of the modified layer, especially scanning speed. This is because scanning speed can great affect modified layer’s organization, which directly determines the quality of the surface oxide film. What’s more, the change of Cu content nearly has no effect on corrosion resistance of modified layer, as well as antibacterial properties.Femtosecond laser Ag alloying was carried out on the surface of the TiNi alloy. The modified layer with uniform micro-nano structure was successfully obtained. Results showed that the layer’s composition was uniform and has been oxidized, after modification. Furthermore, Ag was dissolved into TiNi matrix, however, the Ag content only have a slight rise with the increase of deposition time.The corrosion resistance of femtosecond laser Ag alloying layer was better than TiNi. This is mainly thanks to the TiO2 oxide film generated on TiNi alloy surface. Antibacterial experiments show that the modified layer possesses good antibacterial properties both for gram negative bacteria and gram positive bacteria, by contact killing. What’s more, the higher Ag content, the better antibacterial performance. This is mainly due to Ag ion, which has very strong sterilization ability.