Structure and corrosion resistance of titanium oxide layers produced on NiTi alloy in low-temperature plasma

Abstract

The paper presents comparative results of NiTi corrosion resistance tests of the alloy in initial state and after oxidizing and oxynitriding in low temperature plasma. These processes allow obtaining TiO2 or composite TiO2 + TiN layers with a titanium nitride (TiN) interlayer. Corrosion resistance tests of diffusion layers produced on NiTi were carried out via electrochemical impedance spectroscopy and the potentiodynamic method in Ringer's solution at 37 °C. The results were complemented with analysis of the alloy's structure, surface topography, and elemental distribution in the layers. The results showed an increase in corrosion resistance of NiTi alloy both after glow-discharge oxidation and oxynitriding. Significant shortening of the passive range of oxynitrided layers may result both from differences in surface topography and the thickness of the oxide layers.

Formation of Nitrogen Doped Titanium Dioxide Surface Layer on NiTi Shape Memory Alloy

“…It should be noted that during heating of the NiTi alloy in glow discharge conditions, the cathodic sputtering phenomenon was less intense due to higher pressure in the reaction chamber (2.0 hPa). The surface layer of titanium oxide-rutile, as shown in our earlier studies [ 12 , 19 , 21 ], significantly changed the properties of the NiTi, including its corrosion resistance and mechanical properties. TiO 2 is characterized by good biological properties [ 19 , 21 , 28 , 29 ], including antibacterial properties [ 30 ].…”

“…The nanometric oxide layers formed spontaneously on the surface of the NiTi alloy, the composition of which depends on the conditions of the implant manufacturing process, do not provide sufficient protection against metallosis [ 7 , 8 ]. Therefore, different methods of treating the surface of NiTi alloys are used, which are aimed at both limiting the transfer of nickel to the biological environment as well as shaping the properties of implants, depending on their intended use [ 9 , 10 , 11 , 12 , 13 ]. According to our earlier studies [ 10 , 12 ] and the literature data [ 6 , 9 , 14 , 15 , 16 ], TiO 2 titanium oxide plays an important role in shaping these properties, including the biological properties of NiTi shape memory alloys.…”

“…Therefore, different methods of treating the surface of NiTi alloys are used, which are aimed at both limiting the transfer of nickel to the biological environment as well as shaping the properties of implants, depending on their intended use [ 9 , 10 , 11 , 12 , 13 ]. According to our earlier studies [ 10 , 12 ] and the literature data [ 6 , 9 , 14 , 15 , 16 ], TiO 2 titanium oxide plays an important role in shaping these properties, including the biological properties of NiTi shape memory alloys. Oxide layers can be produced primarily by electrochemical oxidation, gas oxidation or low-temperature glow discharge plasma [ 6 , 12 , 16 , 17 , 18 ].…”

“…According to our earlier studies [ 10 , 12 ] and the literature data [ 6 , 9 , 14 , 15 , 16 ], TiO 2 titanium oxide plays an important role in shaping these properties, including the biological properties of NiTi shape memory alloys. Oxide layers can be produced primarily by electrochemical oxidation, gas oxidation or low-temperature glow discharge plasma [ 6 , 12 , 16 , 17 , 18 ]. They are also used as interlayers for coatings (e.g., carbon layers such as C:N:H; in other words, amorphous hydrogenated nitrogen-containing carbon characterized by good hemocompatibility [ 19 ] or hydroxyapatite coatings for bone implants [ 16 , 20 ].…”

“…The glow discharge-assisted oxidation method allows for production of titanium oxide surface layers on NiTi and titanium alloys, which has been proven to be biocompatible and can be used to enhance the properties of bone and cardiac implants. Throughout modification of technological process parameters like the temperature, time, composition of the gaseous mixture and pressure in the reaction chamber, it is possible to produce diffusive oxide surface layers of controlled phases and chemical compositions, microstructures and surface topographies [ 12 , 23 , 24 ]. Hence, this article focuses on the influence of the cathode sputtering phenomenon on the microstructure and properties of a titanium dioxide surface layer produced on NiTi shape memory alloy using the low-temperature plasma oxidation process.…”