The Tribocorrosion and Corrosion Properties of Thermally Oxidized Ti6Al4V Alloy in 0.9 wt.% NaCl Physiological Saline

Abstract

Thermal oxidation of Ti6Al4V was carried out at 700 °C for 5 h in air atmosphere. The characteristics of morphology and structure, micro-hardness, and tribocorrosion behavior in 0.9 wt.% NaCl solution of thermally oxidized Ti6Al4V alloys were investigated and compared with those of the untreated one. The scanning electron microscope (SEM) and glow discharge spectrometer (GDS) results reveal that the oxide layer is completely coated on the substrate, which is a bilayer structure consisted of oxide film and oxygen diffusion zone (ODZ). X-ray diffraction (XRD) and Raman measurements reveal the rutile phase as the dominant phase. The micro-hardness and surface roughness (Ra) increase about 1.63 and 4 times than those of the untreated one. Thermally oxidized sample obtains corrosion and tribocorrosion resistance property in 0.9 wt.% NaCl solution. The corrosion potential has a more than 500 mV anodic shift, the corrosion current density decreases about 80%. The total material loss volume is reduced by almost an order of magnitude under tribocorrosion behavior, which is due to the improvement of the micro-hardness of the oxide layer and ODZ that reduce the corrosion and the synergistic effect of corrosion and wear.

Corrosion Resistance of a Plasma-Oxidized Ti6Al4V Alloy for Dental Applications

“…There was a similar trend with the passive current density value, I pas , since the lowest value was obtained for specimen oxidized during 3 h, and this value increased for lower or higher oxidation times. De Assis [47] reported an I pas value of 3.5 µA/cm 2 in a Hank's solution, equal to that reported by Cao [17] for a thermally oxidized Ti6AL4V alloy in 0.9% NaCl solution, very close to the value observed in this work for the untreated blank alloy. Unlike the effect of the oxidation time on the I pas value, there was no relationship between the former and the pitting potential value, E pit , as shown in Table 1, where the highest E pit value was obtained for specimen oxidized during 1 h and 8 h, specimens that exhibited two of the highest I pas values.…”

“…Finally, de Assis [47] reported a very stable value of 50 mV in a Hank's solution during 60 h of testing; thus, the values reported here are similar to those reported in the literature. The shift towards more active values at the beginning of the experiment is due to the dissolution of any pre-formed protective TiO 2 or Al 2 O 3 oxides layer, whereas the shift towards nobler values is due to the establishment of protective oxides [15][16][17] and to the thickening of the oxide film improving its corrosion protection ability.…”

“…Among Ti alloys, one of the most remarkable alloys is Ti6Al4V, which is especially useful as an implant material, including dental implants, in the health sector [9][10][11][12][13][14]. The corrosion and oxidation resistance of this alloy is based on the development on their surface of a mixture of TiO 2 and Al 2 O 3 oxides [15][16][17], which provide a very stable passive layer and protect the alloy against the corrosive action of substances in the environment, such as chlorides, sulphates, and acids, among others [18][19][20][21]. However, that corrosion resistance is lowered when aggressive ions such as chloride are present, which makes these alloys highly susceptible to a localized type of corrosion such as pitting.…”

“…Morphology evaluation revealed that the structure of this coating contained uniform submicron porosity and its surface exhibited the highest hydrophobicity. Additionally, Cao et al [17] used thermal oxidation, whereas Öteyaka [32] used cryogenic treatments. Cotolan [33] produced a TiO 2 layer by anodizing a Ti6Al4Nb alloy in sulfuric and acetic acids, corroding them in Hank's solution, and found better properties in the ones anodized in acetic acid.…”

Mechanical Properties, Corrosion Resistance and Bioactivity of Oxide Layers Formed by Isothermal Oxidation of Ti-6Al-7Nb Alloy

“…The high affinity of titanium and its alloys for oxygen can be used to improve corrosion resistance in the biological environment, biocompatibility, bioactivity, surface topography, and mechanical and tribological properties. Of the methods used for this purpose, special attention should be paid to the isothermal oxidation method, which is a simple and economical way to modify the surface of titanium and its alloys [26][27][28][29][30][31]. This technique uses the phenomenon of oxygen diffusion at elevated temperatures and thus allows curing of the surface layer by forming a relatively thick TiO 2 film over the oxygen diffusion zone.…”