Titanium alloys are extensively used in power, chemical and petroleum industries as constructional materials for vessels and heat transfer tubes. Moreover they are candidate materials for nuclear waste disposal. These...Titanium alloys are extensively used in power, chemical and petroleum industries as constructional materials for vessels and heat transfer tubes. Moreover they are candidate materials for nuclear waste disposal. These alloys have superior resistance to localized forms of corrosion compared to stainless steels and Ni-base alloys. However, this resistance is not as remarkable in crevice corrosion conditions in some aggressive media. Electrochemical corrosion tests were conducted on two ASTM Ti grades namely, Ti-2 and Ti-12 in extremely low pH acidic environment. Results indicated that Ti-2 has less resistance to both general and crevice corrosion attack than Ti-12. Both alloys possess better resistance to general corrosion than to crevice corrosion. Also, results showed that the molybdate addition improves remarkably the resistance of Ti-2 to both types of attack. The increase of molybdate ions concentration from 0.03 mol/L to 0.15 mol/L made Ti-2 to be as resistant as, or somewhat higher than, Ti-12. The elecrochemical findings were further supplemented by optical examination of the corroded surface.展开更多
A promising duplex coating was prepared by microarc oxidation(MAO) and enameling processes onto polished Ti6A14V alloy. The TiO2 ceramic coating deposited by MAO was characterized and then combined with an enameling...A promising duplex coating was prepared by microarc oxidation(MAO) and enameling processes onto polished Ti6A14V alloy. The TiO2 ceramic coating deposited by MAO was characterized and then combined with an enameling treatment in order to improve the tribological and corrosion resistance of Ti6A14V alloy. The morphology, phase composition, and hardness of MAO and MAO/enameling-coated Ti6A14V alloy were evaluated by scanning electron microscopy(SEM), X-ray diffraction(XRD), and Vickers microhardness tester, respectively.The tribological performance was investigated using a ballon-disk tribometer. The corrosion resistance was studied using immersion tests and potentiodynamic polarization.Wear tests show that the enamel coating on the MAOcoated surface causes a reduction in the friction coefficient.Immersion tests demonstrate that the duplex coating is more effective in improving the corrosion resistance of Ti6A14V than the MAO coating especially at high temperature(80 ℃). Potentiodynamic polarization curves reveal that the corrosion potential of the duplex coating increases by about 250 mV and the corrosion current density is slightly lower than that of the MAO coating. The duplex coating is superior to the stand-alone MAO coating in improving the tribological and corrosion behavior of Ti6A14V.展开更多
文摘Titanium alloys are extensively used in power, chemical and petroleum industries as constructional materials for vessels and heat transfer tubes. Moreover they are candidate materials for nuclear waste disposal. These alloys have superior resistance to localized forms of corrosion compared to stainless steels and Ni-base alloys. However, this resistance is not as remarkable in crevice corrosion conditions in some aggressive media. Electrochemical corrosion tests were conducted on two ASTM Ti grades namely, Ti-2 and Ti-12 in extremely low pH acidic environment. Results indicated that Ti-2 has less resistance to both general and crevice corrosion attack than Ti-12. Both alloys possess better resistance to general corrosion than to crevice corrosion. Also, results showed that the molybdate addition improves remarkably the resistance of Ti-2 to both types of attack. The increase of molybdate ions concentration from 0.03 mol/L to 0.15 mol/L made Ti-2 to be as resistant as, or somewhat higher than, Ti-12. The elecrochemical findings were further supplemented by optical examination of the corroded surface.
基金financially supported by the Zhejiang Province Science and Technology Program (No. 2014C31126)
文摘A promising duplex coating was prepared by microarc oxidation(MAO) and enameling processes onto polished Ti6A14V alloy. The TiO2 ceramic coating deposited by MAO was characterized and then combined with an enameling treatment in order to improve the tribological and corrosion resistance of Ti6A14V alloy. The morphology, phase composition, and hardness of MAO and MAO/enameling-coated Ti6A14V alloy were evaluated by scanning electron microscopy(SEM), X-ray diffraction(XRD), and Vickers microhardness tester, respectively.The tribological performance was investigated using a ballon-disk tribometer. The corrosion resistance was studied using immersion tests and potentiodynamic polarization.Wear tests show that the enamel coating on the MAOcoated surface causes a reduction in the friction coefficient.Immersion tests demonstrate that the duplex coating is more effective in improving the corrosion resistance of Ti6A14V than the MAO coating especially at high temperature(80 ℃). Potentiodynamic polarization curves reveal that the corrosion potential of the duplex coating increases by about 250 mV and the corrosion current density is slightly lower than that of the MAO coating. The duplex coating is superior to the stand-alone MAO coating in improving the tribological and corrosion behavior of Ti6A14V.