| WU Xuan,GUAN Jing,LIU Jing,LI Kun-mao,YANG Feng,DAI Yan.Corrosion Behavior of TA2 Titanium Alloy Vacuum Induction Carburizing Layer in Fluorine-containing Mixed Acid[J],48(12):304-311 |
| Corrosion Behavior of TA2 Titanium Alloy Vacuum Induction Carburizing Layer in Fluorine-containing Mixed Acid |
| Received:February 16, 2019 Revised:December 20, 2019 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2019.12.037 |
| KeyWord:TA2 induction carburizing fluoric acid impedance polarization curve |
| Author | Institution |
| WU Xuan |
1.School of Materials and Architectural Engineering, Guizhou Normal University, Guiyang , China |
| GUAN Jing |
1.School of Materials and Architectural Engineering, Guizhou Normal University, Guiyang , China |
| LIU Jing |
1.School of Materials and Architectural Engineering, Guizhou Normal University, Guiyang , China |
| LI Kun-mao |
2.School of Materials and Metallurgy, Guizhou University, Guiyang , China |
| YANG Feng |
1.School of Materials and Architectural Engineering, Guizhou Normal University, Guiyang , China |
| DAI Yan |
1.School of Materials and Architectural Engineering, Guizhou Normal University, Guiyang , China |
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| Abstract: |
| The work aims to study the microstructure of the inductive carburized layer of TA2 titanium alloy in CH4 medium, and evaluate the corrosion behavior of carburized layer with high hardness and high wear resistance in the fluorine-containing mixed acid. "Strong seepage-diffusion" was conducted to TA2 titanium alloy by vacuum pulse at 850 ℃, 880 ℃ and 910 ℃. The corrosion resistance of the carburized layer was evaluated by electrochemical workstation and immersion corrosion. In addition, the phase structure, microstructure, corrosion products and chemical states of the carburized layer were analyzed by XRD, SEM and XPS. The TA2 titanium alloy carburized at 910 ℃ could form a thick layer of TiC, and showed good corrosion resistance. Corrosion behavior of TC6 titanium alloy did not occur within the first 120 min in acid solution (0.2%HF+0.2%HNO3), and the corrosion rate was 4.01×10-3 A/cm2 after 120 min. The corrosion rate decreased from 3.32×10-1 A/cm2 to 1.67×10-2 A/cm2 in electrochemical test. The surface of the carburized sample was in a state of overall corrosion, while the non-carburized sample had a pitting corrosion behavior. Fitting results of XPS data after surface corrosion showed that Ti element presented three energy level peaks, mainly in the form of +4 valence, and the fluoride ion was formed by replacing the bond in Ti—OH to form Ti—F. From the results, the strengthened layer formed by vacuum induction carburizing on the surface of TA2 titanium alloy, has an excellent protective function in low concentration of fluorine-containing mixed acid. With the increase of carburizing temperature, the surface carburized layer becomes thicker and has higher impedance film value and smaller corrosion current. Moreover, the presence of a surface carburized layer changes the corrosion behavior of titanium alloy from pitting corrosion to overall corrosion. |
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