| DU Feng,ZHOU Yan-wen,WANG Ying-han,FANG Fang,ZHANG Kai-ce,SU Zhi-wei,XU Shuai,WANG Ding.Modification of Ti6Al4V Bipolar Plate with CrN Film Structure by Plasma Density Control[J],51(4):194-201, 210 |
| Modification of Ti6Al4V Bipolar Plate with CrN Film Structure by Plasma Density Control |
| Received:April 21, 2021 Revised:August 21, 2021 |
| View Full Text View/Add Comment Download reader |
| DOI：10.16490/j.cnki.issn.1001-3660.2022.04.019 |
| KeyWord:TC4 titanium alloy bipolar plate magnetron sputtering plasma density CrN film corrosion resistance |
| Author | Institution |
| DU Feng |
Research Institute of Surface Engineering, School of Materials and Metallurgy, University of Science and Technology Liaoning, Liaoning Anshan , China |
| ZHOU Yan-wen |
Research Institute of Surface Engineering, School of Materials and Metallurgy, University of Science and Technology Liaoning, Liaoning Anshan , China |
| WANG Ying-han |
Research Institute of Surface Engineering, School of Materials and Metallurgy, University of Science and Technology Liaoning, Liaoning Anshan , China |
| FANG Fang |
Research Institute of Surface Engineering, School of Materials and Metallurgy, University of Science and Technology Liaoning, Liaoning Anshan , China |
| ZHANG Kai-ce |
Research Institute of Surface Engineering, School of Materials and Metallurgy, University of Science and Technology Liaoning, Liaoning Anshan , China |
| SU Zhi-wei |
Research Institute of Surface Engineering, School of Materials and Metallurgy, University of Science and Technology Liaoning, Liaoning Anshan , China |
| XU Shuai |
Research Institute of Surface Engineering, School of Materials and Metallurgy, University of Science and Technology Liaoning, Liaoning Anshan , China |
| WANG Ding |
Research Institute of Surface Engineering, School of Materials and Metallurgy, University of Science and Technology Liaoning, Liaoning Anshan , China |
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| Abstract: |
| This paper aims to meet the requirements of using bipolar plates for proton exchange membrane fuel cells. In this paper, the hot-wire enhanced plasma magnetron sputtering technology is used to control the sputtering plasma density by changing the hot-wire discharge current, and a chromium nitride (CrN) film is prepared on the surface of Ti6Al4V (TC4) alloy. As the discharge current of the hot filament increased from 0 A to 32 A, the plasma density in the vacuum chamber increased, and the bias current density of the substrate increased from 0.07 mA/cm2 to 0.7 mA/cm2 under ‒50 V bias; the preferred orientation of the CrN film changed from that of low strain energy. (111) is transformed into the (200) preferred orientation with lower surface energy; the surface morphology of the film changes from a loose quadrangular pyramid to a dense spherical shape; when there is no heating wire, the CrN film shows the (110) diffraction peak of chromium and the chromium. The content is 52.16at.%, which is a metal-rich film; when the hot filament discharge current is 16 A and 32 A, the chromium content of the CrN film drops to 50.79at.% and 49.82at.%, and there is no diffraction peak of Cr, that is, it gradually changes to chromium- poor. The use of hot-wire assisted magnetron sputtering will increase the nitrogen ionization rate and increase the activity, causing the thin film to be depleted in chromium. In the simulated bipolar plate working environment, compared with the TC4 corrosion current density of 1.5×10‒8 A/cm2, the corrosion current density of CrN film decreased from 3×10‒5 A/cm2 without hot wire to 9×10‒9 A/cm2 with hot wire. Fitting equivalent circuit of the electrochemical impedance spectroscopy shows that the resistance between the substrate and the coating appears in the equivalent circuit of the CrN thin film prepared under the condition of no hot wire discharge current, indicating that the loose coating provides a channel for the corrosive liquid. Corrosion is formed between the substrate and the coating; the CrN film prepared under the conditions of 16 A and 32 A hot wire discharge current is the same as the equivalent circuit of the uncoated titanium alloy, indicating that the dense coating can effectively prevent the penetration of corrosive media and has the best corrosion resistance. The contact resistance is 7.95 mΩ.cm2 when there is no hot wire discharge current, the film contact resistance increases to 15.65 mΩ.cm2 when the hot wire discharge current is 16 A, and the film contact resistance increases significantly at 32 A. The preparation of dense CrN film on the surface of titanium alloy, which is a candidate material for proton exchange membrane fuel cell bipolar plate, enhances the corrosion resistance of the substrate; but the chromium-depleted component leads to an increase in film resistance. Preparing a dense and slightly rich CrN film on the surface of a titanium alloy electrode plate or a stoichiometric ratio of equivalent CrN film will meet its use conditions as a fuel cell bipolar plate. |
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