Study On The Properties And Surface Modification Of A New Corrosion Resistant Titanium Alloy

Proton exchange membrane fuel cell is considered to be one of the ideal power devices suitable for human long-term development because of its high energy conversion efficiency,no environmental pollution and abundant raw material resources.As one of the most important components of fuel cells,the bipolar plates work in an acidic environment for a long time,and play an important role in supporting the battery structure,collecting electrons,and transmitting heat.Most of the existing bipolar plate materials are mainly stainless steel and graphite,but the graphite processing performance is poor and the corrosion resistance of stainless steel is insufficient.Therefore,the development of new bipolar plate materials with long life cycle is the focus of current research.Titanium alloy is one of the best candidate materials for metal plates due to its excellent corrosion resistance,good mechanical properties and thermal conductivity.Based on the existing theory,a new corrosion-resistant titanium alloy Ti-6Al-3Mo-2Zr-2Fe was designed in this paper.Through microstructure analysis of Ti-6Al-3Mo-2Zr-2Fe alloy,it is found that the alloy has typicalα+βBimodal organization.Theαphase forms a strong<10-10>fiber texture in the radial direction.Theβphase forms a mixed texture of<101>//ND and<001>//TD in the axial direction.The phase transition temperature ofα+β→βmeasured by traditional metallographic method is between880℃ and 890℃.After heat treatment,the alloy exhibits good mechanical properties.Through heat treatment analysis and mechanical properties test,it is found that the alloy after heat treatment is more suitable for the manufacture of plates.The OCP and corrosion current densities in the simulated environment were-0.59V and 681.2μA/cm~2,respectively,and the current density was stable at 14.7μA/cm~2 at 0.6V constant potential.The ICR is 82mΩcm~2 under 1.4MPa load.The water contact angle is 67°.In order to further improve the comprehensive performance of the plate,this paper uses PVD technology to deposit GLC coating.The temperature and bias voltage will affect the thickness and adhesion of the GLC coating prepared by PVD.When the temperature and bias voltage rises to 300℃and 200V,the coating falls off.The degree of graphitization increases first and then decreases with the increase of temperature,and decreases with the increase of bias voltage.When the bias voltage and temperature are 20V and 200℃,the degree of graphitization of the coating is the highest,and the peak area ratio reaches 3.92.The variation of ICR is consistent with the Raman test results,and the minimum contact resistance is 9.5mΩcm~2.The corrosion resistance of the coating is significantly better than substrate.The corrosion potential is greatly improved,and the corrosion current density is reduced by about 2～3 orders of magnitude.The coating achieves the optimal performance at a bias voltage of 20V and a temperature of 200℃,and the corrosion current density is as low as 0.83μA/cm~2.In contrast,the corrosion performance is less affected by temperature and more affected by bias voltage.Compared with the substrate,the hydrophobicity is significantly improved,and the maximum contact angle reaches 115°.In this paper,GLC coatings were also prepared using a low-cost hydrothermal method.By studying the effects of hydrothermal time and carbonization temperature on the coating performance,it was found that the corrosion resistance of the coating with 6h hydrothermal reaction was not satisfactory,and the corrosion resistance of the coating with 8h and 10h hydrothermal reaction was significantly improved.When the carbonization temperature rises to 600℃,the coating shrinks,resulting in a decrease in corrosion resistance.The performance of the coating carbonized at 400℃ is better.The corrosion resistance of the coating is less affected by the solution concentration.At the same carbonization temperature,the solution concentration has little effect on the graphitization degree of the coating.At the same solution concentration,the carbonization temperature has a great influence on the graphitization temperature of the coating.The degree of graphitization of the coating carbonized at 400℃is lower than that of the coating carbonized at 600℃,but the coating carbonized at 400℃has better conductivity,which is due to the shrinkage of the coating and the exposure of the substrate.At the same carbonization temperature,the solution concentration has little effect on the hydrophobicity of the coating,and the carbonization temperature has a great influence on it.The hydrophobicity of the coating carbonized at 600℃is as high as 129.5°.The comprehensive analysis shows that the coating obtained under the condition of 0.15mol solution concentration,hydrothermal time of 8h and carbonization temperature of 400℃has the best comprehensive performance.The OCP and corrosion current density are 0.57V and 0.71μA/cm~2,respectively.The current density is stable at0.52μA/cm~2 at 0.6V constant potential.