| Titanium and its alloys are a series of high-strength and light-weight structural materials.Because of their good comprehensive mechanical properties and corrosion resistance,they are widely used in marine,shipbuilding and other fields.Commonly used titanium alloy processing methods are traditional casting and forging processes,which have an earlier development time and mature technology,but their processing speed is slow and costly,and titanium alloys are expensive compared to other commonly used metals.And 3D printing technology is an economical and effective processing method,and it is currently a popular method of metal parts processing in the world.However,during service,whether forging or 3D printing titanium alloys,under the action of seawater corrosive media,applied stress,and cathodic protection,it is easy to cause failures such as corrosion and hydrogen embrittlement,resulting in serious accidents and huge economic losses.Therefore,it is of great significance to study the corrosion behavior of forged and 3D printed titanium alloys in the marine environment.In this paper,electrochemical hydrogen charging is a common method used to study the corrosion of metal materials,and the forged Ti-6Al-4V titanium alloy is charged with hydrogen at different times under simulated marine environment conditions to explore its corrosion mechanism.At the same time,study the corrosion mechanism of forged Ti-6Al-4V titanium alloy and SLM printed Ti-6Al-4V titanium alloy in three different systems of 0.05 M H2SO4,3.5 wt.% Na Cl and 0.1M Na OH.The microstructure and corrosion resistance of the alloys prepared by various processes are compared and analyzed.Electrochemical tests were carried out on the forged Ti-6Al-4V alloy with hydrogen charging at different times.The results showed that with the increase of the hydrogen charging time,the polarization resistance of the sample decreases and the corrosion current density increases.The thickness of the passivation film also gradually decreases,and the composition of the passivation film changes,the titanium oxide compound gradually decreases,and the titanium hydride compound gradually increases.It can also be seen from the Mott-Schottky curve that the increase of ND presents a monotonous change,which indicates that the protective ability of the substrate surface film has deteriorated,resulting in a decrease in its corrosion resistance.The Ti-6Al-4V alloy prepared by the two processes was subjected to electrochemical tests in three different solutions.The results showed that the polarization resistance of the forged Ti-6Al-4V alloy in the three solutions was higher than that of the SLM prepared Ti-6Al-4V alloy,but the corrosion current density of the forged Ti-6Al-4V alloy is lower than that of the alloy prepared by SLM,which indicates that the corrosion resistance of the forged Ti-6Al-4V alloy is better than that of SLM prepared Ti-6Al-4V alloy.At the same time,the Mott-Schottky curve results of the two alloys show that the slope of the curve of the forged alloy is greater than that of the alloy prepared by SLM,and the carrier density ND is lower than that of the alloy prepared by SLM,indicating the protective ability of the surface film of the forged alloy on the substrate Stronger.After the Ti-6Al-4V alloy prepared by the two processes was immersed in the three solutions for 3 hours,XPS analysis of the passivation film composition found that with the increase of the sputtering time,the alloy passivation film of the two processes Both Ti O2 gradually decreased,while Ti OOH and Ti gradually increased.The Ti-6Al-4V alloy prepared by the two processes was placed in three solutions for micro-area electrochemical tests.The results showed that the surface impedance of the forged Ti-6Al-4V alloy was more evenly distributed than that prepared by SLM,and the forged alloy The number and intensity of potential peaks are also less,which indicates that the corrosion resistance of the forged Ti-6Al-4V alloy is better than that of the alloy prepared by SLM. |
PDF Full Text Request