Research On The Corrosion Behavior Of Ti-TiN Composites Formed By Laser Selective Melting In Different Media

In recent years,Ti-TiN composites produced by selective laser melting?SLM?could be considered as one of the most suitable candidates in the field of high strength and anti-wear biomedical applications.Even so,it is still unclear whether the service life of Ti-TiN composites as biomedical materials can be drastically extended in comparison to CP-Ti in the environments,such as simulated body fluid or other solution media.With the increasing concerns of this urgent problem,this work first studies the corrosion behavior of Ti-5TiN?5 wt.%TiN?composites in simulated body fluids?Hank's solution?compared to CP-Ti.Then,the corrosion behavior of Ti-TiN composites in 0.5 mol/L HCl solution is studied.The previous research has confirmed that the corrosion resistance of SLM-produced Ti-TiN composites is higher than that of CP-Ti.However,how does the corrosion resistance of Ti-TiN composites change with the increase of TiN content,and the role of TiN particles in the corrosion process is worth exploring.Therefore,the corrosion behavior of Ti-based composites with different TiN contents in the different corrosion media is studied.The main conclusions are as follows:?1?The TiN particles in the Ti-TiN composites have a good interface with the titanium matrix and are homogeneously distributed in the titanium matrix.The CP-Ti composed of the hcp-Ti phase and the Ti-TiN composed of the hcp-Ti and?-TiN phases are both acicular martensite??'?structures.?2?In Hank's solution,the corrosion resistance of Ti-5TiN composites is higher compared to that of CP-Ti.This is because TiN particles are uniformly distributed in the titanium matrix as micro-cathodes,which accelerates the early anodic dissolution of the titanium matrix and makes Ti-5TiN composites preferentially enter the passivation state.?3?In 0.5 M HCl solution,Ti-5TiN composite has a smaller passivation current density and corrosion current density than CP-Ti.When the immersion time extended to 15 days,Ti-5TiN composite has developed from pitting corrosion into uniform corrosion,while CP-Ti has evolved from pitting to large corrosion pits.?4?In 0.5 mol/L HCl/H₂SO₄ solution,the corrosion resistance of Ti-TiN composites increases with the increase of TiN content.The TiN particles act to accelerate the early passivation during the corrosion process.The preferential corrosion process of the alloying reaction layer protects the titanium matrix and the TiN particles inside the reaction layer from further corrosion.With the increase in TiN content,the effect of grain refinement is more pronounced,resulting in more excellent corrosion resistance.In summary,the above results show that the corrosion resistance of SLM-produced Ti-TiN composites is higher than that of CP-Ti.Therefore,Ti-TiN composites not only exhibit high hardness,high wear resistance,but also have high corrosion resistance,which makes it have a wide application in the biomedical field.