Corrosion Properties Of Ti6Al4V Alloy Formed By Selective Laser Melting

Ti6Al4V alloy has been more and more used in dental implants due to its low density,high specific strength,low elastic modulus,non-toxic,long fatigue life,corrosion resistance and good biocompatibility.In this paper,the corrosion resistance of Ti6Al4V alloy prepared by Selective Laser melting（SLM）in artificial saliva was studied.The results are as follows:（1）The corrosion properties of SLM formed Ti6Al4V alloy in simulated artificial saliva were studied and compared with rolled Ti6Al4V alloy.The Ti6Al4V alloy prepared by SLM is equiaxed in cross section and columnar in longitudinal section,and acicular martensite is distributed inside the grains.The rolled Ti6Al4V alloy consists of lamellarαphase and interlamellarβphase.The corrosion resistance of rolled Ti6Al4V alloy is the best,followed by the longitudinal section of SLM formed Ti6Al4V alloy,and the cross section of SLM formed Ti6Al4V alloy has the worst corrosion resistance.The reason is that theβphase content of rolled Ti6Al4V alloy is higher and the grain size is smaller.The higherβphase content increases the charge transfer resistance and reduces the alloy dissolution rate.（2）The effects of laser power and scanning speed on the corrosion properties of Ti6Al4V alloy prepared by SLM in artificial saliva were studied.With the increase of laser power,the pore size of the sample decreases first and then increases,and the content ofβphase increases first and then decreases.When the power is 180W,the sample has the lowest porosity and the highestβphase content.At this time,the sample and corrosion resistance is the best,and the passivation film produced is the densest.With the increase of scanning speed,the porosity andβphase content of the sample increase.When the scanning speed is 1400mm/s,the corrosion resistance of the sample is the best and the passivation film is the densest.The experimental results show that the corrosion resistance of Ti6Al4V alloy prepared by SLM is the best when the laser power is 180W and the scanning speed is1400mm/s.（3）The effect of annealing temperature on the corrosion behavior of Ti6Al4V alloy prepared by SLM in artificial saliva was studied,and the mechanism of corrosion behavior of Ti6Al4V alloy prepared by SLM with different fluoride ion concentration and solution p H was explored.The results show that the corrosion resistance of Ti6Al4V alloy in artificial saliva is enhanced after annealing.The main reason is that the unstableα’phase in the Ti6Al4V alloy prepared by SLM is transformed into stableα+βphase by annealing,which promotes the increase of its corrosion resistance.The specimens annealed at 1050℃had the best corrosion resistance and the most stable and compact passivation film.Because the temperature is above theβphase transition temperature T_β,the content ofβphase in the annealed samples increases greatly at this temperature,and theβphase is rich in V element,which effectively inhibits the dissolution of the passivation film.With the increase of p H,the corrosion resistance increases first and then decreases.