Preparation And Properties Of Ta Coating On 316L Stainless Steel Surface

316L stainless steel has good mechanical properties and corrosion resistance.As implants such as artificial joints or internal fixation implant materials,it has the advantages of easy processing and low cost.However,it can not meet the requirements of long-term implantation because it is prone to corrosion wear during its service.Tantalum has a very bright prospect in surgical fields such as bone repair,joint replacement due to its excellent biocompatibility,bone osteonduction ability and chemical stability.But tantalum is expensive,tantalum implants are hardly formed due to its high melting point.Moreover,implants of tantalum bulk materials cannot be used directly because the great difference about elastic modulus and density between tantalum and human bone.In this paper,tantalum coatings were deposited on 316L stainless steel surface by using doble glow plasma surface alloys technology in order to extend the service life of 316L stainless steel as an internal implant.The effect of alloying temperature and time on composition and morphology of Ta coatings were studied.At the same time,the bonding strength,hydrophilicity,as well as the friction and corrosion properties of Ta coatings in phosphate buffer solution were also analyzed.In addition,the cytocompatibility of Ta coating was evaluated by in vitro cell experiments.The results were obtained as follows:（1）Effects of matrix temperature.Ta coating mainly containsα-Ta,β-Ta,as well as a small amount of Fe Ta,Fe₂Ta and Ta₂C.The coating shows island-like fusion growth.Thickness of diffusion layer increases exponentially with temperature and the bonding strength increases first and then decreases with temperature.The performance test results show that the Ta coating can improve the hydrophilicity,wear resistance and corrosion resistance of 316L stainless steel in PBS solution.When the substrate temperature is 850°C,Ta coating has the best comprehensive performance.The critical load is 111.2 N,wear rate and corrosion rate are 5.36×10^-5mm^-3·n^-1·m^-1 and 0.0018 mm/a,which are 25.1%and 3.4%of the substrate,respectively.（2）Effects of deposition time.The main component of Ta coating deposited for 10 minutes isβ-Ta,and coating mainly composition change toα-Ta with time.The thickness of the deposition layer increases linearly and the thickness of the diffusion layer increases logarithmically with time.The performance test results show that the Ta coatings deposited for 30 min and 60 min have similar excellent properties.Affected by internal stresses and brittle compounds at the interface,the bonding strength and wear resistance of Ta coating deposited for 60 minutes are slightly weaker than that of Ta coating deposited for 30 minutes,but it has the best corrosion resistance because it is thicker and flatter.The critical load of Ta coating deposited for 60 minutes is 105.7 N,the wear rate and corrosion rate are 8.04×10^-5mm^-3·n^-1·m^-1 and 0.0018 mm/a,which are 25.1%and 3.4%of the substrate respectively.（3）Biological performance evaluation.The cell proliferation and protein adhesion on 316L stainless steel and Ta coated samples（850°C,30 and 60 minutes）were evaluated.It was found that Ta coating can promote the adhesion,proliferation and differentiation of osteoblasts.While the Ta coating prepared at850°C,60 minutes is more conducive to the expansion of the cell initial behavior.