Study On Process And Performance Of Ultrasonic Phosphate On 316L Stainless Steel

316L stainless steel has become one of the implant materials in the field of artificial joint, fixed bracket, dental and cardiac surgery because of its excellent mechanical properties, corrosion resistance and relatively low prices. However, there are still problems in the clinical application of316 L stainless steel, such as poor wear resistance and nickel ion release which is harmful to human body. Practice has proved that surface modification can effectively overcome the problems of 316 L stainless steel. The process of phosphating treatment is simple, stable, low cost,which can meet the requirements of mass production. In addition, the phosphating coating has good corrosion resistance, wear resistance and biocompatibility, which is harmless to the human body. So far, the preparation of phosphating coating on the surface of 316 L stainless steel is rarely reported.In this paper, the phosphating treatment on the surface of 316 L stainless steel was conducted in ultrasonic field. The ultrasonic phosphating treatment of 316 L stainless steel were optimized by orthogonal test to obtain the optimum process parameters. In order to enhance the compactness of the coating, sealing treatment is conducted through single factor test to obtain the optimum process parameters. The surface morphology, composition, structure, coating thickness, corrosion resistance, wear resistance, biological activity, blood compatibility and nickel ion release of coatings were systematic studied by using scanning electron microscope, X-ray diffraction, friction and wear spectrometer and electrochemical workstation and so on.Results show that ultrasonic field can significantly accelerate the phosphating speed of 316 L stainless steel. The phosphating coating isuniformly distributed, complete and intact. The coating thickness is 15μm,and the best preparation parameters of ultrasonic phosphating coating are the p H of 2.7, the time of 90 min, the ultrasonic power of 200 w, the temperature of 50℃. The porosity of the phosphating coating decreases from 9.8% to 2.9% after sealing treatment, which shows the obvious improvement of compactness. The best preparation parameters of sealing treatment are the temperature of 80℃, the Na2 Si O3 concentration of10g/L, the time of 15 min. The friction coefficient of sample treated by phosphating treatment, especially the one treated by ultrasonic phosphating treatment, reduces significantly. Its friction coefficient decreases from 0.574 to 0.122, which shows the obvious improvement of wear resistance. The phosphating coating, especially the one after sealing treatment, can obtain higher self corrosion potential. Its self corrosion potential increases from-0.813 V to-0.312 V, which shows the obvious improvement of corrosion resistance. After phosphating treatment in ultrasonic field, the surface of the sample has successfully induced hydroxyapatite. Its anti clotting time increases from 25 min to 60 min above, which means it has excellent biocompatibility. In addition, after the phosphating coating with sealing treatment soaked in simulated body fluid for about 14 days, the release of nickel ion reduces from1.827μg/m L to 0.134μg/m L, which effectively blocks the release of nickel ion.