Biomedical Materials Modification By High Current Pulsed Electron Beam

316L stainless steel (316L SS) and NiTi alloy are the two metallic materials widely used in the biomedical fields. However, as medical implant instrument materials, they will release harmful metal ions after the implantation and its corrosion product will affect the normal physiological functions of the human body. In the present study, the high current pulsed electron beam (HCPEB) technique was employed to modify the surface of 316LSS and NiTi alloy with the aim of improving the corrosion resistance of these two alloys. Meanwhile, the surface properties, the mechanical performances, corrosion behaviors and blood compatibility have been measured and evaluated synthetically by various surface characterization techniques, electrochemical measurements and hemocompatibility experiment. The main results are summarized as follows:1,HCPEB bombardment induces the selective purification on the top surface of 316L stainless steel, surface texturation and rapid surface alloying with Ti. As a result, the corrosion resistance of 316L SS was improved after modification. The details are as follows:The high-current pulsed electron beam is revealed as an effective way to remove the inclusions in the surface, thus realize surface purification of 316L stainless steel. MnS inclusions in the 316L SS are the initiation sites for crater formation during bombardment. The overheated eruption of inclusion itself or inclusion/substrate interface lead to the formation of craters. The MnS inclusion density over the number of HCPEB pulses decreased gradually due to the occurrence of eruption events on the sample surface. The defects generated in the early stage of treatment can be repaired after repeated bombardments, that is, the crater density decreases gradually with the increasing pulses, and the holes in crater centers are also removed.The electrochemical measurement results clearly demonstrate the high potential of the HCPEB technique for improving the corrosion resistance in vitro simulated body environment (37±1℃,Tyrode's simulated body fluid) of 316L SS. The corrosion behaviors of 316L SS after modification closely depended on the number of HCPEB bombardments:(1) 5 pulses of HCPEB have two-side effects on the corrosion resistance of 316L SS: the reduction of inclusions on the surface leads to the reduction of interface capacity and corrosion current density; but at the same time the crater center becomes the sensitive position due to the remnant MnS inclusions and holes, leading to the decrease in the broken potential and the narrower passivation region.