不同打印角度SLM–Ti6Al4V组织结构及其在含氟离子溶液中的腐蚀行为

Microstructure and corrosion behavior of SLM-Ti6Al4V with different fabrication angles in F−-containing solutions

采用金相显微镜、扫描电子显微镜、电化学实验和浸泡实验研究了打印角度30°、45°和60°的SLM-Ti6Al4V试样的组织结构及其在NaF溶液中的腐蚀行为.结果表明,三种试样的组织结构都是原β晶粒内部交叉分布针状α’相;打印角度45°试样中针状α'相尺寸与微观结构晶格畸变程度最小.电化学测试结构表明,三种试样在NaF溶液中的腐蚀行为特征都是随溶液浓度增加,由自发钝化逐渐转变为活性溶解,其临界氟离子浓度分别处于0.0005~0.00075、0.00075~0.001和0.0005~0.00075 mol·L^(−1).浸泡试验结果表明,当NaF浓度低于临界氟离子浓度的时候,试样表面基本保持完整,而高于临界值的时候试样表面发生活性溶解.此外,对比三种试样的耐腐蚀性能可以发现,打印角度为45°试样的耐腐蚀性能优于其他试样的性能.

Selective laser fusion(SLM)is an emerging 3D printing technology that can greatly shorten the processing cycle and reduce the production cost of medical implants,thus offering broad prospects for application in the biomedical field.In addition,its excellent corrosion resistance is a crucial characteristic for its application as a biomedical material.However,the corrosion behavior of SLM–TI6AL4V,especially its corrosion resistance,has not been a focus of extensive study to date.In this study,the microstructures and corrosion behavior of SLM–Ti6Al4V,which was produced via selective laser melting with fabrication angles of 30°,45°,and 60°,in NaF-containing solutions were investigated using metalloscopy,scanning electron microscope,electrochemical measurement,and immersion test.According to microstructural analysis,SLM–Ti6Al4V is characterized by priorβgrains with needleα’phases;the priorβgrains for the sample with the fabrication angle of 45°are most like equiaxed,and theα’phase are the smallest.In addition,the sample with the fabrication angle of 45°has the smallest lattice distortion compared to the others.The electrochemical measurements reveal that with increasing NaF concentration,the corrosion resistance of all three samples deteriorates,and the critical fluoride concentration of the samples with fabrication angles of 30°,45°,and 60°are in the range of 0.0005–0.00075 mol·L^(−1),0.00075–0.001 mol·L^(−1),and 0.0005–0.00075 mol·L^(−1),respectively.From the results of the immersion test,in the solution with NaF concentrations less than the critical value,the surfaces of the three samples remain nearly intact,while in the solutions with more added NaF,active dissolution takes place on the sample surface.Comparing the results of the electrochemical measurements and the immersion test,the sample with the fabrication angle of 45°exhibits superior corrosion resistance.