Postdoctoral Research, Dentistry, LabCorr (Corrosion Laboratory), Department of Materials and Metallurgy (COPPE/UFRJ), Federal University of Rio de Janeiro, Av. Horácio de Macedo 2030 Bloco I Cidade Universitária, Rio de Janeiro, 21941-972, Brazil.
Professor, Metallurgical Engineering, LabCorr (Corrosion Laboratory), Department of Materials and Metallurgy (COPPE/UFRJ), Federal University of Rio de Janeiro, Av. Horácio de Macedo 2030 Bloco I Cidade Universitária, Rio de Janeiro, 21941-972, Brazil.
J Mech Behav Biomed Mater. 2020 Dec;112:104015. doi: 10.1016/j.jmbbm.2020.104015. Epub 2020 Aug 14.
Shape memory and super elastic alloys are commonly used in biomedical and engineering areas, due to their higher elastic deformation characteristics and low elastic module when in martensitic state. For biomaterial applications, the alloy must exhibit adequate corrosion resistance and biocompatibility, especially in chloride environments. The addition of ternary elements in NiTi alloys aim to improve the mechanical properties. Addition of Co increases the elastic limit and reduce the transformation temperature while Cr additions increase the yield strength. However, it was demonstrated that this modification can affect the corrosion resistance of the raw materials. This study aims to assess the corrosion and strain induced corrosion resistance of NiTi alloys modified by Co and Cr additions in the presence of 0.9% NaCl solution. Ternary alloys were compared to NiTi binary alloys, when unstrained and strained within the elastic regime where martensitic transformation is induced. Electrochemical impedance spectroscopy (EIS) and anodic polarization tests were performed on both conditions. Straining electrode corrosion tests were performed under constant electrochemical potential being the electrochemical response registered. Tests using wire samples as straining working electrodes permitted the assessment of the correlation between deformation and the anodic current of the alloys immersed in 0.9% NaCl solution. It was concluded that, despite the mechanical benefits provided by the addition of ternary elements, these additions increased the susceptibility to localized corrosion and the pitting corrosion susceptibility enhanced by stress and corresponding strain.
形状记忆和超弹性合金由于其在马氏体状态下具有较高的弹性变形特性和较低的弹性模量，因此在生物医学和工程领域得到了广泛应用。对于生物材料应用，合金必须具有足够的耐腐蚀性和生物相容性，特别是在氯化物环境中。在 NiTi 合金中添加三元元素旨在改善其力学性能。添加 Co 可以提高弹性极限并降低转变温度，而添加 Cr 则可以提高屈服强度。然而，已经证明这种改性会影响原材料的耐腐蚀性。本研究旨在评估在 0.9%NaCl 溶液存在下，通过 Co 和 Cr 添加改性的 NiTi 合金的腐蚀和应变诱导耐腐蚀性。将三元合金与 NiTi 二元合金进行了比较，在未变形和弹性范围内发生马氏体相变时进行了比较。在这两种条件下都进行了电化学阻抗谱 (EIS) 和阳极极化测试。在恒电化学电位下进行了应变电极腐蚀测试，记录电化学响应。使用线样品作为应变工作电极进行测试，评估了在 0.9%NaCl 溶液中变形和合金阳极电流之间的相关性。研究结果表明，尽管添加三元元素可以提供机械性能上的优势，但这些元素的添加增加了局部腐蚀的敏感性，并增强了应力和相应应变引起的点蚀敏感性。
