Department of Metallurgical and Materials Engineering, Federal University of Rio de Janeiro (COPPE/UFRJ), Cid. Universitária-Centro de Tecnologia-Bloco F, 210, Ilha do Fundão, Postal Box 68505, Rio de Janeiro, RJ, 21941-972, Brazil.
J Mech Behav Biomed Mater. 2021 Apr;116:104323. doi: 10.1016/j.jmbbm.2021.104323. Epub 2021 Jan 15.
This work aims to assess the influence of corrosion on fracture of nickel titanium (NiTi) superelastic wires in physiological solutions (9 g/l NaCl) with and without addition of 1 g/l NaF. The electrochemical cell was coupled to a Hounsfield Tensiometer tensile machine commonly used for corrosion investigation of alloys under stress and strain. Corrosion tests were performed on unstrained and strained conditions up to 4% total strain. This strain limit corresponds to 50% of the total elongation achieved into the superelastic stress plateau of the alloy. All wire specimens were analyzed after testing by scanning electron microscopy (SEM). The results showed that localized corrosion occurred for NiTi wires in solution containing fluoride, while no corrosion attack was detected in NaCl 9 g/l solution. There was no significant difference between the corrosion resistance of unstrained and strained wires. However, brittle like fracture occurred in NaCl + NaF solution within the superelastic domain of the material. The most relevant conclusion achieved is that the use of superelastically strained NiTi in oral environments in the presence of fluoride is followed by significant risk of corrosion induced fracture.
本工作旨在评估在生理溶液（9 g/L NaCl）中添加和不添加 1 g/L NaF 的情况下，腐蚀对镍钛（NiTi）超弹性丝断裂的影响。电化学池与通常用于在应力和应变下研究合金腐蚀的 Hounsfield 拉力试验机耦合。在未受应变和应变条件下进行腐蚀测试，总应变高达 4%。该应变极限对应于合金超弹性应力平台达到的总伸长率的 50%。所有线材试样在测试后均通过扫描电子显微镜（SEM）进行分析。结果表明，在含氟化物的溶液中 NiTi 线材发生局部腐蚀，而在 9 g/L NaCl 溶液中未检测到腐蚀。未受应变和受应变的线材的耐腐蚀性没有显著差异。然而，在材料的超弹性域内，在 NaCl+NaF 溶液中发生了脆性断裂。得出的最相关结论是，在存在氟化物的口腔环境中使用超弹性应变 NiTi 会导致腐蚀诱导断裂的风险显著增加。
