The effects of fretting on Ni-rich ultra-fine grained NiTi superelastic wires have been characterized. Fretting tests have been performed using wire on wire in 90° cross-cylinder configuration until 10⁵ cycles in air at 25 °C. Constant displacement amplitude of 50 µm and normal loads of 10, 20 and 50 N were considered. For a normal load of 10 N, the tribosystem performed in Gross Slip Regime and the predominance of wear damage was observed. Mixed Fretting Regime was instead observed for normal loads of 20 N and 50 N. In these cases, the predominant damage mechanism was crack formation with the cracks oriented normal to the displacement direction. Occurrence of martensitic transformation in the contact region was inferred from the particular shape of the fretting loops. Due to their possible impact on biocompatibility, the debris detached from the tribosystem during the different experiments were collected and characterized by TEM. They consisted in agglomerations of nano-crystalline TiO₂ (rutile) and NiO oxide particles sized between 10 and 20 nm.

微动对富镍超细晶粒NiTi超弹性线材的影响已被表征。使用90°交叉圆柱配置的线对线进行微动测试，直到10 ⁵在25°C的空气中循环。考虑了恒定位移振幅为50 µm，法向载荷为10、20和50N。对于10 N的正常载荷，摩擦系统在大滑移状态下进行，观察到磨损损坏占主导地位。取而代之的是在20 N和50 N的正常载荷下采用混合微动状态。在这些情况下，主要的破坏机理是裂纹的形成，裂纹的取向垂直于位移方向。从微动环的特殊形状可以推断出在接触区域发生了马氏体相变。由于它们可能对生物相容性产生影响，因此收集了在不同实验过程中从摩擦系统分离的碎片，并通过TEM对其进行了表征。它们由纳米晶体TiO _2的团聚组成 （金红石）和NiO氧化物颗粒的尺寸在10到20 nm之间。