Examination of the Corrosion Behavior of Shape Memory NiTi Material for Biomedical Applications

Abstract

In this study, corrosion and wear tests of NiTi alloy (Ni 55%–Ti 45%) samples, known as shape memory alloy, which offer a shape recovery memory effect between memory temperatures ranging from 25 to 35 °C, have been carried out. The standard metallographically prepared samples’ microstructure images were obtained using an optical microscope device and SEM with an EDS analyzer. For the corrosion test, the samples are immersed with a net into the beaker of synthetic body fluid, whose contact with the standard air is cut off. Electrochemical corrosion analyses were performed after potentiodynamic testing in synthetic body fluid and at room temperature. The wear tests of the investigated NiTi superalloy were carried out by performing reciprocal wear tests under 20 N and 40 N loads in a dry environment and body fluid. During wear, a 100CR6-quality steel ball of the counter material was rubbed on the sample surface for a total of 300 m with a unit line length of 13 mm and a sliding speed of 0.04 m/s. As a result of both the potentiodynamic polarization and immersion corrosion tests in the body fluid, an average of 50% thickness reduction in the samples was observed in proportion to the change in the corrosion current values. In addition, the weight loss of the samples in corrosive wear is 20% less than that in dry wear. This can be attributed to the protective effect of the oxide film on the surface at high loads and the effect of reducing the friction coefficient of the body fluid.

Effect of Oxidation Process on Mechanical and Tribological Behaviour of Titanium Grade 5 Alloy

“…The initiation of the wear process in the wear tests occurred at the uppermost OL layer of the oxidised samples. The wear tests were carried out at an average temperature of 24 • C, with a load of 20 N [32][33][34][35][36], a sliding speed of 0.5 m/s, a total sliding distance of 10,000 m, and an ideal humidity level of 45% RH. A 4140-quality steel disc with 59 HRC hardness was used as the counter material determined.…”

Feasibility of a Shape-Memory-Alloy-Actuator System for Modular Acetabular Cups

“…Previous studies conducted by our team [16][17][18] and results from other research groups [19][20][21][22][23][24][25] have shown the potential of shape memory alloys (SMAs), especially nickel-titanium (NiTi), as components for implant applications. NiTi shows sufficient biocompatibility compared to other implant materials, such as Titanium and Titanium alloys, nickel-free stainless steel, or magnesium alloys [26][27][28][29][30][31][32]. Depending on the requirements of the implants or components, NiTi can be coated, for example with hydroxyapatite [33] or diamond-like coating (DLC) [26], to improve corrosion resistance or biocompatibility.…”