Vliv tepelného zpracování na mechanické a superelastické vlastnosti NiTi pro biolékařské aplikace

Abstract

The presented dissertation is focused on the effect of thermal treatment on the mechanical and superelastic properties of NiTi alloy, intended for biomedical applications, especially for use in stomatology. The theoretical part includes all important areas related to both the focus of the dissertation and the biomedical use of the given alloy. Especially, it contains the characteristics of NiTi alloys, medical applications, surface properties, the issue of martensitic transformation and subsequently superelastic behaviour, which is closely connected with this transformation. Precipitation phenomena during heat treatment and their effects are also discussed. The experimental part of the work includes the goals of the work, the characteristics of the experimental material, and then the description and parameters of all analyses that were carried out. The experimental material included semi-finished endodontic instruments, wires and wire fragments of the same diameter. Wires and fragments were made from Nitinol SE508, semi-finished endodontic instruments from Nitinol SE508 and Nitinol SE508ELI. The samples were subjected to heat treatment in the range of 300-500 °C (300, 350, 400, 450 and 500 °C) in a normal oxidizing atmosphere. Samples in the form of wires were intended for two types of tensile stress, in order to determine selected mechanical and superelastic properties. A fractographic study using SEM was also performed on the samples after tensile stressing to fracture. The semi-finished endodontic instruments were intended for a specific fatigue test. The wire fragments were then used to study the structure using optical and scanning electron microscopy and to determine the transformation characteristics using differential scanning calorimetry.