Optimization of the mechanical properties of the metallic components by micro-surface structuring and the improvement of the fatigue behavior

Abstract: Titanium (Ti) and its alloys have proven to be one of the most popular materials in medical applications due to its excellent mechanical properties, biocompatibility corrosion resistance and as well as strength-to-weight ratio. Despite the mechanical strength advantages, Ti implants suffer from unexpected fatigue cracking issues under cyclic loading while moving body. Fatigue cracks frequently initiate and propagate from the surface of the metals by variety of mechanisms in the crystal structure especially persistent slip bands and twinning deformations. Thus, the surface protection of Ti implants through the selection of proper materials is very promising technology to improve their long-term stability and performance safety. Improving the mechanical properties of commercially pure titanium (cp-Ti) and developing advanced coatings on its surface require an understanding of its damage mechanisms. Fracture toughness of cp- Ti with hexagonal close-packed crystal structure is strongly affected by nucleation and subsequent twin growth due to limited number of available slip systems. In view of this, the first part of this study is related to the examination of the twinning deformation during cyclic loading and its effect on cracking mechanism in cp-Ti.
Furthermore, despite the corrosion resistance of Ti, there is a considerable concern of ions release from the implants resulting from the reactions with the hostile body environment which leads to the reduction in their mechanical strength. If the chemical stability of implant material is not sufficient, the released particles and ions can cause an inflammatory reaction in the body, which negatively influences the biocompatibility behavior and better anchoring of the implants with the bone tissue. Another factor that influences the anchoring of the implant is the high elasticity modulus of Ti compared to the elasticity modulus of the bones. The other problem of implants is the significant mismatching between the elastic modulus of Ti and the human bones. As a result, a large part of the mechanical stresses are imposed on the implant in the body, resulting in a phenomenon known as stress shielding effect.
Compared to metallic implant materials, polymer materials offer advantages which defuse the problems already mentioned or contribute to their improvement. The surface of Ti can be modified by the addition of the ECTFE fluoropolymer in order to enhance its mechanical properties. Likewise, the lower elasticity modulus of ECTFE fluoropolymer compared to Ti contributes to an improvement in the biocompatibility behavior of the Implants. The second part of this research study is dedicated to the development of coating systems on the Ti surface and thereby the formation of a composite material. The aim of this coating system is to improve the microstructure behavior of the Ti implants under cyclic loading and thereby optimize their long-term behavior. Electrophoretic deposition (EPD) offers an excellent opportunity to drastically reduce the risk of delamination of the coating material. By introducing hydroxyapatite (HAp) particles into the ECTFE polymer coating, the surface of Ti can be modified, which allows rapid osseo-integration and also acts as a corrosion inhibitor. The findings of this work can contribute to the improvement of the mechanical properties and long- term behavior of Ti implants with sufficient biocompatibility and corrosion resistance

Angaben zum Objekt

• Standort: Deutsche Nationalbibliothek Frankfurt am Main
• Umfang: Online-Ressource
• Sprache: Englisch
• Anmerkungen: Universität Freiburg, Dissertation, 2020

Klassifikation und Themen

• Schlagwort: Titanium and Superalloys Conference ; Advanced Surface Technology Forum (1998 : Waimea, Hawaii) ; Fatigue ; Fatigue ; Titanium ; Technology ; Heat resistant alloys ; Ermüdungsbruch

Beteiligte, Orts- und Zeitangaben

• Ereignis: Veröffentlichung
• (wo): Freiburg
• (wer): Universität
• (wann): 2021
• Urheber: Bosh, Nasim
• Beteiligte Personen und Organisationen: Müller, Claas ; Mozaffari-Jovein, Hadi ; Wilde, Jürgen ; Albert-Ludwigs-Universität Freiburg. Fakultät für Angewandte Wissenschaften

Weitere Informationen

• DOI: 10.6094/UNIFR/193861
• URN: urn:nbn:de:bsz:25-freidok-1938615
• Rechteinformation: Der Zugriff auf das Objekt ist unbeschränkt möglich.
• Letzte Aktualisierung: 25.03.2025, 13:56 MEZ