Lecture
WEB Single-step oxygen diffusion hardening of titanium alloys at reduced oxygen partial pressures – a method towards improved surface properties
Wednesday (23.09.2020) 14:45 - 15:00 F: Functional Materials, Surfaces, and Devices 2 Part of:Single-step oxygen diffusion hardening of titanium alloys at reduced oxygen partial pressures – a method towards improved surface properties
Daniel Dickes, Mike Mosbacher, Uwe Glatzel
Metals and Alloys, University Bayreuth, Bayreuth
daniel.dickes@uni-bayreuth.de
Titanium alloys, e.g. deployed in orthopedic implants or in engine valves, exhibit wear due to sliding contacts with a counterpart. One method of surface treatment to improve wear characteristics of titanium alloys is thermal oxidation. Different approaches of thermal oxidation have been shown in the past. Single-step oxidation at elevated temperatures in an oxidizing environment, such as air, leads to a protective TiO2 layer with only poor adherence. Such a TiO2 layer can be removed in a subsequent thermal treatment performed in vacuum in which oxygen from the TiO2 layer diffuses into the substrate. This leads to a surface near oxygen diffusion zone with an increased hardness compared to the substrate. Aim of this work is to investigate a single-step thermal oxidation method which simultaneously produces an adherent protective TiO2 layer and a distinctive oxygen diffusion zone. For this purpose, a furnace developed in our lab, which allows oxidation at oxygen partial pressure below 10^-12 Pa, is used. The formation of TiO2 layers and oxygen diffusion zones is analyzed by scanning electron microscopy and energy-dispersive X-ray spectroscopy to increase the understanding of underlying reaction- and diffusion kinetics. With regard to a better oxide layer adherence, in depth microhardness profiles of the oxidized specimens are determined and compared with oxygen concentration profiles.
