Author: Helen Adejo
Adejo, Helen, 2021 Tribocorrosion behaviour of titanium alloys for medical applications, Flinders University, College of Science and Engineering
Terms of Use: This electronic version is (or will be) made publicly available by Flinders University in accordance with its open access policy for student theses. Copyright in this thesis remains with the author. You may use this material for uses permitted under the Copyright Act 1968. If you are the owner of any included third party copyright material and/or you believe that any material has been made available without permission of the copyright owner please contact copyright@flinders.edu.au with the details.
The demand for materials to replace lost or damaged tissues and organs has been on the increase in recent years because of an ever-increasing aging population and loss of these organs or tissues through trauma or illness. Titanium and its alloys have emerged as leaders in the field of orthopaedic implants because of their good mechanical properties, lower Young’s modulus, excellent corrosion resistance and excellent biocompatibility. Another important property that needs to be considered for implants is tribocorrosion (a process of material degradation due to the combined effects of wear and corrosion) and is very common at the hip and knee joints where sliding occurs during the movement of the body. The two most commonly used titanium alloys for biomedical applications are Ti-6Al-4V and Ti-6Al-7Nb and the tribocorrosion properties of Ti-6Al-4V has been studied extensively but not so that of Ti-6Al-7Nb and this is very concerning. This study, therefore, aims to study the tribocorrosion properties of Ti-6Al-4V and Ti-6Al-7Nb.
The alloys were received in the as-cast state and electrochemical polarization tests were first conducted on them after appropriate surface preparation in phosphate buffered saline using a Metrohm Autolab potentiostat running on a three-electrode configuration. This was done to investigate the corrosion behaviour of these alloys. Tribocorrosion tests were then performed under anodic conditions using a ball-on-disc tribometer with the alloys as the disc and zirconia as the ball. The tribocorrosion tests were run at four different contact pressures (580.2 MPa, 674.5 MPa, 839.4 MPa and 992.1 MPa) and three different sliding distance (1 mm, 3 mm and 5 mm). During the tests, a constant potential was applied using the Metrohm Autolab potentiostat while also registering the current to measure the effect of the sliding on current. At the end of the tests, characterizations were done using SEM, SEM with EDX, and roughness meter to observe the wear scar and measure the volume loss.
At the end of the tests, it was discovered that Ti-6Al-7Nb had better corrosion resistance properties but poorer tribocorrosion resistance properties on comparing with Ti-6Al-4V. It was also discovered that tribocorrosion resistance reduced with increasing contact pressure and sliding distance for both alloys.
Keywords: Tribocorrosion, Titanium, Electrochemical polarization, Ti6Al4V, Ti6Al7Nb
Subject: Engineering thesis
Thesis type: Masters
Completed: 2021
School: College of Science and Engineering
Supervisor: Dr. Reza Hashemi Oskouei