Electronic Theses and Dissertations (Masters)
Permanent URI for this collectionhttps://hdl.handle.net/10539/38876
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Item Bio-tribocorrosion behavior of low- cost titanium alloys in simulated body fluids(University of the Witwatersrand, Johannesburg, 2023) Rundora, Nicola Ruvimbo; Bodunrin, M.O.; Merwe, Van der; Klenam, D.E.PTitanium and its alloys are considered the gold-standard material in the manufacturing of biomedical implants. This is due to their superior mechanical properties and resistance to corrosion in comparison to the other biomaterials on the market. Titanium and its alloys are however very expensive in comparison and their application and accessibility is thus limited. Issues of toxicity as in the case of the commercial alloy (Ti-6Al-4V) have also been reported. One approach to combat these issues has been the development of new low-cost and less expensive α+β type titanium alloys through the modification of the commercial alloy composition. These efforts led to the development of the following alloys: Ti-3Fe, Ti-4.5Al-1V-3Fe, and Ti-6Al-1V-3Fe. To determine whether these alloys can be utilised for the manufacturing of biomedical implants, they have to undergo a series of screening tests. Some of those tests include wear, corrosion, and tribocorrosion tests. This is the basis of this study. Dry sliding ball-on-disk wear tests were conducted on these alloys. Ti-4.5Al-1V-3Fe and Ti-6Al-1V-3Fe had superior wear resistance to Ti-3Fe, the alloy where the full substitution of V with Fe was employed. Ti-4.5Al-1V-3Fe and Ti- 6Al-1V-3Fe alloys wear resistance was closely comparable to that of the commercial alloy, Ti- 6Al-4V. The corrosion behavior of the experimental alloys was investigated in 0.9 wt.% NaCl solution, Hanks Balanced Salt Solution, prediabetic Hanks Balanced Salt Solution, and diabetic Hanks Balanced Salt Solution. It was important to study the behavior of these alloys in a simulated diabetic environment because of the increase in the number of people living with diabetes and their increased risk of developing different bone and joint disorders. The corrosion behavior of Ti-3Fe was superior to that of the commercial alloy and the other experimental alloys in 0.9 wt.% NaCl solution and Hanks Balanced Salt Solution. In the prediabetic and diabetic Hanks Balanced Salt Solution, the experimental alloys resistance to corrosion was comparable to that of the commercial alloy with Ti-4.5Al-1V-3Fe having the best resistance to corrosion in the prediabetic solution and Ti-6Al-1V-3Fe having the best resistance to corrosion in the diabetic solution. Ti-4.5Al-1V-3Fe and Ti-6Al-1V-3Fe showed tribocorrosion resistance that was comparable to the commercial alloy in both the normal HBSS and diabetic HBSS under both open circuit potential and potentiostatic conditions. These alloys showed better tribocorrosion behavior in the normal HBSS under potentiostatic conditions compared to Ti-3Fe and the commercial alloy. In the diabetic HBSS under potentiostatic conditions, Ti-4.5Al-1V-3Fe had the best resistance to tribocorrosion. The iv | P a g e glucose addition had a slightly negative effect on the tribocorrosion behavior as the wear rates and total worn volume values in such solutions were slightly higher than in the normal solutions. Ultimately, under corrosion and tribocorrosion testing conditions, the partial substitution of V with Fe as beta stabilisers in low-cost titanium alloy designs offered superior properties over the total replacement of V with Fe.