Browsing by Author "Alansari, A."
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Item Open Access A comparative study of the mechanical behaviour of thermally oxidized commercially pure titanium and zirconium(Elsevier, 2017-06-10) Sun, Yong; Alansari, A.The objective of this study is to compare the mechanical behaviour of thermally oxidised commercially pure titanium (CP-Ti) and commercially pure zirconium (CP-Zr). For this purpose, these two bio-metals were thermally oxidised under the same condition (650 °C for 6 h) and the oxidised specimens were characterised using various analytical and experimental techniques, including oxygen uptake analysis, layer thickness and hardness measurements, scratch tests, dry sliding friction and wear tests and tribocorrosion tests in Ringer’s solution. The results show that under the present thermal oxidation condition, 4 times more oxygen is introduced into CP-Zr than into CP-Ti and the oxide layer produced on CP-Zr is nearly 6 times thicker than that on CP-Ti. Thermally oxidised CP-Zr possesses a higher hardness, a deeper hardening depth and better scratch resistance than thermally oxidised CP-Ti. Under dry sliding and tribocorrosion conditions, thermally oxidised CP-Zr also possesses much better resistance to material removal and a higher load bearing capacity than thermally oxidised CP-Ti. Thus, thermally oxidised Zr possesses much better mechanical behaviour than thermally oxidised Ti.Item Open Access Effect of oxidation time on the tribological behavior of thermally oxidized commercially pure zirconium under dry sliding conditions(Elsevier, 2016-11-21) Alansari, A.; Sun, YongThermal oxidation is an effective surface engineering technique to harden the surfaces of zirconium (Zr) and its alloys for improvement in friction and wear performance. In the present investigation, commercially pure zirconium (CP-Zr) is oxidized at 650 °C for a wide range of times from 1 h to 72 h with the aim to study the effect of oxidation time on the tribological performance of CP-Zr. It is found that a dense, pore-free and adherent zirconium dioxide (ZrO2) layer can be produced at the surface for oxidation times less than 12 h. Further increasing oxidation time leads to the gradual development of pores in the inner part of the oxide layer and oxidation breakaway characterized by accelerated oxidation kinetics and crack formation. Oxidation time has a significant effect on the tribological behaviour of thermally oxidized CP-Zr under dry sliding conditions. The 6 m thick oxide layer produced by 6 h treatment possesses the lowest friction, best wear resistance and the highest load bearing capacity. On the other hand, the thicker oxide layers produced by longer treatment times show deteriorated tribological behavior. The results are discussed in terms of the morphology of the oxide layer and crack propagation in the oxide layer and the underlying diffusion zone.Item Open Access Surface finish effect on dry sliding wear behavior of thermally oxidized commercially pure zirconium(Elsevier, 2019-02-01) Alansari, A.; Sun, YongThe aim of this work was to investigate the effect of surface polishing on the wear behavior of thermally oxidized commercial pure zirconium (CP-Zr) under dry sliding conditions. Surface ground CP-Zr with a roughness of 0.21 m (Ra) was thermally oxidized (TO) at 650 °C for 6 h. After TO, some samples were polished to smoothen the surface with a finish of 0.04 m (Ra). The response of the polished and unpolished TO samples to dry sliding wear was investigated under unidirectional sliding conditions. The results show that surface polishing after TO affects the dry sliding wear behavior of TO CP-Zr in several aspects, including coefficient of friction, wear rate, crack formation and oxide layer breakdown. In particular, it is found that smoothening the TO surface favors the formation of semi-circular cracks in the wear track and accelerates oxide layer breakdown during dry sliding. A slightly rough TO surface helps to reduce the tendency of the oxide layer towards cracking and to increase the wear resistance at high contact loads. The mechanisms involved are discussed in terms of asperity contacts, crack formation, propagation and final fracture.