Formation of Titanium Oxide by Thermal-Electrochemical Process on the Blasted Titanium Alloys Substrate

Transcription

1 Advanced Materials Research Vol. 650 (2013) pp (2013) Trans Tech Publications, Switzerland doi: / Formation of Titanium Oxide by Thermal-Electrochemical Process on the Blasted Titanium Alloys Substrate Raden Dadan Ramdan 1,a, Joy Rizki Pangestu Djuansjah 2,b, Mohamed Rafiq Abdul Kadir 3,c, Hadi Nur 4,d, Esah Hamzah 2,e 1 Faculty of Mechanical and Aerospace Engineering, Institut Teknologi Bandung, Jl. Ganesha 10 Bandung, West Java, Indonesia Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, Skudai, Johor Malaysia 3 Faculty of Biomedical Engineering and Health Science, Universiti Teknologi Malaysia, Skudai, Johor Malaysia 4 FInstitut Ibnu Sina For Fundamental Science, Universiti Teknologi Malaysia, Skudai, Johor Malaysia a dadan@material.itb.ac.id, b joy@fkm.utm.my, c rafiqkadie@utm.my, d hadi@kimia.fs.utm.my, e esah@fkm.utm.my Keywords: Titanium oxide, Thermal-electrochemical process, Blasting Abstract. Titanium oxide is believed as one of the key factors that influence the excellent corrosion properties as well as biocompatibility of titanium alloy. In the present research, thermalelectrochemical anodizing processes were performed in order to form thick layer of titanium oxide on titanium alloys (Ti6Al4V) surface. Oxidation temperature, blasting and anodizing voltage were selected as the evaluated parameters process at the present study. It was observed that temperature plays important role in the formation of oxide layer, where the thickness of the oxide increases significantly as temperature increases. However, for the case of oxide layer formed by thermal oxidation at temperature of 950 o C, oxide layer on the non-blasted sample become easily peel off, whereas oxide layer on the blasted sample shows good adhesion properties. In addition, oxide layer on the blasted samples also have thicker layer as compared with oxide on the non-blasted sample. On the other hand, it was observed that further oxidation by anodizing at 43V and 63V create finer oxide layer by the filled up of porosity on the existing oxide layer. However decreasing of oxide layer thickness was also observed after anodizing, which is predicted due to the breaking up the outer oxide layer during anodizing process. Introduction Titanium alloy is among widely used materials for various applications due to its excellent properties. Since the alloy has high strength to weight ratio [1], titanium is used for car components such as spring [2], connecting rods, rocker arms and also rotating parts [3]. On the other hand, due to very stable and highly adherent layer of oxide [4], titanium alloy is applied in replacing various human body parts such as knee, dental implant elbow [5], heart valve [6]. In addition the strength of titanium alloy can be greatly increased by strain hardening process [7]. However application of the alloy is limited up to o C [8] depend on the composition of the alloys. One of the most important characteristics of titanium alloy is its high affinity with oxygen that easily form titania (oxide layer) on the surface of the alloy [9]. This oxide layer formation can reach few atoms thicknesses (5-20atoms thickness) [10]. In addition to the inertness of passivve layer, its high strength to weight ratio and non magnetic characteristic, make this alloy becomes a good choice in the replacement of human bone [5].Other than corrosion resistance, passive layer also important in creating photocatalyst properties of titanium alloys, which has the ability to alter the light energy to higher level of energy and assist in some of the chemical processes [11, 12, 13]. For All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, (ID: /01/13,10:04:08)

2 Advanced Materials Research Vol this purpose, nano sized structure of titania is prefereable due to the size influences on the catalytic activity of titania. One limitaion for the used of titania is its brittleness, therefore one of the clever way in using titania is in the form of coating layer, not as a bulk material. Among methods that normally applied for the production of titania is by thermal oxidation process. It was observed that different temperature may produce different oxide and layer thicknesses [14]. and titanium alloy surface hardness increases when oxidation occurs at high temperature ( 900ºC) [15]. In addition, oxidation at high temperature usually produces porous oxide layer [16]. Depend on the alloying composition, normally other substances such as Al 2 O 3 and V 2 O 5 formed after thermal oxidation process [17]. It was also reported that combination between thermal oxidation and electrochemical method [6] can produce better oxide characteristics than single thermal oxidation process. In the present research, concern is given on the effect of priorblasting process on the formation of oxide layer by thermal-electrochemical process. Variation of temperatures and voltages were also performed during thermal oxidation and electrochemical process respectively. Experimental Works Titanium alloy, Ti6Al4V, with the size of 20mm in diameter and 15mm in thickness was used as the substrate material for the present research. Initially, several samples were treated by sand blasting process whereas others undergo thermal-electrochemical process without sand blasting process. Sand blasting was performed by using silica sand as the blasting particle. Thermal oxidation was performed on both blasted and non-blasted samples at three different temperature 750 o C, 850 o C and 950 o C for 5 hours. Subsequently, electro-chemical process was performed by placing the samples in the H 2 SO 4 solution at room temperature and at different voltages of 43±2V and 63±2V. In order to evaluate the oxide thickness, optical microscope and scanning electron microscope (SEM) characterization were performed on the samples after thermal oxidation and electro-chemical anodizing process, respectively. Surface roughness measurement was also performed on the resulted titania layer, in order to provide more detail description on the process. Results and Discussion Figure 1 shows example of oxide layer formed after thermal oxidation process. Generally the oxide layer has good adhesion properties with the substrate. However, for the case of oxide layer formed by thermal oxidation at temperature of 950 o C, oxide layer on the non-blasted sample become easily peel off, whereas oxide layer on the blasted sample shows good adhesion properties. Generally, increasing oxidizing temperature induces the increasing of the oxide layer thicknesses for both blasted and non blasted samples. In addition, as shown in the Figure.2, blasted samples have thicker samples for all oxidizing temperature as compared to non-blasted samples.this condition is considered due to the higher surface reactivity of the blasted samples by increasing surface area after blasting process.

3 14 Advances in Materials Science and Engineering 45.24µm Figure 1 Sample of oxide layer after thermal oxidation at temperature of 750 o C, for sample without prior blasting process Figure 2 Effect of blasting on the oxide thickness both on the blasted and non-blasted samples Figure 3 shows oxide layer after anodizing process at 43±2V dan 64±2V. Both of the oxide layer well adhere to the substrate, with the thinner layer obtained for the case of sample anodized at 63±2V. This condition is predicted due to higher vibration effect at 63±2V than 43±2V that induce the breaking of outer oxide layer. In addition, Figure 4 and 5 shows profile of oxide layer thickness after anodizing at 43 and 63±2V for both blasted sample oxidized at 750 and 850 o C. It can be seen from these figures that anodizing at both voltages decrease the thickness of the oxide layer. With the similar reason for Fig.3, it is predicted that anodizing process induces in the breaking of outer oxide layer due to vibration effect during the process. On the other hand, interesting features are shown in the figure 6 and 7 for their surface roughness measurement before and after anodizing process. It can be seen from these figures that finer oxide surface observed after anodizing processes. This condition is predicted due to further oxidation during anodizing process that filled up the porosity on the previous oxide layer (resulted from thermal oxidation process). Therefore anodizing process induces two different effects on the existing oxide layer, decreases the thickness and create finer layer.

4 Advanced Materials Research Vol (a) (b) Figure 3. Sample of oxide layer after anodizing at 43±2V (a) and 63±2V (b) for the blasted sample that was oxidized at 850 o C 750 o C 850 o C Figure 4 Effect of anodizing at 43±2V on the thickness of oxide layer 750 o C 850 o C Figure 5 Effect of anodizing at 63±2V on the thickness of oxide layer

5 16 Advances in Materials Science and Engineering 850 o C 750 o C Figure 6 Effect of anodizing process at 43±2V on the surface roughness 850 o C 750 o C Summary Figure 7 Effect of Anodizing process at 63±2V on the surface roughness The present works deal with the formation of titanium oxide (titania) on titanium alloy substrate by thermal-electrochemical processes. It was observed that thicker oxide layer was observed for the blasted samples at all temperatures as compared with non-blasted samples. On the other hand, it was also observed that thinner and finer oxide layer was observed after electro-chemical/anodizing process both at 43±2V and 63±2V. Breaking up the outer part of oxide layer during anodizing process by vibration effect is considered to be responsible for the existence of thinner layer, whereas further oxidation that filled up porosity on the existing oxide layer is predicted to induce finer oxide layer after anodizing process. Acknowledgements This work was financially supported by the ministry of higher education (MOHE) Malaysia and Faculty of Mechanical and Aerospace Engineering Institut Teknologi Bandung.

6 Advanced Materials Research Vol References [1] V. N. Moiseyev: Titanium Alloys:Russian Aircraft and Aerospace Applications (Taylor and Francis, 2005) [2] EH. (Sam) Froes and S.J. Haak: Materials and Science in Sports: Titanium in Automobiles (TMS, 2001) [3] R. Boyer, G. Wlesch and E.W Collings: Materials Properties Handbook: Titanium Alloys, (ASM International, 2003) [4] F.C Campbell : Elements of Metallurgy and Engineering Alloys (ASM International, 2008) [5] International Titanium Association, Medical Data Sheet, Why is titanium the metal of choice for medical application from head to toe (International Titanium Association, 1999) [6] G. Luetjering and J Albrecht: Ti-2003 Science and Technology: Proceedings of the 10th World Conference on Titanium (Wiley VCH, 2004), p.7. [7] V. N. Moiseyev: Titanium Alloys:Russian Aircraft and Aerospace Applications (Taylor and Francis, 2005) [8] W.O. Soboyejo, T.S. Srivatsan: Advanced Structural Materials, Properties, Design Optimization and Applications (CRC Press,2007) [9] Yoshiki Oshida: Bioscience and Bioengineering of Titanium Materials (Elsevier, 2007), p.83 [10] E.P. Lautenschlager and P. Monaghan: Int. Dent. J. (1993) [11] Information on [12] Y. Ichihashi, H. Yarnashita and M. Anpo: J. Phys IV France 7 (1997), C2-883 [13] S. M. Lam, J.C. Sin and M, Abdulrahman: Recent Patents on Photocatalysis Over Nanosized Titanium Dioxide. Recent Patents on Chemical Engineering Vol 1(2008), p.209. [14] H. L. Du, P. K. Datta, D. B. Lewis and J. S. Burnell-Gray: Chem Inform Vol 25(30) (1994) [15] M.Mackert JR Jr, Parry EE, Fairhurst CW Dent Res. Vol 69 (1990), p.1230 [16] Gerhard Welsch, Rodney Boyer, E.W. Collings: Material Properties handbook; titanium alloys (ASM international,2003) [17] S.C. Textor, M,Spencer, ND.Wieland, P.H Vallotton: J Mater Sci Mater Med. Vol 10(1) (1999), p.35 [18] Z. Abdolldhi, A. A. Ziaee M., and A. Afshar: International Journal of Chemical and Biomolecular Engineering Vol.2 (1) (2009), p.44