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Enhanced wear resistance of Ti-5Al-2Nb-1Ta orthopaedic alloy by nitrogen ion implantation
Tribology International 39 (2006) 548–552 www.elsevier.com/locate/triboint
Enhanced wear resistance of Ti-5Al-2Nb-1Ta orthopaedic alloy by nitrogen ion implantation S. Gokul Lakshmia, D. Arivuolib,* a
Crystal Growth Centre, Anna University, Chennai 600 025, India Department of Physics, Anna University, Chennai 600 025, India
b
Received 30 January 2004; received in revised form 5 November 2004; accepted 6 April 2005 Available online 15 June 2005
Abstract The tribological properties of nitrogen implanted Ti-5Al-2Nb-1Ta orthopaedic alloy was studied by performing lubricated pin on disc tests against ultra high molecular weight polyethylene pins. The results were interpreted on the basis of friction coefficient, wear volume loss and by characterising the wear debris to understand the wear mechanism. The results indicated a decrease in wear rate for implanted samples. Detailed investigations of the dose dependence on wear performance were carried out. The friction and wear data show a clear transition in wear modes between implanted and unimplanted alloys. The wear debris confirms the presence of titanium oxide and titanium oxynitride phases for untreated and nitrogen implanted alloy. q 2005 Elsevier Ltd. All rights reserved. Keywords: Hardness; Ion implantation; Lubrication; Titanium; Wear; X-ray diffraction
1. Introduction Titanium has been used for orthopaedic devices due to several beneficial properties such as a low density, low modulus of elasticity, excellent corrosion resistance and biocompatibility. Load bearing components are usually made from Ti/UHMWPE sliding couples [1]. However, Ti and its alloys suffer from poor tribological properties when sliding against Ultra high molecular weight polyethylene (UHMWPE) [2] due to the production of oxide wear debris which limits its use in surgical applications. A considerable amount of effort has been made to overcome this obstacle by forming a hard surface layers on the alloys. In order to improve the wear resistance of titanium and its alloys, they are subjected to various surface treatments such as thermal spraying, plasma vapour deposition processes, anodic oxidation, ion implantation, glow discharge nitriding and laser treatment [3–5]. It has been shown that wear resistance of titanium can be enhanced by ion implantation of N [6–8]. The wear reduction can be attributed to the formation of TiN * Corresponding author. Tel.: C91 44 2220 3159; fax: C91 44 235 2870. E-mail address: [email protected] (D. Arivuoli).
0301-679X/$ - see front matter q 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.triboint.2005.04.003
in the implanted layer due to its high hardness and biocompatibility [9]. Though lubrication is essential for most sliding applications in practical use, few studies using lubricants for ion implanted titanium alloys have been reported [6]. The present work aims at nitrogen ion implantation on the newly developed orthopaedic titanium alloy and the effect of ion dose on the tribological behaviour of Ti-5Al-2Nb-1Ta/UHMWPE sliding couples in lubricated conditions. The enhanced wear performance of nitrogen implanted Ti-5Al-2Nb-1Ta alloy may be of great importance to the orthopaedic prosthesis.
2. Experiment The orthopaedic titanium alloy Ti-5Al-2Nb-1Ta obtained from Kobes steel Ltd., Japan has been used for the present investigations. Workpieces are cut into dimensions of 0.6 !30 mm2. The sample surface is mechanically polished using SiC papers and to a 0.5 alumina finish, degreased ultrasonically in acetone and dried. Nitrogen ion implantations were performed using the 200 keV ion beam generator using isotope separator and ion implanter (ISOSIIM) at saha institute of nuclear physics, Kolkatta, India. The acceleration voltage of 75 keV and a beam
S. Gokul Lakshmi, D. Arivuoli / Tribology International 39 (2006) 548–552
current of 30 mA were employed for the present investigation. The alloys were implanted at a dose rate of 1!1017 and 1!1018 ions/cm2. Vickers microhardness measurements were carried out using Leitz microhardness tester at loads of 25–500 g. Ti2N and Ti phases were identified by X-ray diffraction (XRD) measurements using Cu Ka radiation. Secondary ion mass spectroscopy (SIMS) measurements were carried out to determine the thickness of the ion implanted layer. Pin on disc tribometer was used to investigate the wear behaviour of Ti/UHMWPE couples in unidirectional sliding motion. The conditions in the tribological investigations were chosen with regard to biomedical applications using Hanks solution as lubricant [10] (The composition of Hanks solution (g/l) is 0.185 CaCl2, 0.4 KCl, 0.06 KH2PO4, 0.1 MgCl2.6H2O, 0.1 MgSO4. 7 H2O, 8.0 NaCl, 0.35 NaHCO3, 0.48 Na2HPO4 and 1.00 D glucose). Discs were driven at speed of 0.3 and 0.5 m/s and loads of 2 and 5 N. All the tests were carried out at room temperature. The wear resistance was evaluated by determining the weight loss of the pin and disc and the wear debris formed on the surface. The friction coefficient was determined as a function of sliding distance. X-ray diffraction measurements were carried out to characterise the worn surface after wear measurements.
549
3.2. Secondary ion mass spectroscopy measurements (SIMS) SIMS measurements were carried out in order to determine the depth of the nitrogen implanted alloys. Fig. 2 shows the depth profile for Ti-5Al-2Nb-1Ta alloys ion implanted at a dose rate of 1!1017 and 1! 1018 ions/cm2. The nitrogen concentration was found to increase with ion dose. The thickness of the implanted layer was found to be 120 nm. The nitrogen diffusion after ion implantation is also confirmed from the X-ray diffraction measurements [12]. 3.3. Wear tests The tribological properties of the nitrogen implanted and unimplanted alloys were determined against UHMWPE using pin on disc tribometer at sliding speed of 0.3 and 0.5 m/s. Fig. 3 show the friction coefficients for the ion implanted and unimplanted Ti-5Al-2Nb-1Ta alloys measured at different experimental conditions. The friction coefficient of unimplanted and alloy implanted at lower dose was found to be higher when compared
3. Results and discussion 3.1. Microhardness The Vickers microhardness was measured to find the load bearing capacity of the implanted layer. Fig. 1 shows the load dependent microhardness of the NC ion implanted Ti-5Al-2Nb-1Ta alloys at different doses. The hardness was found to decrease with increasing load. The maximum hardness of 1714Hv was obtained for the alloy implanted at a dose rate of 1!1018 ions/cm2. This is in agreement with the previous report about the increase in microhardness after ion implantation [11].
Fig. 1. Load dependent Vickers microhardness measurements for the alloys implanted at dose rate of (a) 1!1017 ions/cm2 and (b) 1!1018 ions/cm2.
Fig. 2. Secondary ion mass spectroscopy measurements for Ti-5Al2Nb-1Ta alloys implanted at dose rate of (a) 1!1017 ions/cm2 and (b) 1!1018 ions/cm2.
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S. Gokul Lakshmi, D. Arivuoli / Tribology International 39 (2006) 548–552
Fig. 4. Wear volume losses of ion implanted Ti-5Al-2Nb-1Ta discs at (a) 2 N and 0.3 m/s and (b) 5 N and 0.5 m/s. Fig. 3. Coefficient of friction vs sliding distance curves produced under (a) 2 N and 0.3 m/s and (b) 5 N and 0.5 m/s for untreated and implanted alloys.
the alloys implanted at a dose rate of 1!1018 ions/cm2. The reduction in the friction coefficient may be attributed to the formation of thick titanium nitride layer on the surface of the alloy. Figs. 4 and 5 show the volumetric wear loss of the nitrogen implanted Ti-5Al-2Nb-1Ta alloy and UHMWPE pins measured at varying sliding speed and load under lubricated conditions. The wear volume loss for the alloy was found to be less for the alloys implanted at a dose rate of 1!1018 ions/cm2 (Fig. 4). The wear volume loss for the alloys implanted at 1!1017 ions/ cm2 are nearer to that of the untreated alloy. This may be due to the formation of nitrogen solid solution rather than titanium nitride [13] for the alloys implanted at a dose rate of 1!1017 and 1!1018 ions/cm2, respectively. This may also be attributed to the insufficient ion dose and energy of implantation, which result in exposure of the base metal. It is seen from the Fig. 5(b) that maximum volume loss of the pin was observed for sliding velocity of 0.5 m/s and load of 5 N and also when the pin slides against titanium alloy implanted at a dose rate of 1! 1018 ions/cm2. This may be due to the presence of hard TiN surface layer which removes UHMWPE particles when it slides over the nitrided disc. The wear rate was
determined from the wear volume loss and the values obtained are tabulated in Table 1. It is seen from the table that the minimum wear rate was obtained for nitrogen implanted alloys which may due to the increased hardness on the surface formed by nitrogen ion implantation. Saritas et al. [14] has reported that the worn volume decreases with increasing surface hardness for NC, CC and OC ion implanted titanium alloys. The wear volume loss, friction coefficient and wear rate were found to increase with increase in sliding velocity and load. The UHMWPE pins were not stable beyond the load of 5 N when sliding against the ion implanted alloys. The surface of the alloys were characterised by X-ray diffraction measurements. 3.4. X-ray diffraction after wear measurements X-ray diffraction measurements were carried out using Cu Ka radiation at a scan rate of 1 8/min to identify the phases formed after ion implantation. X-ray diffractogram of Ti-5Al-2Nb-1Ta alloy carried out after wear experiments indicate the formation of titanium oxide and oxynitride for untreated and the alloy implanted at a dose rate of 1!1017 ions/cm2 (Fig. 6) at a load of 5 N and sliding velocity of 0.5 m/s.
S. Gokul Lakshmi, D. Arivuoli / Tribology International 39 (2006) 548–552
551
Table 1 Wear rate of Ti-5Al-2Nb-1Ta / UHMWPE couple Specifications
Wear rate (at 2 N/0.3 m/s)! 10K6 mm3/N/m
Wear rate (at 5 N/0.5 m/s)! 10K6 mm3/N/m
Untreated Nitrogen ion implanted at dose of 1!1017 ions/cm2 Nitrogen ion implanted at dose of 1!1018 ions/cm2
8.33 7.22
10.11 9.33
2.77
7.53
4. Conclusions
Fig. 5. Wear volume losses of UHMWPE pins sliding against Ti-5Al-2Nb1Ta disc at (a) 2 N and 0.3 m/s and (b) 5 N and 0.5 m/s.
Nitrogen ion implantation of Ti-5Al-2Nb-1Ta orthopaedic alloy was conducted at an energy of 75 keV and dose rate of 1!1017 and 1!1018 ions/cm2 to enhance the wear resistance of titanium alloy. Pin on disc wear measurements were carried out on the untreated and nitrided alloys at loads 2 and 5 N and sliding velocities 0.3 and 0.5 m/s. The results of the wear test were interpreted on basis of wear volume loss, friction coefficient and by characterising the wear debris. An enhanced wear performance was observed for the alloy implanted at dose rate of 1!1018 ions/cm2 when compared to the untreated and the alloy nitrided at a dose rate of 1!1017 ions/cm2. The wear rate was found to increase with increase in load and sliding velocity. Titanium oxide and oxynitride debris were observed for untreated and the alloys nitrided at lower dose rate and at higher loads and sliding speeds.
Acknowledgements One of the authors Gokul Lakshmi would like to thank Prof. Milan Sanyal, Head, Surface Physics Division for providing the ion implantation facility. She would like to thank Prof. K. Srinivasan, Director, AU-FRG, Anna University, Chennai for permitting to carryout wear experiments. She would like to acknowledge Council of Scientific and Industrial Research, Government of India for the award of Senior Research Fellowship.
References
Fig. 6. X-ray diffraction pattern of (a) untreated and (b) alloy implanted at dose rate of 1!1017 ions/cm2 after wear measurements at 5 N and 0.5 m/s.
[1] Semliksch M. Titanium alloys for hip joint replacements. Clin Mater 1987;2:1–13. [2] Buchanan R, Rigney ED, Williams JM. Wear accelerated corrosion of Ti6Al-4V and nitrogen implanted Ti-6Al-4V. Mechanism and influence of fixed stress magnitude. J Biomed Mater Res 1987;21: 367–77. [3] Vardiman RG, Kent RA. Improvement of fatigue life of Ti-6Al-4V by ion implantation. J Appl Phys 1982;53:690–4.
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S. Gokul Lakshmi, D. Arivuoli / Tribology International 39 (2006) 548–552
[4] Hongbing J, Xia L, Xinxin M, Sun Y. Tribological performance of Ti6Al-4V plasma based ion implanted with nitrogen. Wear 2000;246: 40–5. [5] Rie KT, Lamppe Th. Thermochemical surface treatment of titanium and titanium alloy Ti-6Al-4V by low energy nitrogen ion bombardment. Mater Sci Eng 1985;69:473–81. [6] Hutchings R, Oliver WC. A study of the improved wear performance of nitrogen implanted Ti-6Al-4V. Wear 1983;92:143–53. [7] Itoh Y, Itoh H, Azuma H, Hioki T. Improving the tribological properties of Ti-6Al-4V alloy by nitrogen-ion implantation. Surf Coat Technol 1999;111:172–6. [8] Onate JJ, Alonso F, Garcia A. Improvement of tribological properties by ion implantation. Thin Solid Films 1996;317:471–6. [9] Mortiiner E. Quantitative evaluation of bone apposition and in growth using porous fiber metal implants with a titanium nitride surface. 17th Int Biomater Symp 1991;14:151.
[10] Gokul Lakshmi S, Arivuoli D. Tribological behaviour of Plasma nitrided Ti-5Al-2Nb-1Ta alloy against UHMWPE. Tribology Int 2004;37:627–31. [11] Masami I, Setsuo S, Hisashi H, Yoshiyuki Y, Leszek SW, Ronald AC, et al. Increase of surface hardness induced by O, Ca or P ion implantation into titanium. Surf Coat Technol 2000;128–129:400. [12] Gokul Lakshmi S, Tamilselvi S, Rajendran N, Babi MAK, Arivuoli D. Effect of NC ion implantation on the corrosion behaviour of Ti-6Al7Nb and Ti-5Al-2Nb-1Ta orthopaedic alloys in Hanks solution. J Appl Electrochem 2004;34:27. [13] Pons F, Pivin JC, Farges G. Inhibition of tribo oxidation preceeding wear by single phased TiNx films formed by ion implantation into TiAl6V4. J Mater Res 1987;2:580. [14] Saritas S, Procter RPM, Grant WA. The use of ion implantation to modify the tribological property of Ti-6Al-4V. Mater Sci Eng 1987; 90:297.
Enhanced wear resistance of Ti-5Al-2Nb-1Ta orthopaedic alloy by nitrogen ion implantation S. Gokul Lakshmia, D. Arivuolib,* a
Crystal Growth Centre, Anna University, Chennai 600 025, India Department of Physics, Anna University, Chennai 600 025, India
b
Received 30 January 2004; received in revised form 5 November 2004; accepted 6 April 2005 Available online 15 June 2005
Abstract The tribological properties of nitrogen implanted Ti-5Al-2Nb-1Ta orthopaedic alloy was studied by performing lubricated pin on disc tests against ultra high molecular weight polyethylene pins. The results were interpreted on the basis of friction coefficient, wear volume loss and by characterising the wear debris to understand the wear mechanism. The results indicated a decrease in wear rate for implanted samples. Detailed investigations of the dose dependence on wear performance were carried out. The friction and wear data show a clear transition in wear modes between implanted and unimplanted alloys. The wear debris confirms the presence of titanium oxide and titanium oxynitride phases for untreated and nitrogen implanted alloy. q 2005 Elsevier Ltd. All rights reserved. Keywords: Hardness; Ion implantation; Lubrication; Titanium; Wear; X-ray diffraction
1. Introduction Titanium has been used for orthopaedic devices due to several beneficial properties such as a low density, low modulus of elasticity, excellent corrosion resistance and biocompatibility. Load bearing components are usually made from Ti/UHMWPE sliding couples [1]. However, Ti and its alloys suffer from poor tribological properties when sliding against Ultra high molecular weight polyethylene (UHMWPE) [2] due to the production of oxide wear debris which limits its use in surgical applications. A considerable amount of effort has been made to overcome this obstacle by forming a hard surface layers on the alloys. In order to improve the wear resistance of titanium and its alloys, they are subjected to various surface treatments such as thermal spraying, plasma vapour deposition processes, anodic oxidation, ion implantation, glow discharge nitriding and laser treatment [3–5]. It has been shown that wear resistance of titanium can be enhanced by ion implantation of N [6–8]. The wear reduction can be attributed to the formation of TiN * Corresponding author. Tel.: C91 44 2220 3159; fax: C91 44 235 2870. E-mail address: [email protected] (D. Arivuoli).
0301-679X/$ - see front matter q 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.triboint.2005.04.003
in the implanted layer due to its high hardness and biocompatibility [9]. Though lubrication is essential for most sliding applications in practical use, few studies using lubricants for ion implanted titanium alloys have been reported [6]. The present work aims at nitrogen ion implantation on the newly developed orthopaedic titanium alloy and the effect of ion dose on the tribological behaviour of Ti-5Al-2Nb-1Ta/UHMWPE sliding couples in lubricated conditions. The enhanced wear performance of nitrogen implanted Ti-5Al-2Nb-1Ta alloy may be of great importance to the orthopaedic prosthesis.
2. Experiment The orthopaedic titanium alloy Ti-5Al-2Nb-1Ta obtained from Kobes steel Ltd., Japan has been used for the present investigations. Workpieces are cut into dimensions of 0.6 !30 mm2. The sample surface is mechanically polished using SiC papers and to a 0.5 alumina finish, degreased ultrasonically in acetone and dried. Nitrogen ion implantations were performed using the 200 keV ion beam generator using isotope separator and ion implanter (ISOSIIM) at saha institute of nuclear physics, Kolkatta, India. The acceleration voltage of 75 keV and a beam
S. Gokul Lakshmi, D. Arivuoli / Tribology International 39 (2006) 548–552
current of 30 mA were employed for the present investigation. The alloys were implanted at a dose rate of 1!1017 and 1!1018 ions/cm2. Vickers microhardness measurements were carried out using Leitz microhardness tester at loads of 25–500 g. Ti2N and Ti phases were identified by X-ray diffraction (XRD) measurements using Cu Ka radiation. Secondary ion mass spectroscopy (SIMS) measurements were carried out to determine the thickness of the ion implanted layer. Pin on disc tribometer was used to investigate the wear behaviour of Ti/UHMWPE couples in unidirectional sliding motion. The conditions in the tribological investigations were chosen with regard to biomedical applications using Hanks solution as lubricant [10] (The composition of Hanks solution (g/l) is 0.185 CaCl2, 0.4 KCl, 0.06 KH2PO4, 0.1 MgCl2.6H2O, 0.1 MgSO4. 7 H2O, 8.0 NaCl, 0.35 NaHCO3, 0.48 Na2HPO4 and 1.00 D glucose). Discs were driven at speed of 0.3 and 0.5 m/s and loads of 2 and 5 N. All the tests were carried out at room temperature. The wear resistance was evaluated by determining the weight loss of the pin and disc and the wear debris formed on the surface. The friction coefficient was determined as a function of sliding distance. X-ray diffraction measurements were carried out to characterise the worn surface after wear measurements.
549
3.2. Secondary ion mass spectroscopy measurements (SIMS) SIMS measurements were carried out in order to determine the depth of the nitrogen implanted alloys. Fig. 2 shows the depth profile for Ti-5Al-2Nb-1Ta alloys ion implanted at a dose rate of 1!1017 and 1! 1018 ions/cm2. The nitrogen concentration was found to increase with ion dose. The thickness of the implanted layer was found to be 120 nm. The nitrogen diffusion after ion implantation is also confirmed from the X-ray diffraction measurements [12]. 3.3. Wear tests The tribological properties of the nitrogen implanted and unimplanted alloys were determined against UHMWPE using pin on disc tribometer at sliding speed of 0.3 and 0.5 m/s. Fig. 3 show the friction coefficients for the ion implanted and unimplanted Ti-5Al-2Nb-1Ta alloys measured at different experimental conditions. The friction coefficient of unimplanted and alloy implanted at lower dose was found to be higher when compared
3. Results and discussion 3.1. Microhardness The Vickers microhardness was measured to find the load bearing capacity of the implanted layer. Fig. 1 shows the load dependent microhardness of the NC ion implanted Ti-5Al-2Nb-1Ta alloys at different doses. The hardness was found to decrease with increasing load. The maximum hardness of 1714Hv was obtained for the alloy implanted at a dose rate of 1!1018 ions/cm2. This is in agreement with the previous report about the increase in microhardness after ion implantation [11].
Fig. 1. Load dependent Vickers microhardness measurements for the alloys implanted at dose rate of (a) 1!1017 ions/cm2 and (b) 1!1018 ions/cm2.
Fig. 2. Secondary ion mass spectroscopy measurements for Ti-5Al2Nb-1Ta alloys implanted at dose rate of (a) 1!1017 ions/cm2 and (b) 1!1018 ions/cm2.
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S. Gokul Lakshmi, D. Arivuoli / Tribology International 39 (2006) 548–552
Fig. 4. Wear volume losses of ion implanted Ti-5Al-2Nb-1Ta discs at (a) 2 N and 0.3 m/s and (b) 5 N and 0.5 m/s. Fig. 3. Coefficient of friction vs sliding distance curves produced under (a) 2 N and 0.3 m/s and (b) 5 N and 0.5 m/s for untreated and implanted alloys.
the alloys implanted at a dose rate of 1!1018 ions/cm2. The reduction in the friction coefficient may be attributed to the formation of thick titanium nitride layer on the surface of the alloy. Figs. 4 and 5 show the volumetric wear loss of the nitrogen implanted Ti-5Al-2Nb-1Ta alloy and UHMWPE pins measured at varying sliding speed and load under lubricated conditions. The wear volume loss for the alloy was found to be less for the alloys implanted at a dose rate of 1!1018 ions/cm2 (Fig. 4). The wear volume loss for the alloys implanted at 1!1017 ions/ cm2 are nearer to that of the untreated alloy. This may be due to the formation of nitrogen solid solution rather than titanium nitride [13] for the alloys implanted at a dose rate of 1!1017 and 1!1018 ions/cm2, respectively. This may also be attributed to the insufficient ion dose and energy of implantation, which result in exposure of the base metal. It is seen from the Fig. 5(b) that maximum volume loss of the pin was observed for sliding velocity of 0.5 m/s and load of 5 N and also when the pin slides against titanium alloy implanted at a dose rate of 1! 1018 ions/cm2. This may be due to the presence of hard TiN surface layer which removes UHMWPE particles when it slides over the nitrided disc. The wear rate was
determined from the wear volume loss and the values obtained are tabulated in Table 1. It is seen from the table that the minimum wear rate was obtained for nitrogen implanted alloys which may due to the increased hardness on the surface formed by nitrogen ion implantation. Saritas et al. [14] has reported that the worn volume decreases with increasing surface hardness for NC, CC and OC ion implanted titanium alloys. The wear volume loss, friction coefficient and wear rate were found to increase with increase in sliding velocity and load. The UHMWPE pins were not stable beyond the load of 5 N when sliding against the ion implanted alloys. The surface of the alloys were characterised by X-ray diffraction measurements. 3.4. X-ray diffraction after wear measurements X-ray diffraction measurements were carried out using Cu Ka radiation at a scan rate of 1 8/min to identify the phases formed after ion implantation. X-ray diffractogram of Ti-5Al-2Nb-1Ta alloy carried out after wear experiments indicate the formation of titanium oxide and oxynitride for untreated and the alloy implanted at a dose rate of 1!1017 ions/cm2 (Fig. 6) at a load of 5 N and sliding velocity of 0.5 m/s.
S. Gokul Lakshmi, D. Arivuoli / Tribology International 39 (2006) 548–552
551
Table 1 Wear rate of Ti-5Al-2Nb-1Ta / UHMWPE couple Specifications
Wear rate (at 2 N/0.3 m/s)! 10K6 mm3/N/m
Wear rate (at 5 N/0.5 m/s)! 10K6 mm3/N/m
Untreated Nitrogen ion implanted at dose of 1!1017 ions/cm2 Nitrogen ion implanted at dose of 1!1018 ions/cm2
8.33 7.22
10.11 9.33
2.77
7.53
4. Conclusions
Fig. 5. Wear volume losses of UHMWPE pins sliding against Ti-5Al-2Nb1Ta disc at (a) 2 N and 0.3 m/s and (b) 5 N and 0.5 m/s.
Nitrogen ion implantation of Ti-5Al-2Nb-1Ta orthopaedic alloy was conducted at an energy of 75 keV and dose rate of 1!1017 and 1!1018 ions/cm2 to enhance the wear resistance of titanium alloy. Pin on disc wear measurements were carried out on the untreated and nitrided alloys at loads 2 and 5 N and sliding velocities 0.3 and 0.5 m/s. The results of the wear test were interpreted on basis of wear volume loss, friction coefficient and by characterising the wear debris. An enhanced wear performance was observed for the alloy implanted at dose rate of 1!1018 ions/cm2 when compared to the untreated and the alloy nitrided at a dose rate of 1!1017 ions/cm2. The wear rate was found to increase with increase in load and sliding velocity. Titanium oxide and oxynitride debris were observed for untreated and the alloys nitrided at lower dose rate and at higher loads and sliding speeds.
Acknowledgements One of the authors Gokul Lakshmi would like to thank Prof. Milan Sanyal, Head, Surface Physics Division for providing the ion implantation facility. She would like to thank Prof. K. Srinivasan, Director, AU-FRG, Anna University, Chennai for permitting to carryout wear experiments. She would like to acknowledge Council of Scientific and Industrial Research, Government of India for the award of Senior Research Fellowship.
References
Fig. 6. X-ray diffraction pattern of (a) untreated and (b) alloy implanted at dose rate of 1!1017 ions/cm2 after wear measurements at 5 N and 0.5 m/s.
[1] Semliksch M. Titanium alloys for hip joint replacements. Clin Mater 1987;2:1–13. [2] Buchanan R, Rigney ED, Williams JM. Wear accelerated corrosion of Ti6Al-4V and nitrogen implanted Ti-6Al-4V. Mechanism and influence of fixed stress magnitude. J Biomed Mater Res 1987;21: 367–77. [3] Vardiman RG, Kent RA. Improvement of fatigue life of Ti-6Al-4V by ion implantation. J Appl Phys 1982;53:690–4.
552
S. Gokul Lakshmi, D. Arivuoli / Tribology International 39 (2006) 548–552
[4] Hongbing J, Xia L, Xinxin M, Sun Y. Tribological performance of Ti6Al-4V plasma based ion implanted with nitrogen. Wear 2000;246: 40–5. [5] Rie KT, Lamppe Th. Thermochemical surface treatment of titanium and titanium alloy Ti-6Al-4V by low energy nitrogen ion bombardment. Mater Sci Eng 1985;69:473–81. [6] Hutchings R, Oliver WC. A study of the improved wear performance of nitrogen implanted Ti-6Al-4V. Wear 1983;92:143–53. [7] Itoh Y, Itoh H, Azuma H, Hioki T. Improving the tribological properties of Ti-6Al-4V alloy by nitrogen-ion implantation. Surf Coat Technol 1999;111:172–6. [8] Onate JJ, Alonso F, Garcia A. Improvement of tribological properties by ion implantation. Thin Solid Films 1996;317:471–6. [9] Mortiiner E. Quantitative evaluation of bone apposition and in growth using porous fiber metal implants with a titanium nitride surface. 17th Int Biomater Symp 1991;14:151.
[10] Gokul Lakshmi S, Arivuoli D. Tribological behaviour of Plasma nitrided Ti-5Al-2Nb-1Ta alloy against UHMWPE. Tribology Int 2004;37:627–31. [11] Masami I, Setsuo S, Hisashi H, Yoshiyuki Y, Leszek SW, Ronald AC, et al. Increase of surface hardness induced by O, Ca or P ion implantation into titanium. Surf Coat Technol 2000;128–129:400. [12] Gokul Lakshmi S, Tamilselvi S, Rajendran N, Babi MAK, Arivuoli D. Effect of NC ion implantation on the corrosion behaviour of Ti-6Al7Nb and Ti-5Al-2Nb-1Ta orthopaedic alloys in Hanks solution. J Appl Electrochem 2004;34:27. [13] Pons F, Pivin JC, Farges G. Inhibition of tribo oxidation preceeding wear by single phased TiNx films formed by ion implantation into TiAl6V4. J Mater Res 1987;2:580. [14] Saritas S, Procter RPM, Grant WA. The use of ion implantation to modify the tribological property of Ti-6Al-4V. Mater Sci Eng 1987; 90:297.