Sankara Narayanan TSN

Publications

• 1.69

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  Electrophoretic deposition of nanocomposite (HAp + TiO2) on titanium alloy for biomedical applications

  L. Mohan, D. Durgalakshmi, M. Geetha, T.S.N. Sankara Narayanan, R. Asokamani

  Ceramics International. 05/2012; 38(4):3435-3443.

  This paper reports on the corrosion and scratch behavior of TiO2 + 50%HAp nanoceramic coated Ti–13Nb–13Zr orthopedic implant alloy. An adherent thin coating was obtained using the electrophoretic deposition (EPD) technique at 30 V and sintering at 850 °C. The microstructure of the coated surfaces wa... [more] This paper reports on the corrosion and scratch behavior of TiO2 + 50%HAp nanoceramic coated Ti–13Nb–13Zr orthopedic implant alloy. An adherent thin coating was obtained using the electrophoretic deposition (EPD) technique at 30 V and sintering at 850 °C. The microstructure of the coated surfaces was characterized by optical microscopy, AFM, and SEM, and the composition of the coating was examined using EDAX. The functional groups and formed phases analyzed using FT-IR, and XRD. Further, the adhesion strength of the coatings was evaluated using scratch tester and the corrosion behavior of all samples was tested in Simulated Body Fluid (SBF-Hank's solution) using a potentiodynamic polarization studies. The sintered coating exhibited higher adhesion, lower porosity and higher density compared to unsintered samples, and higher corrosion resistance compared to the substrate. However, the corrosion resistance of the unsintered coating was superior to that of the sintered one due to the presence of minimal interconnected porosity.
• 1.79

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  Fretting Wear Behaviour of Surface Mechanical Attrition Treated Alloy 718

  S. Anand Kumar, S. Ganesh Sundara Raman, T.S.N. Sankara Narayanan, R. Gnanamoorthy

  Surface and Coatings Technology. 01/2012;

  Alloy 718 was subjected to surface mechanical attrition treatment (SMAT) using SAE 52100 steel balls of 5 mm diameter for four different treatment durations (15, 30, 45 and 60 min). Fretting wear tests were conducted at different normal loads on untreated and treated samples for 25,000 cycles using ... [more] Alloy 718 was subjected to surface mechanical attrition treatment (SMAT) using SAE 52100 steel balls of 5 mm diameter for four different treatment durations (15, 30, 45 and 60 min). Fretting wear tests were conducted at different normal loads on untreated and treated samples for 25,000 cycles using alumina as a counterbody material. Microstructural features of the surface layer of samples treated by SMAT were characterized by cross-sectional optical microscopy and transmission electron microscopy. Hardness, surface roughness and residual stress were determined using a nano-indenter, surface roughness tester and X-ray residual stress analyzer respectively. SMAT resulted in the formation of nanocrystallites on the surface and near surface regions, increased hardness, increased surface roughness and compressive residual stress at the surface. Treated samples exhibited lower tangential force coefficient (TFC) compared to untreated samples. Samples treated for 60 min exhibited higher grain refinement, higher hardness, lower surface roughness and higher TFC compared to the samples treated for 30 min. The wear volume and wear rate of samples treated for 30 min were lower compared to those of the untreated samples, which may be attributed to optimum combination of hardness and toughness and a low work hardening rate of the nanocrystalline structure at the surface of the treated samples. In contrast, the wear volume and wear rate of the samples treated for 60 min were higher than those of untreated samples, presumably due to the higher hardness and reduced toughness of the samples treated for 60 min. Highlights ► Surface mechanical attrition treatment (SMAT) on Alloy 718 resulted in nanostructuring of surface. ► SMAT duration had an effect on the crystallite size and properties. ► Fretting wear resistance of samples treated for 30 min was higher than that of samples treated for 60 min. ► Optimum combination of hardness and ductility/toughness is the key factor for better wear resistance
• 2.32

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  Localized corrosion of an ultrafine grained Al-4Zn-2Mg alloy produced by cryorolling

  K. Gopala Krishna, K. Sivaprasad, T.S.N. Sankara Narayanan, K.C. Hari Kumar

  Corrosion Science. 01/2012;

  The effect of microstructure on corrosion behaviour of an ultrafine grained (UFG) Al-4Zn-2Mg alloy produced by cryorolling was investigated. Both UFG and coarse grained (CG) alloys in peak-aged condition were subjected to potentiodynamic polarization and intergranular corrosion (IGC) tests in chlori... [more] The effect of microstructure on corrosion behaviour of an ultrafine grained (UFG) Al-4Zn-2Mg alloy produced by cryorolling was investigated. Both UFG and coarse grained (CG) alloys in peak-aged condition were subjected to potentiodynamic polarization and intergranular corrosion (IGC) tests in chloride solutions. UFG alloy exhibited increased corrosion potential (Ecorr), decreased corrosion current density (icorr) (864 mVSCE, 0.60 μA/cm2) during polarization and lower weight loss during IGC when compared with CG alloy (902 mVSCE, 4.9 μA/cm2). Improved corrosion resistance of UFG alloy is mainly attributed to sub-micrometer grains, absence of coarse MgZn2 anodic precipitates and precipitate-free zones along the grain boundaries.
• 0.84

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  Electrodeposition of hydroxyapatite coating on magnesium for biomedical applications

  M. Jamesh, Satendra Kumar, T. S. N. Sankara Narayanan

  Journal of Coatings Technology and Research. 01/2012;

  The effectiveness of hydroxyapatite (HA) coating prepared by electrodeposition technique in improving the corrosion resistance of commercially pure magnesium (CP-Mg) in simulated body fluid (SBF) is addressed. The coating formed in as-deposited condition is identified as dicalcium phosphate dehydrat... [more] The effectiveness of hydroxyapatite (HA) coating prepared by electrodeposition technique in improving the corrosion resistance of commercially pure magnesium (CP-Mg) in simulated body fluid (SBF) is addressed. The coating formed in as-deposited condition is identified as dicalcium phosphate dehydrate (DCPD) (Brushite), which is converted to HA after immersion in 1 M NaOH at 80°C for 2 h. The XRD patterns and FTIR spectra confirm the formation of DCPD and HA. During electrodeposition, the H2PO4 − ion is reduced and the reaction between Ca2+ ions and the reduced phosphate ions leads to the formation of DCPD, which is converted to HA following treatment in NaOH. The deposition of HA coating enables a threefold increase in the corrosion resistance of CP-Mg. The ability to offer a significant improvement in corrosion resistance coupled with the bioactive characteristics of the HA coating establish that electrodeposition of HA is a viable approach to engineer the surface of CP-Mg in the development of Mg-based degradable implant materials.
• 0.84

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  Corrosion resistant Ti alloy for sulphuric acid medium: Suitability of Ti–Mo alloys

  T. Balusamy, M. Jamesh, Satendra Kumar, T. S. N. Sankara Narayanan

  Materials and Corrosion. 01/2012;

  The corrosion resistance of Ti–Mo (5, 10, 15 and 25 wt% molybdenum) alloys in 5–25% sulphuric acid was evaluated. The Ti–Mo alloys offered a better corrosion resistance than commercially pure titanium (CP-Ti). The higher impedance values, higher phase angle maximum, ability to reach the phase angle ... [more] The corrosion resistance of Ti–Mo (5, 10, 15 and 25 wt% molybdenum) alloys in 5–25% sulphuric acid was evaluated. The Ti–Mo alloys offered a better corrosion resistance than commercially pure titanium (CP-Ti). The higher impedance values, higher phase angle maximum, ability to reach the phase angle maximum at relatively lower frequencies, ability to exhibit a constant phase angle maximum over a wider range of frequencies, higher phase angle values at 0.01 Hz, have confirmed the formation of a stable passive oxide film on Ti–Mo alloys. The study recommends the use of Ti–Mo alloys, particularly Ti–25Mo alloy, as a suitable material of construction for sulphuric acid medium.
• 0.59

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  Effect of Thermal Oxidation on Corrosion Resistance of Commercially Pure Titanium in Acid Medium

  M. Jamesh, Satendra Kumar, T. S. N. Sankara Narayanan

  Journal of Materials Engineering and Performance. 01/2012;

  This article addresses the characteristics of commercially pure titanium (CP-Ti) subjected to thermal oxidation in air at 650 °C for 48 h and its corrosion behavior in 0.1 and 4 M HCl and HNO3 mediums. Thermal oxidation of CP-Ti leads to the formation of thick oxide scales (~20 μm) throughout its su... [more] This article addresses the characteristics of commercially pure titanium (CP-Ti) subjected to thermal oxidation in air at 650 °C for 48 h and its corrosion behavior in 0.1 and 4 M HCl and HNO3 mediums. Thermal oxidation of CP-Ti leads to the formation of thick oxide scales (~20 μm) throughout its surface without any spallation. The oxide layer consists of rutile- and oxygen-diffused titanium as predominant phases with a hardness of 679 ± 43 HV1.96. Electrochemical studies reveal that the thermally oxidized CP-Ti offers a better corrosion resistance than its untreated counterpart in both HCl and HNO3 mediums. The uniform surface coverage and compactness of the oxide layer provide an effective barrier toward corrosion of CP-Ti. The study concludes that thermal oxidation is an effective approach to engineer the surface of CP-Ti so as to increase its corrosion resistance in HCl and HNO3 mediums.
• 0.84

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  Polarization and impedance studies on zinc phosphate coating developed using galvanic coupling

  M. Arthanareeswari, T. S. N. Sankara Narayanan, P. Kamaraj, M. Tamilselvi

  Journal of Coatings Technology and Research. 01/2012; 9(1-DOI: 10.1007/s11998-011-9339-9):39-46.

  Galvanic coupling technique is capable of producing coatings of desired thickness. Good quality coatings can be produced at low temperature. Galvanic coupling of mild steel (MS) with the other cathode materials such as titanium (Ti), copper (Cu), brass (BR), nickel (Ni), and stainless steel (SS) acc... [more] Galvanic coupling technique is capable of producing coatings of desired thickness. Good quality coatings can be produced at low temperature. Galvanic coupling of mild steel (MS) with the other cathode materials such as titanium (Ti), copper (Cu), brass (BR), nickel (Ni), and stainless steel (SS) accelerates iron dissolution, enables quicker consumption of free phosphoric acid and facilitates an earlier attainment of point of incipient precipitation, resulting in a higher amount of coating formation. In the present investigation, potentiodynamic polarization and electrochemical impedance spectra on MS substrates phosphated using galvanic coupling are studied. This study reveals that MS substrates phosphated under galvanically coupled condition possess better corrosion resistance than the substrates phosphated under uncoupled condition.

• Comparison of the fretting corrosion behaviour of Ti-6Al-4V alloy and CP-Ti in Ringer’s solution

  Sivakumar, Kumar, T S N Sankara

  Tribology - Materials Surfaces & Interfaces. 12/2011; 5(4):158-164.

  The fretting corrosion behaviour of Ti?6Al?4V alloy in Ringer’s solution was evaluated and compared with that of commercially pure titanium (CP-Ti). Free corrosion potential, morphology of the fretted zone, extent of formation and accumulation of debris and wear volume were used as parameters of eva... [more] The fretting corrosion behaviour of Ti?6Al?4V alloy in Ringer’s solution was evaluated and compared with that of commercially pure titanium (CP-Ti). Free corrosion potential, morphology of the fretted zone, extent of formation and accumulation of debris and wear volume were used as parameters of evaluation. Both Ti?6Al?4V alloy and CP-Ti behave similarly in terms of change in free corrosion potential as a function of time, morphological features and wear mechanism. Ti?6Al?4V alloy, however, exhibits an increase in corrosion susceptibility, decrease in tendency for repassivation, higher amount of formation and accumulation of debris and an increase in wear volume compared with CP-Ti. The study points out the importance of material selection for implants that would encounter fretting corrosion.
• 2.11

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  Synthesis of manganese zinc ferrite using ferrous pickle liquor and pyrolusite ore

  B. R. V. Narasimhan, Satendra Kumar, T. S. N. Sankara Narayanan

  Environmental Chemistry Letters. 02/2011; 9(2-DOI: 10.1007/s10311-009-0272-4):243-250.

  The possibility of utilizing hydrochloric acid-based waste pickle liquor (WPL) and medium-grade pyrolusite ore to synthesize manganese zinc ferrite was explored. The excess acidity of the WPL was neutralized using mild steel turnings. The unreacted mild steel scrap and suspended solids were removed ... [more] The possibility of utilizing hydrochloric acid-based waste pickle liquor (WPL) and medium-grade pyrolusite ore to synthesize manganese zinc ferrite was explored. The excess acidity of the WPL was neutralized using mild steel turnings. The unreacted mild steel scrap and suspended solids were removed by filtration. Partial precipitation technique was employed to reduce the impurities. The purified WPL was treated with medium-grade pyrolusite ore to prepare the leach liquor to which the required quantities of ferrous chloride and zinc granules were added to maintain stoichiometry in the resultant compound. The hydroxy carbonate of manganese, zinc and iron was precipitated by the addition of a hot solution (70°C) of sodium carbonate (20% v/v), which upon sintering in argon atmosphere yielded manganese zinc ferrite. The addition of sodium lauryl sulfate (SLS) helped in preventing agglomeration of the particles. Sintering at 450°C for 30 min in argon atmosphere has resulted in mixed phases of (Zn,Mn,Fe) (Fe,Mn)2O4 and Mn3O4, which indicates lack of phase purity. Sintering at temperatures higher than 950°C for 5 h in argon atmosphere enabled complete ferritization. The extent of ferritization was found to be a function of sintering time at 950°C. The manganese zinc ferrites synthesized using WPL and medium-grade pyrolusite ore exhibited soft magnetic characteristics.
• 2.32

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  Corrosion behavior of commercially pure Mg and ZM21 Mg alloy in Ringer’s solution – Long term evaluation by EIS

  M. Jamesh, Satendra Kumar, T.S.N. Sankara Narayanan

  Corrosion Science. 02/2011; 53(2-http://dx.doi.org/10.1016/j.corsci.2010.10.011):645-654.

  Evaluation of the corrosion behavior of commercially pure magnesium (CP-Mg) and ZM21 Mg alloy immersed in Ringer’s solution for 92 h by electrochemical impedance spectroscopy (EIS) is addressed. The formation of a compact layer of well-developed rod-like aragonitic CaCO3 crystals and its subsequent ... [more] Evaluation of the corrosion behavior of commercially pure magnesium (CP-Mg) and ZM21 Mg alloy immersed in Ringer’s solution for 92 h by electrochemical impedance spectroscopy (EIS) is addressed. The formation of a compact layer of well-developed rod-like aragonitic CaCO3 crystals and its subsequent thickening with increase in immersion time offers a higher corrosion protective ability for ZM21 Mg alloy. The formation of a mud-crack pattern and a large number of clusters of needle-like crystals offers a relatively lower corrosion resistance for CP-Mg. The study suggests that ZM21 Mg alloy is a promising candidate material for the development of degradable implants. Research highlights ► ZM21 Mg alloy offers a higher corrosion resistance than CP Mg. ► Mg(OH)2 and aragonitic CaCO3 are the corrosion products on CP-Mg and ZM21 Mg alloy. ► Thickening of the corrosion product layer is delayed in CP Mg. ► ZM21 Mg alloy is a promising candidate for degradable implant.
• 1.70

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  Evaluation of corrosion behaviour of Ti–25Mo alloy in chloride medium

  Satendra Kumar, T. S. N. Sankara Narayanan

  Journal of Applied Electrochemistry. 01/2011; 41(1):123-127.

  The corrosion behaviour of Ti–25Mo alloy in 0.9 wt% NaCl was evaluated by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and compared with that of commercially pure titanium (CP-Ti). The corrosion behaviour of Ti–25Mo alloy has been reported for the first time in this pap... [more] The corrosion behaviour of Ti–25Mo alloy in 0.9 wt% NaCl was evaluated by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and compared with that of commercially pure titanium (CP-Ti). The corrosion behaviour of Ti–25Mo alloy has been reported for the first time in this paper. The microstructure and structural characteristics were also examined using optical microscopy and X-ray diffraction (XRD), respectively. The study reveals that Ti–25Mo alloy possesses a β-phase microstructure. The Ti–25Mo alloy exhibits higher passivation range, lower average passive current density (ipass) and higher charge transfer resistance (Rct) compared to that of CP-Ti. Based on the corrosion protection ability, Ti–25Mo alloy can be a suitable alternative material for orthopaedic implant applications.
• 1.77

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  Fretting corrosion behaviour of Ti–6Al–4V alloy in artificial saliva containing varying concentrations of fluoride ions

  B. Sivakumar, Satendra Kumar, T.S.N. Sankara Narayanan

  Wear. 01/2011; 270(3-4):317-324.

  The present communication addresses the fretting corrosion behaviour of Ti–6Al–4V alloy in artificial saliva containing 0, 190, 570 and 1140 ppm of fluoride ions. The fretting corrosion behaviour of Ti–6Al–4V alloy was evaluated based on the change in free corrosion potential (FCP) measured as a fun... [more] The present communication addresses the fretting corrosion behaviour of Ti–6Al–4V alloy in artificial saliva containing 0, 190, 570 and 1140 ppm of fluoride ions. The fretting corrosion behaviour of Ti–6Al–4V alloy was evaluated based on the change in free corrosion potential (FCP) measured as a function of time. The wear morphology and surface profile of the fretted zone, assessed by scanning electron microscopy and non-contact optical profilometer, were used to ascertain the wear mechanism. The cathodic shift in FCP observed with the onset of fretting indicates damage of the passive film. After the fretting motion is ceased, an instantaneous repassivation of Ti–6Al–4V alloy is observed only in artificial saliva. The negative influence of fluoride ions on passive film formation hinders instantaneous repassivation of the damaged areas of the fretted zone. The morphology of the fretted zone reveals the occurrence of adhesive galling in all the cases. The wear volume of the fretted zone of Ti–6Al–4V alloy in artificial saliva free of fluoride ions is 3.26 × 1012 nm3. In presence of 190 ppm of fluoride ions in artificial saliva, the wear volume is increased from 3.26 to 9.87 × 1012 nm3. However, the wear volume is reduced to 6.95 × 1012 nm3 and 3.60 × 1011 nm3 at 570 and 1140 ppm of fluoride ions, respectively. The change in contact configuration from alumina–titanium to titanium-coated alumina–titanium reduced the mutual solubility between alumina and titanium, the extent of trapping and grinding of the wear debris and the wear rate of Ti–6Al–4V alloy in artificial saliva containing 1140 ppm of fluoride ions. The study reveals that the fretting corrosion behaviour of Ti–6Al–4V alloy in artificial saliva shows a strong dependence on the fluoride ion concentration. Research highlights ▶ Fluoride ions hinder instantaneous repassivation of damaged areas of fretted zone. ▶ Adhesive galling is observed both in presence and in absence of fluoride ions. ▶ Wear volume is higher at 190 ppm but lower at 570 and 1140 ppm of fluoride ions. ▶ Change in contact configuration reduced the wear rate at 1140 ppm of fluoride ions.
• 0.09

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  Electrochemical Behaviour of Surface Modified AISI 304 Grade Stainless Steel in Ringer’s Solution

  T. Balusamy, Satendra Kumar, T. S. N. Sankara Narayanan

  Transactions- Indian Institute of Metals. 01/2011; 64(4-5):507-511.

  Stainless steels are widely used as orthopedic implant materials. The main problems with these implant materials are fatigue fracture, fretting fatigue, wear and corrosion. Surface mechanical attrition treatment (SMAT) is a newly developed method to improve the materials properties and performance. ... [more] Stainless steels are widely used as orthopedic implant materials. The main problems with these implant materials are fatigue fracture, fretting fatigue, wear and corrosion. Surface mechanical attrition treatment (SMAT) is a newly developed method to improve the materials properties and performance. In the present study, AISI 304 SS was subjected to SMAT using 2, 5 and 8 mm ∅ 316L SS balls for 15, 30, 45 and 60 min at 50 Hz under vacuum. SMAT of 304 SS increased the surface roughness, induced the formation of mechanical twins, strain induced martensite phase, and increased the defect density, which is a function of the size of the balls and treatment time. SMAT using 5 and 8 mm ∅ balls significantly decreased the corrosion resistance whereas treatment using 2 mm ∅ balls enabled an anodic shift in Ecorr and a marginal decrease in icorr. However, increase in surface roughness leads to the formation of a defective passive film and a decrease in breakdown potential.

• Electro- and electroless composite coatings: Preparation, Properties and Applications

  T.S.N. Sankara Narayanan, S.K. Seshadri

  01/2011;

• Role of Nanomaterials on Tribocorrosion

  T.S.N. Sankara Narayanan

  01/2011;
• 1.84

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  Surface modification of CP-Ti to improve the fretting-corrosion resistance: Thermal oxidation vs. anodizing

  Satendra Kumar, T.S.N. Sankara Narayanan, S. Ganesh Sundara Raman, S.K. Seshadri

  Materials Science and Engineering C. 07/2010; 30(6,):921-927.

  Fretting corrosion is one of the important reasons for the failure of prosthesis made of titanium and titanium alloys under in vivo condition. The fretting-corrosion behaviour of untreated, anodized and thermally oxidized commercially pure titanium (CP-Ti) in Ringer's solution was evaluated base... [more] Fretting corrosion is one of the important reasons for the failure of prosthesis made of titanium and titanium alloys under in vivo condition. The fretting-corrosion behaviour of untreated, anodized and thermally oxidized commercially pure titanium (CP-Ti) in Ringer's solution was evaluated based on the change in free corrosion potential (FCP) measured as a function of time. A comparison of the performance of untreated, anodized and thermally oxidized CP-Ti under fretting-corrosion conditions is reported for the first time in this paper. The study reveals that surface modification of CP-Ti by both anodizing and thermal oxidation improved the fretting-corrosion resistance of CP-Ti and among them the performance of thermally oxidized CP-Ti is superior to that of the anodized one. Adhesive galling is the predominant wear mechanism for untreated CP-Ti, adhesive wear and delamination are found to be operative for anodized CP-Ti whereas an abrasive wear mechanism is operative for thermally oxidized CP-Ti when they are fretted against an alumina ball.
• 1.69

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  Evaluation of fretting corrosion behaviour of CP-Ti for orthopaedic implant applications

  Satendra Kumar, T.S.N. Sankara Narayanan, S. Ganesh Sundara Raman, S.K. Seshadri

  Tribology International. 07/2010; 43(7):1245-1252.

  The fretting corrosion behaviour of CP-Ti in Ringer's solution was studied as a function of normal load, frequency and number of fretting cycles. The restoration ability of CP-Ti after the passive film is damaged due to fretting and as a function of the on-time/off-time ratio (intermittent frett... [more] The fretting corrosion behaviour of CP-Ti in Ringer's solution was studied as a function of normal load, frequency and number of fretting cycles. The restoration ability of CP-Ti after the passive film is damaged due to fretting and as a function of the on-time/off-time ratio (intermittent fretting) was also evaluated. The change in free corrosion potential measured before the onset of fretting, with the onset of fretting, during fretting and after the fretting motion ceases, as a function of time, was used to evaluate the fretting corrosion behaviour. The restoration ability of CP-Ti after the passive film is damaged was ascertained by performing regression analysis of the potential data measured during repassivation. The morphological features of the fretted zone were assessed using scanning electron microscopy. Energy dispersive X-ray analysis was performed at the centre and edge regions of the fretted zone to identify their chemical nature. The study reveals that the excellent corrosion resistance and biocompatibility of CP-Ti are nullified under fretting conditions. Once the passive oxide layer is damaged due to fretting, repassivation is not instantaneous. The significant time delay in reaching the steady state potential implies that CP-Ti remains active and susceptible for corrosion. The difficulty in the instantaneous formation of passive film after the fretting induced damage of the passive film, dissolution of bare Ti from the damaged areas and the possible accumulation of the debris generated during fretting in the surrounding tissues raises concern on the safer use of CP-Ti as an implant material.
• 1.42

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  Thermal oxidation of CP Ti — An electrochemical and structural characterization

  Satendra Kumar, T.S.N. Sankara Narayanan, S. Ganesh Sundara Raman, S.K. Seshadri

  Materials Characterization. 06/2010; 61(6):9-597.

  In the present study commercially pure titanium (CP Ti) samples were oxidized thermally at three different temperatures (500, 650 and 800 °C) for 24 h and evaluation of their morphological and structural characteristics, microhardness and corrosion resistance in Ringer's solution was done. The c... [more] In the present study commercially pure titanium (CP Ti) samples were oxidized thermally at three different temperatures (500, 650 and 800 °C) for 24 h and evaluation of their morphological and structural characteristics, microhardness and corrosion resistance in Ringer's solution was done. The corrosion protective ability of thermally oxidized materials shows a strong dependence on the nature and thickness of the surface oxide layer. Based on the corrosion protective ability, the untreated and thermally oxidized samples can be ranked as follows: CP Ti (800 °C) > CP Ti (650 °C) > CP Ti (500 °C) > untreated CP Ti.
• 1.77

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  Fretting-corrosion mapping of CP-Ti in Ringer's solution

  Satendra Kumar, B. Sivakumar, T.S.N. Sankara Narayanan, S. Ganesh Sundara Raman, S.K. Seshadri

  Wear. 05/2010; 268(11–12):1537-1541.

  Fretting corrosion is a complex phenomena and a variety of factors such as load, contact area, frequency, number of fretting cycles, extent of damage of the fretted zone, trapping of debris between the contacting surfaces, corrosivity of the medium, etc., will determine the fretting-corrosion behavi... [more] Fretting corrosion is a complex phenomena and a variety of factors such as load, contact area, frequency, number of fretting cycles, extent of damage of the fretted zone, trapping of debris between the contacting surfaces, corrosivity of the medium, etc., will determine the fretting-corrosion behaviour. The present paper aims to develop a fretting-corrosion map of commercially pure Ti (CP-Ti) based on its fretting-corrosion behaviour in Ringer's solution under various combinations of load, frequency and number of fretting cycles. Based on the fretting-corrosion behaviour and restoration ability, a fretting-corrosion map of CP-Ti in Ringer's solution is developed for the first time. The fretting-corrosion map of CP-Ti in Ringer's solution enables identification of various regimes depending on the nature of predominant phenomenon for a given set of conditions. Since fretting corrosion is the dominant phenomenon at lesser duration of fretting at 5 and 10 Hz for a load of 3 and 5 N, the safer use of CP-Ti, particularly for hip and knee implants, is a major concern.
• 0.27

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  Influence of galvanic coupling on the formation of zinc phosphate coating

  M. Arthanareeswari, T.S.N. Sankara Narayanan, P. Kamaraj, M. Tamilselvi

  Indian Journal of Chemical Technology. 05/2010; 17(3):167-175.

  The influence of galvanic coupling of mild steel (MS) with titanium, copper, brass, nickel and stainless steel (SS) on the phosphatability is elucidated. The galvanic couple accelerates metal dissolution, enables quicker consumption of free phosphoric acid and facilitates an earlier attainment of po... [more] The influence of galvanic coupling of mild steel (MS) with titanium, copper, brass, nickel and stainless steel (SS) on the phosphatability is elucidated. The galvanic couple accelerates metal dissolution, enables quicker consumption of free phosphoric acid and facilitates an earlier attainment of point of incipient precipitation, resulting in higher amount of coating formation. The surface morphology of the coatings exhibit more uniform coating for the mild steel substrates phosphated under coupled conditions. XRD pattern of the zinc phosphate coating formed under coupled condition confirms the presence of phosphophyllite rich coating. The potential-time measurements are also carried out. The study reveals that galvanic coupling of mild steel with metals that are nobler than steel during phosphating proved to be beneficial in accelerating the coating formation.