Fretting damage is normally expected in biomedical implants due to body movements. Titanium alloys are most commonly used for biomedical devices and surface modified alloys have superior tribological properties to virgin materials. In the present study, the fretting wear resistance of physical vapour deposition (PVD) TiN coated, ion implanted and thermally oxidised biomedical alloys have been investigated and compared. PVD TiN coating has shown the best fretting wear resistance with minimum friction coefficient, less wear scar depth and diameter, and minimum wear rate compared to other coatings. The ion implanted specimen has undergone fretting assisted electrochemical dissolution to give higher wear loss after the modified layer has eroded away. Thermal oxidation has shown intermediate response to fretting. Fretting resistance can be improved with layers of high hardness and thickness. © 2007 Institute of Materials, Minerals and Mining.

M. Kamaraj

Department of Metallurgical and Materials Engineering

Rajappa Gnanamoorthy

Department of Mechanical Engineering

Biomaterials

Hardness

Ion implantation

Physical vapor deposition

Titanium alloys

Titanium nitride

tribology

Biomedical devices

FRETTING WEAR

Thermal oxidation

wear rate

Wear of materials

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Fretting wear studies on PVD TiN coated, ion implanted and thermally oxidised biomedical titanium alloys

Surface Engineering

The microstructure, hardness and wear properties of atmospheric plasma spray coating of TiO2 and Al2O3-13TiO 2 with incremental hydrogen fractions (11·1-23·8%) in primary gas have been investigated in this work. TiO2 coating shows a fine bead-like surface structure, while Al2O3- 13TiO 2 predominantly exhibits a splat-like morphology. The microstructure shows a slight refinement in the structure for the highest hydrogen content possibly due to the higher specific enthalpy of the plasma plume. Both coatings show the highest hardness for samples coated with the highest hydrogen content possibly due to the refined structure. The roughness shows a mild decreasing trend for TiO2 coating, while the reverse trend is observed for Al2O3-13TiO2 coating. The wear loss and friction coefficient show a flat trend (0·4-0·6) for all the hydrogen contents. The worn tracks show a compacted mixture of ceramic, graphite and metallic particles. © 2013 Institute of Materials, Minerals and Mining.

Microstructure and dry sliding wear behaviour of titania and alumina-titania coatings

The influence of Cu and Ni nanoparticle suspensions (2 wt-%) in commercially available engine oil (15W40) has been investigated on friction and wear behaviour of Al2O3-13TiO2 coatings. Lab synthesised nano-Cu and Ni suspensions have been compared with one commercially available nano-Cu suspension. Results show that lab synthesised Cu and Ni increases the oil viscosity by 12 and 20% for Ni and Cu respectively. However, the commercially available nano-Cu has reduced the viscosity by 8%. Lab synthesised Cu and Ni showed slightly reduced friction coefficient with significantly higher mass loss compared to virgin base oil and commercially available nano-Cu. The abrasive nature of these particles may possibly predominate in higher viscosity medium generating steady wear particles from the softer counterpart. Commercially available nano-Cu shows higher and irregular friction profile with mass loss equal to base oil possibly due to reduced viscosity. © 2013 Institute of Materials, Minerals and Mining.

Lubricated sliding wear behaviour of Al2O3–13TiO2coatings

Fretting is a form of adhesive wear normally occurring at the contact points gradually leading to premature of load bearing medical implants made of titanium alloys. The aim of this work is to characterize the fretting fatigue damage features of PVD TiN coated, plasma nitrided and thermally oxidized Ti-6Al-4V and Ti-6Al-7Nb contact pairs. Fretting damage is applied with calibrated proof ring and contact pad arrangement. The results are compared with fretting damage of uncoated alloys. The damage progression during fretting process is apparently explained with friction coefficient curves. Plasma nitrided pairs performed better in terms of fretting fatigue lives with low friction coefficient of friction. PVD TiN coated pairs have experienced early failures due to third body mode of contact interaction with irregular friction coefficient pattern. Thermally oxidized pairs have experienced early failures due to high case thickness as well as irregular development of modified layer. © 2005 Elsevier B.V. All rights reserved.

Materials Science and Engineering A

Damage characterization of unmodified and surface modified medical grade titanium alloys under fretting fatigue condition

Rolling element bearings experience fretting wear type of failures due to small relative oscillatory motion existing between races and rolling elements of the bearing. Small oscillatory motion between contacting surfaces that occur due to overall machine or system vibration and unexpected loads in service causes accumulation of wear debris in the contact zone and accelerate the wear process. A fretting wear test rig is designed and developed in the laboratory for understanding the fretting wear behavior of bearing materials. The test rig is designed for testing at slip amplitudes ranging from 20 to 200 μm and test frequencies ranging from 1 to 30 Hz. Preliminary studies for understanding the fretting wear characteristics were conducted on hardened and tempered bearing steel, En31 and widely employed hardened and tempered structural steel, En24 at various normal loads. Coefficient of friction during fretting tests was high during the initial stages of fretting tests and reached a steady state. The coefficient of friction depends on the normal load. Wear scar morphology reveals the nature of contact exhibited by the fretting contacts. © 2004 Elsevier Ltd. All rights reserved.

Materials and Design

Development of a fretting wear test rig and preliminary studies for understanding the fretting wear properties of steels

Fretting fatigue is a form of adhesive wear damage due to small oscillatory movement between two contacting bodies under the action of uniform or non-uniform cyclic loads. Cyclic loads may be experienced due to vibration of one or both the bodies eventually leading to failure at the contact area. Fretting damage is also experienced by load bearing implants within the body environment such as hip joints, knee joints, bone plates, etc. Damage characterization is important from the view of minimizing in-vivo failures. Titanium alloys are frequently used as bioimplants due to its excellent biocompatibility and low modulus of elasticity compared to stainless steel or Co-Cr-Mo alloys. Fretting wear damage of load bearing implants can be minimized through suitable surface modification process. Ti-6Al-4V and Ti-6Al-7Nb are commonly used for biomedical applications and PVD TiN coated alloys are used for our fretting fatigue studies. Fretting fatigue life of PVD TiN coated alloys improved compared to uncoated alloys. © 2005 Elsevier B.V. All rights reserved.

Surface and Coatings Technology

Characterization of fretting fatigue damage of PVD TiN coated biomedical titanium alloys

Nanotechnology

Tribology International

Enhanced wear resistance of Ti-5Al-2Nb-1Ta orthopaedic alloy by nitrogen ion implantation

Journal	Surface Engineering
ISSN	02670844
Open Access	No