Why does titanium alloy wear cobalt chrome alloy despite lower bulk hardness: A nanoindentation study?

Moharrami, Noushin; Langton, David; Saygıner, Osman; Bull, SJ

doi:10.1016/j.tsf.2013.06.020

Cited by 60 publications

(60 citation statements)

References 30 publications

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“…The wear fractions for a CoCr alloy head and Ti alloy stem combination have been specified as 0.9 and 0.1 respectively. This is due to preferential oxidation of the Ti alloy over the CoCr, which increases the hardness of the Ti and wears the un-oxidised CoCr, as has been published previously (Bishop et al, 2013;Bone et al, 2015;Langton et al, 2011a;Moharrami et al, 2013). …”

Section: Implementation Of the Wear Lawsupporting

confidence: 51%

“…Further investigation is required to consider the effect of the surface roughness on the wear rates at the taper junction of THRs and will form the basis of a future study. Finally, the wear fraction used in this study is based on the theory of titanium hardening in vivo, which happens where the wear depth reaches to around 0.15 µm (Moharrami et al, 2013). Although this wear depth occurs at an early stage of the wear analysis, further investigation is required to consider varying the wear fraction during the wear analysis.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

A large taper mismatch is one of the key factors behind high wear rates and failure at the taper junction of total hip replacements: A finite element wear analysis

Ashkanfar

Langton

Joyce

2017

Journal of the Mechanical Behavior of Biomedical Materials

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A large taper mismatch is one of the key factors behind high wear rates and failure at the taper junction of total hip replacements: A finite element wear analysis.http://researchonline.ljmu.ac.uk/5442/ Article LJMU has developed LJMU Research Online for users to access the research output of the University more effectively. Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Users may download and/or print one copy of any article(s) in LJMU Research Online to facilitate their private study or for non-commercial research. You may not engage in further distribution of the material or use it for any profit-making activities or any commercial gain.The version presented here may differ from the published version or from the version of the record. Please see the repository URL above for details on accessing the published version and note that access may require a subscription. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Chromium femoral heads, which had been in service for 5.1 years in average, to validate the FE analyses. It was found that a large taper mismatch (e.g. 9.12´ ) results in a high wear rate (2.960mm 3 per million load cycles). Such wear rates can have a major negative effect on the clinical outcomes of these implants. It was also found that even a slight reduction in mismatch significantly reduced the magnitude of the wear rates (0.069mm 3 per million load cycles on average for 6´ taper mismatch). It is recommended that the cone angles of femoral head and femoral trunnion should be manufactured to produce a taper mismatch of less than 6´ at the taper junction.

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Section: Implementation Of the Wear Lawsupporting

confidence: 51%

Section: Discussionmentioning

confidence: 99%

A large taper mismatch is one of the key factors behind high wear rates and failure at the taper junction of total hip replacements: A finite element wear analysis

Ashkanfar

Langton

Joyce

2017

Journal of the Mechanical Behavior of Biomedical Materials

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“…A scenario where passivated cobalt exists alongside depassivated titanium is conceivable given the higher bulk hardness of Co-Cr and the even harder carbides present in as-cast and HC wrought Co-Cr [16]. Through micromotion these carbide asperites are more than capable of disrupting the softer titanium oxide layer [60].…”

Section: Mixed-alloy Couplesmentioning

confidence: 99%

“…Possibly pointing at the cause, sputter pit depth measurements demonstrate that the oxide thickness in titanium alloys is significantly greater (150>nm) than the oxide layer formed on Co-Cr, which is only several nanometers thick. Furthermore, nanoindentation studies have found that the thicker titanium oxide is significantly harder than the unoxidized Co-Cr surface [60].This interplay between oxidation and wear-altering material changes alludes to the coupled and complex relationship between wear and corrosion. …”

Section: Mechanically Assisted Corrosionmentioning

confidence: 99%

In-Vivo Corrosion and Fretting of Modular TI-6AL-4V/CO-CR-MO Hip Prostheses: The Influence of Microstructure and Design Parameters

González¹,

Luís²

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The purpose of this study was to evaluate the incidence of corrosion and fretting in 48 retrieved titanium-6aluminum-4vanadium and/or cobalt-chromium-molybdenum modular total hip prosthesis with respect to alloy material microstructure and design parameters. The results revealed vastly different performance results for the wide array of microstructures examined. Severe corrosion/fretting was seen in 100% of as-cast, 24% of low carbon wrought, 9% of high carbon wrought and 5% of solution heat treated cobaltchrome. Severe corrosion/fretting was observed in 60% of Ti-6Al-4V components.Design features which allow for fluid entry and stagnation, amplification of contact pressure and/or increased micromotion were also shown to play a role. 75% of prosthesis with high femoral head-trunnion offset exhibited poor performance compared to 15% with a low offset. Large femoral heads (>32mm) did not exhibit poor corrosion or fretting. Implantation time was not sufficient to cause poor performance; 54% of prosthesis with greater than 10 years in-vivo demonstrated none or mild corrosion/fretting. v Effect of heat treatments on Ti-6Al-4V microstructure. Effect of heat treatments on Ti-6Al-4V mechanical propertiesFracture toughness values for equiaxed and highly transformed microstructuresTi-6Al-4V ASTM mechanical and compositional requirements Summary of modular total hip prosthesis retrieval studies during the past 25 years. As-received prostheses catalogingGeneral prostheses feature cataloging Macroscopic Examination. Overall implant examination, i.e. non-surface specific. Porous Surface Coating TypesFemoral head and femoral stem dimensional variables Modular junction dimensional variablesCorrosion and Fretting Scoring Criteria Worst fretting or corrosion score distribution by moment arm length.Worst fretting/corrosion score distribution for either head or trunnion by implantation time in-vivo. Cobalt-Carbon phase diagram illustrating the lever rule principle that dictates the fraction AB/AC of the constituent phases which will be liquid at the sintering temperature AC. i.e. an increase in carbon content will decrease the temperature required for adhering porous coatings.Porous coated as-cast cobalt-chrome stem Effect of Cooling Rates and Highest Temperature on Ti-6Al-4V Microstructure Finite element analysis predicting greater wear at the trunnion surface as femoral head is increased from 32mm to 56mm.Material, contact conditions and environmental variables governing potential for fretting wear.Pitting corrosion phenomena and associated reactions and surface features. Ion channeling contrast enhanced image of taper subsurface at 6,000X magnification, revealing differences in morphology near the surface.FIB trench subsurface regions selected for energy dispersive spectroscopy analysis.Cobalt, chromium, and molybdenum elemental weight percent at different depths as determined by EDS.(Left to right) 1. FIB sample pull out of as-cast carbide in matrix. 2. Areas from which EDS and TEM diffraction patterns were taken. 3. TEM im...

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“…The surface hardness of the titanium is only about 6-8GPa and considerably lower than the 17GPa hardness of the ZTA and is not expected to be able to scratch it. However, once implanted in the human body the both components are exposed to aqueous conditions at a temperature of 37 o C. In such conditions the titanium alloy will oxidise forming a surface oxide [51] with a hardness of about 15GPa (Figure 10b) whilst the ZTA undergoes chemomechanical softening and its hardness is reduced to a similar level (Figure 10a). The titanium oxide produced is x-ray amorphous and shows no chemomechanical softening.…”

Section: Chemomechanical Effects On Complex Contactsmentioning

confidence: 99%

The origins of chemomechanical effects in the low-load indentation hardness and tribology of ceramic materials

et al. 2015

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We have used high-resolution techniques (nanoindentation, atomic force microscopy) to further isolate and identify environmental effects previously reported as possibly affecting both the microindentation response of a range of ceramic materials and their tribological behaviour. In order to make meaningful comparisons, these new experiments have been conducted alongside conventional Knoop and Vickers microhardness experiments conducted under identical conditions on the same samples. A range of polycrystalline, single crystal and amorphous ceramic materials have been studied including some only available as coatings. Our results show that thin adsorbate-modified layers (of dimensions ~1nm) are almost invariably present on all the materials studied but their presence is not directly identifiable by nanoindentation in most cases even if it does affect friction response. However, in crystalline materials, (1012 sapphire and ZnO), we have been able to distinguish a further softening effect seen as a thicker layer (tens of nm) and believed associated with an adsorption-induced near-surface band-structure change affecting the motion of charged dislocations. This produces a measurable softening that is clearly evident in nanoindentation tests but less clear in microindentation tests. Finally, we present conclusions on the suitability of indentation testing for studying these phenomena, together with the implications of chemomechanical effects for influencing tribological performance and, thus, materials selection.

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Why does titanium alloy wear cobalt chrome alloy despite lower bulk hardness: A nanoindentation study?

Cited by 60 publications

References 30 publications

A large taper mismatch is one of the key factors behind high wear rates and failure at the taper junction of total hip replacements: A finite element wear analysis

A large taper mismatch is one of the key factors behind high wear rates and failure at the taper junction of total hip replacements: A finite element wear analysis

In-Vivo Corrosion and Fretting of Modular TI-6AL-4V/CO-CR-MO Hip Prostheses: The Influence of Microstructure and Design Parameters

The origins of chemomechanical effects in the low-load indentation hardness and tribology of ceramic materials

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