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Research Papers: Coatings & Solid Lubricants

Nanomechanical and Wear Behavior of Microtextured Carbide-Coated CoCrMo Alloy Surfaces

[+] Author and Article Information
Geriel A. Ettienne-Modeste

e-mail: ettieng1@umbc.edu

L. D. Timmie Topoleski

e-mail: topoleski@umbc.edu
Department of Mechanical Engineering,
University of Maryland Baltimore County,
Baltimore, MD 21250

1Present address: Warfighter Survivability Branch, Altus Engineering, LLC, ARL/SLAD, 4502 Darlington Road, Aberdeen, MD 21005.

Contributed by the Tribology Division of ASME for publication in the Journal of Tribology. Manuscript received November 15, 2012; final manuscript received May 13, 2013; published online July 3, 2013. Assoc. Editor: Dae-Eun Kim.

J. Tribol 135(4), 041301 (Jul 03, 2013) (11 pages) Paper No: TRIB-12-1204; doi: 10.1115/1.4024642 History: Received November 15, 2012; Revised May 13, 2013

The nanomechanical properties of a CoCrMo medical implant alloy and a novel microtextured carbide-coated CoCrMo alloy (MTCC) surface—hardness and elastic modulus—were examined using nanoindentation. The MTCC surfaces may be a successful alternative bearing material for artificial joints. Understanding the nanomechanical, material properties, and surface morphology of the MTCC–CoCrMo surface are important for designing wear resistant artificial joints. The microtextured carbide surfaces were created using a microwave plasma-assisted chemical vapor deposition reaction (MPCVD). Nanomechanical properties, volumetric wear properties, and surface morphology were measured and used to determine the performance of the conventional CoCrMo alloy and MTCC surfaces (processed for either 2 or 4 h) in static environments and under severe wear conditions. The hardness, elastic modulus, and surface parameters of the 4-h MTCC surfaces were always greater than the 2-h MTCC and CoCrMo alloy surfaces. The nanomechanical properties changed for the CoCrMo alloy and 2-h and 4-h MTCC surfaces after, in contrast to before, wear testing. This indicates that the wear mechanisms affect the nanomechanical results. Overall, the 4-h MTCC surfaces had greater wear resistance than the 2-h MTCC or CoCrMo alloy surfaces.

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Figures

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Fig. 7

(a) Mean hardness, (b) mean elastic modulus, and (c) average surface roughness (Ra) of the mirror-finished CoCrMo alloy and 2-h and 4-h MTCC surfaces before wear testing (control). The error bars represent standard error of mean.

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Fig. 8

(a) Mean hardness and (b) mean elastic modulus of the 2-h and 4-h MTCC surfaces before wear testing (control) and after 106 wear cycles lubricated in BCS 50%. The error bars represent standard error of mean. * represents significant statistical difference with p < 0.05.

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Fig. 9

Surface profilometry 3D map (left) and oblique (right) profiles of the wear scars on (a) uncoated CoCrMo alloy and (b) 2-h and (c) 4-h MTCC surfaces after 106 wear cycles with BCS 50% lubricant at 37 ( ± 2)  °C

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Fig. 1

Nanoindented sites (indicated by white arrows) were separated by 4 mm for the (a) repolished 2-h and (b) repolished 4-h MTCC specimens after 106 wear cycles

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Fig. 5

(a) Load-depth curves and (b) the average and standard deviation plots for the load-displacement curves of the CoCrMo alloy and 2-h and 4-h MTCC polished specimens and (c) and (d) the 2-h MTCC as-deposited specimen before wear with a constant loading rate of 6000 μN/s

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Fig. 4

Volumetric wear versus number of cycles for the CoCrMo alloy and 2-h and 4-h MTCC surfaces from the CoCrMo-on-CoCrMo and the MTCC-on-MTCC wear couple systems. The error bars represent one standard deviation; lines connecting data do not represent any functional relation.

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Fig. 3

Optical images (100X) of the (a) CoCrMo and (c) 2-h and (d) 4-h MTCC before wear and the (b) CoCrMo and (e) 2-h and (f) 4-h MTCC after 106 wear cycles. Scale bar is 50 μm in all images.

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Fig. 2

SEM images (1000–2000X) of the (a) and (c) 2-h and (b) and (d) 4-h MTCC before and the (e) 2-h and (f) 4-h MTCC after 106 wear cycles. The peak width distance (PW) is ∼1 μm. The polished CoCrMo surfaces were featureless and are not included here.

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Fig. 6

(a) Load-depth curves and the (b) average and standard deviation plots for the load-displacement curves of the 2-h and 4-h MTCC lubricated in BCS 50% during wear test. A constant loading rate of 6000 μN/s was used for the nanoindentation tests.

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