Research Papers: Friction and Wear

Elevated Temperature Fretting Wear Behavior of Cobalt-Based Alloys

[+] Author and Article Information
C. H. Sathisha

Manufacturing and Materials Technologies,
GE Global Research,
122 Whitefield Road,
Bangalore 560066, India
e-mail: sathishchs@mail.com

B. N. Ravikumar

Department of Mechanical Engineering,
Bangalore Institute of Technology,
R Road, V V Puram,
Bangalore 560004, India
e-mail: ravikumarbn_bit@yahoo.co.in

K. Anand

Materials and Process Engineering,
GE Power and Water,
122 Whitefield Road,
Bangalore 560066, India
e-mail: k.anand@ge.com

T. Shalini

Materials Characterization Lab,
GE Global Research,
122 Whitefield Road,
Bangalore 560066, India
e-mail: shalini.t@ge.com

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received November 6, 2014; final manuscript received May 27, 2015; published online January 18, 2016. Assoc. Editor: Satish V. Kailas.

J. Tribol 138(3), 031601 (Jan 18, 2016) (8 pages) Paper No: TRIB-14-1271; doi: 10.1115/1.4031831 History: Received November 06, 2014; Revised May 27, 2015

Structural parts in gas turbines undergo fretting wear, and as clearances open up, it turns into impact wear. Uncoated cobalt-based substrates that are used in such applications show poor resistance to fretting/impact damage and undergo extensive/unacceptable level of degradation. Commonly used substrate materials such as uncoated cobalt-based materials show poor resistance to fretting/impact wear. This study is focused on assessing the performance of high velocity oxyfuel (HVOF) tungsten carbide (WC) coatings and sintered tungsten carbide inserts as potential solutions for mitigating this issue. Sintered WC12Co with grain size range from 0.2 μm to 4.5 μm and HVOF coating with composition of WC–17%Co was tested. It was found that the HVOF coatings performed better than sintered material and the behavior was attributed to the hard WC particles surrounded by the higher volume fraction of cobalt binder. In the HVOF coating, the normal load was better accommodated by the decarburized WC but a fairly tough binder-surrounding matrix. An additional factor is that the sintered WC had significant volume fraction of undesirable W2C phase, which apparently underwent fracture during the test, thus showing an inferior behavior compared to the HVOF WC coating.

Copyright © 2016 by ASME
Topics: Wear , Coatings , Temperature
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Fig. 1

Dynamic and Static fixtures on the fretting test equipment

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Fig. 2

SEM image of (a) sintered WC–12Co and (b) HVOF-coated WC–17Co at 7000×

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Fig. 4

Vickers hardness of baseline and WC–Co materials systems

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Fig. 5

(a) Schematic representation of the profilometry measurement and (b) representative profilometry curve which shows material transfer and loss

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Fig. 6

Normalized wear rate of tested materials

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Fig. 7

Photographs of tested (a) CoNiCrW, (b) SPS WC–12Co, and (c) HVOF WC–17Co

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Fig. 8

SEM surface morphology of bulk CoNiCrW at (a) 500× and (b) 4000× magnifications

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Fig. 9

SEM surface morphology of bulk WC-12Co at (a) 500× and (b) 4000× magnifications

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Fig. 10

SEM surface morphology of HVOF-coated WC–17Co at (a) 500× and (b) 4000× magnifications

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Fig. 11

Subsurface SEM of bulk CoNiCrW (a) 500× and (b) 5000×

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Fig. 12

Subsurface SEM of bulk WC–12Co (a) 500× and (b) 5000×

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Fig. 13

Subsurface SEM of HVOF-coated WC–17CO (a) 500× and (b) 5000×




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