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The fracture of diamond coatings by high velocity sand erosion

The fracture of diamond coatings by high velocity sand erosion
The fracture of diamond coatings by high velocity sand erosion
This paper describes a study of the behaviour of diamond coatings when subjected to solid particle erosion from sand particles. The coatings were deposited by chemical vapour deposition (CVD) onto tungsten substrates and tested using a high velocity air–sand erosion test facility. The erosion tests were conducted using particle impact velocities of between 33 and 268 m/s. Examination of the eroded test specimens showed that the principal damage features were circumferential cracks and pin-holes. Comparison with Hertz impact theory revealed that the measured circumferential crack diameters were more than double the predicted Hertzian contact diameter. Moreover, a trend of increasing circumferential crack diameter with coating thickness, which is not predicted by Hertz, was found. Instead, the crack diameters showed good agreement with those predicted by the theory of stress wave reinforcement, which is more commonly associated with liquid impact damage of brittle materials. During impact, the bulk compression and shear waves are reflected at the rear surface of debonded regions of the coating to return to the front surface and reinforce the Rayleigh surface wave, which generates a tensile stress. Where this stress exceeds the local tensile strength of the coating, a ring of cracks surrounding the area of impact is created. The results from the present study, therefore, suggest that stress wave reflection is responsible for the formation of the cracks at locally debonded regions of the coating. This hypothesis was supported by images acquired using scanning acoustic microscopy, which showed that circumferential cracks and pin-holes were only found on areas of the coating that had become delaminated by multiple particle impacts during the erosion tests.
diamond, erosion, fracture, impact, scanning acoustic microscopy, coating, stresses
1478-6435
285-310
Wheeler, D.W.
d276c145-56e0-48d0-ae37-a84dda92a947
Wood, R.J.K.
d9523d31-41a8-459a-8831-70e29ffe8a73
Wheeler, D.W.
d276c145-56e0-48d0-ae37-a84dda92a947
Wood, R.J.K.
d9523d31-41a8-459a-8831-70e29ffe8a73

Wheeler, D.W. and Wood, R.J.K. (2009) The fracture of diamond coatings by high velocity sand erosion. Philosophical Magazine, 89 (3), 285-310. (doi:10.1080/14786430802616557).

Record type: Article

Abstract

This paper describes a study of the behaviour of diamond coatings when subjected to solid particle erosion from sand particles. The coatings were deposited by chemical vapour deposition (CVD) onto tungsten substrates and tested using a high velocity air–sand erosion test facility. The erosion tests were conducted using particle impact velocities of between 33 and 268 m/s. Examination of the eroded test specimens showed that the principal damage features were circumferential cracks and pin-holes. Comparison with Hertz impact theory revealed that the measured circumferential crack diameters were more than double the predicted Hertzian contact diameter. Moreover, a trend of increasing circumferential crack diameter with coating thickness, which is not predicted by Hertz, was found. Instead, the crack diameters showed good agreement with those predicted by the theory of stress wave reinforcement, which is more commonly associated with liquid impact damage of brittle materials. During impact, the bulk compression and shear waves are reflected at the rear surface of debonded regions of the coating to return to the front surface and reinforce the Rayleigh surface wave, which generates a tensile stress. Where this stress exceeds the local tensile strength of the coating, a ring of cracks surrounding the area of impact is created. The results from the present study, therefore, suggest that stress wave reflection is responsible for the formation of the cracks at locally debonded regions of the coating. This hypothesis was supported by images acquired using scanning acoustic microscopy, which showed that circumferential cracks and pin-holes were only found on areas of the coating that had become delaminated by multiple particle impacts during the erosion tests.

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More information

Published date: January 2009
Additional Information: The National Centre for Advanced Tribology at Southampton (nCATS), School of Engineering Sciences, University of Southampton, Highfield, Southampton SO17 1BJ, UK
Keywords: diamond, erosion, fracture, impact, scanning acoustic microscopy, coating, stresses
Organisations: Engineering Mats & Surface Engineerg Gp

Identifiers

Local EPrints ID: 64815
URI: https://eprints.soton.ac.uk/id/eprint/64815
ISSN: 1478-6435
PURE UUID: 83715df8-51e2-4b8e-be5e-af8ee3b1b694
ORCID for R.J.K. Wood: ORCID iD orcid.org/0000-0003-0681-9239

Catalogue record

Date deposited: 21 Jan 2009
Last modified: 14 Mar 2019 01:52

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