Solid particle erosion of CVD diamond coatings
Solid particle erosion of CVD diamond coatings
Diamond coatings deposited on both tungsten and tungsten carbide-cobalt substrates were investigated. The thickness of the coatings ranged from 10 to 200mm and the samples were supplied in both as-grown and lapped forms. The coatings were characterised using a number of techniques including X-ray diffraction, Raman spectroscopy, indentation, surface profilometry as well as optical and electron microscopy. The grain size and surface roughness were also measured for comparison with the size of damage features generated in the erosion studies. The results revealed that the coatings were close to natural diamond in both chemical (i.e. negligible graphite content) and mechanical (i.e. hardness and elastic modulus) characteristics.
In the erosion studies, two test facilities were used: a water-sand slurry rig and a high velocity air-sand rig. The erodent used was silica sand with average diameters 135mm, 194mm and 235mm with the velocities in the range 16 to 268 m s-1 and 90° nominal impact angle. The erosion rates were plotted against particle kinetic energy and compared with those for cemented tungsten carbide and stainless steel. At 268 m s-1, the most erosion-resistant coating was a 120mm lapped sample, which had an erosion resistance more than 10 times that of cemented WC-7Ni. The coatings were examined both pre- and post-test by scanning electron microscopy in order to determine the degradation mechanisms. Ultrasonic imaging and taper polishing of eroded samples were also performed to reveal sub-surface damage and to elucidate its contribution to coating degradation. The results suggest that the erosion mechanism consists of a three-stage process consisting of micro-chipping, development of pin-holes and interfacial debonding, followed by catastrophic failure.
University of Southampton
Wheeler, David William
8fd7733b-8f2a-47d0-8878-dbe4d570037d
2001
Wheeler, David William
8fd7733b-8f2a-47d0-8878-dbe4d570037d
Wheeler, David William
(2001)
Solid particle erosion of CVD diamond coatings.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
Diamond coatings deposited on both tungsten and tungsten carbide-cobalt substrates were investigated. The thickness of the coatings ranged from 10 to 200mm and the samples were supplied in both as-grown and lapped forms. The coatings were characterised using a number of techniques including X-ray diffraction, Raman spectroscopy, indentation, surface profilometry as well as optical and electron microscopy. The grain size and surface roughness were also measured for comparison with the size of damage features generated in the erosion studies. The results revealed that the coatings were close to natural diamond in both chemical (i.e. negligible graphite content) and mechanical (i.e. hardness and elastic modulus) characteristics.
In the erosion studies, two test facilities were used: a water-sand slurry rig and a high velocity air-sand rig. The erodent used was silica sand with average diameters 135mm, 194mm and 235mm with the velocities in the range 16 to 268 m s-1 and 90° nominal impact angle. The erosion rates were plotted against particle kinetic energy and compared with those for cemented tungsten carbide and stainless steel. At 268 m s-1, the most erosion-resistant coating was a 120mm lapped sample, which had an erosion resistance more than 10 times that of cemented WC-7Ni. The coatings were examined both pre- and post-test by scanning electron microscopy in order to determine the degradation mechanisms. Ultrasonic imaging and taper polishing of eroded samples were also performed to reveal sub-surface damage and to elucidate its contribution to coating degradation. The results suggest that the erosion mechanism consists of a three-stage process consisting of micro-chipping, development of pin-holes and interfacial debonding, followed by catastrophic failure.
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Published date: 2001
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Local EPrints ID: 464349
URI: http://eprints.soton.ac.uk/id/eprint/464349
PURE UUID: d59f8939-e0ba-4441-95a6-8549edab0529
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Date deposited: 04 Jul 2022 22:19
Last modified: 16 Mar 2024 19:26
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Author:
David William Wheeler
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