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Wear modelling of diamond-like carbon coatings against steel in deionised water

Wear modelling of diamond-like carbon coatings against steel in deionised water
Wear modelling of diamond-like carbon coatings against steel in deionised water
Diamond-Like Carbon (DLC) coatings are thin protective surface coatings used to reduce friction and minimise wear in a wide range of applications. The focus of this work is the use of DLC coatings within Rolls-Royce’s pressurised water reactors. A strong understanding of material behaviour in this environment is compulsory due to the stringent safety requirements of the nuclear industry. Wear testing of a range of commercial DLC coatings against steel in water, and the dependence of the tribology on normal load, sliding distance, and environmental species, was examined. Wear depth was observed to increase with normal load, and increase non-linearly with sliding distance. Uniquely, it was suggested that the tribology of a DLC coating in water was controlled by the velocity accommodation mode (VAM) of the transfer layer. When interfacial sliding was the dominant VAM, the carbonaceous transfer layer was present at all times, and a low specific wear rate was observed. When shear and recirculation of debris was the dominant VAM, the carbonaceous transfer layer initially present was replaced by iron oxide species, and a high specific wear rate was observed as a result of a three-body mechanism involving hematite.

Two individual wear models were developed to predict the wear depth of a DLC coating sliding against steel in water. Each model represents a novel extension to the current literature regarding the modelling of wear. Firstly, an analytical differential equation was derived to predict the wear depth of a ball and a flat surface, in relation to any phenomenological law for wear volume. Secondly, a unique formulation of an incremental wear model for an arbitrary geometry was developed for a DLC coating which included the growth of a transfer layer. An efficient methodology was presented to allow fast integration of the equations whilst damping numerical instabilities. A comparison between the analytic and computational wear models showed a strong agreement in the model predictions, with a comparative error of less than 5%.
Sutton, Daniel Christopher
b7a9d943-e954-44a2-b070-4e9f3f5e5d4f
Sutton, Daniel Christopher
b7a9d943-e954-44a2-b070-4e9f3f5e5d4f
Wood, Robert
d9523d31-41a8-459a-8831-70e29ffe8a73

Sutton, Daniel Christopher (2014) Wear modelling of diamond-like carbon coatings against steel in deionised water. University of Southampton, Engineering and the Environment, Doctoral Thesis, 219pp.

Record type: Thesis (Doctoral)

Abstract

Diamond-Like Carbon (DLC) coatings are thin protective surface coatings used to reduce friction and minimise wear in a wide range of applications. The focus of this work is the use of DLC coatings within Rolls-Royce’s pressurised water reactors. A strong understanding of material behaviour in this environment is compulsory due to the stringent safety requirements of the nuclear industry. Wear testing of a range of commercial DLC coatings against steel in water, and the dependence of the tribology on normal load, sliding distance, and environmental species, was examined. Wear depth was observed to increase with normal load, and increase non-linearly with sliding distance. Uniquely, it was suggested that the tribology of a DLC coating in water was controlled by the velocity accommodation mode (VAM) of the transfer layer. When interfacial sliding was the dominant VAM, the carbonaceous transfer layer was present at all times, and a low specific wear rate was observed. When shear and recirculation of debris was the dominant VAM, the carbonaceous transfer layer initially present was replaced by iron oxide species, and a high specific wear rate was observed as a result of a three-body mechanism involving hematite.

Two individual wear models were developed to predict the wear depth of a DLC coating sliding against steel in water. Each model represents a novel extension to the current literature regarding the modelling of wear. Firstly, an analytical differential equation was derived to predict the wear depth of a ball and a flat surface, in relation to any phenomenological law for wear volume. Secondly, a unique formulation of an incremental wear model for an arbitrary geometry was developed for a DLC coating which included the growth of a transfer layer. An efficient methodology was presented to allow fast integration of the equations whilst damping numerical instabilities. A comparison between the analytic and computational wear models showed a strong agreement in the model predictions, with a comparative error of less than 5%.

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Published date: March 2014
Organisations: University of Southampton, nCATS Group

Identifiers

Local EPrints ID: 366526
URI: http://eprints.soton.ac.uk/id/eprint/366526
PURE UUID: a696751d-621f-4e2b-ac72-ec3891436447
ORCID for Robert Wood: ORCID iD orcid.org/0000-0003-0681-9239

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Date deposited: 15 Oct 2014 12:39
Last modified: 06 Jun 2018 13:06

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Contributors

Author: Daniel Christopher Sutton
Thesis advisor: Robert Wood ORCID iD

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