Interfacial bonding controls friction in diamond–rock contacts
File(s)
Accepted version
Author(s)
Type
Journal Article
Abstract
Understanding friction at diamond–rock interfaces is crucial to increase the energy efficiency
of drilling operations. Harder rocks usually are usually more difficult to drill; however, poor
performance is often observed for polycrystalline diamond compact (PDC) bits on soft calcitecontaining rocks, such as limestone. Using macroscale tribometer experiments with a
diamond tip, we show that soft limestone rock (mostly calcite) gives much higher friction
coefficients compared to hard granite (mostly quartz) in both humid air and aqueous
environments. To uncover the physicochemical mechanisms that lead to higher kinetic friction
at the diamond–calcite interface, we employ nonequilibrium molecular dynamics simulations
(NEMD) with newly developed Reactive Force Field (ReaxFF) parameters. In the NEMD
simulations, higher friction coefficients are observed for calcite than quartz when water
molecules are included at the diamond–rock interface. We show that the higher friction in
water-lubricated diamond–calcite than diamond–quartz interfaces is due to increased
interfacial bonding in the former. For diamond–calcite, the interfacial bonds mostly form
through chemisorbed water molecules trapped between the tip and the substrate, while mainly
direct tip-surface bonds form inside diamond–quartz contacts. For both rock types, the rate of
interfacial bond formation increases exponentially with pressure, which is indicative of a
stress-augmented thermally activated process. The mean friction force is shown to be linearly
dependant on the mean number of interfacial bonds during steady-state sliding. The
agreement between the friction behaviour observed in the NEMD simulations and tribometer
experiments suggests that interfacial bonding also controls diamond–rock friction at the
macroscale. We anticipate that the improved fundamental understanding provided by this
study will assist in the development of bit materials and coatings to minimise friction by
reducing diamond–rock interfacial bonding
of drilling operations. Harder rocks usually are usually more difficult to drill; however, poor
performance is often observed for polycrystalline diamond compact (PDC) bits on soft calcitecontaining rocks, such as limestone. Using macroscale tribometer experiments with a
diamond tip, we show that soft limestone rock (mostly calcite) gives much higher friction
coefficients compared to hard granite (mostly quartz) in both humid air and aqueous
environments. To uncover the physicochemical mechanisms that lead to higher kinetic friction
at the diamond–calcite interface, we employ nonequilibrium molecular dynamics simulations
(NEMD) with newly developed Reactive Force Field (ReaxFF) parameters. In the NEMD
simulations, higher friction coefficients are observed for calcite than quartz when water
molecules are included at the diamond–rock interface. We show that the higher friction in
water-lubricated diamond–calcite than diamond–quartz interfaces is due to increased
interfacial bonding in the former. For diamond–calcite, the interfacial bonds mostly form
through chemisorbed water molecules trapped between the tip and the substrate, while mainly
direct tip-surface bonds form inside diamond–quartz contacts. For both rock types, the rate of
interfacial bond formation increases exponentially with pressure, which is indicative of a
stress-augmented thermally activated process. The mean friction force is shown to be linearly
dependant on the mean number of interfacial bonds during steady-state sliding. The
agreement between the friction behaviour observed in the NEMD simulations and tribometer
experiments suggests that interfacial bonding also controls diamond–rock friction at the
macroscale. We anticipate that the improved fundamental understanding provided by this
study will assist in the development of bit materials and coatings to minimise friction by
reducing diamond–rock interfacial bonding
Date Issued
2021-08-16
Date Acceptance
2021-08-05
Citation
The Journal of Physical Chemistry C: Energy Conversion and Storage, Optical and Electronic Devices, Interfaces, Nanomaterials, and Hard Matter, 2021, 125, pp.18395-18408
ISSN
1932-7447
Publisher
American Chemical Society
Start Page
18395
End Page
18408
Journal / Book Title
The Journal of Physical Chemistry C: Energy Conversion and Storage, Optical and Electronic Devices, Interfaces, Nanomaterials, and Hard Matter
Volume
125
Copyright Statement
© 2021 American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form in J. Phys. Chem. C, after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acs.jpcc.1c02857
Sponsor
Baker Hughes Oilfield Operations LLC
Royal Academy Of Engineering
Engineering & Physical Science Research Council (EPSRC)
Identifier
https://pubs.acs.org/doi/10.1021/acs.jpcc.1c02857
Grant Number
4510848438
RF\201920\19\269
EP/N025954/1
Subjects
Science & Technology
Physical Sciences
Technology
Chemistry, Physical
Nanoscience & Nanotechnology
Materials Science, Multidisciplinary
Chemistry
Science & Technology - Other Topics
Materials Science
REACTIVE FORCE-FIELD
TOTAL-ENERGY CALCULATIONS
STICK-SLIP VIBRATIONS
MOLECULAR-DYNAMICS
DEPENDENT FRICTION
TRIBOLOGICAL PERFORMANCE
SURFACE-ROUGHNESS
ROOT CAUSE
WEAR
WATER
03 Chemical Sciences
09 Engineering
10 Technology
Physical Chemistry
Publication Status
Published
Date Publish Online
2021-08-16