DLC coatings have properties that make them useful for oil and gas applications. DLC coatings can be deposited using CVD or PVD techniques. Key properties of DLC coatings include high hardness, low friction, and corrosion resistance. These properties allow DLC coatings to improve tribology, reduce corrosion, and prevent fouling in oil and gas production equipment and components. Widespread use of DLC coatings in oil and gas is still limited but growing due to benefits for components like valves, pumps, and pipes.

1. DLC Coatings in Oil and Gas Production
Tomasz Liskiewicz* and Amal Al-Borno
Charter Coating Service (2000) Ltd.
No. 6, 4604 13th Street NE
Calgary, AB, T2E 6P1, Canada
* tliskiewicz@chartercoating.com

2. Outline
• Background
• Types and properties of DLC coatings
• Deposition techniques
• Surface functionality of DLC coatings
• DLC coatings in oil and gas applications
•
- tribology
•
- corrosion
•
- anti-fouling
• Summary

3. Material Integrity Management in Oil and Gas
Asset Integrity management
• improves plant reliability and safety
• whilst reducing un-planned maintenance and repair costs
Materials
Performance
Monitoring
Modelling
Predicting
Chemical
Developments
Surface
Engineering
Improving

4. Role of Surface Engineering
What is Surface Engineering?
→ Engineer’s perspective
“… makes possible the design
and manufacture of
engineering components with
combination of bulk and surface
properties unobtainable in a
single monolithic material”
Bell, 1985

5. Surface Engineering Technologies

6. What DLC Coating is?
• DLC is a generic term describing a range of amorphous carbon
• Diamond & graphite the most well-known allotropes of carbon
different type of bonding between carbon atoms
Diamond
• hard
• sp3 hybridized bonds
resulting in strong C-C
bonds
Graphite
• soft and slippery
• sp2 hybridized bonds forming
weak bonding between the
atomic planes
DLC - Diamond-like carbon coatings have a mixture
of sp3 and sp2 bonds

7. Types of DLC Coatings
The ratio of sp3/sp2 bonds
and the hydrogen content
in the coating determine
the properties
of DLC films

8. Types of DLC Coatings
a-C
a-C:H
ta-C
ta-C:H
Amorphous, non-hydrogenated carbon (a-C)
coatings: dominated by sp2 bonds and have
typically less than 1% of hydrogen
Hydrogenated amorphous carbon (a-C:H) films:
varying amounts of sp3/sp2 bonds and hydrogen
content resulting in a wide range of properties
Tetrahedral amorphous carbon (ta-C): the highest
fraction of sp3 bonds; synthesized typically from
solid graphite - do not contain a much hydrogen;
closest to diamond
Hydrogenated tetrahedral amorphous carbon (taC:H): typically around 30% hydrogen content and
variable fraction of sp3/sp2 bonds

9. Properties of DLC Coatings
The hydrogen content affects the structure of DLC coatings and it
can vary from less than 1% in non-hydrogenated DLC films to
about 60% in hydrogenated DLC films
Diamond
Graphite
Glassy C
Evaporated C
Sputtered C
ta-C
ta-C:H
a-C:H hard
a-C:H soft
sp3
(%)
100
0
0
0
5
80-88
70
40
60
H
(%)
0
0
0
0
0
0
30
30-40
40-60
Density
(g cm-3)
3.5
2.3
1.3-1.5
1.9
2.2
3.1
2.4
1.6-2.2
1.2-1.6
Hardness
(GPa)
100
3
3
80
50
10-20
<10

10. Deposition Techniques
DLC coatings are metastable materials and deposition methods
of DLC films are non-equilibrium processes where energetic ions
interact with the surface.
• Chemical Vapor Deposition (CVD)
• Physical Vapor Deposition (PVD)
CVD
PVD

11. Chemical Vapor Deposition
Deposition of a solid coating on a heated surface from a chemical
reaction in a vapour phase
• heat-activated process
• not restricted to line-of-sight deposition
• deep recesses, holes and other difficult 3D configurations can be
coated
Limitations:
• major disadvantage: temperatures of 600oC and above so many
substrates are not thermally stable at these temperatures
• chemical precursors (often hazardous and toxic)

12. Chemical Vapor Deposition

13. Modified Chemical Vapor Deposition
PECVD (Plasma Enhanced CVD)
• radio frequency (RF) is used to induce plasma in the deposition gas
• as a result higher deposition rate is achieved at relatively low
temperature
Inert gas
Process gas
Process chamber
RF power
Plasma
Water cooled electrode
To vacuum pump
Part to be coated

14. Physical Vapor Deposition
Material is vaporized from a solid source in the form of atoms or
molecules, transported in the form of a vapor through a vacuum or
low pressure gaseous environment to the substrate where it
condenses.
•
•
•
•
•
typical PVD film thickness: a few nanometers to 10 micrometers
can be used to deposit films of elements and compounds
low deposition temperature: 200-300oC
can coat prior heat treated steels, minimal component distortion
more environmentally friendly than traditional coating processes
such as electroplating

15. Physical Vapor Deposition
Limitations:
• line-of-sight transfer of deposited material
• selection of the best PVD technology may require some experience
and/or experimentation

16. PVD/PECVD Coating Platform
• Full scale industrial components and R&D samples
• Fully automated
• Repeatable coating composition

17. DLC Deposition
Amorphous
Metal-doped
Silicon-doped
hydrogenated
DLC
DLC
DLC
Type
Sputtered
DLC
Hydrogenfree DLC
WC-C:H
a-C:H
a-C:H-Si
a-C
ta-C
PVD/PECVD
PECVD
PECVD
PVD
PVD
800-2200
1500-3500
1500-2500
2000-4000
3000-7000
Coefficient of friction
0.1-0.2
0.05-0.15
0.05-0.1
0.05-0.1
0.02-0.1
Internal stress
(GPa/µm)
0.1-1.5
1-3
1-3
2-6
1-3
Thickness (µm)
1-10
1-10
1-10
1-3
1-3
Industrial use
yes
yes
yes
yes
yes
Mass production
+++
+++
++
+++
++
Method
Hardness (HV0.05)
[IHI Hauzer Techno Coating B.V., DLC Coating: www.hauzertechnocoating.com/en/plasma-coating-explained/dlc-coating/]

18. Functionality of DLC coatings
Functionality can be tailored to specific applications
• General Properties: high hardness, low friction, electrical
insulation, anti-corrosion, chemical inertness, optical
transparency, biological compatibility, ability to absorb
photons selectively, smoothness, and resistance to wear.
Properties most relevant in oil & gas production:
1. Improved tribology
2. Reduced corrosion
3. Anti-fouling

19. Functionality – Improved Tribology
Tribology is the science and engineering of interacting surfaces in
relative motion
• Word tribology derives from the Greek verb tribo “Ι rub”
• Solves problems of the reliability at the interface
• Includes the study and application
of the principles of:
- friction,
- lubrication
- wear

20. Tribology in Oil and Gas Applications
• gate valves
• gate seats
• ball valves
• pumps
• drill bits
• bearings
• components of blow out preventers
• interfaces under vibrations

21. Functionality – Reduced Corrosion
Integrity
Management
Inspection
Management
Asset Integrity
Management
Corrosion
Management
Material
selection
Project Quality
Management
Reliability &
Maintenance
Management
Corrosion
prediction
Failure Analysis

22. Erosion-Corrosion
Complex degradation mechanism which involves
electrochemical processes, mechanical processes and
interactive/synergistic processes
TVL = C’ + CE + E + EC
TVL – total volume loss
C’ – corrosion under static conditions
CE – enhancement of corrosion due to erosion
E – erosion
EC - enhancement of erosion due to corrosion
[V.A.D. Souza, A. Neville, Wear 263 (2007) 339-346]

23. Functionality – Anti-fouling
CaCO3 or BaSO4
Fluid flow
Foulant
deposition
Deposit
removal
Deposit
Fouling substrate
Fouling
Blocking of pipes
and valves
Stoppages in
production
Underdeposit
corrosion

24. Functionality – Anti-fouling
Mineral Scale
Inhibition
Chemical
treatment
Bulk and
surface
Non-chemical
treatment
Inhibitors
Regular
Green
Metal
Surfaces
Other
surfaces
• Surface Engineering
• Coatings
• DLC

25. DLC Coatings in Oil and Gas
Applications:
• Protection against erosion-corrosion
• Protection against fouling
• Protection of internal bores
• Protection of flow control devices
5 μm x 5 μm

26. Surface Design for Impact/Erosion
• Toughness
• Elasticity (sufficiently elastic to deflect and absorb impact energy)
• Adhesion (flexible well-adhered coating/substrate interface )
Normal impact angle: the coating should be sufficiently elastic to
avoid high-stress peaks
Inclined impact angle: the coating should be hard enough to avoid
grooving

27. Surface Design for Impact/Erosion
Ductile

Erosion
• ductile materials experience
high erosion rates around
20° to 30° impact angle
•
Brittle
30
60
Impact Angle,  (degrees)
90
[K. Haugen, 0. Kvernvold, A. Ronold, R. Sandberg, Wear 186-187 (1995) 179-188]
brittle materials experience
high erosion rates at 90°
impact angle

28. Surface Design for Impact/Erosion
Ductile substrate
Ploughing
Brittle substrate
Cracking
Surface
engineered
solution
Coating
Ductile substrate
Hard wear resistant thin
coating for ductile substrate
protection
Ductile substrate for impact
energy dissipation

29. Anti-fouling Applications
Key parameters for surface design
strategy against scale formation:
• Surface energy (wettability)1
• Relationship between the time
constant for bulk and surface
deposition2
• Induction time and saturation (prescaled surfaces show much higher
growth rates than clean surfaces)3
1.
2.
3.
W Cheong, A Neville, P H Gaskell, S Abbott, 2008, SPE 114082.
F-A. Setta, A. Neville, Desalination, 281 (2011), pp. 340–347.
M. Ciolkowski. A. Neville, X. Hu, E. Mavredaki, SPE, 2012, pp. 254-263.

30. Anti-fouling Applications
The surface is acting as a nucleation site for crystals to
heterogeneously initiate and grow
This process can be controlled by surface coatings
DLC offer excellent potential for controlling calcium carbonate
formation and has a profound effect on the initial stages of scale
formation*
* W.C. Cheong, P.H. Gaskell, A. Neville, Journal of Crystal Growth, 363 (2013), pp. 7-21.

31. Internal Bores
• Drawback of PVD technology: line-of-sight deposition
• PECVD equipment handles situation better but struggles with
large length:diameter situations
Proprietary technology developed around 2005 to address tubular
components
W.J. Boardman, A.W. Tudhope, R.D. Mercado,
Method and system for coating internal surfaces of
prefabricated process piping in the field, United
States Patent 7300684.

32. Internal Bores
• Plasma generated within the pipe itself
• coating deposited on the internal wall of the pipe
• multilayer Si-DLC coating up to 50 microns thick was generated
• internal bores and enclosures up to 3 meters and aspect ratio of
1:40 (length:diameter)
•
•
•
D. Lusk, M. Gore, W. Boardman, T. Casserly, K. Boinapally, M. Oppus, D. Upadhyaya, A. Tudhope, M. Gupta,
Y. Cao, S. Lapp, Thick DLC films deposited by PECVD on the internal surface of cylindrical substrates,
Diamond and Related Materials, 17 (2008), pp. 1613-1621.
W. Boardman, K. Boinapally, T. Casserly, M. Gupta, C. Dornfest, D. Upadhyaya, Y. Cao, M. Oppus, Corrosion
and Mechanical Properties of Diamond-like Carbon Films Deposited Inside Carbon Steel Pipes, NACE
Corrosion, 2008, Paper 08032, pp. 1-11.
M. Gore, W. Boardman, Emergence of Diamond-like Carbon Technology: One Step Closer to OCTG
Corrosion Prevention, SPE International Conference on Oilfield Corrosion, 2010, Paper 131120, pp.1-9.

33. Flow Control Devices
DLC coatings - efficient solution for a variety of flow control devices,
e.g. heart valves components and fuel injection valves
The same properties relevant to flow control devices in oil and gas
DLCs especially cost effective on high value components
(crucial for operation and safety of equipment and personnel)
Examples:
shut-off and knife gates, choke, check, stop, control, balancing,
diaphragm, n-way, pneumatically actuated and butterfly valves

34. Flow Control Devices
DLC coatings provide durability of flow control devices by:
• Corrosion protection and chemical resistance to harsh media
• Superior mechanical properties against abrasive and adhesive
wear (toughness and hardness)
• Low coefficient of friction to increase trouble-free function and
increase precision (elimination of adhesion cold welding and
galling)
• Anti-fouling properties preventing biological growth

35. Opportunities
• Low penetration of oil and gas sector - significant opportunity
to tap into existing expertise from other industry sectors
where DLC coatings are well established, e.g. automotive;
• Increased functionality of existing components and systems
can be achieved by application of DLC coatings maximizing
their reliability;
• With their superior corrosion and mechanical properties, DLC
coatings can provide increased efficiency and energy savings;
• Increased safety can be achieved by application of more
reliable surface technologies;
• PECVD is a constantly developing field with novel emerging
applications and technologies (e.g. low temperature
deposition DLC films on polymers).

36. Challenges
• Achieving deposition process repeatability leading to perfect
coating reproducibility (consistent quality);
• Achieving more stable and less sensitive processes (wider
process windows);
• Developing technologies and methods for large scale/large
area DLC deposition;
• Bringing down capital investment costs and optimizing the
operational cost models;
• Developing further science behind DLC coatings deposition
and application for improved understanding of their
functionality.

37. Conclusions
• DLC coatings - diverse group of amorphous carbon films with
a wide range of engineering properties;
• Tailoring of DLC coating properties for specific applications by
designing coating architecture;
• Three qualities of DLC coatings with the greatest relevance for
oil and gas applications have been identified, these include:
(i) Improved tribological properties; (ii) Reduced corrosion;
and (iii) Anti-fouling properties;
• Application of DLC coatings in oil and gas sector is still very
low, comparing to other sectors - it is expected that demand
for this type functional coatings will grow.