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

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

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 Chemical

Developments Surface

Engineering

Predicting Improving

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

Surface Engineering Technologies

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

DLC - Diamond-like carbon coatings have a mixture of sp3 and sp2 bonds

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

Types of DLC Coatings

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

Types of DLC Coatings

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 (ta-C:H): typically around 30% hydrogen content and variable fraction of sp3/sp2 bonds

a-C

a-C:H

ta-C

ta-C:H

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

sp3 (%)

H (%)

Density (g cm-3)

Hardness (GPa)

Diamond 100 0 3.5 100

Graphite 0 0 2.3

Glassy C 0 0 1.3-1.5 3

Evaporated C 0 0 1.9 3

Sputtered C 5 0 2.2

ta-C 80-88 0 3.1 80

ta-C:H 70 30 2.4 50

a-C:H hard 40 30-40 1.6-2.2 10-20

a-C:H soft 60 40-60 1.2-1.6 <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)

PVD CVD

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)

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

Modified Chemical Vapor Deposition

Plasma

Inert gas Process gas

RF power

Water cooled electrode

Part to be coated To vacuum pump

Process chamber

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

Physical Vapor Deposition

Limitations: • line-of-sight transfer of deposited material • selection of the best PVD technology may require some experience

and/or experimentation

PVD/PECVD Coating Platform

• Full scale industrial components and R&D samples • Fully automated • Repeatable coating composition

DLC Deposition

Metal-doped DLC

Amorphous hydrogenated

DLC

Silicon-doped DLC

Sputtered DLC

Hydrogen-free DLC

Type WC-C:H a-C:H a-C:H-Si a-C ta-C

Method PVD/PECVD PECVD PECVD PVD PVD

Hardness (HV0.05) 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 +++ +++ ++ +++ ++

[IHI Hauzer Techno Coating B.V., DLC Coating: www.hauzertechnocoating.com/en/plasma-coating-explained/dlc-coating/]

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

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

• gate valves

• gate seats

• ball valves

• pumps

• drill bits

• bearings

• components of blow out preventers

• interfaces under vibrations

Tribology in Oil and Gas Applications

Functionality – Reduced Corrosion

Material selection

Corrosion prediction

Failure Analysis

Asset Integrity Management

Inspection Management

Integrity Management

Project Quality Management

Corrosion Management

Reliability & Maintenance Management

Complex degradation mechanism which involves electrochemical processes, mechanical processes and

interactive/synergistic processes

Erosion-Corrosion

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]

Functionality – Anti-fouling

CaCO3 or BaSO4 Fluid flow

Foulant deposition Deposit

removal

Fouling substrate

Deposit

Fouling

Blocking of pipes and valves

Stoppages in production

Underdeposit corrosion

Functionality – Anti-fouling

Mineral Scale Inhibition

Chemical treatment

Bulk and surface

Inhibitors

Regular

Green

Non-chemical treatment

Metal Surfaces

Other surfaces

• Surface Engineering • Coatings • DLC

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

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

[K. Haugen, 0. Kvernvold, A. Ronold, R. Sandberg, Wear 186-187 (1995) 179-188]

Surface Design for Impact/Erosion

30 60 90

Impact Angle, (degrees)

Ero

sio

n

Ductile

Brittle

• ductile materials experience high erosion rates around 20° to 30° impact angle

• brittle materials experience high erosion rates at 90° impact angle

Surface Design for Impact/Erosion

Ductile substrate

Coating

Ductile substrate Brittle substrate Ploughing Cracking

Surface engineered

solution

Hard wear resistant thin coating for ductile substrate protection

Ductile substrate for impact energy dissipation

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 (pre-scaled surfaces show much higher growth rates than clean surfaces)3

1. W Cheong, A Neville, P H Gaskell, S Abbott, 2008, SPE 114082. 2. F-A. Setta, A. Neville, Desalination, 281 (2011), pp. 340–347. 3. M. Ciolkowski. A. Neville, X. Hu, E. Mavredaki, SPE, 2012, pp. 254-263.

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.

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.

Internal Bores

• 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.

• 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)

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

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

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).

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.

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.