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DLC coatings in oil and gas production


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Diamond-like carbon (DLC) coatings are recognized in many sectors as a promising way of controlling wear and the corrosion performance of components. DLC coatings are unique in the sense that they are a diverse group of amorphous carbon films with a wide range of engineering properties. This allows the tailoring of DLC coating properties for specific applications by choosing suitable deposition method and adjusting their architectures. In this presentation, three qualities of DLC coatings with the greatest relevance for oil and gas applications are identified; these include: (i) improved tribological properties; (ii) reduced corrosion; and (iii) anti-fouling properties. Successful applications of DLC coatings in petroleum production are reviewed, giving examples of protection against erosion-corrosion and fouling in flow control devices and in components where protection of internal surfaces in cylindrical structures is required. The application of DLC coatings in the oil and gas sectors is still very low, compared to other sectors; therefore, it is expected that demand for this type functional coatings has potential for steady growth.

Published in: Technology

DLC coatings in oil and gas production

  1. 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 *
  2. 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. 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. 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. 5. Surface Engineering Technologies
  6. 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. 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. 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. 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. 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. 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. 12. Chemical Vapor Deposition
  13. 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. 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. 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. 16. PVD/PECVD Coating Platform • Full scale industrial components and R&D samples • Fully automated • Repeatable coating composition
  17. 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:]
  18. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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.