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Atmospheric Plasma Spray

Atmospheric Plasma Spray. Hossein Movla 1,* with significant contributions from Jafar Fathi 2 , Sirous Khorram 3 , Mohammad Ali Mohammadi 2,4 , Arash Nikniazi 1 , Foozieh Sohrabi 2 And With Special Thanks to Mohammad Soltanpour

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Atmospheric Plasma Spray

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  1. Atmospheric Plasma Spray Hossein Movla1,* with significant contributions from JafarFathi2, SirousKhorram3, Mohammad Ali Mohammadi2,4, ArashNikniazi1, FooziehSohrabi2 And With Special Thanks to Mohammad Soltanpour 1 Department of Solid State Physics, Faculty of Physics, The University of Tabriz, Tabriz 2 Department of Atomic and Molecular Physics, Faculty of Physics, The University of Tabriz, Tabriz 3 Plasma lab, Research Institute for Applied Physics and Astronomy (RIAPA), The University of Tabriz 4 Sahand Plasma Focus Lab, Research Institute for Applied Physics and Astronomy (RIAPA), The University of Tabriz, Tabriz

  2. Fourth state of matter • Gas-like • Consists of neutral atoms/molecules, ions, and electrons • High energy, highly reactive substance • Electrons have 10,000 K worth of energy • Activates surfaces What is Plasma?

  3. Gas discharge plasma Electric field causes • acceleration of electrons • electron-impact ionization • current to flow through gas

  4. Negative and positive charges balance each other • Plasma is electrically neutral. Property known as quasi-neutrality • Plasma is electrically conductive • Electrical conductivity comparable to that of metals at room temperature Electrical properties of plasma

  5. Thermal and nonthermal plasmas • If Te ≈ Tionthen we have a thermal plasma • If Te» Tionthen plasma is nonthermal or nonequilibrium or cold plasma • In a thermal plasma, there is Local Thermodynamic Equilibrium (LTE) • LTE requires… • Te ≈ Tion • Excitation equilibrium • Chemical equilibrium Thermal and nonthermal plasma

  6. Natural plasma • Lightning strikes, high pressure, high luminosity • Aurora borealis, low pressure, low luminosity • Man-made plasma • Flames, low ionisation level • Glow discharge, low pressure 1 eV = 7740 K Natural and man-made plasma Source: Boulos et al. “Thermal Plasmas Fundamentals and Applications V. 1, 1994, Vol. 1”

  7. Non-equilibrium plasma • Electrons at 10-20,000 ºC • Ions, molecules at 60-80 ºC • Relatively uniform energy distribution • Does not require special vacuum chambers like low pressure plasma Atmospheric Plasma

  8. D.C. Discharges • Corona • High V, Low I • At sharp point • Glow Discharge • V ~ 100’s V, I ~mA’s • Cathode fall 150-550 V, depends on gas and cathode material • Arc • 10’s of volts, A-kA • Cathode spots Physics of the Vacuum Arc – The Arc Discharge

  9. Paschen curves breakdown voltage • At atmospheric pressure: • Breakdown voltage is very high • Breakdown mechanism is often streamer breakdown (spatially nonuniform) Breakdown voltage increases with the product of gas pressure & electrode separation Gas discharge plasma Schütze et al. 1998

  10. Dissociation • N2↔ N + N • O2↔ O + O • Recombination • N + O ↔ NO • N + O2↔ N2 • Ionization • NO ↔ NO+ + e- • N2↔ N2+ + e- • N ↔ N+ + e- • N+ ↔ N++ + e- • O2↔ O2+ + e- • O ↔ O+ + e- • O+ ↔ O++ + e- • Ar↔ Ar+ + e- • Ar+↔Ar++ + e- Composition of a plasma gasGas mixtures - Air

  11. Glow • ‘individual’ secondary emission of electrons by: • Ions (depends on ionization energy, not kinetic energy) • Excited Atoms • Photons • Not enough! • Multiplication in avalanche near cathode • Need high cathode drop (100’s of V’s) • Used in sputtering to accelerate bombarding ions into ‘target’ cathode Arc • Collective electron emission • Current at cathode concentrated into cathode spots • Combination of thermionic and field emission of electrons • Can get sufficient electron current • Low cathode voltage drop (10’s of V’s) • High temp. in cathode spot gives high local evaporation rate – used in vacuum arc deposition Difference between Glow and Arc – cathode electron emission process

  12. High intensity arcs • Free burning arcs, e.g. steel furnaces • Wall stabilized arcs, e.g. arc lamp (lab studies) • Convection-stabilized arcs, e.g. hot button plasma torches • Magnetically stabilized arcs, e.g. plasma torches with magnetic field • Thermal RF discharge • Capacitive coupling: HF electrical field • Inductive coupling: Time-varying magnetic field • Microwave discharge • The discharge is part of the MW circuit. Impacts plasma configuration and volume • Low pressure operation results in deviation from equilibrium • More recently, stable higher pressure plasma possible Generating a thermal plasma

  13. Lighting • Steel Melting Furnaces • Cutting and Welding • Thermal spray • Atmospheric plasma spray (APS) • Vacuum plasma spray (VPS) • Chemical Vapour deposition (CVD) • Physical Vapour deposition (PVD) • Waste Recycling Commercial Plasma Applications

  14. high temperature resistance, • high corrosion resistance, • chemical inertness, • high hardness, • high wear, abrasion and erosion resistance, • creep resistance, • good adhesion, • high fracture toughness, • good thermal conductivity, • thermal shock resistance, • smooth surface/low porosity, and • thermal fatigue cracking resistance. Why Coating?

  15. Pure Carbides (TiC, ZrC, HfC, NbC, TaC, WC) • Cemented Carbides, and • Tungsten Carbide/Cobalt Coatings (WC/Co) • Titanium Carbide-based Coatings (TiC-TaC-NbC, TizAlC) • Chromium Carbide-based Coatings (CrZrAlC) • Boride-based Coatings (CrB2, BN) • Oxide Coatings • Alumina-based Coatings (A12O3/TiO2, A12O3/ZrO2) • Chromia-based Coatings (Cr2O3) • Metallic Coatings • Refractory Metal Coatings (Mo, Ti and W) • Superalloy Coatings (NiCoCrAlY) • Diamond Coatings Wear and Corrosion-resistant Coatings

  16. Chemical coatings • Sol-gel coatings • Chemical Vapor deposition (CVD) • Physical Vapor deposition (PVD) • Vacuum Evaporation technique • Sputtering methods • Laser ablation • Thermal Spraying Coating Methods

  17. 39% were produced by physical vapor deposition techniques (PVD) • 26% by chemical vapor deposition (CVD) • 23% by thermal spraying • 12% by wet processing including sol-gel technique Ceramic Coatings in the Industrial Environment annual average growth rate of 12% US $3 billion by the year 2000 US $6.5 billion by the year 2009 individual annual growth rates are: engines (28%), marine equipment (18%), chemical processing (15%), military (11%)', and construction (11%).

  18. 80% Coating Total projected sales = $4.1 billion (1995) 7.8 % Carbides 5.2% Nitrides 4.2% Oxides 2.8% Other

  19. There are three basic methods of creating and delivering the necessary molten metal, spray, and these are ： • Flame spraying • Arc spraying and • Plasma spraying. three basic methods

  20. flame spraying Temperature limited by internal heat of gasses Oxyacetylene torch ( T = 2700 ºC) Detonation gun (D-gun) ( T = 3200 ºC) Jet Kotesystem ( T = 3000 ºC) Hypervelocity oxyfuelgun ( T = 3000 ºC) Arc spraying Temperature unlimited, controlled by energy input Electric arc wire-spraying Air plasma spraying (APS) ( T = 15000 ºC) Inductive plasma (IPS) ( T > 15000 ºC) Reduced pressure ('vacuum') plasma ( T > 15000 ºC) RF-Plasma spraying ( T > 15000 ºC) Low pressure laser spraying ( LPLS ) ( T = 10000 ºC)

  21. Plasma acts as a resistive heating element that cannot melt and fail • Torch operates with most gases – not a combustion process • Temperature unlimited (T > 15000 ºC) • High temperatures, presence of ions, free electrons and UV allow for highly efficient coating • The high intensity plasma heat allows for designing compact systems • Vacuum not applied • No by-products (reduced by-products) • High efficient and Cost-effective Advantages of Plasma Systems

  22. Types of plasma torches Source: Camacho, S.L., “Industrial-worthy plasma torches: state of the art”, Pure and Appl. Chem, Vol 60, No. 5, pp 619-632, 1988

  23. Plasma Spray Gun

  24. Choosing the best type of Plasma Spray • Solving the technological problems of Plasma spray production • Producing protective coatings using the method of gas-dynamic spraying, • improving technological effectiveness of spraying • Reducing the cost of materials for spraying • Manufatoring a lab-scale plasma spray The objective of the our work are:

  25. New technology perception • Control of NOx emissions from air torch • Developing markets for slag • Scale-up risks • Limitation of size of commercially available torches • Markets’ risks Plasma Disadvantages/Challenges

  26. Using a high-power rectifier (36 KW) • Coating of multiple materials by changing the deposition parameters • Processing of oxygen sensitive materials due to processing in controlled atmosphere. • Robotic control • Use of reactive gases such as hydrogen to reduce impurities such as carbon and oxygen. • Techniques to enable the VPS of the ultra-fine powders are currently being evaluated. • Modeling the processes in this system • Manufacturing an industrial-scale of plasma spray Future Work

  27. Thanksfor your attention

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