repetition: electrochemistry - tu wien€¦ · repetition: electrochemistry process types cathodic...

Repetition: ElectrochemistryProcess types

Cathodic deposition

Electrolessdeposition

Anodic oxidation

Repetition: Cathodic Deposition

+

+

-

-Me S+ -

Basic set up Potential curve

Basic characteristics:Metallic substratesMostly aqueous solutionsNarrow parameter window in TLarge parameter window of chemical additives

+-K A

x

U(x)

300 nm

Cathode fall:cathode screened bypositive ions

++++

Repetition: Anodic OxidationChemistry:

32kJ170023 OAlO3Al2

Alumina grows to thick films, because pores enablecontact to the metallic substrate.

The initially porous coating can be infiltratedand colored. Afterwards it is densified.

The method is extremely shape conserving.No additional coating is deposited, only the substratematerial is transformed.

Repetition: Electroless Deposition+ Reduction of metal ions by electrons which are supplied

by a reagens introduced into the solution.+ The reaction takes place only at a catalytic surface

(metal surface, because electrons can easily be set free).+ To sustain the deposition process, the deposited

material has to be auto-catalytic.+ If there is no catalytic surface (insulator):

activation by PdCl2 or SnCl2 ; Pd or Sn are directlydeposited on the surface. They act catalytically.

+ Reagences:Natrium-Hypophosphite: Ni, CoNatrium-Boron Hydride: Ni, AuDimethylaminborane: Ni, Co, Au, Cu, AgHydrazine: Ni, Au, PdFormaldehyde: Cu

Thermal Spraying: Process Types

Thermal spraying

High velocity spraying

Detonation spraying

Arc discharge spraying

Cold gas spraying

Further Information: http://www.gts-ev.deGesellschaft thermisches Spritzen (Society of Therrmal Spraying, in German)

Thermal Spraying With Wire

1. Acetylene/Oxygen2. Wire or stick3. Burner nozzle4. Acetylene/Oxygen flame with spray particles5. Substrate

Thermal Spraying With Powder

1. Acetylene/Oxygen2. Powder container3. Burner nozzle4. Carrier gas+powder5. Acetylene/Oxygen flame with spray particles 6. Substrate

High Velocity Spraying (HVOF)

1. Burner gas/Oxygen2. Powder3. Burner nozzle with/without water cooling5. Burner gas /Oxygen flame with spray particles6. Substrate

HVOF=High Velocity Oxygen Fuel

Detonation Spraying

1. Acetylene2. Oxygen3. Nitrogen4. Powder5. Ignition device ("Spark plug")6. Water cooled exit pipe7. Substrate

Plasma Spraying

1. Inert gas2. Cooling water3. DC current4. Pulverized spray material5. Cathode6. Anode7. Substrate

Cold Gas Spraying

1. Carrier gas2. Heating elements3. Powder supply4. Supersonic nozzle5. Spray stream6. Coating7. Substrate

Thermal Spraying: Process Characteristics

Thermal spraying

HVOFHigh Vel.-

spray

Detonationspray

Arc spray

Atmos. Plasmaspr.

VacuumPlasmaspr.

Gas Temperature [°C]

3000 3000 4000 4000 12000-16000

12000-16000

Particle velocity [m/s]

40 800 800 100 200-400 300-600

Adhesion[Nmm-2]

8 >70 >70 12 60-80 >70

Oxide content[%]

10-15 1-5 1-5 10-20 2-3 ppm

Porosity[%]

10-15 1-2 1-2 10 2-3 <0.5

Spray flow[kg/h]

2-6 3-8 1 10-25 2-10 3-15

Relative costs[1=low]

1 3 4 2 4 5

Thermal Spraying: Fundamentals

DS

d

Partially melted droplet hits substrate:

"Sombrero Morphology"

2,0

3,1

iS vdD = Density of melt

vi = Impact velocity= Viscosity of melt

Thermal Spray: Coating Morphology

500 µm

200 µm

Thermal Spray: Applications

Automotive

Medical

Home

Industry

Mechanical Plating

Packaging into protective sheets Welding to distance frame

1. Base material (substrate)2. Coating material3. Separation layer (Glas wool, MgO or Al2 O3 )4. Sheet, closed by crimping or welding5. Welded distance frame6. Weld seam7. Evacuation pipe

Detonation Plating

1. Base material (Substrate)2. Distance3. Coating material4. Ignition device5. Explosive material6. Plated coating material7. Accelerated coating material8. Detonation residues9. Detonation front10. Unburnt detonation material11. Wavy transition zone12. Material stream with high velocity13. Shock front in air

Build Up Welding: Process Types

Flame Build Up Welding

Arc Build Up Welding

Sub Powder (UP) Build Up Welding

Plasma Build Up Welding

Laser Build Up Welding

Flame Build Up Welding

Gas-powder-process

Arc Build Up Welding

Tungsten-Inert gas-process("WIG")

Metal-Inert gas-process("MIG")

Sub Powder (UP) Build Up Welding

Band electrode Double band1. Power supply2. Band electrode3. Band feed4. Contact clamps5. Loose powder6. Cinder7. Coating8. Substrate

Plasma Build Up Welding

Powder Wire (Plasma-MIG)

1. Tungsten cathode 6. RF generator (for ignition)2. Argon 7. Coating3. Welding powder 8. Base Material4. Welding wire 9. Hot wire-power supply5. Hot wire 10. Oscillating movement

Plasma-Hot Wire

Laser Build Up Welding I

Welding powder Laser

Low thermal load of substrateThin, but existing bond zone (some µm)Possibility to create complex shapes

Laser- Build Up Welding II

Laser trace

Base material is not deformed, but a thin bond zone is clearly visible. The resulting compound has excellent properties.

WC-particles in Ni-matrix

Base material

Laser Build Up Welding : 3d-Objects

Weld powder

3d-shape

Laser

3d-Pile On

Finished Object

Low thermal load of substrateThin, but existing bond zone (some µm)Possibility to create complex shapes

Melt Dipping

Dipping of workpiece through flow agent film

Flow agent attatched to workpiece in advance

Anti corrosion coatings (e. g.: Zn)Zn is sacrificial layer, i. e. it is consumed with a rate of2-8µm/yearConsumption rate depends on environmental conditions (SO2 ).

Modern Zn Melt Dipping Plant