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