gas dynamics of cold spray & control of deposition
TRANSCRIPT
Gas Dynamics of Cold Spray
& Control of Deposition
Ozan Ç. Özdemir, Christian A. Widener
Advanced Materials Processing and Joining Laboratory
South Dakota School of Mines and Technology
31 January 2017
Discovery and Technology Target
• Discovered in the 1980s at the Russian Academy of Sciences
• Line of sight process
• Coating thickness > 10 𝜇𝑚
• Extend expensive part life
– Structural and geometrical surface repair
– Crack growth prevention
• Coating of similar and dissimilar materials
– Corrosion prevention
• Additive-subtractive manufacturing
2
High Pressure Cold Spray
System
Cold Spray
Meter
or
Substrate
SS316
Spray GunPBI Nozzle
Powder
Feed Line
SoD
Aligned
with Axis
Converging Diverging Nozzle
3
Nozzle
• Expansion ratio defines the Mach number of nozzle
– 𝐸𝑥𝑝𝑎𝑛𝑠𝑖𝑜𝑛 𝑅𝑎𝑡𝑖𝑜 =𝑁𝑜𝑧𝑧𝑙𝑒 𝑒𝑥𝑖𝑡 𝑑𝑖𝑎𝑚𝑒𝑡𝑒𝑟 2
𝑁𝑜𝑧𝑧𝑙𝑒 𝑡ℎ𝑟𝑜𝑎𝑡 𝑑𝑖𝑎𝑚𝑒𝑡𝑒𝑟 2
• Mach number changes throughout nozzle
– 𝑀𝑎𝑐ℎ =𝐺𝑎𝑠 𝑆𝑝𝑒𝑒𝑑
𝑆𝑝𝑒𝑒𝑑 𝑜𝑓 𝑆𝑜𝑢𝑛𝑑=
𝑉𝑔𝑎𝑠
𝛾𝑅𝑇
• Gas velocity depends on gas inlet temperature
4
Gas Behavior
Air
Tungsten
Helium
P = 900 psi
T = 700 C
Velocity Field
Su
bst
rate
Helium
P = 900 psi
T = 700 C
Thermal Field
Su
bst
rate
Air
Tungsten
5
Gas Impingement and
Standoff Distance
• Bow shock is stronger with lower standoff distances
• Increasing standoff distance causes falloff of particles
• Increased dispersion in the particle footprint
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Gas Impingement
Velocity
Su
bst
rate
Air
Tungsten Nozzle
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Gas Impingement
Temperature
Su
bst
rate
8
Particle Acceleration
Image Source: https://www.grc.nasa.gov/www/k-12/airplane/dragsphere.html
Gas Flow
Particle drag generated by gas-particle
velocity difference
Accelerating
particles
9
Bonding Criterion
• What makes particles stick?
– Particle impact velocity
– Size dependence
11
Deposition
Dense
Coating
Substrate 12
Video 3:https://youtu.be/Pu_zAsTnNKwVideo 2 Link: https://youtu.be/UV80RfGWxlo
System & Equipment Control
Effects on Quality
13
Gas Temperature
Gas Pressure
Powder• Size
• Material
• Prep
Gas
• Air
• Nitrogen
• Helium
• Mixed Gas
Nozzle
• Material
• Geometry
Standoff Distance
• How Far Away?
Substrate
• Surface Roughness
• Shape
Selecting Gas
Impact Velocity = 685 m/s
Impact Velocity = 1030 m/s
cost of helium is 6 times that of nitrogen
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Particle Size
Nitrogen
Helium
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Powder Particle Size
Selection
Nitrogen Helium
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Changing Gas PressureNozzle Conditions
Velocity Temperature
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Changing Gas PressureParticle Impact
Velocity Temperature
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Changing Gas Temperature
Nozzle
Velocity Temperature
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Changing Gas Temperature
Particle Impact
Velocity Temperature
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Changing Nozzle Expansion Ratio
Nozzle
Velocity Temperature
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Pressure Temperature
Selection
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Changing Nozzle Expansion Ratio
Particle Impact
Velocity Temperature
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Changing Nozzle LengthNozzle
Velocity Temperature
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Changing Nozzle LengthParticle Impact
Velocity Temperature
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Standoff DistanceNozzle
Velocity Temperature
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Standoff DistanceParticle Impact
Velocity Temperature
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Powder MaterialNozzle
Velocity Temperature
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Powder MaterialParticle Impact
Velocity Temperature
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Powder MaterialAluminum Impact
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Powder MaterialTitanium Impact
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Powder MaterialTantalum Impact
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Powder Heat Treatment
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Particle testing with nanoindentation
If we get 20% softening
with heat treatment
Economics
• Total spray time
• Pressure and temperature optimization
• Deposition efficiency
• Deposition rate per volume of gas
• Nozzle throat diameter
• Powder feeding rate
• Gas mixing
34
Gas Mixing for Impact Control
350% 𝐻𝑒 10% 𝐻𝑒 30% 𝐻𝑒 50% 𝐻𝑒 70% 𝐻𝑒
Powder Feed Rate
36
Powder Feed Rate
Particle Impact
Velocity Temperature
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Equipment Inspection and
Alignment
38Nozzle Wear
Aligned Misaligned
39
Aligned vs Misaligned
Video 4: https://youtu.be/qDbErxtm3HcVideo 1: https://youtu.be/HGUVTPXgWNQ
Aligned Small Inner Diameter Aligned Large Inner Diameter
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Small vs Large Feeder Tube
Video 1: https://youtu.be/HGUVTPXgWNQ Video 5: https://youtu.be/FhZb7bvNd9o
Guide to Deposition
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Sample: 50 𝜇𝑚 aluminum particle sprayed with helium
particle range: 10 𝜇𝑚 to 100 𝜇𝑚in helium and nitrogen
Questions
42
Ozan C. Ozdemir
Graduate Research AssistantPh.D. Candidate in Mechanical Engineering
AMP LabSouth Dakota School of Mines and Technology
Tel: +1 (605) 651-0629E-mail: [email protected]
Christian A. Widener
Director AMP Lab / AMPTECH & R3S CentersAssociate Professor Mechanical/Materials
Engineering Departments
Tel: +1 (605) 394-6924E-mail: [email protected]