cold gas dynamic spray

8/10/2019 Cold Gas Dynamic Spray

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Cold Spray


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Spraying of Composites

Zhou coated a carbon fibre polymer matrix composite with pure

Al and Al/Cu bi-metallic (with Al as a binding layer)

Copper, zinc, tin was also tried but unsuccessfully deposited

Found that gas heating softened the substratebetter bonding

Parameters for spraying pure Al:

standoff distance 20mm

Nitrogen gas = 1.2MPa

temperature of 300C

Parameters for spraying Cu: standoff distance 15mm

pressure 1.9 MPa

temperature 450 C


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Spraying of Plastic Substrate

Zhang investigated the effects of spraying Al powder onto

plastic (ABS).

Coating was thin and not continuous and that only relatively

small particles adhered to the surface.

Heavy erosion of the plastic substrate was also reported.


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Spraying of Plastic Substrate

Lupoi experimented using low density powder so as to reduce

erosion

Experimented with Al, Cu and tin

Al: slight erosion, no deposition

Cu: heavy erosion

Found that tin was most suitable for spraying a variety of

plastics (ABS, polypropylene, polystyrene)

Use of tin proved successful in reducing erosion

Parameters for spraying Tin:

pressure 5-30 bar, air

standoff distance: 103 mm

temperature not stated


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Carbon Nanotubes (CNT)

Why? Improved strength, toughness, conductivity

CNT Composites:

CNT/aluminium

CNT/polymer: improves matrix tensile strength

CNT/silica: improved bending strength and fracture toughness

CNT/copper: improved yield strength, tensile strength


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Dispersing CNT

Blending/mixing

Spray drying

Ball milling

Turbula mixer


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Cold Sprayed CNT

Bakshi prepared (spray drying):

Al-CNT

Al-Si-CNT

5% CNT in Al-Si eutectic powder

Mixed with pure Al in proportions of 10wt% and 20wt%

Substrate 6061 Al alloy


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CNT - Bakshi

Parameters: Temperature not stated but below 600K


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CNT - Bakshi


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CNT/Cu (Used Sintering & hot

pressing processes) Used to enhance the strength of CNTs (carbon nanotubes)

with reinforced Al matrix composites by introducing Cu into

the composite material

The nano-sized Cu powder and CNTs were mixed into

composite powder through high energy ball milling process Used sintering and hot extrusion process

The weight percent of CNT is 1.0 for 5 vol.% of CNT/Cu

nanocomposite and 2.2 for 10 vol.% of CNT/Cu

nanocomposites


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Measurement Methods

Density measurement (water displacement)

Optical microscopy (microstructure)

Scanning Electron Microscope (morphology, particle size

distribution, fracture surfaces)

Microhardness

Nanoindentation

Tensile testing


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Possible ideas:

Glass fibre substrate

Al powder

Cu powder

tin

Why? Applications for structural, electronic or thermalconductivity.


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Carbon nanotubes

Al powder (perhaps Al-Si)

Cu powder (hasnt been done before using cold spray process)


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Plastic powders

Used in South Africa: Nylon and polyethelene


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Metallic Powder Properties

Aluminium

Relatively low density, good electrical conductor and thermal

conductor, corrosion resistant, high yield strength

Zinc

Corrosion resistant, thermal conductor

Copper

Good electrical conductor and thermal conductor, corrosion

resistant, ductile, non magnetic

Tin Good electrical conductor and thermal conductor, corrosion

resistant

Nickel

Corrosion resistant, easily magnetised

cold gas dynamic spray

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