Splat Morphology of HVOF Thermally Sprayed Nylon

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Splat Morphology of HVOF Thermally Sprayed Nylon

• Matt Chalker
• Milan Ivosevic
• Dr. Richard Cairncross

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Goals

• Learn About Thermal Spray Processes
• Learn Modeling Software Flow-3D
• Create Video of Morphing Nylon Splats
• Determine Time Table for Splats from Impact to
  Solidification

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Thermal Spray

• Old Coating Technique
• Melting substance, spraying molten substance onto
  substrate
• Many processes, each suited for different
  applications

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HVOF Thermal Spray of Polymers

• HVOF Developed for Ceramics
• Polymers attempted recently
• Combustion occurs inside chamber
• Thermal Conductivity low
• Temperature/Phase Gradient Develops

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HVOF Thermal Spray of PolymersDiagram
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Potential Applications

• Solventless Paint
• Good Corrosion Resistance
• Good Abrasion Qualities
• Great in Marine Evironments
• Good Protection for Off-Shore Oil Rigs or Bridges

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HVOF Spraying Parameters

• Material - Pure Nylon-11 D-60
• Substrate - Glass 1x1x1/16
• Spray Distance 9
• Max Transverse Velocity, 1 Pass
• HVOF Nozzle Length 6
• Nozzle I.D. 5/16
• O2 Flow 310 scfh
• H2 Flow 695 scfh
• Powder Feed Setting 0.8 rpm
• Powder Gas Flow 80 scfh

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Video of Splat Morphing

• Splats not always dome shaped
• Splats become Fried Eggs under certain
  conditions
• Domes instead of Fried Eggs if substrate
  pre-heated

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Nylon 11 D-60Fried-Egg SEM Image
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Preliminary Tasks

• Construct Heater and Insulation
• Calibrate Heater
• Configure Set-Up
• Observe Test-Splats Melting
• Determine Temperature at Lens of Microscope

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Substrate Heater Requirements

• Small, Must be fairly compact
• Insulation to Protect Microscope
• Clip or Mount to Hold Slides
• Raised Structure to conform to Microscope
• Variable Temperature Control
• Insulated Electrical Contacts

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Substrate Heater
Thermocouple
Thermocouple Receiver
Heater
Substrate
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Test Set-Up
Microscope
Variac
Thermocouple
Thermocouple Receiver
Heater
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Set-Up for Video Production
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Melting Splat Video
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Notes from Video

• Flow begins at a recorded temperature lower than
  Nylons melting temperature
• Melting Temperature approximately 180oC
• Flow at approximately 140oC
• The smaller splats flow before the larger splats
• The lower features on the eggs flow early as well

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Low Temperature Flow

• Second Cycle Melting Temperature different
• Experimental error could be a factor
• Thermocouple cement not thermally conductive
  enough

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Future Experimentation

• Confirm Temperature using Different Thermocouples
• Confirm Temperature using Oven
• Compare Results to DSC Results
• Create Model of Results in Flow-3D
• Use Previous Results to Create Timeline

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Acknowledgments

• Dr. Richard Knight
• Greg Fridman
• Dustin Doss
• Varun Gupta