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To obtain a particular coating the following conditions must be met:
Whether the material to be sprayed can be processed into a material form suitable for spraying.
Whether the spraying materials will produce some undesirable but unavoidable phenomena and results during the spraying process.
Whether the spray material can be heated sufficiently during the spraying process.
Whether the spray material can be accelerated enough during the spraying process.
Benefits of using thermal spray technology:
Limitations of Thermal Spray Technology:
Change the surface properties of parts to meet the overall performance requirements of equipment.
Sensitive to stress during application.
Restore part dimensions.
Poor impact resistance.
Protects against wear and corrosion.
Cannot bear point loads.
Extended service life.
No added structural strength (not welded).
Lower cost than replacing new parts.
The bonding form of the coating is mechanical bonding.
Reduce downtime.
The coating is porous and permeable.
Less processing is required.
Line-of-sight processing, limited application.
The base material cost is low.
coating stress.
Coating thickness is limited.
Part preparation:
Process limitations.
Removes fatigued or corroded metal.
Difficult to process after coating.
Repair welding defects.
Parts are cleaned and degreased.
Spraying:
Mask areas not to be coated (masking).
Rotate and move parts as required by spraying parameters.
Surface sandblasting.
Note deviation and spray rate.
Keep parts clean.
Use acceptable settings (airflow, voltage, etc.).
Parts or coatings must not be overheated.
The most commonly used thermal spray processes:
Wire flame spraying.
85% of coating failures are caused by poor surface preparation:
Powder flame spraying.
Use Al2O3.
Arc spraying.
Arc and flame spraying and materials with low bonding strength: use 36-40 mesh Al2O3.
Plasma spraying.
Most HVOF and plasma: use 60 Al2O3 abrasive.
High Velocity Oxygen Fuel (HVOF).
Post-coating processing:
Cost composition of thermal spraying process:
Don't take any metalworking methods you know for granted.
Material.
Pay attention to the problem of point loading.
Labor costs and daily expenses.
Reduce resection rate.
power consumption.
Rough machining to close tolerances, then grinding/polishing.
gas consumption.
Don't expect a fine finish from machining.
Other fuels (such as aviation kerosene).
Equipment spare parts and consumables.
How to choose a process reasonably:
Overspray loss.
Expenses.
operating costs.
How to assess what kind of coating you need:
system capability.
Bond strength.
material capacity.
Density/porosity.
coating quality.
permeability.
coating thickness.
Thickness required.
Operating skill level.
Surface polishing requirements.
repeatability.
what kind of wear and tear.
noise level.
what kind of corrosion.
Dust.
Operating temperature.
What is the reason for success? How can it be more economical?
How to successfully get coated:
Understand the applicable environment.
Whether to choose thermal spraying process:
Choose the right material.
Whether the application requirements meet the limitations of thermal spray.
Choose the appropriate application process.
Is the surface being sprayed accessible for "line-of-sight" work?
Prepare the parts properly.
Is the cost structure economical?
Use correct spray parameters.
Can my plant/personnel handle this part or job?
Handle parts with care to prevent surface contamination.
Is there sufficient workload to support the investment?
Post spray properly.
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