Spray system with combined kinetic spray and thermal spray ability
View Patent ↗Disclosed is a system and a method for simultaneously applying a kinetic spray coating and a thermal spray coating onto a substrate using a single application nozzle to produce a combined coating. The system may include a higher heat capacity gas heater to permit both the thermal spray and the kinetic spray. The method involves providing two populations of particles to the nozzle simultaneously wherein one population is thermally softened in the nozzle under the spray parameters and the other is not. The system increases the versatility of the spray nozzle and addresses several problems inherent in kinetic spray applied coatings.
1. A method of coating a substrate comprising the steps of:
a) providing at least a first population of particles and a second population of particles to be sprayed each population having an average nominal diameter of from 106 to 250 microns;
b) providing a supersonic nozzle having a throat with a diameter of from 1.5 to 3.5 millimeters and located between a converging region and a diverging region, directing a flow of a gas through the nozzle, maintaining the gas at a selected temperature, and injecting the first and second populations of particles into the nozzle at the same time and entraining the first and second populations of particles in the flow of the gas;
c) the temperature of the gas selected to be insufficient to thermally soften the first population of particles in the nozzle and accelerating the first population of particles to a velocity sufficient to result in direct bonding of the first population of particles onto a substrate positioned opposite the nozzle, and the temperature of the gas selected to be sufficient to heat the second population of particles to a temperature at or above their melting temperature in the nozzle thereby melting the second population of particles and accelerating the molten second population of particles to a velocity sufficient to result in adherence of the second population of particles on the substrate; thereby forming a coating on the substrate that is a combination of the first and second populations of particles.
2. The method of claim 1 , wherein step a) comprises providing at least a first and a second population of particles that differ from each other in at least one of size, shape, or material composition.
3. The method of claim 1 , wherein step b) comprises providing air, argon, nitrogen, or helium as the gas.
4. The method of claim 1 , wherein step b) comprises maintaining the gas at a temperature of from 300 degrees Celsius to a temperature that is seven fold above the highest melting temperature of the first and second populations of particles.
5. The method of claim 1 , wherein step b) comprises injecting at least one of the first and the second populations of particles into the converging region of the nozzle prior to the throat.
6. The method of claim 1 , wherein step b) comprises injecting at least one of the first and the second populations of particles directly into the diverging region of the nozzle after the throat.
7. The method of claim 1 , wherein step c) comprises accelerating the first and second populations of particles to a velocity of from 300 to 1500 meters per second.
8. The method of claim 1 , wherein step c) comprises heating the second population of particles to a temperature of from their melting temperature to a temperature 400 degrees Celsius above their melting temperature.
9. The method of claim 1 , wherein step c) comprises heating the second population of particles to a temperature of from their melting temperature to a temperature 200 degrees Celsius above their melting temperature.
10. The method of claim 1 , wherein step c) comprises heating the second population of particles to a temperature of from their melting temperature to a temperature 100 degrees Celsius above their melting temperature.
11. The method of claim 1 , wherein step c) comprises positioning a substrate comprising a metal, an alloy, a ceramic, a plastic, a semi-conductor, wood, paper, or mixtures thereof opposite the nozzle.
12. The method of claim 1 , wherein step a) comprises providing first and second populations of particles comprising a metal, an alloy, a ceramic, a polymer, or mixtures of thereof.
13. The method of claim 1 , wherein step b) comprises injecting the first and second populations of particles each through a tube having an inner diameter of from 0.4 to 3.0 millimeters in diameter.
14. The method of claim 1 , wherein step b) comprises providing the nozzle having the diverging region with a length of from 60.0 to 400.0 millimeters in length.
15. The method of claim 1 , wherein step a) comprises providing a mixture of the first and the second population of particles.