Method and apparatus for thermal spraying of metal coatings using pulsejet resonant pulsed combustion
View Patent ↗An apparatus and method for thermal spraying a metal coating on a substrate is accomplished with a modified pulsejet and optionally an ejector to assist in preventing oxidation. Metal such as Aluminum or Magnesium may be used. A pulsejet is first initiated by applying fuel, air, and a spark. Metal is inserted continuously in a high volume of metal into a combustion chamber of the pulsejet. The combustion is thereafter controlled resonantly at high frequency and the metal is heated to a molten state. The metal is then transported from the combustion chamber into a tail pipe of said pulsejet and is expelled therefrom at high velocity and deposited on a target substrate.
1. A method of spraying a coating, comprising the steps of:
combusting, resonantly, a fuel-air mixture in a pulsejet; and,
inserting continuously a metal wire into said pulsejet.
2. A method as claimed in claim 1 for thermal spraying a metal coating, comprising the steps of:
initiating a pulsejet;
inserting, continuously, a high volume of metal into a combustion chamber of said pulsejet;
combusting and controlling, resonantly, at high frequency a fuel-air mixture in said combustion chamber;
heating said metal to a molten state;
producing a fine molten spray through interaction with combustion-driven, gasdynamic waves;
transporting said molten metal from said combustion chamber into a tail pipe of said pulsejet;
transporting said molten metal within said tail pipe of said pulsejet at a high velocity;
expelling said molten metal from said tail pipe of said pulsejet in a thermal spray at a high velocity; and,
depositing said molten metal as a thermal spray onto a sample at the end of said tail pipe.
3. A method for thermal spraying a coating as claimed in claim 2 further comprising the steps of:
entraining a volume of an inert gas around said molten metal; and,
impinging said molten metal on said sample located in proximity to said tailpipe of said pulsejet.
4. A method for thermally spraying a coating as claimed in claim 2 wherein said metal is selected from the group consisting of aluminum and magnesium.
5. A method for thermally spraying a coating as claimed in claim 2 wherein said fuel mixture comprises a fuel selected from the group consisting of nitromethane, methanol, and gasoline.
6. A method for thermally spraying a coating as claimed in claim 2 wherein said resonant pulsed combustion utilizes a head and a valve between said head and said combustion chamber.
7. A method for thermal spraying a coating as claimed in claim 1 further comprising the steps of:
entraining a volume of an inert gas around said molten metal; and,
impinging said molten metal on said sample located in proximity to said tailpipe of said pulsejet.
8. A method for thermally spraying a coating, comprising the steps of:
inserting a metal wire into a combustion chamber of a pulsejet;
combusting a mixture of fuel and air in said combustion chamber of said pulsejet;
heating said metal wire and forming molten metal particles which travel in a high velocity wave of combustion products into a tail pipe of said pulsejet as a result of said combustion;
expelling said molten metal at a high velocity and frequency;
impinging said molten metal as a thermal spray onto a sample at the end of said tail pipe; and,
forming a vacuum in said combustion chamber further disintegrating any molten metal particles left in said tail pipe and further repeating said steps.
9. A method for thermal spraying a coating as claimed in claim 8 further comprising the steps of:
entraining a volume of an inert gas around said molten metal; and,
impinging said molten metal on said sample located in proximity to said tailpipe of said pulsejet.
10. A method for high volume, high velocity surface deposition of protective metallic coatings, comprising the steps of:
creating a non-steady resonant combustion process in a confined volume;
heating a metal to its melting point by passing it through a flame; and,
thermally spraying said melted metal on a substrate.
11. A method for high volume, high velocity surface deposition of protective metallic coatings as claimed in claim 10 wherein the step of creating a non-steady resonant combustion process in a confined volume is performed without external actuation or control.
12. A method for high volume, high velocity surface deposition of protective metallic coatings as claimed in claim 10 wherein the step of creating a non-steady resonant combustion process in a confined volume is performed using air-fuel ratio and volumetric control.