Thermal spray gun with improved thermal efficiency and nozzle/barrel wear resistance

Abstract

The present invention discloses a thermal spray apparatus with improved thermal efficiency and wear resistance in both the nozzle and barrel combustion chamber. Specifically, disclosed herein is a thermal spray apparatus for spraying substrate coatings, comprising a high velocity oxygen fuel (HVOF) gun wherein said gun includes a combustion chamber generating heated flow therefrom and a nozzle downstream from said chamber. The nozzle and/or chamber contain a first layer of material heated by the flow, and a second layer of material which contacts the first layer when said first layer is heated. The first layer has a thermal conductivity that is lower than said second layer and preferably a lower thermal expansion coefficient. In use, the contact of the first heated layer of material with the second layer operates to remove heat from the first layer therein providing automatic/self-regulating temperature control of the HVOF apparatus.

1. A thermal spray apparatus with improved thermal efficiency and wear resistance for spraying substrate coatings comprising:
 a high velocity oxygen fuel (HVOF) gun for spraying wherein said gun includes a combustion chamber generating heated flow therefrom and a nozzle downstream from said chamber,  
 said nozzle and/or chamber comprising a first layer of material heated by said heated flow, and a second layer of material which contacts said first heated layer of material, said first layer having a thermal conductivity lower than said second layer.  
 
     
     
       2. The apparatus of  claim 1 , wherein said first layer has a thermal expansion coefficient “a” and said second layer has a thermal expansion coefficient “b” wherein a<b. 
     
     
       3. The apparatus of  claim 1 , wherein, at room temperature, said first layer and said second layer are spaced apart from one another. 
     
     
       4. The apparatus of  claim 3 , wherein said first layer and said second layer are spaced apart about 0.001-0.010 inches. 
     
     
       5. The apparatus of  claim 3  wherein said spacing is about 0.002-0.006 inches. 
     
     
       6. The apparatus of  claim 3  wherein said spacing is about 0.002-0.004 inches. 
     
     
       7. The apparatus of  claim 3  wherein said spacing is about 0.002 inches. 
     
     
       8. The apparatus of  claim 1 , wherein said first layer is selected from the group consisting of stainless steel, nickel, a nickel based alloy, a ceramic material, and a mixture thereof, and said second layer is selected from the group consisting of copper, silver, aluminum, brass, bronze, and a mixture thereof. 
     
     
       9. The apparatus of  claim 1 , wherein said first layer has a hardness value of at least about 400 HV. 
     
     
       10. The apparatus of  claim 1  wherein said second material which contacts said first heated layer removes heat from said first layer into said second layer. 
     
     
       11. A method for self-regulating heat losses from an HVOF thermal spray apparatus containing a combustion chamber and a nozzle downstream from and in flow communication with said combustion chamber for receiving a heated HVOF stream therefrom comprising:
 positioning a first layer of material in said combustion chamber or said nozzle with a thermal conductivity “x”,  
 positioning a second layer of material in said combustion chamber or said nozzle in non-contacting relationship with said first layer, said second layer having a thermal conductivity “y”, wherein x<y;  
 heating said first layer so that said first layer contacts said second layer and said second layer removes heat from said first layer into said second layer, whereupon said first layer returns to said non-contacting position.  
 
     
     
       12. The method of  claim 11 , wherein the first layer has a thermal expansion coefficient that is less than said second layer. 
     
     
       13. The method of  claim 11  wherein said heating causes said first and second layers to cycle through a plurality of said non-contacting and contacting heat removal positions. 
     
     
       14. A nozzle for use with a high velocity oxygen fuel ( HVOF )  gun of a thermal spray apparatus and for generating a heated flow, the nozzle having a first layer of material heated by said heated flow, and a second layer of material which contacts said first heated layer of material, said first layer having a thermal conductivity lower than said second layer for spray coatings with improved thermal efficiency and wear resistance, and wherein at room temperature, said first layer and said second layer are spaced apart from one another.   
     
     
       15. The nozzle of  claim 14  wherein said first layer has a thermal expansion coefficient “a” and said second layer has a thermal expansion coefficient “b” wherein a<b. 
     
     
       16. The nozzle of  claim 14  wherein said first layer and said second layer are spaced apart about  0 . 001 -   0 . 010  inches.   
     
     
       17. The nozzle of  claim 14  wherein said spacing is about  0 . 002 -   0 . 006  inches.   
     
     
       18. The nozzle of  claim 14  wherein said spacing is about  0 . 002 -   0 . 004  inches.   
     
     
       19. The nozzle of  claim 14  wherein said spacing is about  0 . 002  inches. 
     
     
       20. The nozzle of  claim 14  wherein said first layer is selected from the group consisting of stainless steel, nickel, a nickel based alloy, a ceramic material, and a mixture thereof, and said second layer is selected from the group consisting of copper, silver, aluminum, brass, bronze, and a mixture thereof. 
     
     
       21. The nozzle of  claim 14  wherein said first layer has a hardness value of at least about  400  HV. 
     
     
       22. The nozzle of  claim 14  wherein said second material which contacts said first heated layer removes heat from said first layer into said second layer. 
     
     
       23. A method for self- regulating heat losses from an HVOF thermal spray apparatus containing a combustion chamber and a nozzle downstream from and in flow communication with said combustion chamber for receiving a heated HVOF stream therefrom comprising:      positioning a first layer of material in said nozzle with a thermal conductivity “x”,        positioning a second layer of material in said nozzle in non - contacting relationship with first layer, said second layer having a thermal conductivity “y”, wherein x<y,        heating said first layer so that said first layer contacts said second layer and said second layer removes heat from said first layer into said second layer whereupon said first layer returns to said non - contacting position.     
     
     
       24. The method of  claim 23  wherein the first layer has a thermal expansion coefficient that is less than said second layer. 
     
     
       25. The method of  claim 23  wherein said heating causes said first and second layers to cycle through a plurality of said non- contacting and contacting heat removal positions.   
     
     
       26. A combustion chamber for use with a high velocity oxygen fuel ( HVOF )  gun of a thermal spray apparatus and for generating a heated flow, the combustion chamber having a first layer of material heated by said heated flow, and a second layer of material which contacts said first heated layer of material, said first layer having a thermal conductivity lower than said second layer for spraying coatings with improved thermal efficiency and wear resistance, and wherein at room temperature, said first layer and said second layer are spaced apart from one another.   
     
     
       27. The combustion chamber of  claim 26  wherein said first layer has a thermal expansion coefficient “a” and said second layer has a thermal expansion coefficient “b” wherein a<b. 
     
     
       28. The combustion chamber of  claim 26  wherein said first layer and said second layer are spaced apart about  0 . 001 -   0 . 010  inches.   
     
     
       29. The combustion chamber of  claim 26  wherein said spacing is about  0 . 002 -   0 . 006  inches.   
     
     
       30. The combustion chamber of  claim 26  wherein said spacing is about  0 . 002 -   0 . 004  inches.   
     
     
       31. The combustion chamber of  claim 26  wherein said spacing is about  0 . 002  inches. 
     
     
       32. The combustion chamber of  claim 26  wherein said first layer is selected from the group consisting of stainless steel, nickel, a nickel based alloy, a ceramic material, and a mixture thereof, and said second layer is selected from the group consisting of copper, silver, aluminum, brass, bronze, and a mixture thereof. 
     
     
       33. The combustion chamber of  claim 26  wherein said first layer has a hardness value of at least about  400  HV. 
     
     
       34. The combustion chamber of  claim 26  wherein said second material which contacts said first heated layer removes heat from said first layer into said second layer. 
     
     
       35. A method for self- regulating heat losses from an HVOF thermal spray apparatus containing a combustion chamber and a nozzle downstream from and in flow communication with said combustion chamber for receiving a heated HVOF stream therefrom comprising:      positioning a first layer of material in said combustion chamber with a thermal conductivity “x”,        positioning a second layer of material in said combustion chamber in non - contacting relationship with first layer, said second layer having a thermal conductivity “y”, wherein x<y,        heating said first layer so that said first layer contacts said second layer and said second layer removes heat from said first layer into said second layer whereupon said first layer returns to said non - contacting position.     
     
     
       36. The method of  claim 34  wherein the first layer has a thermal expansion coefficient that is less than said second layer. 
     
     
       37. The method of  claim 34  wherein said heating causes said first and second layers to cycle through a plurality of said non- contacting and contacting heat removal positions.