Dynamic dehydriding of refractory metal powders
View Patent ↗Refractory metal powders are dehydrided in a device which includes a preheat chamber for retaining the metal powder fully heated in a hot zone to allow diffusion of hydrogen out of the powder. The powder is cooled in a cooling chamber for a residence time sufficiently short to prevent re-absorbtion of the hydrogen by the powder. The powder is consolidated by impact on a substrate at the exit of the cooling chamber to build a deposit in solid dense form on the substrate.
1. A method of forming a metallic deposit, the method comprising:
supplying a metal hydride powder to a spray-deposition nozzle;
within the spray-deposition nozzle, (i) heating the metal hydride powder to decrease a hydrogen content thereof, thereby forming a metal powder substantially free of hydrogen, and (ii) cooling the metal powder for a sufficiently small cooling time to prevent reabsorption of hydrogen into the metal powder; and
spraying the metal powder from the spray-deposition nozzle on a substrate to form a solid deposit thereon.
2. The method of claim 1 , wherein the spray-deposition nozzle comprises converging and diverging sections.
3. The method of claim 1 , wherein a distance between an outlet of the spray-deposition nozzle and the substrate is less than approximately 10 mm.
4. The method of claim 1 , wherein heating of the metal hydride powder and the cooling of the metal powder are performed under a positive pressure of an inert gas.
5. The method of claim 1 , wherein a hydrogen content of the metal hydride powder is greater than approximately 3900 ppm before heating.
6. The method of claim 1 , wherein a hydrogen content of the metal powder is less than approximately 100 ppm after it is sprayed.
7. The method of claim 6 , wherein the hydrogen content of the metal powder is less than approximately 50 ppm after it is sprayed.
8. The method of claim 1 , wherein the metal hydride powder comprises a refractory metal hydride powder.
9. The method of claim 1 , wherein an oxygen content of the solid deposit is less than approximately 200 ppm.
10. The method of claim 1 , wherein spraying the metal powder comprises cold spraying the metal powder.
11. The method of claim 1 , wherein a hydrogen content of the metal hydride powder decreases by at least two orders of magnitude during heating.
12. The method of claim 1 , wherein an oxygen content of the metal powder does not increase during cooling.
13. The method of claim 1 , further comprising providing an inert gas within the spray-deposition nozzle.
14. The method of claim 1 , wherein forming the solid deposit substantially prevents oxygen absorption into the metal powder.