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-absorption 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 for dehydriding, the method comprising:
heating a metal hydride powder, to decrease a hydrogen content thereof, in a preheat chamber comprising a converging portion of a nozzle, thereby forming a metal powder substantially free of hydrogen;
cooling the metal powder in a cooling chamber (i) in communication with the preheat chamber, and (ii) comprising a diverging portion of the nozzle, for a sufficiently small cooling time to prevent reabsorption of hydrogen into the metal powder; and
thereafter, depositing the metal powder on a substrate to form a solid deposit.
2. The method of claim 1 , wherein a distance between an outlet of the cooling chamber and the substrate is less than approximately 10 mm.
3. 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.
4. The method of claim 1 , wherein a hydrogen content of the metal hydride powder is greater than approximately 3900 ppm before heating.
5. The method of claim 1 , wherein a hydrogen content of the metal powder is less than approximately 100 ppm after it is deposited.
6. The method of claim 5 , wherein the hydrogen content of the metal powder is less than approximately 50 ppm after it is deposited.
7. The method of claim 1 , wherein the metal hydride powder comprises a refractory metal hydride powder.
8. The method of claim 1 , wherein an oxygen content of the solid deposit is less than approximately 200 ppm.
9. The method of claim 1 , wherein the metal powder is deposited by spray deposition.
10. The method of claim 9 , wherein the metal powder is deposited by cold spray.
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 , wherein a length of the preheat chamber along a direction of travel of the metal hydride powder from the preheat chamber to the cooling chamber is at least approximately 0.074 mm.
14. The method of claim 13 , wherein the length of the preheat chamber is at least approximately 1.382 mm.
15. The method of claim 1 , further comprising providing an inert gas within the preheat chamber and the cooling chamber.
16. The method of claim 1 , wherein forming the solid deposit substantially prevents oxygen absorption into the metal powder.