Patent EA-002736-B1 (EA)
Title: Low oxygen refractory metal powder for powder metallurgy
Inventor: KUMAR PRABHAT
IPC: B22F1/145
Filed: 2000-08-18
Abstract: 1. A process for producing metal powders, comprising the steps of: providing a hydride powder of a first metal, said first metal being selected from the group consisting of tantalum, niobium, and alloys of said metals with each other or one or both of them with other metals, the hydride having an oxygen content of under 300 ppm, heating said metal hydride in the presence of a metal having a higher affinity for oxygen, removing the metal having a higher affinity for oxygen from the metal, to form a powder of the first metal with an oxygen content less than 300 ppm. 2. The process of claim 1 wherein the final oxygen content of the metal powder is less than 200 ppm. 3. The process of claim 1 wherein the final oxygen content of the metal powder is less than 100 ppm. 4. The process of claim 1 wherein said heating is performed under vacuum. 5. The process of claim 1 wherein said heating is performed under a positive pressure of argon. 6. The process of claim 1 wherein said metal of greater affinity is selected from the group consisting of magnesium and calcium. 7. The process of any of claims 1, 2 or 3 wherein said metal powder has a transverse rupture strength of between about 1,100 to about 7,700 psi when compressed with a pressure of between 40,000 to about 100,000 psi. 8. A process for producing formed powder metallurgy products comprising the steps of: providing a hydride powder of a first metal, which is substantially a refractory metal having an oxygen content greater than a target level,  heating said metal hydride in the presence of a metal having a higher affinity for oxygen than the hydride, removing the metal having a higher affinity for oxygen from the first metal, to form a metal powder with an oxygen content less than the target level, and forming a metallurgical product from said metal powder with an oxygen content less than the target level. 9. The process of claim 8 wherein said metallurgical product is formed by compressing said metal powder to about 75 to 92% of theoretical. 10. The process of claim 8 wherein the forming step is a sequence of steps selected from the group of sequences consisting of (a) cold isostatic pressing, hot isostatic pressing and thermomechanial processing, (b) cold isostatic pressing, vacuum sintering and thermomechanical processing, (c) hermetic encapsulation, hot extrusion and thermomechanical processing, (d) cold isostatic pressing, hermetic encapsulation, hot extrusion and thermomechanical processing and (e) uniaxial cold pressing, vacuum sintering, repressing and resintering. 11. The process of claim 8, wherein the forming step comprises spray forming, alone or in combination with other steps. 12. The process of claim 8 wherein the forming step comprises plasma activated sintering alone or in a combination with other steps. 13. The process of any of claims 8 - 12 wherein the first metal is selected from the group consisting of tantalum, niobium and alloys of said metals with each other and/or other metals. 14. A formed product as made by the process of claim 13. 15. A formed product as made by the process of claim 8.