Process for preparing metal powders having low oxygen content, powders so-produced and uses thereof

Abstract

The present invention is directed to a process for the preparation of a metal powder having a purity at least as high as the starting powder and having an oxygen content of 10 ppm or less comprising heating said metal powder containing oxygen in the form of an oxide, with the total oxygen content being from 50 to 3000 ppm, in an inert atmosphere at a pressure of from 1 bar to 10 −7 to a temperature at which the oxide of the metal powder becomes thermodynamically unstable and removing the resulting oxygen via volatilization. The metal powder is preferably selected from the group consisting of tantalum, niobium, molybdenum, hafnium, zirconium, titanium, vanadium, rhenium and tungsten. The invention also relates to the powders produced by the process and the use of such powders in a cold spray process.

1 . A process for the preparation of a metal powder having a purity of at least as high as the starting powder and having an oxygen content of 10 ppm or less comprising heating said metal powder containing oxygen in the form of an oxide, with the total oxygen content being from 50 to 3000 ppm, in an inert atmosphere at a pressure of from 1 bar to 10 −7  to a temperature at which the oxide of the metal powder becomes thermodynamically unstable and removing the resulting oxygen via volatilization. 
     
     
         2 . The process of  claim 1 , wherein said metal powder is selected from the group consisting of tantalum, niobium, molybdenum, hafnium, zirconium, titanium, vanadium, rhenium and tungsten. 
     
     
         3 . The process of  claim 1 , wherein the metal powder has a purity of at least 99.9%. 
     
     
         4 . The process of  claim 2 , wherein said metal is tantalum and wherein said powder is heated in an inert gas atmosphere at a pressure of from 1 bar to 10 −7  bar and a temperature of from about 1700° C. to about 3800° C. 
     
     
         5 . The process of  claim 2 , wherein said metal is niobium and said powder is heated in an inert gas atmosphere at a pressure of from 10 −3  bar to 10 −7  bar and a temperature of from about 1750° C. to about 3850° C. 
     
     
         6 . The process of  claim 2 , wherein said metal is tungsten and wherein said powder is heated in an inert gas atmosphere at a pressure of from 1 bar to 10 −7  bar and a temperature of from about 1200° C. to about 1800° C. 
     
     
         7 . The process of  claim 2 , wherein said metal is molybdenum and wherein said powder is heated in an inert gas atmosphere at a pressure of from 1 bar to 10 −7  bar and a temperature of from about 1450° C. to about 2300° C. 
     
     
         8 . The process of  claim 2 , wherein said metal is titanium and said powder is heated in an inert gas atmosphere at a pressure of from 10 −3  bar to 10 −7  bar and a temperature of from about 1800° C. to about 2500° C. 
     
     
         9 . The process of  claim 2 , wherein said metal is zirconium and said powder is heated in an inert gas atmosphere at a pressure of from 10 −3  bar to 10 −7  bar and a temperature of from about 2300° C. to about 2900° C. 
     
     
         10 . The process of  claim 2 , wherein said metal is hafnium and said powder is heated in an inert gas atmosphere at a pressure of from 10 −3  bar to 10 −7  bar and a temperature of from about 2400° C. to about 3200° C. 
     
     
         11 . An unpassivated tantalum powder having a surface area of from about 100 cm 2 /g to about 10,000 cm 2 /g, having an oxygen content of 10 ppm or less, having a hydrogen content of 1 ppm or less, a magnesium content of 1 ppm or less, an alkali metal content of 1 ppm or less, and a combined iron plus nickel plus chromium content of 1 ppm or less. 
     
     
         12 . A unpassivated niobium powder having a surface area of from about 100 cm 2 /g to about 10,000 cm 2 /g, having an oxygen content of 10 ppm or less, having a hydrogen content of 1 ppm or less, a magnesium content of 1 ppm or less, an alkali metal content of 1 ppm or less, and a combined iron plus nickel plus chromium content of 1 ppm or less. 
     
     
         13 . A unpassivated tungsten having a surface area of from about 100 cm 2 /g to about 10,000 cm 2 /g, an oxygen content of 5 ppm or less, a carbon content of 5 ppm or less and a hydrogen content of 1 ppm or less. 
     
     
         14 . A unpassivated molybdenum powder having a surface area of from about 100 cm 2 /g to about 10,000 cm 2 /g, an oxygen content of 10 ppm or less and a hydrogen content of 1 ppm or less. 
     
     
         15 . A unpassivated titanium powder having a surface area of from about 100 cm 2 /g to about 10,000 cm 2 /g, an oxygen content of 10 ppm or less and a hydrogen content of 1 ppm or less. 
     
     
         16 . A unpassivated zirconium powder having a surface area of from about 100 cm 2 /g to about 10,000 cm 2 /g, an oxygen content of 10 ppm or less and a hydrogen content of 1 ppm or less. 
     
     
         17 . A unpassivated hafnium powder having a surface area of from about 100 cm 2 /g to about 10,000 cm 2 /g, an oxygen content of 10 ppm or less and a hydrogen content of 1 ppm or less. 
     
     
         18 . In a cold spray process comprising spraying a metal powder onto a substrate at a supersonic velocity, the improvement wherein the powder is the tantalum powder of  claim 11 . 
     
     
         19 . In a cold spray process comprising spraying a metal powder onto a substrate at a supersonic velocity, the improvement wherein the powder is the niobium powder of  claim 12 . 
     
     
         20 . In a cold spray process comprising spraying a metal powder onto a substrate at a supersonic velocity, the improvement wherein the powder is the tungsten powder of  claim 13 . 
     
     
         21 . In a cold spray process comprising spraying a metal powder onto a substrate at a supersonic velocity, the improvement wherein the powder is the molybdenum powder of  claim 14 . 
     
     
         22 . In a cold spray process comprising spraying a metal powder onto a substrate at a supersonic velocity, the improvement wherein the powder is the titanium powder of  claim 15 . 
     
     
         23 . In a cold spray process comprising spraying a metal powder onto a substrate at a supersonic velocity, the improvement wherein the powder is the zirconium powder of  claim 16 . 
     
     
         24 . In a cold spray process comprising spraying a metal powder onto a substrate at a supersonic velocity, the improvement wherein the powder is the hafnium powder of  claim 17 .