Methods for in situ formation of dispersoids strengthened refractory alloy in 3D printing and additive manufacturing
Methods of fabricating objects using additive manufacturing are provided. The methods create in situ dispersoids within the object. The methods are used with refractory alloy powders which are pretreated to increase the oxygen content to between 500 ppm and 3000 ppm or to increase the nitrogen content to between 250 ppm and 1500 ppm. The pretreated powders are then formed into layers in an environmentally controlled chamber of an additive manufacturing machine. The environmentally controlled chamber is adjusted to have between 500 ppm and 200 ppm oxygen. The layer of pretreated powder is then exposed to a transient moving energy source for melting and solidifying the layer; and creating in situ dispersoids in the layer.
1 . A method of fabricating an object from refractory powder alloys using additive manufacturing comprising:
(a) selecting a refractory alloy powder from the group consisting of niobium refractory alloy powder, rhenium refractory alloy powder, tantalum refractory alloy powder, molybdenum refractory alloy powder and tungsten refractory alloy powder;
(b) pretreating the refractory alloy powder in an environmentally controlled inert gas chamber by heating the refractory alloy powder in an oxygen and nitrogen containing atmosphere at a temperature between about 250° F. to about 750° F. for a period of between about 20 to 120 minutes to increase an oxygen content in the refractory alloy powder to between 500 ppm and 3000 ppm or to increase a nitrogen content in the refractory alloy powder to between 250 ppm and 1500 ppm; and
(c) exposing the refractory alloy powder after pretreating to a transient energy source to melt and solidify the refractory alloy powder;
wherein dispersoids are formed in situ in a layer with the dispersoids having diameters of between 1 micron and 10 microns.
2 . The method of claim 1 further comprising: adjusting the environmentally controlled inert gas chamber to have between 250 ppm and 1000 ppm nitrogen.
3 . The method of claim 1 further comprising adjusting the oxygen content of the environmentally controlled inert gas chamber to be between 500 ppm and 2000 ppm.
4 . The method of claim 1 , wherein the refractory alloy powder is niobium refractory alloy powder.
5 . The method of claim 1 , wherein the refractory alloy powder is tungsten refractory alloy powder.
6 . The method of claim 1 , wherein the refractory alloy powder is rhenium refractory alloy powder.
7 . The method of claim 1 , wherein the refractory alloy powder is tantalum refractory alloy powder.
8 . The method of claim 1 , wherein the refractory alloy powder is molybdenum refractory alloy powder.
9 . The method of claim 1 , wherein the oxygen content of the refractory alloy powder is between 750 ppm and 1500 ppm.
10 . The method of claim 1 which further comprises repeating step (c) until the object is fabricated.
11 . The method of claim 1 , wherein the niobium refractory alloy powder is niobium alloy C-103.
12 . The method of claim 1 , wherein the transient energy source is a moving energy source.
13 . The method of claim 1 , wherein the transient energy source is a stationary energy source.
14 . The method of claim 1 , wherein the transient energy source is a laser beam.