Stress induced crystallographic phase transformation and texturing in tubular products made of cobalt and cobalt alloys
A method of producing a superalloy gun barrel includes providing a tubular workpiece made of a cobalt-based superalloy material, the workpiece having at least about 30% by weight of fcc phase and having an inner diameter and an outer diameter. The method further includes placing the workpiece on a mandrel such that the inner diameter is adjacent to the mandrel and compressing the outer diameter of the workpiece at a temperature below a recrystallization temperature of the workpiece using a combination of axial and radial forces so that the mandrel contacts the inner diameter and imparts a compressive hoop stress to the inner diameter of the workpiece.
1. A method of producing a superalloy gun barrel, the method comprising:
providing a tubular workpiece having at least about 30% by weight of fcc phase and having an inner diameter and an outer diameter, wherein the workpiece is made of a cobalt-based superalloy material;
placing the workpiece on a mandrel such that the inner diameter is adjacent to the mandrel; and
compressing the outer diameter of the workpiece at a temperature below a recrystallization temperature of the workpiece using a combination of axial and radial forces so that the mandrel contacts the inner diameter and imparts a compressive hoop stress to the inner diameter of the workpiece, wherein compressing the outer diameter of the workpiece causes at least a portion of the fcc phase to transform to an hcp crystal structure on the inner diameter of the workpiece.
2. The method of claim 1 , wherein compressing the outer diameter of the workpiece causes the fcc phase to transform to the hcp crystal structure, increasing, by at least two times, an amount of basal planes radially oriented perpendicular to the inner diameter of the workpiece.
3. The method of claim 1 , wherein the compressed workpiece forms a liner and further comprising placing the liner on an inner diameter of the gun barrel.
4. The method of claim 1 , wherein compressing the outer diameter of the workpiece subjects the workpiece to at least about a 20% wall reduction.
5. The method of claim 4 , wherein the workpiece has at least about 25% by weight of hcp phase with the basal planes radially oriented perpendicular to the inner diameter of the workpiece after the wall reduction.
6. The method of claim 4 , wherein the wall reduction is at least about 30%.
7. The method of claim 4 , wherein the wall reduction is at least about 50%.
8. The method of claim 1 , further comprising forming a rifling on an inner diameter of the workpiece.
9. The method of claim 8 , wherein the mandrel forms the rifling on the inner diameter.
10. The method of claim 1 , further comprising annealing the workpiece after compressing the outer diameter of the workpiece.
11. The method of claim 1 , wherein the outer diameter is compressed using a metal forming process, and the metal forming process is selected from the group consisting of radial forging, rotary swaging, pilgering, flowforming, and combinations thereof.
12. The method of claim 11 , wherein the metal forming process is flowforming, and the flowforming includes at least two flowforming passes.
13. The method of claim 1 , wherein the tubular workpiece is produced by rotary forging or rotary swaging.
14. The method of claim 1 , wherein the inner diameter is about one inch or more.
15. The method of claim 1 , wherein the temperature is around room temperature.
16. The method of claim 1 , wherein the workpiece includes at least 50% by weight fcc phase.
17. The method of claim 1 , wherein the workpiece includes at least 80% by weight fcc phase.
18. The method of claim 1 , further comprising annealing the workpiece after compressing the outer diameter of the workpiece.
19. A superalloy gun barrel produced according to the method of claim 1 .
20. A superalloy liner produced according to the method of claim 1 , the liner to be used within an inner diameter of a gun barrel.