Electron beam additive manufacturing

Patent metadata

Field	Value
Publication number	US-11141809-B2
Application number	US-201615780864-A
Country	US
Kind code	B2
Filing date	Dec 1, 2016
Priority date	Dec 4, 2015
Publication date	Oct 12, 2021
Grant date	Oct 12, 2021

Abstract

A method and apparatus particularly for additively manufacturing materials that are susceptible to hot cracking. The additive manufacturing process may include a leading energy beam (16) for liquefying a raw material to form a melt pool (20), and a trailing energy beam (17) directed toward a trailing region of the melt pool. The trailing energy beam may be configured to enhance agitation and/or redistribution of liquid in the melt pool to prevent hot cracking, reduce porosity, or improve other characteristics of the solidified part. The method and apparatus also may improve processing parameters, such as adjusting vacuum level to prevent volatilization of alloying agents, or providing a chill plate to control interpass temperature. The process may be used to form new articles, and also may be used to enhance tailorability and flexibility in design or repair of pre-existing articles, among other considerations.

First claim

What is claimed is:

1. A method of additive manufacturing, comprising:
providing a raw material in solid state form;
exposing the raw material to a leading energy beam thereby liquefying the raw material;
forming a melt pool with the liquefied raw material, the melt pool having a leading region and a trailing region; and
exposing the trailing region of the melt pool to a trailing energy beam;
wherein a distance between the trailing energy beam and the leading energy beam varies as the trailing energy beam trails the leading energy beam;
wherein the distance between the trailing energy beam and the leading energy beam varies between at least (i) a first position of the trailing energy beam that is closer to the leading energy beam and (ii) a second position of the trailing energy beam that is further away from the leading energy beam, and
wherein the trailing energy beam cycles back to the first position after reaching at least the second position.

2. The method of additive manufacturing according to claim 1 ,
wherein the forming the melt pool with the liquefied raw material is performed as the leading energy beam moves in a travel direction along an x-y plane;
wherein the leading region of the melt pool is proximal to the leading energy beam as the leading energy beam moves in the travel direction; and
wherein the trailing region of the melt pool trails the leading region as the leading energy beam moves in the travel direction.

3. The method of additive manufacturing according to claim 1 , further comprising:
solidifying the melt pool to form a re-solidified layer that trails the trailing region as the trailing energy beam moves in the travel direction; and
repeating at one or more locations for building a three-dimensional structure re-solidified layer by re-solidified layer.

4. The method of additive manufacturing according to claim 1 ,
wherein the raw material is a metal or metal alloy; and
wherein the trailing region exposed to the trailing energy beam includes a solid-liquid phase.

5. The method of additive manufacturing according to claim 1 ,
wherein the trailing energy beam has a power level, power density, and/or pulsation that is configured to prevent hot cracking as the melt pool solidifies by disrupting a dendritic microstructure in the trailing region of the melt pool.

6. The method of additive manufacturing according to claim 1 ,
wherein the trailing region of the melt pool includes a liquid interface, a solid interface, and a transition region between the liquid interface and the solid interface; and
wherein the trailing energy beam is configured in a pattern that corresponds to a shape of the transition region along an x-y plane.

7. The method of additive manufacturing according to claim 1 ,
wherein the trailing energy beam is configured in a pattern selected from the group consisting of: chevron-shaped, arc-shaped, crescent-shaped, or parabolic-shaped.

8. The method of additive manufacturing according to claim 1 ,
wherein the trailing energy beam is spaced apart from the leading energy beam so that the trailing energy beam is maintained in a transition region of the trailing region, the transition region being between a liquid interface and a solid interface of the melt pool and including a solid-liquid phase.

9. The method of additive manufacturing according to claim 1 ,
wherein the trailing energy beam has a power level, power density, and/or pulsation that is configured to agitate the trailing region of the melt pool for reducing hot cracking and/or porosity when the melt pool solidifies.

10. The method of additive manufacturing according to claim 9 ,
wherein the trailing energy beam has a power level, power density, and/or pulsation that is configured to redistribute liquid constituents in the trailing region of the melt pool so as to replenish lost volume at solidifying regions of the melt pool.

11. The method of additive manufacturing according to claim 1 ,
wherein the raw material is a metal wire.

12. The method of additive manufacturing according to claim 1 ,
wherein the trailing energy beam has a power level, power density, voltage potential, and/or current that is different than a power level, power density, voltage potential, and/or current of the leading energy beam.

13. The method of additive manufacturing according to claim 1 ,
wherein the combined power levels of the leading energy beam and the trailing energy beam represents a total power level, and wherein the total power level is in the range of 1 kW to 10 kW.

14. The method of additive manufacturing according to claim 1 , further including the steps:
solidifying the melt pool to form a re-solidified layer;
exposing the re-solidified layer to the trailing energy beam for stress relieving and/or annealing the re-solidified layer.

15. A method of tailoring the properties of a pre-existing article, comprising:
utilizing the additive manufacturing process according to the method of claim 1 ;
wherein the composition of the raw material is different than a material that forms a major component of the pre-existing article, the composition of the raw material being tailored to provide unique qualities to the pre-existing article.

16. The method of additive manufacturing according to claim 1 being selected from the group consisting of:
i) direct energy deposition, including direct metal deposition, laser deposition wire, laser deposition powder, laser consolidation, laser engineering net shape, electron beam direct melting;
ii) powder bed fusion, including direct metal laser sintering, selective laser sintering, selective laser melting, electron beam melting; and
iii) other additive manufacturing methods in which a melt pool is produced and solidified.

17. The method of additive manufacturing according to claim 1 , wherein the raw material is an aluminum alloy having aluminum as a major component.

18. The method of additive manufacturing according to claim 1 ,
wherein the melt pool is autogenously formed and solidified independent of adding a separate filler material to the melt pool that is different from the raw material.

19. The method of additive manufacturing according to claim 1 , wherein:
the providing the raw material in solid state form includes providing a metal alloy in solid state form, the metal alloy having a plurality of alloying agents; and
the exposing the raw material to the leading energy beam thereby liquefying the raw material includes heating the metal alloy to a processing temperature that is beyond the melting point of the metal alloy;
wherein the additive manufacturing is conducted in a vacuum chamber;
wherein one of the plurality of alloying agents has a highest vapor pressure at the processing temperature among the plurality of alloying agents; and
wherein a pressure level of the vacuum chamber is equal to or greater than the vapor pressure of the alloying agent having the highest vapor pressure among the plurality of alloying agents.

20. The method of additive manufacturing according to claim 19 ,
wherein the pressure level of the vacuum chamber is in the range of 500 microtorr to 3,000 microtorr.

21. The method of additive manufacturing according to claim 19 ,
wherein the metal alloy is Al 6061 and the processing temperature is in the range of 580 degrees Celsius to 652 degrees Celsius; and
wherein the pressure level of the vacuum chamber is in the range of 2,000 microtorr to 3,000 microtorr.

22. A m

Assignees

• Raytheon Co

Inventors

• Nelson Norman Dana
• Carlsten Curtis B
• Pistorino Mark J

Classifications

• B22F12/45

  Two or more · CPC title

• B22F10/38

  to achieve specific product aspects, e.g. surface smoothness, density, porosity or hollow structures · CPC title

• B22F10/364

  for post-heating, e.g. remelting · CPC title

• B22F10/32

  of the atmosphere, e.g. composition or pressure in a building chamber · CPC title

• B22F10/25

  Direct deposition of metal particles, e.g. direct metal deposition [DMD] or laser engineered net shaping [LENS] · CPC title