Metal powder composition for laser sintering

• US 20040182202A1
• Filed: 03/02/2004
• Published: 09/23/2004
• Est. Priority Date: 03/19/2003
• Status: Abandoned Application

• Current Assignee: 3D Systems, Inc. (3D Systems Corporation)
• Original Assignee: 3D Systems, Inc. (3D Systems Corporation)
• Inventors: Newell, Kenneth J., Schmidt, Kris Alan, Geving, Brad
• Application Number:
  US10/791,079
• Publication Number:
  US 20040182202A1
• Time in Patent Office: Days
• US Class Current: 75/252
• CPC Class Codes: B22F 10/16 by embedding the binder within the powder bed
• CPC Class Codes: B22F 2003/248 Thermal after-treatment
• CPC Class Codes: B22F 2202/03 Treatment under cryogenic or supercritical conditions
• CPC Class Codes: B22F 2998/10 Processes characterised by the sequence of their steps
• CPC Class Codes: B22F 2999/00 Aspects linked to processes or compositions used in powder metallurgy
• CPC Class Codes: B22F 3/24 After-treatment of workpieces or articles B22F3/1146 takes precedence
• CPC Class Codes: B22F 3/26 Impregnating making ferrous alloys by impregnation C22C33/0242
• CPC Class Codes: B33Y 10/00 Processes of additive manufacturing
• CPC Class Codes: B33Y 40/00 Auxiliary operations or equipment, e.g. for material handling
• CPC Class Codes: B33Y 70/10 Composites of different types of material, e.g. mixtures of ceramics and polymers or mixtures of metals and biomaterials
• CPC Class Codes: C22C 33/02 by powder metallurgy working metallic powder B22F
• CPC Class Codes: Y02P 10/25 Process efficiency

Abstract

A powder blend for use in laser sintering and a method for forming tough, strong, wear-resistant, corrosion-resistant infiltrated metal products are provided. The powder blend comprises a steel alloy, a polymeric binder and a high melting temperature fine particulate which are blended together, then applied layer by layer to a working surface in a laser sintering system, exposed a layer at a time to fuse together the powder until a green part of high strength is formed, and then the green part is infiltrated with a metal infiltrant in a non-reducing gas atmosphere at an effective temperature for an effective period of time. The preferred steel is a mild steel alloy.

Claims

1. A powder blend for use in a laser sintering process comprising a steel alloy selected from the group consisting of a mild steel alloy, a carbon steel and a stainless steel, a polymeric binder and a high melting temperature fine particulate.

2. The powder blend according to claim 1 wherein the steel alloy ranges in size from less than about 90 microns to about 4 microns.

3. The powder blend according to claim 2 wherein the steel alloy ranges in size from less than about 75 microns to about 8 microns.

4. The powder blend according to claim 2 wherein the steel alloy is less than about 45 microns.

5. The powder blend according to claim 1 wherein the steel alloy is spherical.

6. The powder blend according to claim 2 wherein the high melting temperature fine particulate has a particle size less than about 10 microns.

7. The powder blend according to claim 6 wherein the high melting temperature fine particulate has a particle size less than about 2 microns.

8. The powder blend according to claim 7 wherein the high melting temperature fine particulate comprises greater than about 5 weight percent and less than about 15 weight percent of the powder blend.

9. The powder blend according to claim 8 wherein the high melting temperature fine particulate comprises about 8 weight percent of the powder blend.

10. The powder blend according to claim 1 wherein the polymeric binder is a thermoplastic or a thermoset.

11. The powder blend according to claim 1 wherein the polymeric binder is selected from the group consisting of polyethylene, polypropylene, polyacetal, polymethacrylate, polyvinylacetate, nylon, wax, phenolic and combinations thereof.

12. The powder blend according to claim 11 wherein the polymeric binder is nylon.

13. The powder blend according to claim 12 wherein the nylon is one selected from the group consisting of polymers and co-polymers of nylon 6, nylon 9, nylon 10, nylon 11, and nylon 12.

14. The powder blend according to claim 1 further comprising a flow agent.

15. The powder blend according to claim 14 wherein the flow agent is fumed silica.

32. The powder blend according to claim 9 wherein the high melting temperature fine particulate is tungsten carbide.

16. A method of forming a tough, strong, wear-resistant, corrosion-resistant, infiltrated metal product comprising the steps of:

a. mixing together a powder blend comprising a steel alloy selected from the group consisting of a mild steel alloy, a carbon steel and a stainless steel, a polymeric binder and a high melting temperature fine particulate;

b. applying a layer of the powder blend to a working surface in a laser sintering system;

c. exposing the layer of the powder blend to heat energy to fuse together the steel alloy and high melting temperature fine particulate by the melting and subsequent rehardening of the binder material;

d. applying a new layer of powder blend and exposing the new layer of powder blend in sequential fashion repeatedly until a three-dimensional green metal part is formed; and

e. infiltrating a green metal part with metal infiltrant in a gas atmosphere at an effective temperature for an effective time period.

17. The method according to claim 16 wherein using a powder blend comprising about 88.75 to about 92.75 weight percent mild steel alloy;

about 6 to about 9 percent tungsten carbide, and

about 1.25 to about 2.25 weight percent polymer binder.

18. The method according to claim 16 further comprising using copper and/or copper containing alloys as a metal infiltrant.

19. The method according to claim 18 further comprising using a gas selected from the group consisting of nitrogen, argon, or a nitrogen argon blend as the gas atmosphere during infiltration.

20. The method according to claim 19 using nitrogen as the gas atmosphere during infiltration.

21. The method according to claim 19 further comprising performing the infiltrating using an infiltration cycle having a peak temperature of about 1070°

C.

22. The method according to claim 16 further comprising exposing the infiltrated green metal part to a heat treatment cycle.

23. The method according to claims 20 further comprising using a fine grit alumina packing medium as a support material to encase the green metal part during infiltration.

24. The method according to claim 17 further comprising using a powder blend having about 8 weight percent high melting temperature fine particulate,

about 1.6 to about 2.1 weight percent nylon binder, and

the remainder a mild steel alloy.

25. The method according to claim 24 further comprising deagglomerating the mild steel alloy to a range in size from less than about 90 microns to about 4 microns.

26. The method according to claim 24 further comprising deagglomerating the mild steel alloy to a range in size from less than about 75 microns to about 8 microns.

27. The method according to claim 25 further comprising deagglomerating the high melting temperature fine particulate.

28. The method according to claim 27 further comprising using a high melting temperature fine particulate having a particle size less than about 10 microns.

29. The method according to claim 22 further comprising performing the heat treatment cycle having a peak temperature of about 840°

C. for at least one hour, quenching the infiltrated part with room temperature nitrogen to reduce the part temperature over an effective time, sub-cooling the part to about −

79°

C. over at least a 90 minute period, return the part to room temperature, and temper the part for about 3 hours at about 163°

C.

30. The method according to claim 16 further comprising prior to infiltrating, absorbing nitrogen into a mild steel alloy in the green metal part.

31. The method according to claim 30 further comprising prior to infiltrating, maintaining the green metal part at a temperature in excess of about 850°

C. and less than about 900°

C. for about 4 to about 6 hours in a nitrogen atmosphere.

33. The method according to claim 28 further comprising using tungsten carbide as the high melting temperature fine particulate.