Method of producing high-temperature parts by way of low-temperature sintering

• US 5,284,695 A
• Filed: 03/20/1992
• Issued: 02/08/1994
• Est. Priority Date: 09/05/1989
• Status: Expired due to Fees

• Current Assignee: Board of Regents of the University of Texas System (University of Texas System)
• Original Assignee: Board of Regents of the University of Texas System (University of Texas System)
• Inventors: Vail, Neal K., Barlow, Joel W.
• Primary Examiner(s): Powell, William A.
• Application Number:
  US07/854,246
• Time in Patent Office: 690 Days
• Field of Search: 264/22, 264/41-43, 264/56, 264/60, 264/61, 264/63, 264/109, 264/125, 156/62.2, 156/272.8, 219/121.65, 219/121.66, 428/206, 428/241, 428/283, 428/323, 428/325, 428/357, 428/402, 428/406
• US Class Current: 264/497
• CPC Class Codes: B22F 10/16 by embedding the binder within the powder bed
• CPC Class Codes: B22F 10/34 of powder characteristics, e.g. density, oxidation or flowability
• CPC Class Codes: B22F 12/41 characterised by the type, e.g. laser or electron beam
• CPC Class Codes: B22F 2003/1052 assisted by energy absorption enhanced by the coating or powder
• CPC Class Codes: B22F 2998/10 Processes characterised by the sequence of their steps
• CPC Class Codes: B22F 3/004 Filling molds with powder feeding material to presses in general B30B15/302
• CPC Class Codes: B22F 3/26 Impregnating making ferrous alloys by impregnation C22C33/0242
• CPC Class Codes: B29C 64/165 using a combination of solid and fluid materials, e.g. a powder selectively bound by a liquid binder, catalyst, inhibitor or energy absorber
• CPC Class Codes: B33Y 10/00 Processes of additive manufacturing
• 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: C04B 2235/3248 Zirconates or hafnates, e.g. zircon
• CPC Class Codes: C04B 2235/3427 Silicates other than clay, e.g. water glass
• CPC Class Codes: C04B 2235/5436 micrometer sized, i.e. from 1 to 100 micron
• CPC Class Codes: C04B 2235/6026 Computer aided shaping, e.g. rapid prototyping
• CPC Class Codes: C04B 2235/608 Green bodies or pre-forms with well-defined density
• CPC Class Codes: C04B 2235/616 Liquid infiltration of green bodies or pre-forms
• CPC Class Codes: C04B 2235/665 Local sintering, e.g. laser sintering
• CPC Class Codes: C04B 35/14 based on silica
• CPC Class Codes: C04B 35/622 Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
• CPC Class Codes: C04B 35/6269 Curing of mixtures
• CPC Class Codes: C04B 35/628 : Coating the powders or the macroscopic reinforcing agents
• CPC Class Codes: C04B 35/6316 : Binders based on silicon compounds
• CPC Class Codes: C04B 35/634 : Polymers C04B35/636 takes precedence
• CPC Class Codes: C04B 35/63424 : Polyacrylates; Polymethacrylates
• CPC Class Codes: C04B 35/64 : Burning or sintering processes C04B33/32 takes precedence ; powder metallurgy B22F
• CPC Class Codes: C22C 1/1036 : starting from a melt
• CPC Class Codes: G05B 2219/49013 : Deposit layers, cured by scanning laser, stereo lithography SLA, prototyping
• CPC Class Codes: Y02P 10/25 : Process efficiency
• CPC Class Codes: Y10T 428/24893 : including particulate material
• CPC Class Codes: Y10T 428/252 : Glass or ceramic [i.e., fired or glazed clay, cement, etc.] [porcelain, quartz, etc.]
• CPC Class Codes: Y10T 428/29 : Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof

Abstract

A method of producing high temperature parts by way of relatively low temperature sintering is disclosed. A powder is produced, for example by spray drying a slurry, in which particles of a high temperature material such as a ceramic are partially coated with a low temperature material such as a polymer. The powder is subjected to selective laser sintering, or another heat-based layerwise additive process, to form a green part where the ceramic particles are bound by the polymer. The green part is permeated with a cementing agent having high temperature properties when cured; the cementing agent binds the exposed ceramic surfaces in the green part. The polymer is then removed, leaving the high temperature part. Additional cementing agent, or another high temperature material, may then be added to the part after removal of the polymer.

Claims

1. A method for producing a part, comprising:

forming a porous green part comprising particles of a first material bound by a second material, the second material having a lower melting point than said first material, and wherein surfaces of said first material are exposed within said porous green part;

applying a cementing agent to said porous green part to bind said exposed surfaces of said first material; and

removing said second material.

2. The method of claim 1, wherein said step of forming said porous green part comprises:

producing a powder comprising said first and second materials;

applying a layer of said powder at a target surface;

directing energy at selected locations of said layer corresponding to a part cross-section to fuse particles of said first material with said second material thereat;

repeating said applying and directing steps to form a three-dimensional part in layerwise fashion; and

removing unfused powder from said part.

3. The method of claim 2, wherein said directing step comprises:

scanning a laser over said layer of powder.

4. The method of claim 2, wherein said directing step comprises:

placing a mask over said layer of powder; and

exposing said masked layer of powder to a light source.

5. The method of claim 2, wherein said step of producing a powder comprises:

mixing particles of said first material with said second material to form a slurry;

spray drying said slurry to form the powder.

6. The method of claim 5, wherein said particles of said first material agglomerate during said spray drying step so that particles of the powder produced by said spray drying step have surfaces at which said first material is exposed.

7. The method of claim 6, wherein said first material comprises a ceramic.

8. The method of claim 7, wherein said second material comprises a polymer in an emulsion.

9. The method of claim 6, wherein said second material comprises a polymer.

10. The method of claim 1, further comprising:

after the step of removing said second material, repeating the step of applying a cementing agent.

11. The method of claim 1, further comprising:

after the step of removing said second material, applying a third material to said part.

12. The method of claim 1, wherein said first material comprises a ceramic.

13. The method of claim 12, wherein said second material comprises a polymer.

14. A part produced by the process comprising the steps of:

forming a porous green part comprising particles of a first material bound by a second material, the second material having a lower melting point than said first material, and wherein surfaces of said first material are exposed within said porous green part;

applying a cementing agent to said porous green part to bind said exposed surfaces of said first material;

curing said cementing agent; and

removing said second material.

15. The part of claim 14, wherein said step of forming said porous green part comprises:

producing a powder comprising said first and second materials;

applying a layer of said powder at a target surface;

directing energy at selected locations of said layer corresponding to a part cross-section to fuse particles of said first material with said second material thereat;

repeating said applying and directing steps to form a three-dimensional part in layerwise fashion; and

removing unfused powder from said part.

16. The part of claim 15, wherein said directing step comprises:

scanning a laser over said layer of powder.

17. The part of claim 15, wherein said step of producing a powder comprises:

mixing particles of said first material with said second material to form a slurry; and

spray drying said slurry to form the powder;

wherein said particles of said first material agglomerate during said spray drying step so that particles of the powder produced by said spray drying step have surfaces at which said first material is exposed.

18. The part of claim 14, wherein said first material comprises a ceramic, and wherein said second material comprises a polymer.

19. The part of claim 14, further comprising:

after the step of removing said second material, repeating the step of applying a cementing agent.

20. The part of claim 14, further comprising:

after the step of removing said second material, applying a third material to said part.

21. The part of claim 15, wherein at least one of the directing steps directs energy at a first location of a first layer, and also directs energy at a plurality of locations of said first layer surrounding said first location and separated from said first location by unfused powder, so that said three-dimensional part formed by the repeating step has at least one internal structure.