Metal and ceramic containing parts produced from powder using binders derived from salt

• US 6,508,980 B1
• Filed: 07/07/2000
• Issued: 01/21/2003
• Est. Priority Date: 09/26/1997
• Status: Expired due to Term

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Allen, Samuel, Hadjiloucas, Constantinos, Sachs, Emanuel M., Yoo, Helen J.
• Primary Examiner(s): Jenkins, Daniel J.
• Application Number:
  US09/509,284
• Time in Patent Office: 928 Days
• Field of Search: 419/36, 419/37, 419/45, 419/27
• US Class Current: 419/45
• CPC Class Codes: B22F 1/10 Metallic powder containing lubricating or binding agents; Metallic powder containing organic material
• CPC Class Codes: B22F 1/105 containing inorganic lubricating or binding agents, e.g. metal salts
• CPC Class Codes: B22F 10/14 by jetting of binder onto a bed of metal powder
• CPC Class Codes: B22F 2003/1042 with support for articles to be sintered
• CPC Class Codes: B22F 2998/00 Supplementary information concerning processes or compositions relating to powder metallurgy
• CPC Class Codes: B22F 2999/00 Aspects linked to processes or compositions used in powder metallurgy
• CPC Class Codes: B22F 3/001 Starting from powder comprising reducible metal compounds making ferrous alloys starting from compounds C22C33/0235
• CPC Class Codes: B22F 3/1035 Liquid phase sintering
• CPC Class Codes: B33Y 10/00 Processes of additive manufacturing
• CPC Class Codes: Y02P 10/25 Process efficiency

Abstract

Parts made from powder use a material that originates from a salt to bind powder particles together. The salt may be provided dissolved in a solution, as molten salt, or as a dry powder. The figure is an electron micrograph of a cross section of a silver nitrate bound product with a skeleton of steel powder.

Claims

1. A method for forming a body from powder using a three-dimensional printing process, comprising the steps of:

a. providing a layer of powder of a first material, granules of said powder layer contacting one another;

b. printing on said layer of powder, at one or more selected regions, a liquid vehicle that contains a metal salt that will cause said powder granules to be bound together at said selected regions;

c. repeating said steps a and b of providing a layer of powder and printing a liquid on said layer additional times until a desired amount of printed powder has been provided, said selected regions defining a body; and

d. maintaining said printed liquid and powder under conditions such that a metal, which is different from said first material, and which originates from said salt solution, forms at interfaces between said powder granules, and binds adjacent granules to each other within each layer and between layers, said maintaining step comprising further processing said body at a temperature above which metal from said salt, reduces onto said powder granules at said interfaces.

2. The method of claim 1, said step of further processing comprising the step of further processing said body at a temperature above which said reduced metal begins to sinter.

3. The method of claim 1, said step of further processing comprising the step of further processing said body at a temperature above which said reduced metal begins to melt.

8. The method of claim 1, said reduced metal being formed such that it loosely binds said granules to each other to form a bound body, said method further comprising the steps of:

a. removing said loosely bound body of granules with reduced metal at interfaces therebetween from any surrounding granules of powder that are not bound by any such reduced metal; and

b. further processing said body at a temperature above which said reduced metal sinters.

9. The method of claim 8, said step of further processing comprising the step of further processing said body at a temperature above which said sintered metal begins to melt.

10. The method of claim 8, further comprising, between said steps of removing said loosely bound body and further processing said body at a temperature above which said reduced metal sinters, the step of settering said removed body in another, settering powder.

15. The method of claim 1 said reducing step comprising the step of firing said powder body in an environment that contains a reducing agent.

16. The method of claim 15, said reducing agent comprising hydrogen.

44. The method of claim 1, further comprising, after said step of printing and before said step of repeating, the step of drying said printed layer, and further, wherein said step of repeating also includes repeating said step of drying said printed layer.

45. The method of claim 1, further comprising, the step of drying said printed layers, said step of drying being conducted to dry at least two of said layers substantially simultaneously.

46. The method of claim 45, said step of drying comprising drying substantially all of said layers substantially simultaneously, after all of said layers have been provided and printed.

4. A method for forming a body from powder using a three-dimensional printing process, comprising the steps of:

a. providing a layer of powder of a first material, granules of said powder layer contacting one another;

b. printing on said layer of powder, at one or more selected regions, a liquid vehicle that contains a metal salt that will cause said powder granules to be bound together at said selected regions;

c. repeating said steps a and b of providing a layer of powder and printing a liquid on said layer additional times until a desired amount of printed powder has been provided, said selected regions defining a body;

d. drying said body, in any number of layers, from one at a time to all of said layers simultaneously, such that crystallized metal salt from said salt solution loosely binds said granules to each other to form a bound body;

e. removing said loosely bound body of granules from any surrounding, unbound powder; and

f. maintaining said printed liquid and powder under conditions such that a metal, which is different from said first material, and which originates from said salt solution, forms at interfaces between said powder granules, and binds adjacent granules to each other within each layer and between layers, said maintaining step comprising further processing said body at a temperature above which metal from said crystallized salt reduces onto said powder granules at said interfaces.

5. The method of claim 4, said step of further processing comprising the step of further processing said body at a temperature above which said reduced metal begins to sinter.

6. The method of claim 4, said step of further processing comprising the step of further processing said body at a temperature above which said reduced metal begins to melt.

7. The method of claim 4, further comprising, between the steps of removing said loosely bound body and further processing said body at a temperature above which metal reduces, the step of settering said removed body in another, settering powder.

11. A method for forming a body from powder using a three-dimensional printing process, comprising the steps of:

a. providing a layer of powder of a first material, granules of said powder layer contacting one another;

b. printing on said layer of powder, at one or more selected regions, a liquid vehicle that contains a metal salt and a polymeric binder, that will cause said powder granules to be bound together;

c. repeating said steps a and b of providing a layer of powder and printing a liquid on said layer additional times until a desired amount of printed powder has been provided, said selected regions defining a body;

d. drying said layers, either individually or in groups, such that said granules loosely bind to each other to form a bound body;

e. removing said loosely bound granules from any surrounding, unbound powder; and

f. maintaining said printed liquid and powder under conditions such that a metal which is different from said first material, and which originates from said salt solution, forms at interfaces between said powder granules, and binds adjacent granules to each other within each layer and between layers, said maintaining step comprising further processing said body at a temperature above which metal from said salt reduces onto said powder granules at said interfaces.

12. The method of claim 11, said step of further processing comprising the step of further processing said body at a temperature above which said reduced metal begins to sinter.

13. The method of claim 11, said step of further processing comprising the step of further processing said body at a temperature above which said reduced metal begins to melt.

14. The method of claim 11, further comprising, between said steps of removing and further processing said body at a temperature above which metal from said salt reduces, the further step of settering said removed body in another, settering powder.

17. A method for forming a body from powder using a three-dimensional printing process, comprising the steps of:

a. providing a layer of powder of a first material, granules of said powder layer contacting one another;

b. printing on said layer of powder, at one or more selected regions, a liquid vehicle that contains a metal salt that will cause said powder granules to be bound together at said selected regions;

c. repeating said steps a and b of providing a layer of powder and printing a liquid on said layer additional times until a desired amount of printed powder has been provided, said selected regions defining a body; and

d. maintaining said printed liquid and powder under conditions such that a metal, which is different from said first material, and which originates from said salt solution, forms at interfaces between said powder granules, and binds adjacent granules to each other within each layer and between layers, said maintaining step comprising reducing said salt from said liquid so as to form a metal film at said interfaces between said powder granules.

18. The method of claim 17, said salt comprising a film forming salt.

19. The method of claim 18, said salt comprising salt that reduce to metal only at a temperature above that at which the immediate precursor to said reduced metal is molten.

20. The method of claim 17, said salt comprising silver nitrate.

47. The method of claim 17, said salt comprising a salt that reduces to a metal and forms a film at a temperature below a temperature at which said metal of said salt begins to melt.

48. The method of claim 17, said step of maintaining comprising reducing said salt from said liquid so as to form a metal film at said interfaces between said powder granules, said reduction step being carried out at a temperature below a temperature at which said metal of said film begins to melt.

21. A method for forming a body from powder using a three-dimensional printing process, comprising the steps of:

a. providing a layer of metal powder of a first mate rial, granules of said powder layer contacting one another;

b. printing on said layer of metal powder, a liquid vehicle that contains a salt that will cause said powder granules to be bound together;

c. repeating said steps a and b of providing a layer of powder and printing a liquid on said layer, additional times until a desired amount of printed powder has been provided;

d. maintaining said liquid and metal powder under conditions such that a metal, which originates from said salt solution, reduces from said salt while s aid salt is in said liquid vehicle and adheres to said powder granules at interfaces between said powder granules, and binds adjacent granules to each other within said layer and between layers.

22. The method of claim 21, said step of maintaining said liquid and powder being conducted between said steps of printing and repeating, such that it is also repeated with said steps of providing powder and printing liquid.

23. The method of claim 21, said step of maintaining said liquid and powder being conducted after said step of repeating.

24. The method of claim 22, said step of maintaining said liquid and powder being conducted both between said steps of printing and repeating and after said step of repeating.

25. The method of claim 21, said reducing step comprising the step of contacting said liquid containing salt to said granules.

26. The method of claim 21, said step of reducing said salt to a metal while said salt is in said liquid vehicle resulting in binding of granules of said powder which have been contacted by said solution, said method further comprising the step of removing said bound granules from any unbound granules, to form a body.

27. The method of claim 21, further comprising the steps of:

a. further processing said body of granules at a temperature above which said reduced metal from said salt sinters thereby resulting in a body of granules that are bound to each other by said sintered metal; and

b. removing said bound body from any unbound metal powder granules.

28. The method of claim 21, further comprising the steps of:

a. further processing said body of granules at a temperature above which said reduced metal from said salt melts, thereby resulting in a body of granules that are bound to each other by said melted metal; and

b. removing said bound body from any unbound powder granules.

29. The method of claim 26, said reduced metal being deposited such that it loosely binds said granules to each other to form a bound body, said method further comprising the steps of:

a. removing said loosely bound body of granules with reduced metal at necks therebetween from any surrounding granules that are not bound by any such reduced metal; and

b. further processing said body at a temperature above which said reduced metal sinters.

30. The method of claim 29, said step of further processing comprising the step of further processing said body at a temperature above which said sintered metal begins to melt.

31. The method of claim 29, further comprising, between said steps of removing said loosely bound body and further processing said body at a temperature above which said reduced metal sinters, the step of settering said removed body in another, settering powder.

32. The method of claim 21, said liquid solution further containing a polymeric binder, said maintaining step comprising the steps of:

a. drying said body, such that said granules loosely bind to each other to form a body;

b. removing said body of loosely bound granules from any surrounding, unbound powder; and

c. further processing said body at a temperature above which said reduced metal from said salt sinters at necks where said granules contact each other.

33. The method of claim 32, said step of further processing comprising the step of further processing said body at a temperature above which said reduced metal begins to melt.

34. The method of claim 32, further comprising, between said steps of removing said loosely bound body and further processing said body at a temperature above which said reduced metal sinters, the step of settering said removed body in another, settering powder.

35. The method of claim 21, said powder and said liquid vehicle selected such that said reducing step comprises a displacement reaction.

36. The method of claim 21, said powder and said liquid solution comprises a metal salt solution, said solution and said metal powder being chosen such that the metal of the powder is capable of providing electrons to metal ions of said salt as metal of said powder dissolves into said solution.

37. The method of claim 21, further wherein said metal of said salt is more negative (noble) as measured on the electromotive force series, than said metal of said metal powder.

38. A method for forming a body from powder, comprising the steps of:

a. providing a volume of powder of a first material, granules of said powder volume contacting one another;

b. while maintaining said granules of said volume of powder substantially stationary relative to each other, providing in said volume of powder, a liquid vehicle that contains a metal salt, which will cause said granules to be bound together; and

c. maintaining said liquid and powder under conditions such that a metal, which is different from said first material and which originates from said salt solution, forms at interfaces between said powder granules, and binds adjacent granules to each other, said step of maintaining said liquid and powder comprising the step of processing said liquid and powder to form necks of said metal between said powder granules, which necks bind said granules, said step of processing said liquid and powder comprising;

i. drying said body; and

ii. further processing said body at a temperature above which metal from said salt reduces onto said powder granules at interfaces where said granules contact each other.

39. The method of claim 38, said step of further processing comprising the step of further processing said body at a temperature above which said reduced metal begins to sinter.

40. The method of claim 38, said step of further processing comprising the step of further processing said body at a temperature above which said reduced metal begins to melt.

41. A method for forming a body from powder, comprising the steps of:

a. providing a volume of powder of a first material, granules of said powder volume contacting one another;

b. while maintaining said granules of said volume of powder substantially stationary relative to each other, providing in said volume of powder, a liquid vehicle that contains a metal salt, which will cause said granules to be bound together; and

c. maintaining said liquid and powder under conditions such that a metal, which is different from said first material and which originates from said salt solution, forms at interfaces between said powder granules, and binds adjacent granules to each other, said step of maintaining said liquid and powder comprising reducing said salt to a metal.

42. The method of claim 41, said reducing step comprising the step of firing said powder body in an environment that contains a reducing agent.

43. The method of claim 42, said reducing agent comprising hydrogen.

49. A method for forming a body from powder using a three-dimensional printing process, comprising the steps of:

a. providing a layer of powder of a first material, granules of said powder layer contacting one another;

b. printing on said layer of powder, at one or more selected regions, a liquid vehicle that contains a metal compound that will cause said powder granules to be bound together at said selected regions;

c. repeating said steps a and b of providing a layer of powder and printing a liquid on said layer additional times until a desired amount of printed powder has been provided, said selected regions defining a body; and

d. maintaining said printed liquid and powder under conditions such that a metal, which is different from said first material, and which originates from said liquid vehicle and metal compound, forms at interfaces between said powder granules, and binds adjacent granules to each other within each layer and between layers, said maintaining step comprising further processing said body at a temperature above which said compound, reacts to form a metal onto said powder granules at said interfaces.

50. The method of claim 49, said step of further processing comprising further processing said body at a temperature above which said compound reduces to form a metal.

51. The method of claim 49, said step of further processing comprising further processing said body at a temperature above which said compound decomposes to form a metal.

52. The method of claim 49, said step of further processing comprising further processing said body under conditions such that said compound reduces to form a metal.

53. The method of claim 49, said step of further processing comprising further processing said body under conditions such that said compound decomposes to form a metal.