Method for the manufacture of a shaped body as well as a green compact

• US 9,393,088 B2
• Filed: 11/09/2011
• Issued: 07/19/2016
• Est. Priority Date: 11/09/2010
• Status: Active Grant

• Current Assignee: Degudent GmbH (Astrazeneca PLC)
• Original Assignee: Degudent GmbH (Astrazeneca PLC)
• Inventors: Hachenberg, Jrg, Zellmann, Gerhard, Steinke, Rudi, Vollmann, Markus, Wissel, Irmgard, Hock, Elmar, Fecher, Stefan, Volkl, Lothar
• Primary Examiner(s): Kastler, Scott
• Assistant Examiner(s): LUK, VANESSA TIBAY
• Application Number:
  US13/292,132
• Publication Number:
  US 20120114516A1
• Time in Patent Office: 1,714 Days
• US Class Current: 1/1
• CPC Class Codes: A61C 13/0022 Blanks or green, unfinished dental restoration parts
• CPC Class Codes: A61K 6/84 comprising metals or alloys
• CPC Class Codes: B22F 2003/247 Removing material: carving, cleaning, grinding, hobbing, honing, lapping, polishing, milling, shaving, skiving, turning the surface
• CPC Class Codes: B22F 2003/248 Thermal after-treatment
• CPC Class Codes: B22F 2301/15 Nickel or cobalt
• CPC Class Codes: B22F 3/02 Compacting only
• CPC Class Codes: B22F 3/1021 Removal of binder or filler removal of binder from ceramics C04B35/638
• CPC Class Codes: B22F 3/11 Making porous workpieces or articles
• CPC Class Codes: B22F 3/16 in successive or repeated steps
• CPC Class Codes: B22F 3/24 After-treatment of workpieces or articles B22F3/1146 takes precedence
• CPC Class Codes: C22C 19/05 with chromium
• CPC Class Codes: C22C 19/053 with the maximum Cr content being at least 30% but less than 40%
• CPC Class Codes: C22C 19/055 with the maximum Cr content being at least 20% but less than 30%
• CPC Class Codes: C22C 19/07 based on cobalt

Abstract

A method for manufacturing a shaped body, comprising creating a mixture of a metal powder and binding agent, compacting the mixture to form a green compact, heating the green compact to a debinding start temperature T₁, debinding the green compact by controlled heating of the green compact from start temperature T₁ to end temperature T₂ at a heat-up rate R₁, presintering the debindered green compact to the presinter end temperature T_VS at a heat-up rate R_HVS, cooling the green compact from the presinter end temperature T_VS at a cool-down rate R_KVS, whereby at least the heat-up rate R_HVS, the presinter end temperature T_VS, and the cool-down rate R_KVS are tuned relative to each other in such a way that the presintered green compact forming a blank has a surface porosity of 16% to 22% after presintering, and machining and sintering of the blank to form the shaped body.

Claims

1. A method for the manufacture of a shaped body, a dental prosthesis, or part thereof, the method comprising:

preparing a mixture of a metal powder and a binding agent;

compacting the mixture to form a green compact;

heating the green compact from room temperature to a debinding start temperature T₁;

debinding the green compact, wherein the green compact at first is heated to the debinding start temperature T₁, with 350°

C.≦

T₁≦

550°

C., and subsequently is heated in a temperature range between T₁ and the debinding temperature T₂, with 550°

C.≦

T₂≦

650°

C., and wherein T₂>

T₁, at a heat-up rate R₁, with 1 K/min≦

R₁≦

5 K/min, to T₂, so that the green compact suffers no damage;

presintering of the debindered green compact to a presinter end temperature T_VS at a heat-up rate R_HVS;

cooling the green compact from the presinter end temperature T_VS at a cooling rate R_KVS, whereby at least the heat-up rate R_HVS, the presinter end temperature T_VS, and the cooling rate R_KVS are tuned relative to each other in such a way that the presintered green compact, forming a blank, possesses a surface porosity between 16% and 22% after presintering,

material-removing machining of the blank; and

sintering to final density of the machined blank to form the shaped body.

2. The method of claim 1, characterized in that after being heated to the presinter end temperature T_VS, the green compact is held at the presinter end temperature T_VS for the duration of a holding time t_VS before it is cooled at the cooling rate R_KVS.

3. The method of claim 2, wherein the green compact is cooled at the cooling rate R_KVS to a temperature T₃ where 450°

C.≦

T₃≦

650°

C.

4. The method of claim 1, wherein the green compact is held at the debinding end temperature T₂ for a time period t₂ with 1 min≦

t₂≦

20 min.

5. The method of claim 1, characterized in that the compacted green compact used is a green compact with a surface porosity between 16% and 27%.

6. The method of claim 5, wherein the surface porosity of the compacted green compact is between 18% and 22%.

7. The method of claim 1, characterized in that a nickel-chromium alloy, or a cobalt-chromium alloy is used as the metal powder, wherein, for a cobalt-chromium alloy, the following composition is used:

Cobalt;

50% to 70% by weight

Chromium;

20% to 35% by weight

Molybdenum;

0% to 10% by weight

Tungsten;

0% to 20% by weight

Other elements;

less than 10% by weight,

wherein the sum total adds up to 100% by weight,

wherein, for a nickel-chromium alloy, the following composition is used;

Nickel;

50% to 70% by weight

Chromium;

20% to 35% by weight

Molybdenum;

0% to 10% by weight

Tungsten;

0% to 20% by weight

Other elements;

less than 10% by weight

with a sum total of 100% by weight.

8. The method of claim 1, characterized in that the green compact is held for the duration of a holding time t_VS at the presinter end temperature T_VS, such that when a higher T_VS is selected, a shorter holding time t_VS is set.

9. The method of claim 8, wherein 650°

C.≦

T_VS≦

1100°

C.

10. The method of claim 1, characterized in that for a presinter end temperature T_VS of 650°

C.≦

T_VS<

750°

C., the holding time t_VS is 10 min≦

t_VS≦

200 min.

11. The method of claim 10, wherein 30 min≦

t_vs≦

100 min.

12. The method of claim 10, wherein 50 min≦

t_vs≦

80 min.

13. The method of claim 10, wherein 1 K/min≦

R_HVS≦

200 K/min and 1 K/min≦

R_KVS≦

200 K/min.

14. The method of claim 13, wherein 1 K/min≦

R_HVS≦

50 K/min.

15. The method of claim 13, wherein 1 K/min≦

R_HVS≦

20 K/min.

16. The method of claim 13, wherein 1 K/min≦

R_KVS≦

50 K/min.

17. The method of claim 13, wherein 1 K/min≦

R_KVS≦

20 K/min.

18. The method of claim 10, wherein 1 K/min≦

R_KVS≦

200 K/min.

19. The method of claim 1, characterized in that for a presinter end temperature T_VS of 750°

C.≦

T_VS<

850°

C., the holding time t_VS is 5 min≦

t_VS≦

60 min, and the heat-up rate R_HVS and the cool-down rate R_KVS is 5 K/min≦

R_HVS≦

200 K/min and 5 K/min≦

R_KVS≦

200 K/min.

20. The method of claim 19, wherein 10 min≦

t_vs≦

30 min.

21. The method of claim 19 wherein 5 K/min≦

R_HVS≦

20 K/min.

22. The method of claim 19, wherein 5 K/min≦

R_KVS≦

20 K/min.

23. The method of claim 1, characterized in that, for a presinter end temperature T_VS with 850°

C.≦

T_VS<

950°

C., the holding time t_VS is set to 5 min≦

t_VS≦

30 min and 15 K/min≦

R_KVS≦

200 K/min.

24. The method of claim 23, wherein 10 min≦

t_vs≦

20 min.

25. The method of claim 23, wherein 15 K/min≦

R_HVS≦

200 K/min and 15 K/min≦

R_KVS≦

200 K/min.

26. The method of claim 25, wherein 15 K/min≦

R_HVS≦

50 K/min.

27. The method of claim 25, wherein 15 K/min≦

R_KVS≦

50 K/min.

28. The method of claim 1, characterized in that for a presinter end temperature T_VS with 950°

C.≦

T_VS≦

1100°

C. the holding time t_VS is set to 5 min≦

t_VS≦

20 min.

29. The method of claim 28, wherein 30 K/min≦

R_HVS≦

200 K/min and 30 K/min≦

R_KVS≦

200 K/min.

30. The method of claim 29, wherein 30 K/min≦

R_HVS≦

100 K/min.

31. The method of claim 29, wherein 30 K/min≦

R_KVS≦

100 K/min.

32. The method of claim 1, characterized in that the green compact is kept at a presinter end temperature T_VS (in K) for a time period t_VS whereby

t/2<

t_VS<

2t

with;

33. The method of claim 32, characterized in that the heating time with an approximately constant heat-up rate R_HVS and the cooling time with an approximately constant cool-down rate R_KVS are set within the range between 650°

C. and the presinter end temperature T_VS, specified in degree Celsius, in a way so that they satisfy the condition;

34. The method of claim 32, wherein c₀−

c<

2%.

35. The method of claim 32, wherein c₀>

c.

36. The method of claim 32, wherein 18%<

c<

20%.

37. The method of claim 1, characterized in that the metal alloy is atomized into a powder and is mixed with a wax- and/or cellulose-based binding agent to produce a mixture.

38. The method of claim 37, wherein the green compact is produced by way of isostatic or axial pressing of the mixture consisting of the metal powder and the binding agent, at a pressure p with 100 MPa≦

p≦

1,000 MPa, or using a metal powder injection moulding process.

39. The method of claim 38, wherein 200 MPa≦

p≦

600 MPa.

40. The method of claim 37, wherein at least the debinding and presintering are carried out in the absence of oxygen.

41. The method of claim 40, wherein at least the debinding and presintering are carried out in a member selected from the group consisting of an inert gas atmosphere, a reducing atmosphere, a forming gas atmosphere, and a vacuum.