Casting shapes

• US 4,818,562 A
• Filed: 03/24/1988
• Issued: 04/04/1989
• Est. Priority Date: 03/04/1987
• Status: Expired due to Fees

• Current Assignee: Westinghouse Electric Corporation (Paramount Global (f/k/a ViacomCBS Inc.))
• Original Assignee: Westinghouse Electric Corporation (Paramount Global (f/k/a ViacomCBS Inc.))
• Inventors: Arcella, Frank G., Lessmann, Gerald G.
• Primary Examiner(s): Silverman, Stan
• Application Number:
  US07/172,991
• Time in Patent Office: 376 Days
• Field of Search: 427/53.1, 427/180, 427/185, 427/197, 427/202, 427/203, 427/204, 427/205, 219/121 LA, 219/121 LE, 219/121 LF, 219/121 LP, 219/121 LW, 219/121 LY, 264/29.3, 264/109, 264/113, 264/125, 118/429, 118/DIG. 5, 118/641-643
• US Class Current: 427/597
• CPC Class Codes: B22D 23/06 Melting-down metal, e.g. metal particles, in the mould
• CPC Class Codes: B22F 1/00 Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
• CPC Class Codes: B22F 1/09 Mixtures of metallic powders
• CPC Class Codes: B22F 1/12 Metallic powder containing non-metallic particles containing lubricating or binding agents or organic material B22F1/10
• CPC Class Codes: B22F 10/10 Formation of a green body
• CPC Class Codes: B22F 10/28 Powder bed fusion, e.g. selective laser melting [SLM] or electron beam melting [EBM]
• CPC Class Codes: B22F 12/17 to heat the build chamber or platform
• CPC Class Codes: B22F 12/41 characterised by the type, e.g. laser or electron beam
• CPC Class Codes: B22F 12/49 Scanners
• CPC Class Codes: B22F 2202/15 Use of fluidised beds
• CPC Class Codes: B22F 2998/00 Supplementary information concerning processes or compositions relating to powder metallurgy
• 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 3/004 Filling molds with powder feeding material to presses in general B30B15/302
• CPC Class Codes: B29C 41/10 by fluidisation
• CPC Class Codes: B29C 64/153 using layers of powder being selectively joined, e.g. by selective laser sintering or melting
• CPC Class Codes: C23C 26/02 applying molten material to the substrate
• CPC Class Codes: Y02P 10/25 Process efficiency
• CPC Class Codes: Y10S 118/05 Fluidized bed

Abstract

Disclosed is a method of casting a shape. A laser or electron gun is directed at a fusible powder in a fluidized bed. The beam melts the powder and the melted powder fuses and solidifies on a surface to form the shape. Also disclosed is apparatus for casting a shape. The apparatus includes a fluidized bed containing a fluidized powder, a surface within the bed on which the shape is cast, an electron beam or laser directed at the surface, which has an energy sufficient to fuse the powder, means for controlling the level of the powder in the fluidized bed relative to the surface, and means for controlling the horizontal position of the surface relative to the beam.

Claims

1. A method of casting a shape comprising directing a laser or electron gun at fusible powder in a fluidized bed, where said beam melts said powder and said melted powder fuses and solidifies on a surface, forming said shape.

2. A method according to claim 1 wherein said powder is selected from the group consisting of metals, ceramics, plastics, and mixtures thereof.

3. A method according to claim 1 wherein said powder is a mixture of different kinds of particles.

4. A method according to claim 3 wherein said powder is a mixture of metal particles and ceramic particles.

5. A method according to claim 2 wherein said powder is metal powder.

6. A method according to claim 5 wherein said powder is a mixture of at least two different metals.

7. A method according to claim 5 wherein said powder comprises titanium.

8. A method according to claim 7 wherein said titanium is contaminated with an element selected from the group consisting of sodium, magnesium, chlorine, and mixtures thereof.

9. A method according to claim 5 wherein said metal is an alloy.

10. A method according to claim 9 wherein said alloy is an alloy of titanium.

11. A method according to claim 10 wherein said alloy has the approximate composition 90% Ti-6% Al-4% V.

12. A method according to claim 5 wherein said powder comprises tungsten.

13. A method according to claim 1 wherein the composition of said powder is changed as said shape is formed.

14. A method according to claim 1 wherein said powder in said bed is heated.

15. A method according to claim 14 wherein said powder is heated by an electrical resistance heater in said fluidized bed.

16. A method according to claim 1 wherein said powder is fluidized with a gas that reacts with said powder when it is fused.

17. A method according to claim 16 wherein said gas is methane and said powder is a metal, whereby a metal carbide is formed.

18. A method according to claim 17 wherein said gas is nitrogen and said powder is a metal, whereby a metal nitride is formed.

19. A method according to claim 1 wherein said powder is fluidized with an inert gas.

20. A method according to claim 1 wherein said beam is a laser beam.

21. A method according to claim 20 wherein said laser beam is from a C0₂ laser.

22. A method according to claim 1 wherein said powder is not fluidized when it is melted.

23. A method according to claim 1 wherein said beam is directed downward at 90°

to said surface.

24. A method according to claim 1 wherein more than one beam is directed at the same powder.

25. A method according to claim 1 wherein a single beam is split and is directed at powder in different areas of said fluidizing bed, whereby two identical shapes are formed on said surface.

26. A method according to claim 1 wherein at least two beams are directed at powder in different areas of said fluidized bed, whereby two identical shapes are formed on said surface.

27. A method according to claim 1 wherein said shape is lowered in said fluidized bed as it forms, so that the top of said powder in said bed is higher than said shape.

28. A method according to claim 1 wherein the level of said powder in said fluidized bed is raised as said shape forms so that said level is above the top of said shape.

29. A method according to claim 28 wherein the level of said powder in said fluidized bed is raised by increasing the pressure of the gas used to fluidize said powder.

30. A method according to claim 28 wherein the level of said powder in said fluidized bed is raised by adding powder to said bed.

31. A method according to claim 1 wherein said powder that forms said shape is replaced by adding more powder to said bed.

32. A method according to claim 1 wherein the level of said powder above said shape is determined by a sensor.

33. A method according to claim 1 wherein said beam is fixed and said surface moves horizontally.

34. A method according to claim 33 wherein said surface, is moved manually.

35. A method according to claim 33 wherein the horizontal movement of said surface is controlled by a computer.

36. A method according to claim 1 wherein said surface is fixed and said beam is moved relative to said surface.

37. A method according to claim 36 wherein said beam is moved manually.

38. A method according to claim 36 wherein the movement of said beam is controlled by a computer.

39. A method according to claim 1 wherein said surface is horizontal and flat.

40. A method of casting a near net shape comprising:

(A) fluidizing a laser-fusible powder in a fluidized bed to a level slightly higher than the level of a surface within said fluidized bed;

(B) stopping said fluidizing of said powder, whereby a layer of said powder is deposited on said surface;

(C) directing a laser beam downward at said layer of powder while changing the horizontal position of said surface relative to said laser beam, whereby said powder fuses on said surface;

(D) fluidizing said powder to a level slightly higher than the top of said fused powder; and

(E) repeating steps (B), (C), and (D) until said near net shape is completed.

44. A method according to claim 40 wherein said powder is selected from the group consisting of metals, ceramics, plastics, and mixtures thereof.

45. A method according to claim 40 wherein said powder is a mixture of different kinds of particles.

46. A method according to claim 45 wherein said powder is a mixture of metal particles and ceramic particles.

47. A method according to claim 44 wherein said powder is a metal powder.

48. A method according to claim 47 wherein said powder is a mixture of at least two different metals.

49. A method according to claim 47 wherein said powder comprises titanium.

50. A method according to claim 49 wherein said titanium is contaminated with an element selected from the group consisting of sodium, magnesium, chlorine, and mixtures thereof.

51. A method according to claim 47 wherein said metal is an alloy.

52. A method according to claim 51 wherein said alloy is an alloy of titanium.

53. A method according to claim 52 wherein said alloy has the approximate composition 90% Ti-6% Al-4% V.

54. A method according to claim 47 wherein said powder comprises tungsten.

55. A method according to claim 40 wherein the composition of said powder is changed as said shape is formed.

56. A method according to claim 40 wherein said powder in said bed is heated.

57. A method according to claim 56 wherein said powder is heated by an electrical resistance heater in said fluidized bed.

58. A method according to claim 40 wherein said powder is fluidized with a gas that reacts with said powder when it is fused.

59. A method according to claim 58 wherein said gas is methane and said powder is a metal, whereby a metal carbide is formed.

60. A method according to claim 59 wherein said gas is nitrogen and said powder is a metal, whereby a metal nitride is formed.

61. A method according to claim 40 wherein said powder is fluidized with an inert gas.

62. A method according to claim 40 wherein said laser beam is from a C0₂ laser.

63. A method according to claim 40 wherein said beam is directed downward at 90°

to said surface.

64. A method according to claim 40 wherein said laser beam is split and is directed at powder in different areas of said fluidizing bed, whereby two indentical shapes are formed on said surface.

65. A method according to claim 40 wherein the level of said powder in said fluidized bed is rasied by increasing the pressure of the gas used to fluidize said powder.

66. A method according to claim 40 wherein the level of said powder in said fluidized bed is raised by adding powder to said bed.

67. A method according to claim 40 wherein said powder that forms said shape is replaced by adding more powder to said bed.

68. A method according to claim 40 wherein the level of said powder above said shape is determined by a sensor.

69. A method according to claim 40 wherein said beam is fixed and said surface moves horizontally.

70. A method according to claim 69 wherein said surface is moved manually.

71. A method according to claim 69 wherein the horizontal movement of said surface is controlled by a computer.

72. A method according to claim 40 wherein said surface is fixed and said laser beam is moved relative to said surface.

73. A method according to claim 72 wherein said beam is moved manually.

74. A method according to claim 72 wherein the movement of said laser beam is controlled by a computer.

75. A method according to claim 40 wherein said surface is horizontal and flat.

41. A method of forming a metal casting of a near net shape comprising:

(A) fluidizing metal powder in a fluidized bed to a level about 1/32 to about 1 inch above the level of a horizontal surface within said fluidized bed;

(B) stopping said fluidizing of said powder, whereby a layer of said powder is deposited on said surface;

(C) directing a C0₂ laser beam having a power sufficient to melt said metal powder downward at said layer of powder, while changing the horizontal position of said horizontal surface relative to said laser beam, whereby said melted powder fuses on said surface and solidifies, forming a horizontal cross-section of said near net shape;

(D) fluidizing said powder in said fluidized bed so that said level is about 1/32 to about 1 inch above the top of said horizontal cross section; and

(E) repeating steps (B), (C), and (D) until said metal casting is formed.

42. A method according to claim 41 wherein said level is maintained by lowering said horizontal surface.

43. A method according to claim 42 wherein said level is maintained by raising the level of said powder.

76. A method according to claim 41 wherein said metal powder is a mixture of at least two different metals.

77. A method according to claim 41 wherein said powder comprises titanium.

78. A method according to claim 77 wherein said titanium is contaminated with an element selected from the group consisting of sodium, magnesium, chlorine, and mixtures thereof.

79. A method according to claim 41 wherein said metal is an alloy.

80. A method according to claim 79 wherein said alloy is an alloy of titanium.

81. A method according to claim 80 wherein said alloy has the approximate composition 90% Ti-6% Al-4% V.

82. A method according to claim 41 wherein said metal powder comprises tungsten.

83. A method according to claim 41 wherein the composition of said metal powder is changed as said shape is formed.

84. A method according to claim 41 wherein said metal powder in said bed is heated.

85. A method according to claim 84 wherein said metal powder is heated by an electrical resistance heater in said fludized bed.

86. A method according to claim 41 wherein said metal powder is fluidized with a gas that reacts with said metal powder when it is fused.

87. A method according to claim 86 wherein said gas is methane, whereby a metal carbide is formed.

88. A method according to claim 86 wherein said gas is nitrogen, whereby a metal nitride is formed.

89. A method according to claim 41 wherein said metal powder is fluidized with an inert gas.

90. A method according to claim 41 wherein said beam is directed downward at 90°

to said surface.

91. A method according to claim 41 wherein said laser beam is split and is directed at powder in different areas of said fluidizing bed, whereby two identical shapes are formed on said surface.

92. A method according to claim 41 wherein the level of said metal powder in said fluidized bed is raised by increasing the pressure of the gas used to fluidize said metal powder.

93. A method according to claim 92 wherein the level of said metal powder in said fluidized bed is raised by adding metal powder to said bed.

94. A method according to claim 41 wherein said metal powder that forms said shape is replaced by adding more metal powder to said bed.

95. A method according to claim 41 wherein the level of said metal powder above said shape is determined by a sensor.

96. A method according to claim 41 wherein said beam is fixed and said surface moves horizontally.

97. A method according to claim 96 wherein said surface is moved manually.

98. A method according to claim 96 wherein the horizontal movement of said surface is controlled by a computer.

99. A method according to claim 41 wherein said surface is fixed and said beam is moved relative to said surface.

100. A method according to claim 99 wherein said beam is moved manually.

101. A method according to claim 99 wherein the movement of said beam is controlled by a computer.

102. Apparatus for casting a shape comprising:

(A) a fluidized bed;

(B) a surface within said bed;

(C) an electron gun or a laser having an energy sufficient to fuse powder within said fluidized bed, where the output beam of said electron gun or said laser is directed at said surface;

(D) means for controlling the level of powder in said fluidized bed relative to said surface;

(E) means for controlling the horizontal position of said surface relative to said beam.

103. Apparatus according to claim 102 including means for changing the composite of power in said fluidized bed as said shape is cast.

104. Apparatus according to claim 102 including means for heating powder in said bed.

105. Apparatus according to claim 104 wherein said means for heating said powder is an electrical resistance heater placed in said fluidized bed.

106. Apparatus according to claim 102 wherein said beam is a laser beam.

107. Apparatus according to claim 104 including means for rapidly oscillating said laser beam over said surface as said surface moves horizontally.

108. Apparatus according to claim 102 wherein said laser beam is from a C0₂ laser.

109. Apparatus according to claim 102 wherein said beam is directed downward at 90°

to said surface.

110. Apparatus according to claim 102 wherein more than one beam is directed at said surface.

111. Apparatus according to claim 102 including means for splitting a single beam into at least two beams, and for directing each beam at different areas of said surface in said fluidizing bed, whereby identical shapes can be formed on said surface.

112. Apparatus according to claim 102 wherein at least two beams can be directed at different areas of said surface in said fluidized bed, whereby two identical shapes can be formed on said surface.

113. Apparatus according to claim 102 including means for lowering said shape in said fluidized bed as it is formed.

114. Apparatus according to claim 102 including means for raising the level of powder in said fluidized bed as said shape is formed.

115. Apparatus according to claim 114 wherein said means for raising the level of said powder in said fluidized bed is means for increasing the pressure of the gas used to fluidize said powder.

116. Apparatus according to claim 102 including means for adding powder to said bed.

117. Apparatus according to claim 102 including sensor means for determining the level of powder in said fluidized bed that is above said shape.

118. Apparatus according to claim 102 wherein said beam is fixed and said surface is horizontally moveable.

119. Apparatus according to claim 118 wherein said surface is manually moveable.

120. Apparatus according to claim 118 wherein the horizontal movement of said surface is controlled by a computer.

121. Apparatus according to claim 102 wherein said surface is fixed and said beam is moveable relative to said surface.

122. Apparatus according to claim 121 wherein said beam is manually moveable.

123. Apparatus according to claim 121 wherein the movement of said beam is controlled by a computer.

124. Apparatus according to claim 102 wherein said surface is horizontal and flat.

125. Apparatus for casting a near net shape comprising:

(A) a fluidized bed having surface therein;

(B) means for fluidizing powder within said bed to a level slightly above the level of said surface;

(C) a laser, the beam of which is directed downward at said surface;

(D) means for changing the horizontal position of said surface relative to said laser beam; and

(E) means for changing the level of said powder in said fluidized bed relative to said surface.

126. Apparatus for forming a metal casting of a near net shape comprising:

(A) a fluidized bed;

(B) a horizontal surface within said fluidized bed;

(C) means for fluidizing metal powder in said fluidized bed to a level about 1/32 to about 1 inch above said horizontal surface;

(D) a C0₂ laser that produces a laser beam having a power sufficient to melt said fluidized metal powder above said horizontal surface;

(E) means for directing said laser beam at said surface;

(F) means for changing the horizontal position of said horizontal surface relative to said laser beam; and

(G) means for changing the level of said metal powder in said fluidized bed relative to said horizontal surface.