Method for improving metallurgical bond in bimetallic castings
First Claim
1. In the method of making a bicast article in which a solid metal preform is positioned in a mold and a molten metal is cast about the portions of said preform exposed in said mold, the improvement which comprises coating said exposed portions prior to the casting step with a boron containing alloy having a melting range below the melting range of either said preform or said cast metal, fusing said alloy into said preform without significant interalloying with the metal preform, said alloy having a major ingredient the same as the major ingredient of at least one of the metals to be joined, and heat treating the resulting bicast article after solidification of the molten metal at a temperature below the melting range of either said preform or the solidified metal to cause diffusion of boron into the preform and into the solidified metal.
0 Assignments
0 Petitions
Accused Products
Abstract
Method for making a bicast article in which a solid metal preform is positioned in a mold and a molten metal is cast around portions of the preform which are exposed in the mold. In accordance with the present invention, the exposed portions are coated prior to the casting step with a boron containing alloy which is compatible with the preform and with the metal to be cast about it, the boron containing alloy having a melting range below the melting range of either the preform or the cast metal. The alloy also has a major ingredient which is the same as the major ingredient of at least one of the metals to be joined. After solidification of the molten metal in the casting cavity, the resulting bicast article is heat treated at a temperature below the melting range of either the preform or the solidified metal to cause diffusion of boron into the preform and into the solidified metal thereby providing an improved metallurgical bond.
60 Citations
14 Claims
- 1. In the method of making a bicast article in which a solid metal preform is positioned in a mold and a molten metal is cast about the portions of said preform exposed in said mold, the improvement which comprises coating said exposed portions prior to the casting step with a boron containing alloy having a melting range below the melting range of either said preform or said cast metal, fusing said alloy into said preform without significant interalloying with the metal preform, said alloy having a major ingredient the same as the major ingredient of at least one of the metals to be joined, and heat treating the resulting bicast article after solidification of the molten metal at a temperature below the melting range of either said preform or the solidified metal to cause diffusion of boron into the preform and into the solidified metal.
-
14. A composite metallic article comprising a first nickel base superalloy bonded to a second nickel base superalloy through an intermediate bonding zone of a nickel base alloy containing boron, both said first and second nickel base superalloys having boron diffused therein from said bonding zone, and the interface between said first and second superalloys with said bonding zone being characterized by small columnar grains extending perpendicular to said interface.
Specification