Method of joining concentric cylinders
AssigneeNorthrop Corporation
InventorsRobert R. Moats, Woodrow L. Bowen
Life of this patent
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Abstract
A method of forming a composite metal-ceramic helix structure suitable for TWT application. The method includes concentrically joining a metal cylinder disposed within a ceramic cylinder to form a high strength hermetic bond therebetween having good thermal conductivity. Prior to joining the cylinders a predetermined quantity of heat vaporizable liquid is disposed within the metal cylinder and its ends are sealed off. During the brazing process the liquid vaporizes ensuring intimate contact between the concentric cylinders. Thereafter the metal cylinder ends are removed and the resulting concentric structure machined into a helical shape.
Claims15
A method of making a metal-lined ceramic structure from a ceramic cylindrical member having a relatively small inner diameter thereof on the order of 0.100 inches and a ductile metal cylinder having a relatively small outer diameter thereof on the order of but slightly less than the inner diameter of the ceramic cylindrical member, comprising:
- applying a thin moly-maganese metallic coating to the inner surface of the ceramic cylinder bore,
- overcoating said moly-maganese metallic coating with a thin nickel plating,
- applying a thin coating of silver to the outer cylindrical surface of said metal cylinder,
- inserting the silver coated metal cylinder within the metallic coated bore of said ceramic cylinder,
- forming an airtight seal at one end of the silver coated metal cylinder,
- placing a predetermined quantity of liquid water within the metal cylinder,
- forming an airtight seal at the other end of the silver coated metal cylinder wherein the predetermined quantity of liquid water is contained within the sealed metal cylinder,
- heating the sealed metal cylinder and the surrounding ceramic cylinder to a temperature of at least 850 degrees centigrade in a hydrogen atmosphere and vaporizing said liquid water contained in said sealed ductile metal cylinder to expand said ductile material into intimate contact with the inner bore of said ceramic cylinder and producing a molten state of the metallic coating, silver and nickel and to braze the inner metal cylinder to the surrounding ceramic cylinder,
- cooling the brazed cylinders to room temperature and returning said vaporized water to a liquid at atmospheric pressure,
- severing the sealed ends from the metal cylinder extending beyond the ends of the ceramic cylinder, and
- removing said liquid water from said metal cylinder.
A method of forming a composite metal-ceramic helix from a ceramic member having a relatively small inner diameter on the order of 0.100 inches and a ductile metal cylinder having a relatively small outer diameter on the order of but slightly less than the inner diameter of the ceramic cylinder member, comprising:
- applying to an inner surface of the ceramic cylinder bore a first metallic coating facilitating the joining of the ceramic cylinder to the ductile metal cylinder,
- applying to an outer cylindrical surface of said metal cylinder a second metallic coating facilitating the joining of the metal cylinder to the ceramic cylinder,
- inserting the metallic coated metal cylinder within the metallic coated bore of said ceramic cylinder,
- forming an airtight seal at a first end of the metallic coated metal cylinder,
- placing a predetermined quantity of liquid water within the metal cylinder,
- forming an airtight seal at a second end of the metallic coated metal cylinder wherein the predetermined quantity of liquid water is contained within the sealed metal cylinder,
- heating in a hydrogen atmosphere the sealed metal cylinder and the surrounding ceramic cylinder to a temperature facilitating brazing between the metal cylinder and the ceramic cylinder and vaporizing said liquid water contained in said sealed ductile metal cylinder to expand said ductile metal into intimate contact with the inner surface of said ceramic cylinder, and producing a molten state in the first and second metallic coatings and brazing the outer surface of the inner metal cylinder to the inner surface of the outer ceramic cylinder,
- cooling the brazed metal and ceramic cylinders to room temperature and returning said vaporized water to a liquid state at atmospheric pressure,
- severing from the brazed metal and ceramic cylinders the first and second sealed ends of the metal cylinder extending beyond the ends of the ceramic cylinder,
- removing said liquid water from said metal cylinder, and
- machining the brazed and concentrically joined metal and ceramic cylinders into a helical configuration.
A method of forming a composite metal-ceramic helix from a pair of ceramic members having a configuration which, when assembled, forms a cylindrical structure having a relatively small inner diameter on the order of 0.100 inches, and a ductile metal cylinder having a relatively small outer diameter on the order of but slightly less than the inner diameter of the assembled ceramic members, comprising:
- applying to a first surface of each of the ceramic members a first metallic coating facilitating the joining of the ceramic members to the ductile metal cylinder,
- assembling the ceramic members so as to form a cylindrical structure and restraining the ceramic members so as to retain said assembled configuration,
- inserting the metal cylinder within a bore formed in the assembled ceramic members,
- forming an airtight seal at a first end of the metal cylinder,
- placing a predetermined quantity of liquid water within the metal cylinders,
- forming an airtight seal at a second end of the metal cylinder wherein the predetermined quantity of liquid water is contained within the sealed metal cylinder,
- heating in a hydrogen atmosphere the sealed metal cylinder and the surrounding assembled ceramic members to a temperature facilitating brazing between the metal cylinder and the ceramic members and vaporizing said liquid water contained in said sealed ductile metal cylinder to expand said ductile metal into intimate contact with the inner surface of said ceramic members, producing a molten state in the first metallic coating and brazing the outer surface of the inner metal cylinder to the inner surface of the assembled ceramic members wherein the metal cylinder and ceramic members form a concentrically joined structure,
- cooling the brazed metal cylinder and ceramic members to room temperature and returning said vaporized water to a liquid state at atmospheric pressure,
- severing from the brazed metal cylinder and ceramic members the first and second sealed ends of the metal cylinder extending beyond the ends of the ceramic members,
- removing said liquid water from said metal cylinder, and
- machining the brazed and concentrically joined metal cylinder and ceramic members into a helical configuration.
Dependencies are inferred from the claim text.