WEAPON BARREL AND METHOD OF MAKING SAME

BACKGROUND OF THE INVENTION

The present invention relates to a barrel for use in a weapon.

Weapons, such as machine guns, mortars, howitzers, and cannons, commonly have barrels along which projectiles move. The barrel of a weapon may have one or more spiral grooves which induce spin on a projectile as it moves through the barrel. Alternatively, the barrel may have a smoothbore.

The projectile which moves along a barrel may be a single-piece item, like a bullet. Alternatively, the projectile may include a casing containing a payload of projectiles and/or explosive materials. The projectile may be a sabot. A plurality of projectiles may move along the barrel at the same time. The weapon barrel may be mounted on a vehicle, such as an aircraft, tank or ship.

During use, a weapon may be fired rapidly. Rapid fire of a weapon may induce heating of the barrel of the weapon. When a weapon is fired for a substantial period of time, the barrel of the weapon may heat to a temperature high enough to be detrimental the structural strength and/or other characteristics of the barrel. In order to improve the characteristics of a barrel of a weapon, various barrel designs have been previously suggested. Some of these suggestions are disclosed in U.S. Pat. Nos. 4,756,677; 5,341,719; and 7,963,202.

SUMMARY OF THE INVENTION

The present invention relates to a weapon barrel housing and the method by which the weapon barrel housing is formed. The weapon barrel housing is cast as one piece of a superalloy directionally solidified from one end portion of the weapon barrel housing to the opposite end portion of the weapon barrel housing. The directionally solidified superalloy has first properties in a direction parallel to a central axis of the weapon barrel housing. In a direction transverse to a central axis of the weapon barrel housing, the directionally solidified superalloy has second properties which are different than the first properties.

The directionally solidified superalloy of the weapon barrel housing may be cast with a columnar grain crystallographic structure. Alternatively, the superalloy of the weapon barrel housing may be cast with a plurality of single crystal sections, at least one of which extends between opposite end portions of the weapon barrel housing. As another alternative, the superalloy of the weapon barrel housing may be cast as a single crystal.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features of the invention will become more apparent upon a consideration of the following description taken in connection with the accompanying drawings wherein:

FIG. 1 is a schematic illustration of a weapon barrel housing formed of a superalloy which is directionally solidified to have a columnar grain crystallographic structure which extends between opposite end portions of the weapon barrel housing;

FIG. 2 is a schematic illustration of a weapon barrel housing formed of a superalloy which is directionally solidified to have a plurality of single crystal sections, at least some of which extend between opposite end portions of the weapon barrel housing;

FIG. 3 is a schematic illustration of a weapon barrel housing formed of a superalloy which is directionally solidified as a single crystal which extends between opposite end portions of the weapon barrel housing;

FIG. 4 is a schematic illustration depicting the manner in which a superalloy is directionally solidified to form the weapon barrel housing of FIG. 1 with a columnar grain crystallographic structure;

FIG. 5 is a schematic illustration depicting the manner in which a seed crystal casting is formed with a plurality of sections which extend between opposite end portions of the seed crystal casting and are formed as single crystals having parallel primary crystallographic growth axis orientations;

FIG. 6 is a schematic illustration of the seed crystal casting formed with the apparatus of FIG. 5;

FIG. 7 is a schematic illustration depicting the manner in which a portion of the seed crystal casting of FIG. 6 is utilized in the directional solidification of a superalloy to form a weapon barrel housing having a plurality of single crystal sections which have parallel primary crystallographic growth axis orientations; and

FIG. 8 is a schematic illustration depicting the manner in which a single crystal seed is utilized in directional solidification of a superalloy to form an entire weapon barrel housing as a single crystal of a superalloy.

DESCRIPTION OF SPECIFIC PREFERRED EMBODIMENTS OF THE INVENTION
Columnar Grained
Weapon Barrel Housing

A weapon barrel housing 10 (FIG. 1) is integrally formed as one piece of a directionally solidified superalloy having a nonequiaxed crystallographic grain structure. The cast metal of the weapon barrel housing 10 of FIG. 1 has a columnar grain crystallographic structure. The long, thin crystals of the columnar grain crystallographic structure have longitudinal central axes which extend parallel to a longitudinal central axis of the weapon barrel housing 10. The weapon barrel housing 10 is free of generally spherical, randomly oriented crystals.

The weapon barrel housing 10 has a cylindrical central passage 12 which extends between a base end portion 14 and a muzzle end portion 16 of the weapon barrel housing 10. It is contemplated that the weapon barrel housing 10 may be the only component of the barrel of a weapon. Alternatively, the weapon barrel housing 10 may be one of a plurality of components which together form the barrel of a weapon.

The base end portion 14 of the weapon barrel housing 10 is connected with a suitable support structure (not shown). This support structure may be an aircraft, tank or ship. Rather than being connected with a vehicle, the weapon barrel housing 10 may be associated with a weapon which is carried by a soldier. It is contemplated that the weapon barrel housing 10 may be enclosed by a sheathing, framework, or other component of the weapon barrel to provide a weapon barrel assembly. Alternatively, the weapon barrel housing 10 may be utilized without any or with a minimum of other components.

The weapon barrel housing 10 (FIG. 1) has a cylindrical outer side surface which is coaxial with the cylindrical passage 12. The passage 12 extends axially through the housing 10. However, it is contemplated that the passage 12 could have a closed end disposed in the base end portion 14 of the weapon barrel housing 10.

Although the illustrated weapon barrel housing 10 has a uniform configuration (cylindrical) throughout its length, it is contemplated that the configuration of the housing may vary along the length of the housing. For example, the base end portion 14 may have a polygonal cross sectional configuration while the muzzle end portion 16 has a cylindrical cross sectional configuration. The specific configuration of the weapon barrel housing 10, including the axial extent of the housing, will vary as a function of the type of weapon in which the housing is to be utilized. However, it is contemplated that the housing 10 will have an overall length which is at least ten times the diameter of the cylindrical passage 12 which extends through the housing. Of course, the housing 10 may be designed for use in a weapon which does not require a length which is at least ten times as great as the diameter of the passage 12.

The weapon barrel housing 10 (FIG. 1) is cast as one piece of a directionally solidified superalloy. When a molten superalloy metal is directionally solidified in a mold to form the weapon barrel housing 10, the metal solidifies from one end of the mold toward the opposite end of the mold without significant inward solidification from surfaces of the mold which extend transverse to the one end of the mold. The molten superalloy in the mold solidifies in the same direction throughout the length of the mold cavity in which the weapon barrel housing 10 in cast.

The superalloy of which the housing 10 is cast, is a nickel based superalloy having a known composition. It should be understood that superalloys other than a nickel based superalloy may be used to form the weapon barrel housing 10. For example, a cobalt based superalloy may be used to form the weapon barrel housing 10.

The nickel based superalloy forming the weapon barrel housing 10 is directionally solidified from the base end portion 14 to the muzzle end portion 16 of the housing 10. However, the nickel based superalloy forming the weapon barrel housing 10 may, if desired, be solidified from the muzzle end portion 16 to the base end portion 14. There is solidification of the nickel based superalloy forming the weapon barrel housing 10 only in a direction away from one end portion of the weapon barrel housing toward the opposite end portion of the weapon barrel housing.

The nickel based superalloy forming the weapon barrel housing 10 is directionally solidified as one piece with a columnar grain crystallographic structure. The columnar grains have been indicated schematically by lines in FIG. 1. The columnar grains forming the crystallographic structure of the weapon barrel housing 10 have longitudinal central axes extending generally parallel to each other and parallel to a central axis 22 of the passage 12 and of the weapon barrel housing 10. It is contemplated that at least some of the columnar grains forming the weapon barrel housing 10 may extend transverse to or have portions which extend transverse to the axis 22. For example, at least some of the columnar grains forming the base end portion 14 may extend somewhat transversely to the axis 22. However, the cast weapon barrel housing 10 does not contain a significant quantity of equiaxed grains, that is, generally spherical, randomly oriented grains.

The nickel based superalloy forming the weapon barrel housing 10 is solidified with the longitudinal central axes of the columnar grains extending parallel to direction in which the molten superalloy metal is solidified. Since the molten superalloy metal forming the weapon barrel housing 10 is solidified from one end portion 14 to the axially opposite end portion 16, the longitudinal central axes of the columnar grains of the solidified superalloy have primary growth or Z axes 26 parallel to the longitudinal central axis 22 of the weapon barrel housing. The secondary growth axes of each of the elongated columnar grains have been illustrated schematically as the X axis 28 and Y axis 30 in FIG. 1. The X and Y axes 28 and 30 are randomly oriented relative to the Z or primary axes 26 of the columnar grains.

The columnar grains forming the weapon barrel housing 10 have anisotropic properties. The properties of the weapon barrel housing 10 in a direction extending along, that is parallel to the central axis 22 of the housing, have a first set of characteristics. The properties of the weapon barrel housing 10 in directions transverse (perpendicular) to the central axis 22 will have a second set of characteristics. The second set of characteristics correspond to the properties of the columnar grains in the X and Y axis directions 28 and 30. Due to the random orientation of the X and Y axes 28 and 30 relative to the Z axis 26 of each of the columnar grains, the properties of the weapon barrel housing 10 will tend to be the same in any direction extending perpendicular to the central axis 22.

The columnar grains forming the crystallographic structure of the weapon barrel housing 10 will have one set of properties, that is the properties corresponding to the Z axis 26, in a direction parallel to the central axis 22 of the housing. However, the weapon barrel housing 10 will have properties in a transverse direction, that is, in either the X or Y direction or any direction between the X and Y directions and extending perpendicular to the Z axis, which are the same. Properties of the weapon barrel housing 10 in a direction perpendicular to the Z axis may be similar to the properties of an equiax casting formed of the same superalloy as the weapon barrel housing 10.

In an equiaxed casting, the metal solidifies with generally spherical crystals in a random orientation. Therefore, an equiaxed casting will have the same properties whether measured along the Z axis 26, X axis 28 or Y axis 30. By forming the weapon barrel housing 10 with a columnar grain crystallographic structure, the weapon barrel housing has properties, that is, structural characteristics, as measured along the Z axis 26, which are superior to the properties or structural characteristics measured along the X axis 28 and/or the Y axis 30. The Z axis 26 of each columnar grain extends parallel to the direction in which the columnar grain is solidified.

The superior properties of the weapon barrel housing 10, as measured along the Z axis 26, enable the weapon barrel housing to withstand severe conditions which are present when a weapon is rapidly fired and projectiles are moved at high speeds through the passage 12 for a relatively long period of time. A weapon barrel housing 10 having an equiaxed crystallographic structure would not have these superior properties along the Z axis 26 and could not withstand the severe operating conditions, that is, rapid fire conditions, which the weapon barrel housing 10 can withstand.

Plural Single Crystal
Weapon Barrel Housing

A weapon barrel housing 40 (FIG. 2) is integrally formed as one piece of a directionally solidified superalloy having a nonequiaxed crystallographic grain structure. The one piece of cast metal forming the weapon barrel housing 40 has a plurality of integrally cast single crystal sections 42. The single crystal sections 42 have longitudinal central axes which extend parallel to a longitudinal central axis 46 of the one piece weapon barrel housing 40. The weapon barrel housing 40 is free of generally spherical, randomly oriented crystals, that is, equiaxed crystals.

The weapon barrel housing 40 has a cylindrical central passage 50 which extends between a base end portion 54 and a muzzle end portion 56 of the weapon barrel housing 40. It is contemplated that the weapon barrel housing 40 may be the only component of the barrel of a weapon. Alternatively, the weapon barrel housing 40 may be one of a plurality of components which together form the barrel of a weapon.

The base end portion 54 (FIG. 2) of the weapon barrel housing 40 is connected with a suitable support structure (not shown). This support structure may be, an aircraft, tank or ship. Rather than being connected with a vehicle, the weapon barrel housing 40 may be associated with a weapon which is carried by a soldier. It is contemplated that the weapon barrel housing 40 may be enclosed by a sheathing, framework, or other components of the weapon barrel to provide a weapon barrel assembly. Alternatively, the weapon barrel housing 40 may be utilized without any or with a minimum of other components.

The weapon barrel housing 40 has a cylindrical outer side surface which is coaxial with the cylindrical passage 50. The passage 50 extends axially through the housing 40. However, it is contemplated that the passage 50 could have a closed end disposed in the base end portion 54 of the weapon barrel housing 40. If this is done, the base end portion 54 may have a noncylindrical configuration.

Although the weapon barrel housing 40 has a uniform configuration (cylindrical) throughout its length, it is contemplated that the configuration of the housing may vary along the length of the housing. For example, the base end portion 54 may have a polygonal cross sectional configuration while the muzzle end portion 56 has a cylindrical cross sectional configuration. The specific configuration of the weapon barrel housing 40, including the axial extent of the housing, will vary as a function of the type of weapon in which the housing is to be utilized. However, it is contemplated that the housing 40 will have an overall length which is at least ten times the diameter of the passage 50 which extends through the housing. Of course, the housing 40 may be designed for use in a weapon which does not require a length which is at least ten times as great as the diameter of the passage 50.

The weapon barrel housing 40 (FIG. 2) is cast as one piece of a directionally solidified superalloy. When a molten superalloy metal is directionally solidified in a mold to form the weapon barrel housing 40, the metal solidifies from one end of the mold toward the opposite end of the mold without significant inward solidification from surfaces of the mold which extends transverse to the one end of the mold. The molten superalloy in the mold solidifies in the same direction throughout the length of the mold cavity in which the weapon barrel housing 40 is cast.

The superalloy of which the housing 40 is cast, is a nickel based superalloy having a known composition. It should be understood that superalloys other than a nickel based superalloy may be used to form the weapon barrel housing 40. For example, a cobalt based superalloy may be used to form the weapon barrel housing 40.

The nickel based superalloy forming the weapon barrel housing 40 is directionally solidified from the base end portion 54 to the muzzle end portion 56 of the housing 40. However, the nickel based superalloy forming the weapon barrel housing 40 may, if desired, be solidified from the muzzle end portion 56 to the base end portion 54. There is solidification of the nickel based superalloy forming the weapon barrel housing 40 only in a direction away from one end portion of the weapon barrel housing toward the opposite end portion of the weapon barrel housing.

The nickel based superalloy forming the weapon barrel housing 40 is solidified as one piece with a plurality of integrally formed sections 42. Each of the fixedly interconnected sections 42 is formed as a single crystal. The single crystal forming the crystallographic structure of any one of the sections 42 has a primary growth direction extending parallel to the growth directions of the other sections 42 and the central axis 46 of the weapon barrel housing 40. The plurality of single crystal sections 42 are integrally cast as one piece of metal which forms the housing 40. Each single crystal section 42 is formed by a single crystal of the superalloy and is free of substantially spherical, randomly oriented crystals, that is, equiaxed crystals.

Each of the sections 42 of the weapon barrel housing 40 are solidified with a primary or Z growth axis 62 (FIG. 2) which extends parallel to the central axis 46 of the weapon barrel housing 40. The primary or Z axis 62 may be referred to as the [001] growth axis. The primary or Z growth axis 62 of each of the sections 42 extends parallel to the central axis 46 of the weapon barrel housing 40. Each of the single crystal sections 42 are directionally solidified in a direction parallel to the primary growth axis 62 and the central axis 46 of the weapon barrel housing 40.

Each of the single crystal sections 42 of the weapon barrel housing 40 has a secondary or X growth axis 64 (FIG. 2). The secondary or X growth axis 64 may be referred to as the [100] growth axis. The secondary growth axis 64 extends perpendicular to the primary or Z growth axis 62. A second secondary or Y growth axis 66 extends perpendicular to the primary or Z growth axis 62 and perpendicular to the first secondary or X growth axis 64. The second secondary or Y growth axis may be referred to as [010] growth axis.

Each of the sections 42 of the weapon barrel housing 40 have secondary growth axes 64 and 66 which are disposed in predetermined orientations relative to the central axis 46 of the weapon barrel housing 40. By having the secondary growth axes 64 and 66 in predetermined orientations relative to the central axis 46 of the weapon barrel housing, each of the single crystal sections 42 may have secondary axes 64 and 66 which are disposed in orientations which tend to maximize the properties, that is, the physical characteristics, of the weapon barrel housing 40. The secondary axes 64 and 66 of each of the plurality of sections 42 may be in the same orientation or different orientations relative to the central axis 46 of the weapon barrel housing 40.

For example, it is contemplated that each of the single crystal sections 42 may have secondary growth axes 64 and 66 which are disposed in the same orientation relative to the central axis 46 of the weapon barrel housing 40. In this example, the secondary (X) growth axis 64 of each single crystal section 42 of the weapon barrel housing 40 may be coincident with a radius of the passage 50. This would result in the secondary growth axis 64 of each of the single crystal sections 42 extending perpendicular to and intersecting the central axis 46 of the weapon barrel housing 40. As another example, the secondary growth axes 64 and 66 of each of the single crystal sections 42 may each be skewed at an angle of 45 degrees to a radius of the passage 50.

Regardless of what orientation is selected for the secondary growth axes 64 and 66, the primary or Z growth axis 62 of each of the single crystal sections 42 will extend parallel to the central axis 46 of the weapon barrel housing 40. In the last example, secondary axes X and Y of adjacent sections 42 will be skewed relative to each other. This would result in the secondary axes X and Y of one section 42 of the weapon barrel housing 40 being skewed relative to the secondary axes X and Y of adjacent sections of the weapon barrel housing. However, the secondary axes 64 and 66 of sections 42 which are disposed on diametrically opposite sides of the weapon barrel housing 40 may be disposed in the same orientation.

As a third example, the single crystal sections 42 may have secondary axes 64 and 66 which are disposed in the same spatial relationship relative to each other. Thus, the first secondary growth axis 64 of one single crystal section 42 may extend parallel to the first secondary growth axes 64 of all of the other single crystal sections forming the weapon barrel housing 40. Of course this would result in the second secondary or Y growth axis 66 of each of the single crystal sections 42 extending parallel to the second secondary or Y growth axis 66 of all of the other single crystal sections 42.

Each of the single crystal sections 42 extends between axially opposite ends of the weapon barrel housing 40. Thus, each single crystal section 42 extends between the base end portion 54 and the muzzle end portion 56 of the weapon barrel housing 40. However, it is contemplated that during casting of the weapon barrel housing 40, some of the single crystal sections 42 may crowd out other single crystal sections. This would result in some of the single crystal sections 42 extending for the entire length of the weapon barrel housing 40 while other single crystal sections extend for only a portion of the length of the weapon barrel housing 40.

In the example where some of the single crystal sections 42 crowd out other single crystal sections during casting of the one piece weapon barrel housing 40, a relatively large number of single crystal sections would be disposed in one end portion of the weapon barrel housing 40 and a relatively small number of single crystal sections 42 would be disposed in the opposite end portion of the weapon barrel housing. The largest number of single crystal sections 42 will be disposed in the end portion of the weapon barrel housing 40 from which the metal forming the weapon barrel housing is solidified. For example, if the weapon barrel housing 40 is directionally solidified from the base end portion 54 to the muzzle end portion 56 of the weapon barrel housing, a relatively large number of single crystal sections 42 may be disposed in the base end portion 54 of the weapon barrel housing while a smaller number of single crystal sections 42 are disposed in the muzzle end portion 56 of the weapon barrel housing 40.

The primary or Z growth axis 62 of each of the sections 42 extends parallel to the central axis 46 of the weapon barrel housing 40. The secondary growth axes 64 and 66 (FIG. 2) are disposed in a pattern of orientations which maximizes the properties of the weapon barrel housing 40 for the particular weapon with which the weapon barrel housing is to be used. For example, if rifling is to be formed in the passage 50, the secondary axes 64 and 66 may be oriented to facilitate machining of the weapon barrel housing 40. Alternatively, the pattern in which the secondary axes 64 and 66 are disposed may be selected to maximize the properties of the weapon barrel housing 40 during use of a weapon with which it is associated.

It is contemplated that the single crystal sections 42 of the weapon barrel housing 40 may be disposed with secondary growth axes 64 and 66 in any one of many different orientations. For example, a radius of the passage 50 may extend from the axis 46 through a center of one section 42, that is, midway between sections 42 disposed on opposite sides of the one section. The radius of the passage 50 would extend through a center 70 (FIG. 2) from which the secondary axes 64 and 66 extend.

Alternatively, the sections 42 may be oriented in the weapon barrel housing 40 so that the secondary axes 64 and 66 of each of the sections 42 extends parallel to the secondary axes of the other sections. As another example, the sections 42 may be oriented with one of the secondary axes, for example, the secondary axis 64, extending through the central axis 46 of the weapon barrel housing 40. The specific orientation of the secondary axes 64 and 66 will depend upon the characteristics which are desired for the weapon barrel housing 40.

By properly selecting the orientation of the secondary growth axes 64 and 66, the weapon barrel housing 10 has superior properties along the central axis 46 of the weapon barrel housing 40 and along axes extending transverse to the central axis of the weapon barrel housing. These superior properties enable the weapon barrel housing 40 to be readily machined and/or to withstand severe conditions which are present when a weapon is rapidly fired and projectiles are moving at high speeds through the passage 50 for a relatively long period of time. A weapon barrel housing having an equiaxed crystallographic structure would not have these superior properties along the central axis 46 of the equiaxed weapon barrel housing and/or along axes extending transverse to the central axis of the equiaxed weapon barrel housing.

Single Crystal Weapon
Barrel Housing

A weapon barrel housing 80 (FIG. 3) is integrally formed as one piece of a directionally solidified superalloy having a nonequiaxed crystallographic grain structure. The cast metal of the weapon barrel housing 80 has a single crystal crystallographic structure. In the embodiment of the weapon barrel housing illustrated in FIG. 2, the weapon barrel housing 42 is formed by a plurality of sections 42. Each of the sections 42 is formed by a single crystal. In the embodiment of FIG. 3, the entire weapon barrel housing 80 is formed by a single crystal of a directionally solidified superalloy. The weapon barrel housing 80 is free of generally spherical, randomly oriented crystals.

The weapon barrel housing 80 has a central passage 82 which extends between a base end portion 84 and a muzzle end portion 86 of the weapon barrel housing 80. It is contemplated that the weapon barrel housing 80 may be the only component of the barrel of a weapon. Alternatively, the weapon barrel housing 80 may be one of a plurality of components which together form a barrel of a weapon.

The base end portion 84 of the weapon barrel housing 80 is connected with a suitable support structure (not shown). This support structure may be an aircraft, tank or ship. Rather than being connected with a vehicle, the weapon barrel housing 80 may be associated with a weapon which is carried by a soldier. It is contemplated that the weapon barrel housing 80 may be enclosed by a sheathing, framework, or other component of the weapon barrel to provide a weapon barrel assembly. Alternatively, the weapon barrel housing 80 may be utilized without any or with a minimum of other components.

The weapon barrel housing 80 (FIG. 3) has a cylindrical outer side surface which is coaxial with the cylindrical passage 82. The passage 82 extends axially through the housing 80. However, it is contemplated that the passage 82 could have a closed end disposed in the base end portion 84 of the weapon barrel housing 10.

Although the illustrated weapon barrel housing 80 has a uniform configuration (cylindrical) throughout its length, it is contemplated that the configuration of the housing may vary along the length of the housing. For example, the base end portion 84 may have a polygonal cross sectional configuration while the muzzle end portion 86 has a cylindrical cross sectional configuration. The specific configuration of the weapon barrel housing 80, including the extent of the housing, will vary as a function of the type of weapon in which the housing is to be utilized. However, it is contemplated that the weapon barrel housing 80 will have an overall length which is at least ten times the diameter of the passage 82 which extends through the housing. Of course, the housing 80 may be designed for use in a weapon which does not require a length which is at least ten times as great as the diameter of the passage 82.

The weapon barrel housing 80 (FIG. 3) is cast as one piece of a directionally solidified superalloy. When a molten superalloy metal is directionally solidified in a mold to form the weapon barrel housing 80, the metal solidifies from one end of the mold toward the opposite end of the mold without significant inward solidification from surfaces of the mold which extend transverse to the one end of the mold. The molten superalloy in the mold solidifies in the same direction throughout the length of the mold cavity in which the weapon barrel housing 80 is cast.

The superalloy of which the housing 80 is cast is a nickel based superalloy having a known composition. It should be understood that superalloys other than a nickel based superalloy may be used to form the weapon barrel housing 80. For example, a cobalt based superalloy may be used to form the weapon barrel housing 80.

The nickel based superalloy forming the weapon barrel housing 80 is directionally solidified from the base end portion 84 of the housing 80. However, the nickel based superalloy forming the weapon barrel housing 80 may, if desired, be solidified from the muzzle end portion 86 to the base end portion 84. There is solidification of the nickel based superalloy forming the weapon barrel housing 80 only in a direction away from one end portion of the weapon barrel housing toward the opposite end portion of the weapon barrel housing.

The nickel based superalloy forming the weapon barrel housing 80 is solidified as a single crystal having a primary or Z growth axis 92, that is, the [001] axis, which extends along the direction of growth of the single crystal forming the weapon barrel housing 80. The primary growth axis 92 of the single crystal forming the weapon barrel housing 80 is parallel to the longitudinal central axis 94 of the weapon barrel housing 80. A first secondary growth axis 94 extends perpendicular to the primary axis 92. A second secondary or Y growth axis 96 extends perpendicular to the primary growth axis 92 and the first secondary growth axis 94. The primary axis 92 may be referred to as the [001] axis. The first secondary or X axis may be referred to as [100] axis. The second secondary or Y axis may be referred to as the [010] axis.

The properties of the directionally solidified superalloy forming the single crystal of the weapon barrel housing 80 are different along each of the axes 92, 94 and 96. The primary axis 92 is aligned with, that is parallel to the central axis 94 of the weapon barrel housing 80. The secondary axes 94 and 96 are positioned relative to the weapon barrel housing 80 to maximize the properties of the weapon barrel housing.

It is contemplated that it may be desired to have one of the secondary axes 94 and 96 coincident with a radius of the passage 82. Of course the other secondary axis would be perpendicular to the radius which is coincident with the one secondary axis. It should be understood that the secondary axes 94 and 96 may have any desired orientation.

Casting Columnar Grained
Weapon Barrel Housing

The columnar grained weapon barrel housing 10 of FIG. 1 is cast of nickel based superalloy by directionally solidifying molten metal of the superalloy with a nonequiaxed crystallographic structure. To cast of the weapon barrel housing 10, a mold 110 having an empty cylindrical mold cavity 114 is positioned on a chill plate 116. Once this has been done, the mold 110 is raised into a furnace chamber.

In the furnace chamber, the mold 110 and core 115 are preheated. Molten metal, that is a superalloy, is then poured into the mold cavity 114. The molten metal solidifies between the core 115 and mold 110 as the chill plate 116 is moved downward away from the furnace chamber. The chill plate 116 causes the molten metal to solidify upwardly, in a direction away from the chill plate, as the chill plate is moved downward and the mold 110 is withdrawn from the furnace chamber.

It is contemplated that the furnace in which the molten metal is cast may have any one of many known constructions. For example, the furnace may have a construction similar to the construction disposed in U.S. Pat. No. 3,841,384 and/or U.S. Pat. No. 6,443,213. The disclosures in the aforementioned U.S. Pat. Nos. 3,841,384 and 6,443,213 are hereby incorporated herein in their entirety by this reference thereto.

As the chill plate 116 moves downward away from the furnace chamber, molten nickel based superalloy in the mold cavity 114 solidifies in an upward direction with a columnar grain crystallographic structure. The molten metal in the mold cavity 114 solidifies upwardly from the chill plate 116 to gating and a sprue connected with the upper end portion of the mold cavity. There is no significant inward solidification from side surfaces of the mold cavity 114. Therefore, the molten metal directionally solidifies from the lower end portion of the mold 110 to the upper end portion of the mold.

After the molten metal has been directionally solidified in the mold cavity in the manner previously described, the cast molten metal is removed from the mold cavity. Molten metal which solidified in the sprue and/or gating connected with the mold cavity 116 are removed from the cast metal article. The cast metal (superalloy) article is machined to form the weapon barrel housing 10 of FIG. 1. The weapon barrel housing 10 will have a columnar grained crystallographic structure with longitudinal central axes of the columnar grains extending parallel to the central axis 22 of the weapon barrel housing 10. The columnar grains have been schematically indicated by lines in FIG. 4.

Casting Plural Single
Crystal Weapon Barrel Housing

The weapon barrel housing 40 of FIG. 2 is cast with a plurality of single crystal sections 42. Each of the sections 42 is formed by only a single crystal of a directionally solidified superalloy. The plurality of single crystal sections 42 are simultaneously cast and are integrally formed as the one piece weapon barrel housing 40.

To cast the weapon barrel housing 40 with a plurality of single crystal sections 42, a plurality of seed crystals are provided. Since the single crystal sections 42 (FIG. 2) are disposed in an annular array, an annular array of seed crystals is utilized to initiate the formation of the single crystal sections. The seed crystals in the annular array of seed crystals, for use in initiating formation of the single crystal sections 42, have parallel primary growth axes 62. Each of the seed crystals 42 has a predetermined orientation of the first and second secondary axes 64 and 66. It should be understood that the seed crystals may be disposed in an array which is not annular.

The annular array of seed crystals, required to cast the weapon barrel housing 40 of FIG. 2, is obtained by forming a tubular cylindrical seed crystal casting 130 (FIGS. 5 and 6). The seed crystal casting 130 is formed in the manner illustrated schematically in FIG. 5. However, it should be understood that the seed crystal casting 130 may be formed in a different manner if desired.

To form the seed crystal casting 130, a cylindrical mold 134 (FIG. 5) is filled with a molten nickel based superalloy 136. Since the seed crystals are to be disposed in an annular array, a cylindrical core 138 is provided in the mold 134. A longitudinal central axis of the cylindrical core 138 is coincident with a longitudinal axis of the mold 134.

The molten metal 136 in the mold 134 is solidified as one piece with a plurality of seed segments having crystallographic growth axes, corresponding to the axes 62, 64 and 66 of FIG. 2, which are the same as the desired crystallographic growth axes of the sections 42 of the weapon barrel housing 40. The primary axis of each of the seed segments, corresponding to the primary axis 62 of FIG. 2, extends parallel to a central axis of the cylindrical core 138. The secondary axes of each of the seed segments, corresponding to the secondary axes 64 and 66 of FIG. 2, are in a pattern of orientations corresponding to the desired orientations of the secondary axes of the single crystal sections 42.

To initiate directional solidification of the molten metal alloy 136 (FIG. 5) with the desired primary or Z axis [001] orientation, the desired first secondary or X axis [100] orientation, and the desired second secondary or Y axis [010] orientation, corresponding to the axes 62, 64 and 66 of FIG. 2, a plurality single crystal selectors 142-150 (FIG. 5) are provided in an annular array. The single crystal selectors 142-150 initiate solidification of the molten metal 136 in the mold 134 with various portions of the solidified metal having desired crystallographic orientations.

Each of the single crystal selectors 142-150 is effective to initiate solidification of the portion of the molten metal alloy 136 disposed directly above a crystal selector with the same crystallographic orientation as in which metal solidifies in the crystal selector. Thus, the portion of the molten metal alloy 136 disposed directly above the crystal selector 142 is solidified with primary and secondary crystallographic growth axes in orientations determined by the crystal selector 142. Similarly, the molten metal disposed directly above the crystal selector 144 is solidified with primary and secondary crystallographic growth axes in orientations determined by the single crystal selector 144. The crystal selectors 146-150 determine the orientation of the crystallographic growth axes in the portions of the molten metal 136 disposed directly above each of the crystal selectors.

Although five single crystal selectors 142-150 have been illustrated schematically in FIG. 5, it is contemplated that a greater or lesser number of single crystal selectors may be utilized if desired. For example, eight or four single crystal selectors may be utilized. Of course, this results in the molten alloy 136 solidifying with the same number of sections, corresponding to the sections 42 of FIG. 2, as the number of single crystal selectors 142-150 provided between a chill plate 154 and the mold 134. To cast the illustrated weapon barrel housing 40 of FIG. 2 with eight single crystal sections 42, eight single crystal selectors were utilized. Rather than using the single crystal selectors 142-150, a plurality of a seed crystals may be utilized.

The single crystal selectors 142-150 have a known construction which is the same as is disclosed in U.S. Pat. No. 5,062,469 issued Nov. 5, 1991 to Monte, et al. for Mold and Method for Casting a Single Crystal Metal Article. The disclosure in the aforementioned U.S. Pat. No. 5,062,469 is hereby incorporated herein in its entirety by this reference thereto. It should be understood that single crystal selectors having a construction which is different than the construction of the single crystal selectors 142-150 may be utilized. It is also contemplated that the seed crystals with known orientations of the primary and secondary growth axes may be utilized to initiate solidification of portions of the molten alloy 136 with a desired crystallographic orientation.

A seed crystal casting 130 formed with the apparatus of FIG. 5 is illustrated schematically in FIG. 6. The seed crystal casting 130 has a cylindrical outer side surface 160 and a cylindrical inner side surface 162. The outer and inner side surfaces 160 and 162 are disposed in a coaxial relationship with each other.

The seed crystal casting 160 is integrally cast as one piece. The seed crystal casting 160 may be considered as being divided into eight single crystal segments 166 which have been illustrated schematically in FIG. 6. The single crystal segments 166 extend between axially opposite ends of the unitary, cylindrical seed crystal casting 130.

To form the one piece seed crystal casting 130, eight single crystal selectors, that is, one for each segment 166, were utilized. There is one single crystal segment 166 corresponding to each of the eight sections 42 (FIG. 2) of the weapon barrel housing 40. It should be understood that there may be either a greater or lesser number of single crystal segments 166. Of course, the number of single crystal segments 166 will correspond to the desired number of sections 42 in the weapon barrel housing 40.

Solidification of the molten metal 136 (FIG. 5) to form the segments 166 (FIG. 6) is initiated by the single crystal selectors 142-150 (FIG. 5). Each single crystal selector 142-150 initiates solidification of the molten metal in one of the segments 166. Molten metal in each of the segments 166 solidifies with a crystallographic structure which corresponds to the crystallographic structure of the solidified molten metal in one of the single crystal selectors 142-150. In the illustrated example of the seed crystal casting 130 (FIG. 6), eight single crystal selectors were used to initiate solidification of the molten metal 136 (FIG. 5) to form the single crystal segments 166. Thus, the crystallographic structure of each one of the segments 166 is determined by the one of the single crystal selectors 142-150 which initiates solidification of the molten metal to form the one segment 166.

The single crystal selectors 142-150 may be constructed and orientated so as to initiate formation of each of the segments 166 with the same crystallographic structure. Alternatively, each of the single crystal selectors 142-150 may be constructed and oriented so as to form each of the segments 166 with a different crystallographic structure. It should be understood that any desired number of single crystal selectors 142-150 may be provided to form a corresponding number of single crystal segments 166.

Each of the single crystal segments 166 is formed as a single crystal having a primary or Z axis 62 which extends parallel to a longitudinal central axis 172 of the seed crystal casting 130. However, the secondary axes 64 and 66 of each segment 166 may be disposed in any desired orientation relative to a central axis 172 of the seed crystal casting 130. For example, the first secondary or X axis 64 for each of the segments may be aligned with a radius that extends from the central axis 172 through the center of one of the segments 166. As another alternative, the secondary growth axes 64 and 66 of each one of the single crystal segments 166 may be offset by forty-five degrees from a radius which extends from the central axis 172 through the center of one the segment 166. As still another alternative, the segments 166 may have a crystallographic structure in which the first secondary or X axes 64 of the single crystal segments 166 are all parallel to each other. Of course, this would result in the second secondary or Y axes 66 being parallel to each other.

The seed crystal casting 130 (FIG. 6) is separated into a plurality of sections 178. To form the sections 178, the seed crystal casting 130 is cut at locations indicated by dashed lines 182 in FIG. 6. This results in the formation of a plurality of annular seed rings. Each of the annular seed rings contains a plurality of segments 166 having crystallographic structure determined by the single crystal selectors 142-150 (FIG. 5) utilized to initiate solidification of the molten metal 136 to form the seed crystal casting 130.

Each section 178 of the seed crystal casting 130 has eight segments 166 which correspond to the eight sections 42 of the weapon barrel housing 40 of FIG. 2. Each of the segments 166 of a section 178 of the seed crystal casting 130 has a crystallographic structure which corresponds to the desired crystallographic structure of one of the sections 42 of the weapon barrel housing 40 (FIG. 2). Of course, the seed crystal casting 130 may be provided with a greater or lesser number of segments 166 and the weapon barrel housing 40 formed with a corresponding number of sections 42.

When the weapon barrel housing 40 is to be formed, an annular section 178 of the seed crystal casting 130 is positioned on a chill plate 186 (FIG. 7) at the bottom of a cylindrical mold 188. The mold 188 has a cylindrical inner side surface 190 with a diameter which corresponds to the desired diameter of the weapon barrel housing 40. A core 192 is positioned in a coaxial relationship with the central axis of the mold 188 and extends into a circular central opening in the section 178 of the seed crystal casting 130 disposed on the chill plate 186. The core 192 has a size corresponding to the desired size of the passage 50 (FIG. 2) in the weapon barrel housing 40.

Molten metal 196 is poured into the mold 188 around the core 192. The lower end portion of the molten metal 196 engages the section 178 of the seed crystal casting 130. The molten metal is a superalloy, specifically, a nickel based superalloy. However, it should be understood that a different superalloy may be utilized. For example, the molten metal 196 may be a cobalt based superalloy.

The section 178 (FIG. 7) of the seed crystal casting 130 is cooled by the chill plate 186. The section 178 of the seed crystal casting 130 initiates solidification of the molten metal 196 at the location where the molten 196 engages of the segments 166 of the section of the seed crystal casting. Each of the segments 166 of the section 178 of the seed crystal casting 130 initiates solidification of the molten metal which engages the segment with the same crystallographic structure as the segment. This results in the molten metal 196 solidifying in the mold 188 to form sections 42 (FIG. 2) of the weapon barrel housing 40 with a crystallographic structure which corresponds to the crystallographic structure of the segment 166 which initiated solidification of the molten metal which forms the weapon barrel housing 40.

As the molten metal 196 solidifies upwardly in the mold 188 (FIG. 7), the sections 42 (FIG. 2) of the weapon barrel housing 40 grow upwardly from the section 178 (FIG. 7) of the seed crystal casting 130. The sections 42 of the weapon barrel housing 40 grow upwardly from the lower end of the body 196 of molten metal, that is, from the upper side of the section 178 of the seed crystal casting 130. This results in directional solidification of the molten metal 196 in the mold 188 in an upward direction without significant inward solidification from the inner side surface 190 of the mold 188. The molten metal 196 solidifies as a plurality of single crystal sections 42 (FIG. 2) which are free of generally spherical, randomly oriented crystals.

To effect a directional solidification casting of the molten superalloy 196 in the mold 188, the empty mold 188 (FIG. 7) is moved upward into a furnace chamber. The empty mold 188 and core 192 are preheated in the furnace chamber. At this time, the chill plate 186 is effective to cool at least the lower portion of the section 178 of the seed crystal casting 130. The molten superalloy metal 196 is then poured into the preheated mold 188. The molten metal 196 solidifies against the section 178 of the seed crystal casting 130. At least the lower portion of the section 178 of seed crystal casting 130 is cooled by the chill plate 186.

The chill plate 186 is moved downward to withdraw the section 178 of the seed crystal casting 130 and the mold 188 from the furnace chamber. As this happens, the molten metal 196 in the mold cavity solidifies upwardly from the section 178 of the seed crystal casting. This occurs without significant inward solidification from the inner side surface 190 of the mold 188. Therefore, there is upward directional solidification of the molten metal 196 in the mold 188.

It is contemplated that the furnace may have any one of many known constructions. It is also contemplated that directional solidification of the molten metal in the mold 188 may be effected in any desired manner. If desired, the furnace may have a construction similar to the construction disclosed in the aforementioned U.S. Pat. Nos. 3,841,384 and/or 6,443,213.

As the sections 42 (FIG. 2) of the weapon barrel housing 40 grow upwardly from the section 178 (FIG. 7) of the seed crystal casting 130, some of the sections 42 of the weapon barrel housing 40 may crowd out other sections. Thus, the weapon barrel housing 40 is formed with eight sections 42, corresponding to the eight segments 166 of the section 178 of the seed crystal casting 130. These eight sections 42 extend between opposite ends of the weapon barrel housing.

Alternatively, the weapon barrel housing 40 may have eight sections 42, corresponding to each of the segments 166, at one end portion, such as, the base end portion 54 (FIG. 2), of the weapon barrel housing 40. A smaller number of sections 42 would be located at the opposite end portion, such as, the muzzle end portion 56, of the weapon barrel housing 40. Two or more of the sections 42 would extend from the one end portion to the opposite end portion of the weapon barrel housing 40. The other sections 42 of the weapon barrel housing 40 would terminate at locations between the end portions of the weapon barrel housing.

Casting Single Crystal
Weapon Barrel Housing

To cast the single crystal weapon barrel housing 80 (FIG. 3), a single crystal seed 202 (FIG. 8) is positioned in a mold 204 on a chill plate 206. The mold 204 has a cylindrical configuration with a cylindrical inner side surface 207. A cylindrical core 208 is positioned in a coaxial relationship with the inner side surface 207 of the mold 204. The core 208 may have a diameter which is the same as the diameter of the passage 82 (FIG. 3) in the weapon barrel housing 80.

Molten metal 212 is poured into the mold 204 and engages a flat annular upper surface of the single crystal seed 202. The molten metal 212 is a superalloy which is nickel based. However, the molten metal 212 may be a cobalt based superalloy if desired. The molten metal 212 solidifies as a single crystal which forms the entire weapon barrel housing 80.

The molten metal 212 solidifies upward, as viewed in FIG. 8, to form the weapon barrel housing 80 (FIG. 3) as a single crystal which extends between the base end portion 84 and muzzle end portion 86 of the weapon barrel housing. Directional solidification of the molten metal 212 (FIG. 8) begins at the upper side surface 214 of the single crystal seed 202 and continues upwardly to an upper end of the mold 204 as the mold is withdrawn from a furnace chamber. The molten metal 212 solidifies upwardly in the mold 204 without significant inward solidification from the inner side surface 207 of the mold 204. The molten metal 212 solidifies without forming generally spherical, randomly oriented crystals.

The single crystal seed 202 is formed of the same metal as the molten metal 212. The single crystal seed 202 has a crystallographic structure which corresponds to the desired crystallographic structure for the single crystal weapon barrel housing 80 (FIG. 3). Thus, the single crystal seed 202 has a primary axis, corresponding to the primary axis 92, which extends parallel to the coincident central axes of the core 208 and inner side surface 207 of the mold 204. The secondary axes 94 and 96 of the single crystal seed have orientations which correspond to the desired secondary orientations for the weapon barrel housing 80. For example, the first secondary or X axis, corresponding to the axis 94 in FIG. 3, may extend through coincident central axes 218 of the core 208, mold 204, and seed crystal 202. Of course, the secondary axis 94 may have a different orientation if desired.

CONCLUSION

In view of the foregoing description, it is apparent that the present invention relates to a weapon barrel housing 10, 40, or 80 and the method by which the weapon barrel housing is formed. The weapon barrel housing 10, 40 or 80 is cast as one piece of a superalloy directionally solidified from one end portion 14, 54 or 84 of the weapon barrel housing to the opposite end portion 16, 56, or 86 of the weapon barrel housing. The directionally solidified superalloy has first properties in a direction parallel to a central axis 12, 46, or 94 of the weapon barrel housing. In a direction transverse to a central axis 12, 46, or 94 of the weapon barrel housing, the directionally solidified superalloy has second properties which are different than the first properties.

The directionally solidified superalloy of the weapon barrel housing 10 may be cast with a columnar grain crystallographic structure. Alternatively, the superalloy of the weapon barrel housing may be cast with a plurality of single crystal sections 42, at least one of which extends between opposite end portions 54 and 56 of the weapon barrel housing 40. As another alternative, the superalloy of the weapon barrel housing 80 may be cast as a single crystal.

WEAPON BARREL AND METHOD OF MAKING SAME

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