Backer for electron beam hole drilling

Claim 1

A method for drilling a hole with an energy beam, such as an electron beam, through a workpiece having an entrance surface toward which the beam propagates and through which it first penetrates, and an exit surface which the beam last penetrates, comprising: (a) intimately contacting a backer with the exit surface, the backer being characterized by a particulate bonded together with a binder, the particulate and binder having properties which avoid forming reaction products deleterious to the workpiece during hole drilling and the backer being further characterized by being adapted to removal, at least in part, as a liquid after drilling; (b) directing an energy beam onto a portion of the entrance surface with an intensity sufficient to produce a hole in the workpiece, penetrate the exit surface, and generate within the backer gaseous products sufficient to expel molten workpiece material from the hole at the entrance surface in a direction opposite to the beam propagation; and (c) removing the backer by converting it to at least a partial liquid state with a means wich does not adversely affect the workpiece.

Claim 2

A method for drilling a hole with an energy beam, such as an electron beam, through a workpiece having an entrance surface toward which the beam propagates and through which it first penetrates, and an exit surface which the beam last penetrates, comprising: (a) intimately contacting a backer with the exit surface, the backer being characterized by a particulate bonded together with a binder, the particulate and binder having properties which avoid forming reaction products deleterious to the workpiece during hole drilling and the backer being further characterized by being adapted to removal, at least in part, as a liquid after drilling; (b) directing an energy beam onto a portion of the entrance surface with an intensity sufficient to produce a hole in the workpiece, penetrate the exit surface, and generate within the backer gaseous products sufficient to expel molten workpiece material from the hole at the entrance surface in a direction opposite to the beam propagation; and (c) removing the backer by converting it to at least a partial liquid state with a means wich does not adversely affect the workpiece.

Claim 6

The method of claims 1 or 2 where the particulate is an inorganic nonmetallic and the binder is a polymer liquifiable at a temperature less than about 300° F. (150° C.)

Claim 7

The method for drilling a hole with an electron beam in a hollow gas turbine airfoil article having a beam entrance surface defining the exterior of the article, toward which the beam propagates and through which it first penetrates, and an interior surface defining a cavity, into which the beam last penetrates, comprising: filling the interior cavity with a backer, the backer being characterized by an inorganic nonmetallic particulate bonded to itself and to the interior surface with a polymeric binder, the materials and quantities being chosen to prevent beam penetration and contain the gas pressure generated therewithin by the action of an energy beam; directing an energy beam onto a portion of the entrance surface of the article with an intensity sufficient to produce a hole in the wall of the article and to additionally penetrate the backer; generating sufficient vapor pressure under the action of the beam on the backer to expel molten workpiece material from the hole at the entrance surface, in a direction opposite to the beam propagation; preventing the beam from striking the wall opposing the wall being drilled, by absorption of excess energy in the backer; and removing the backer by converting it at least in part to a liquid, using a means which does not adversely affect the article, such means being chosen from either melting or leaching; to form a hole of substantial uniform symmetry along its length in the article wall and to minimize the formation of burrs, recast layers, and other hole defects which lower the performance of the article.

Claim 8

The method for drilling a hole with an electron beam in a hollow gas turbine airfoil article having a beam entrance surface defining the exterior of the article, toward which the beam propagates and through which it first penetrates, and an interior surface defining a cavity, into which the beam last penetrates, comprising: filling the interior cavity with a backer, the backer being characterized by an inorganic nonmetallic particulate bonded to itself and to the interior surface with a polymeric binder, the materials and quantities being chosen to prevent beam penetration and contain the gas pressure generated therewithin by the action of an energy beam; directing an energy beam onto a portion of the entrance surface of the article with an intensity sufficient to produce a hole in the wall of the article and to additionally penetrate the backer; generating sufficient vapor pressure under the action of the beam on the backer to expel molten workpiece material from the hole at the entrance surface, in a direction opposite to the beam propagation; preventing the beam from striking the wall opposing the wall being drilled, by absorption of excess energy in the backer; and removing the backer by converting it at least in part to a liquid, using a means which does not adversely affect the article, such means being chosen from either melting or leaching; to form a hole of substantial uniform symmetry along its length in the article wall and to minimize the formation of burrs, recast layers, and other hole defects which lower the performance of the article.

Claim 14

The method of drilling a hole with an energy beam, such as an electron beam, through the first section of a workpiece having at least two spaced apart sections lying along the path of the beam, wherein the space between the sections is at least partially filled with a solid backer in intimate contact with the beam exit surface of the first section during hole dirlling, and wherein the backer is converted into at least a partial liquid state while it is being placed into and removed from the space.

Claim 15

The method of drilling a hole with an energy beam, such as an electron beam, through the first section of a workpiece having at least two spaced apart sections lying along the path of the beam, wherein the space between the sections is at least partially filled with a solid backer in intimate contact with the beam exit surface of the first section during hole dirlling, and wherein the backer is converted into at least a partial liquid state while it is being placed into and removed from the space.