Metal founding – Means to shape metallic material – Including means to hold or position preformed product part...
Reexamination Certificate
2002-03-11
2003-06-24
Dunn, Tom (Department: 1725)
Metal founding
Means to shape metallic material
Including means to hold or position preformed product part...
C164S332000, C164S333000
Reexamination Certificate
active
06581671
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a method and apparatus for completing articles of manufacture from preformed components and, more particularly, to a method and apparatus for infiltrating preformed porous components comprising particulates and that may have been formed by a method of layered-manufacturing. The method and apparatus disclosed has particular applicability for large and/or heavy articles of manufacture formed of such components or assemblies of such components that, because of their mass, may require some form of structural support during the sintering and subsequent infiltration process.
2. State of the Art
Various methods of forming metal components have been known for generations, including conventional methods such as casting, forging, and machining. However, because of a need to produce more complex metal components, conventional techniques have proved to be inadequate for some applications, such as the manufacture of drill bits for subterranean drilling, and thus have actually limited the degree of complexity of such manufactured components.
One method that is not so limited in its ability to produce very complex components is layered-manufacturing as disclosed in U.S. Pat. No. 5,433,280, assigned to the assignee of the present invention and incorporated herein for all purposes by this reference. The '280 patent discloses a method of fabricating a drill bit body or 30 bit component in a series of sequentially superimposed layers or slices. As disclosed, a drill bit is designed as a three-dimensional “solid” model using a computer-aided design (CAD) program, which allows the designer to size, configure and place all internal and external features of the bit, such as (by way of example) internal fluid passages and bit blank voids, and external cutter sizes, rakes and locations as well as the height, thickness, profile and orientation of lands and ridges on the bit face and the orientation, depth and profile of waterways on the bit face and junk slots on the bit gage. The CAD program then numerically “slices” the solid model into a large number of thin planar layers.
After the mathematical slicing or layering is performed by the CAD program, a horizontal platen is provided on which a granular or particulate material such as a tungsten carbide coated with a laser-reactive bonding agent such as a polymer, a resin, and/or a low melting point metal such as Wood's metal or a lead alloy, or tungsten carbide intermixed with such a laser-reactive bonding agent is deposited in a thin, uniform layer. A finely focused laser, a focused light source such as from an incandescent or discharge type of lamp, or other energy beams, programmed to follow the configuration of the lowermost or base section or layer of the bit body, is directed on the powder layer to melt the bonding agent and bond the metal particles together in the areas of the layer represented as solid portions of the bit in the model. Another layer of powder is then uniformly deposited over the first, now-bonded layer, after which the metal particles of the second layer are bonded to each other and simultaneously to the first layer by the laser. The process continues until all layers or slices of the bit, as represented by the solid numerical model, have been deposited and bonded, resulting in a mass of bonded-particulate material comprising a bit body which faithfully depicts the computer model in every dimensional respect. In areas of each layer which are not to form a part of the completed article, the laser does not traverse and bond the particles. Thus, a drill bit, or at least a bit body comprised of bonded-particulate material, may be fabricated directly from the CAD-generated solid model without the necessity of designing and fabricating molds and without the delicate, artistic hand labor currently required for bit details.
The bit body may then be placed in a furnace where it may be preheated to substantially remove the bonding agent. In such instances, certain metal powders may be at least preliminarily sintered or fused, such sintering to be enhanced or completed if necessary in a later furnacing operation.
If a powdered metal coated with a bonding agent or metal intermixed with a bonding agent is employed as the particulate material as mentioned above, the resulting bit body is a porous and permeable metal mass akin to a sponge or an open-cell foam which can be imbibed with suitable hardenable infiltrants, either metallic, non-metallic, or a combination thereof, to complete the bit body. If an infiltrant in liquid form at room temperature, such as certain polymers, is employed, the bit may be mass infiltrated via capillary, gravity, and/or pressurized flow at room temperature, while if an infiltrant that is solid at room temperature is employed, the bit would be mass infiltrated by capillary, gravity, and/or pressurized flow in a furnace, induction coil, or other heating methods known in the art of fabricating matrix-type drill bits from loose tungsten carbide powders contained in a mold.
U.S. Pat. No. 5,433,280 also discloses a tungsten carbide or other suitable powder or mix of powders (either metallic or non-metallic) having desired physical characteristics for a matrix substantially uniformly premixed with a powdered polymeric (or other nonmetallic) or metallic infiltrant powder, the premix deposited in layers and the infiltrant powder at least partially fused by a laser to bond the tungsten carbide particles into a matrix and define the bit body shape. After the layering and fusing process is completed, since the infiltrant is already in place, the bit body is heated in a furnace to effect complete in situ infiltration of the matrix. In another alternative to the foregoing procedure, layers of matrix powder alternating with layers of infiltrant powder are deposited. In either case, additional infiltrant may be added during infiltration to fill any infiltrant-deprived voids in the infiltrant-consolidated metal powder matrix. If an infiltrant-coated tungsten carbide or other suitable powder or mix of powders in a layered fashion is employed, a laser may be used to melt the infiltrant coating at least enough to cohere each layer, and the completed bit body placed in a furnace for an in situ infiltration of the bit body, with additional infiltrant being provided if necessary, as noted above.
While it is known in the art to infiltrate conventionally cast particulate metallic articles of manufacture, such as drill bits, with an infiltrant while still contained within their casting mold, layered-manufacturing does not require or generate a mold as a result of the manufacturing process. While it is known that relatively small size and weight components may be infiltrated in a “free-standing” manner by placing the infiltrant around the component and heating until the infiltrant is imbibed or wicked into the component, the frictional properties of the layered component maintaining its configuration, such a “free-standing” approach has not proved to be practical for many larger, heavier and more complex layered-manufactured components, including drill bits and bit components such as blades. During high-temperature infiltration of such a massive layered-manufactured component, when the bonding agent effectively burns away, the mass of metallic particles is left with little or no cohesiveness and thus little or no internal structural strength for self-support. The component thus tends to collapse of its own weight during infiltration. Accordingly, it would be advantageous to provide either supplemental physical or other support for the three-dimensional component structure to ensure that the article of manufacture retains its layered-manufactured configuration during the infiltration process.
BRIEF SUMMARY OF THE INVENTION
Accordingly, a method and apparatus for infiltrating preformed porous components that may have been fabricated from particulates using a layered-manufacturing technique, such as the method disclosed in U.S. Pat. No.
Butcher Trent N.
Findley Sidney L.
Smith Redd H.
Baker Hughes Incorporated
Dunn Tom
Lin I.-H.
TraskBritt
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