Patent Description:
Welding of superalloys presents a variety of technical challenges because of the high strength (and corresponding low ductility) that these alloys are optimized to achieve. One challenge involves the weld filler metal wires, which are typically fabricated to provide a specific/particular alloy deposit, i.e., a desired deposit composition for a specific superalloy, for routine processing via arc welding (e.g., GTAW, PAW, GMAW etc.) or for beam (e.g., laser) processing with wire (e.g., LBW). Such specificity limits any flexibility of trying to achieve a variety of compositions of superalloy deposits. Prior art is disclosed by <CIT>, <CIT> and <CIT>.

It should be appreciated that the present inventor has recognized the above limitations of prior art weld filler metal wires and electrodes, and now discloses a new electrode for use in a weld operation. The object is met by an apparatus of claim <NUM> and a method of claim <NUM>. Preferred emodiments are disclosed in the dependent claims.

According to the invention, an electrode for use in a welding operation is included in an apparatus of welding. The electrode comprises a metal cylinder defining a hollow core therebetween. The hollow core provides a conduit for delivering one or more materials therebetween via a delivery means. The cylinder may be formed of pure metals or metal alloys for forming a desired superalloy material composition, while materials delivered via the conduit comprises a balance of composition resulting deposit achieves the desired superalloy composition as a result of at least the combination of the cylinder materials and core delivered materials. It should be appreciated that the pure metal or metal alloy of the cylinder be of a material that is readily extruded (e.g., plastically shaped) into its cylindrical form. According to the invention the electrode further comprises a flux material surrounding the cylinder. The flux material may also contribute to the desired superalloy composition as a result of the weld operation. The delivery means may be a carrier assist gas or a mechanical assembly operably connected to the electrode for delivering the one or more materials to a delivery end of the electrode.

The present inventor has developed a novel method and apparatus for depositing a variety of difficult to deposit alloys. The method involves a variation of a shielded metal arc welding (SMAW) process, which is also referred to as stick welding or coated electrode welding. The novel process involves the use of an electrode consisting of a hollow metal or metal alloy sheath/core which is surrounded by a shielding means, i.e., an adherent coating flux. In operation, the metal alloy of the hollow sheath/core conducts welding current while the flux coating provides shielding. During the welding operation, the hollow metal sheath/core melts off and provides, e.g., the base material for the deposit, e.g., a pure nickel or alloyed nickle, iron etc., while the filler material delivered via the hollow core provides, e.g., the remaining materials required for forming the desired deposit. The flux coating melts during the weld operation, releases shielding gases, and provides a slag (first molten and then solid) to protect the molten deposit from atmospheric reactions. It should be appreciated that the flux may also contribute to the deposit's chemistry and may act to remove impurities from the molten pool.

It should be appreciated that the inventor's novel electrode now provides the flexibility for forming a variety of deposit superalloy compositions from a single electrode. For example, for a nickel based superalloy, an electrode comprising a pure nickel metal cylinder can be used to form any nickel based deposit superalloy composition, as the remaining or balance compositional constituents for forming the desired deposit composition may now be delivered via the hollow core of the electrode. Said another way, it is now possible to form, e.g., multiple types of nickel deposits, by changing the materials delivered through the electrode hollow core to form the desired deposit instead of changing the electrode. The electrode may include and be applied to other materials, in addition to the superalloys referenced herein, e.g., stainless steels, oxide dispersion strengthened alloys, etc., where the metal cylinder would be formed of the, e.g., iron, while the remaining constituents for forming stainless steel deposits are provided via the hollow core.

Referring now to the drawings wherein the showings are for purposes of illustrating embodiments of the subject matter herein only and not for limiting the same, <FIG> is a schematic illustration of one exemplary embodiment of a welding apparatus including electrode <NUM>.

The electrode <NUM> is a SMAW electrode <NUM> and includes a cylinder <NUM>, i.e., a metal cylinder or tube, defining a hollow core <NUM> therebetween for establishing an electrical current during a weld operation. The core <NUM> may be cylindrically shaped defining an interior (i.e., a core interior) adapted or sized to provide a conduit for delivery of materials <NUM>, i.e. erg- , a stream of powdered feed materials (e.g., metal alloy powder and/or other constituents) and a material delivery means, e.g., a carrier (assist) gas or rotary system, therebetween.

The metal cylinder <NUM> may be formed of a ductile material, such as elemental metals, e.g., iron, nickel, cobalt, aluminum, or extrudable metal alloy materials including a subset of elements of a composition contributing to define a desired, e.g., superalloy, material, e.g., nickel or nickel alloy (e.g., CM247, Inconel <NUM>, Inconel <NUM>, Haynes <NUM>, ER NiCr-<NUM>. In operation, the conduit <NUM>, i.e., the hollow cored portion of the electrode <NUM>, may facilitate the delivery of a balance of the compositional constituents, e.g., Cr, Mo, Ti, Al, W, Mo, C, Ta, etc., in a powder form and with the carrier gas. It should be appreciated that the combination of the cylinder material and the core delivered materials results, after possible anticipated volatile losses, in achieving the deposited superalloy composition.

The carrier (assist) gas may be any known type of arc welding assist gas, e.g., argon, helium, hydrogen, carbon dioxide, oxygen, nitrogen, etc. or blends thereof, and may be optionally required depending upon what embodiment of the electrode <NUM> is provided. The feed rate of powder with assist gas may be regulated in concert with, e.g., the burn-off rate of the electrode <NUM> to achieve the desired superalloy deposit composition. The inventor has identified increased and potentially unlimited flexibility in this approach to lean or enrich the core powder feed rate or to regulate core powder composition to modulate deposit composition.

With continued reference to the figures, the electrode <NUM> further includes a shielding means <NUM> to provide shielding from, e.g., atmospheric reactions when an arc is established between the end of the electrode and substrate to be welded. According to the invention, the shielding means is an adherent flux coating <NUM> which surrounds the metal alloy cored portion <NUM> of the electrode <NUM>. The flux coating <NUM> Provides shielding, i.e., during the SMAW operation and protection from, e.g., atmospheric reactions when an arc is established between the end of the electrode and substrate to be welded.

The flux coating <NUM> may be a full flux coating such that it is capable of providing complete shielding, e.g., during the SMAW operation shielding, without any further assistance, e.g., from another shielding source. Additionally or alternatively, the flux coating <NUM> may be a reduced flux coating, which may require an additional shielding means to assist with the shielding function. Additionally, the shielding means may be flux material projected or delivered through the conduit <NUM>. The conduit delivered flux may be provided along with any hollow core feed materials, e.g., either mixed therewith and simultaneously fed or as conglomerate particles.

In a further example, not forming part of the present invention, the shielding means <NUM> may be an assist gas which may be fed around or through the conduit <NUM> to provide additional shielding, e.g., at the point of welding. The additional shielding means may be provided with any of the flux coatings (full or reduced). Additionally, an auxiliary shielding gas may also be provided, e.g., at the point of welding, to provide additional shielding, e.g., at an outer surface of the metal alloy tubular core wire <NUM>. In yet a further embodiment, additional powdered flux may also be projected or delivered through the conduit <NUM> to assist in shielding as the additional shielding means.

With continued reference to the figures, and now <FIG>, a further embodiment of the apparatus including the electrode <NUM> is provided. In the embodiment of <FIG>, the delivery means for delivering materials through the hollow core <NUM> may be a mechanical assembly <NUM> to mechanically deliver the feed materials (e.g., powder) through the conduit <NUM>. In one embodiment, the mechanical assembly <NUM> may be a rotary screw or auger <NUM> (<FIG>) which may be operationally configured to control the flow and/or throughput of materials through the core <NUM>.

The auger <NUM> may be configured to retract or be withdrawn axially relative to the electrode <NUM> and at a burn-off rate of the electrode <NUM>. Additionally or alternatively, the electrode <NUM> may move or be projected over, e.g. a fixed auger during the weld operation.

Delivery of the feed materials (i.e., powder) via the auger <NUM> may be determined by the speed of rotation of the auger <NUM>, and size (depth) and interval of auger threading (flutings). Additionally or alternatively, the auger delivery end, i.e., the end where the powder is being delivered via the auger <NUM>, should be at or reside in the proximity of the welding end of the electrode <NUM> (e.g., ARC of <FIG>).

In yet another exemplary embodiment, the delivery means may be one or more acoustic or ultrasonic waves projected from an acoustic or ultrasonic device or system. The ultrasonic system may be configured, e.g., to generate and/or impose ultrasonic waves to the electrode <NUM> to enhance delivery of the materials through the conduit <NUM>. The waves may be directed towards the electrode <NUM> or towards the materials within the conduit <NUM> for directionally controlling the flow and throughput of materials within the conduit <NUM> and through the electrode <NUM>.

It should be appreciated that the mechanical delivery means may be used with the carrier assist gas or in lieu of any gas assisted propulsion of core feed materials through the electrode <NUM>. Any combination of delivery means may be used for delivering the core feed materials via the conduit <NUM>.

With continued reference to the figures, and now <FIG>, a welding technique (method) <NUM> utilizing embodiments of the electrode <NUM> is provided. It should be appreciated that any steps disclosed herein are not required to be performed in any particular order, and are hereby provided for exemplary purposes. For example, steps for delivering the materials via the hollow core <NUM> may occur prior to forming the weld pool, while forming the weld pool, or once the weld pool has been formed.

The method <NUM> includes melting the electrode <NUM> to form a deposit of, e.g., a material composition, e.g., a superalloy material composition on a superalloy substrate (<NUM>). It should be appreciated that during the weld process, the electrode <NUM> is handled, i.e., via an electrode holder <NUM>, also known as a stinger <NUM>. According to the invention, the stinger <NUM> defines an interior or opening having at least a portion thereof sized or adapted to facilitate the feeding of materials <NUM> and/or the delivery means <NUM> (e.g., propulsion gas, auger) therethrough. For example, <FIG> shows an embodiment of the stinger <NUM> with an interior <NUM> adapted to receive the auger <NUM> therethrough for delivery of the feed materials <NUM> at the delivery end of the electrode <NUM> near the point of welding.

The electrode <NUM> is held by the stinger <NUM> opposite the delivery end of the feed materials <NUM>, i.e., opposite the welding end. Portions of any electrode coatings, i.e., flux coating <NUM>, is removed or stripped (SC, <FIG>) in order for the stinger <NUM> to hold the electrode <NUM> (e.g., the metal cylinder <NUM>) and to thereby establish a welding current connection during the welding operation.

During the welding process the electrode <NUM> is consumed at the point of welding, i.e. it is melted and becomes part of a weld pool, as does the flux coating <NUM>. To form the weld pool, the substrate is melted, via an electric arc.

The metal cylinder <NUM> may comprise pure metals for forming, e.g., the desired superalloy material deposit composition. The core feed materials <NUM> comprising a balance of compositional constituents for forming the desired superalloy material deposit are delivered through the conduit <NUM>, e.g., via the delivery means, at a delivery end of the electrode proximate to or at the point of welding (<NUM>). Upon consumption of the metal cylinder, the core delivered materials, and the flux coating, the combination of the melted cylinder <NUM> and delivered materials <NUM> result in the deposit achieving the desired superalloy material composition.

It should be appreciated that in operation, the flux coating <NUM> upon consumption generates a shielding gas that shields the weld pool and surrounding heated area and protects the substrate from atmospheric contamination. The flux also enters the weld pool and forms a slag on the surface of the weld pool which may remain on a weld bead when the weld pool solidifies into a weld bead. While present in the volume of the weld pool, it should be appreciated that the flux may also deoxidize and/or remove impurities present in the weld pool. While present on the surface, the slag may also help shape the weld pool during solidification. The flux coating <NUM> may be neutral, i.e., may have virtually no effect on deposit composition, or alternatively, the flux may be active, i.e., making additions to the deposit composition or compensating for volatile losses during processing, e.g., the weld operation.

Additionally or alternatively, the method <NUM> may include removing any slag resulting from melting of the flux coating <NUM> via any means for removing slag from a surface of a substrate known in the art and chosen with sound judgment (<NUM>).

After slag removal, if needed, the method <NUM> may include steps for finishing the substrate or component and preparing the component to be used in operation (<NUM>). In this step <NUM>, and upon removal of any slag, the finishing and preparation steps may include heat treating the component, e.g., via a furnace, e.g., a high heat vacuum furnace. Additionally or alternatively, and prior to or after heat treatment, the component may be finished or machined to reduce undesired structures from the surface of the substrate, e.g., via a chip-removing method (e.g., using abrasive blasting media), and/or a grinding method. Additionally or alternatively, the finishing steps may include non-destructive testing methods to test the integrity of the component.

Claim 1:
An apparatus of welding
including an electrode (<NUM>) comprising:
a metal cylinder (<NUM>) defining a weld end and a hollow interior (<NUM>),
powdered feed materials (<NUM>) positioned in the hollow interior (<NUM>) and movable with respect to the metal cylinder towards the weld end of the electrode,
a delivery means operable to move the powdered feed materials with respect to the metal cylinder, and
an adherent flux coating (<NUM>) surrounding the metal cylinder (<NUM>), and
using an electrode holder (<NUM>) defining an interior or opening having at least a portion thereof sized or adapted to facilitate the feeding of the powdered feed materials (<NUM>) and/or the delivery means therethrough,
wherein the electrode (<NUM>) is held by the electrode holder (<NUM>) opposite the weld end, wherein portions of the flux coating (<NUM>) are removed or stripped in order for the electrode holder (<NUM>) to hold the metal cylinder (<NUM>) and to thereby establish a welding current connection during the welding operation.