WO2017132020A1 - Revêtement par flux thermique faible de superalliages utilisant un matériau d'alimentation à cœur - Google Patents

Revêtement par flux thermique faible de superalliages utilisant un matériau d'alimentation à cœur Download PDF

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Publication number
WO2017132020A1
WO2017132020A1 PCT/US2017/013888 US2017013888W WO2017132020A1 WO 2017132020 A1 WO2017132020 A1 WO 2017132020A1 US 2017013888 W US2017013888 W US 2017013888W WO 2017132020 A1 WO2017132020 A1 WO 2017132020A1
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Prior art keywords
metal
flux
powdered
weight
slag
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English (en)
Inventor
Gerald J. Bruck
Ahmed Kamel
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Siemens Energy Inc
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Siemens Energy Inc
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Priority claimed from US15/008,893 external-priority patent/US20160144441A1/en
Application filed by Siemens Energy Inc filed Critical Siemens Energy Inc
Publication of WO2017132020A1 publication Critical patent/WO2017132020A1/fr
Anticipated expiration legal-status Critical
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
    • B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
    • B23K35/36—Selection of non-metallic compositions, e.g. coatings or fluxes; Selection of soldering or welding materials, conjoint with selection of non-metallic compositions, both selections being of interest
    • B23K35/3601—Selection of non-metallic compositions, e.g. coatings or fluxes; Selection of soldering or welding materials, conjoint with selection of non-metallic compositions, both selections being of interest with inorganic compounds as principal constituents
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
    • B23K35/02—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape
    • B23K35/0222—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape for use in soldering or brazing
    • B23K35/0244—Powders, particles or spheres; Preforms made therefrom
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
    • B23K35/02—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape
    • B23K35/0255—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape for use in welding
    • B23K35/0261—Rods, electrodes or wires
    • B23K35/0266—Rods, electrodes or wires flux-cored
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
    • B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
    • B23K35/36—Selection of non-metallic compositions, e.g. coatings or fluxes; Selection of soldering or welding materials, conjoint with selection of non-metallic compositions, both selections being of interest
    • B23K35/3601—Selection of non-metallic compositions, e.g. coatings or fluxes; Selection of soldering or welding materials, conjoint with selection of non-metallic compositions, both selections being of interest with inorganic compounds as principal constituents
    • B23K35/3602—Carbonates, basic oxides or hydroxides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
    • B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
    • B23K35/36—Selection of non-metallic compositions, e.g. coatings or fluxes; Selection of soldering or welding materials, conjoint with selection of non-metallic compositions, both selections being of interest
    • B23K35/3601—Selection of non-metallic compositions, e.g. coatings or fluxes; Selection of soldering or welding materials, conjoint with selection of non-metallic compositions, both selections being of interest with inorganic compounds as principal constituents
    • B23K35/3603—Halide salts
    • B23K35/3605—Fluorides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
    • B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
    • B23K35/36—Selection of non-metallic compositions, e.g. coatings or fluxes; Selection of soldering or welding materials, conjoint with selection of non-metallic compositions, both selections being of interest
    • B23K35/3601—Selection of non-metallic compositions, e.g. coatings or fluxes; Selection of soldering or welding materials, conjoint with selection of non-metallic compositions, both selections being of interest with inorganic compounds as principal constituents
    • B23K35/3607—Silica or silicates
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K9/00—Arc welding or cutting
    • B23K9/04—Welding for other purposes than joining, e.g. built-up welding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K9/00—Arc welding or cutting
    • B23K9/12—Automatic feeding or moving of electrodes or work for spot or seam welding or cutting
    • B23K9/124—Circuits or methods for feeding welding wire
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K9/00—Arc welding or cutting
    • B23K9/16—Arc welding or cutting making use of shielding gas
    • B23K9/173—Arc welding or cutting making use of shielding gas and of a consumable electrode
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K9/00—Arc welding or cutting
    • B23K9/23—Arc welding or cutting taking account of the properties of the materials to be welded
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2101/00—Articles made by soldering, welding or cutting
    • B23K2101/001—Turbines
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2103/00—Materials to be soldered, welded or cut
    • B23K2103/18—Dissimilar materials
    • B23K2103/26—Alloys of Nickel and Cobalt and Chromium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
    • B23P6/00—Restoring or reconditioning objects
    • B23P6/002—Repairing turbine components, e.g. moving or stationary blades, rotors
    • B23P6/007—Repairing turbine components, e.g. moving or stationary blades, rotors using only additive methods, e.g. build-up welding

Definitions

  • Embodiments of the invention relate generally to the field of metals joining, and more particularly to the welding clad buildup and repair of superalloy materials using a hollow cored feed material containing powdered flux and powdered metal with a cold metal transfer process.
  • Welding processes vary considerably depending upon the type of material being welded. Some materials are more easily welded under a variety of conditions, while other materials require special processes in order to achieve a structurally sound joint without degrading the surrounding substrate material.
  • GMAW gas metal arc welding
  • MIG metal inert gas
  • MAG metal active gas
  • Flux protected processes include submerged arc welding (SAW) where flux is commonly fed, flux cored arc welding (FCAW) where the flux is included in the core of the electrode and shielded metal arc welding (SMAW) where the flux is coated on the outside of the filler electrode.
  • SAW submerged arc welding
  • FCAW flux cored arc welding
  • SMAW shielded metal arc welding
  • superalloy materials are among the most difficult materials to weld due to their susceptibility to weld solidification cracking and strain age cracking.
  • the term "superalloy” is used herein as it is commonly used in the art; i.e., a highly corrosion and oxidation resistant alloy that exhibits excellent mechanical strength and resistance to creep at high temperatures.
  • Superalloys typically include a high nickel or cobalt content. Examples of superalloys include alloys sold under the trademarks and brand names Hastelloy, Inconel alloys (e.g. IN 738, IN 792, IN 939), Rene alloys (e.g.
  • CMSX e.g. CMSX-4
  • weld repair of some superalloy materials has been accomplished successfully by preheating the material to a very high temperature (for example to above 1600 °F. or 870 °C.) in order to significantly increase the ductility of the material during the repair.
  • This technique is referred to as hot box welding or superalloy welding at elevated temperature (SWET) weld repair and it is commonly accomplished using a manual gas tungsten arc welding (GTAW) process.
  • GTAW manual gas tungsten arc welding
  • hot box welding is limited by the difficulty of maintaining a uniform component process surface temperature and the difficulty of maintaining complete inert gas shielding, as well as by physical difficulties imposed on the operator working in the proximity of a component at such extreme temperatures.
  • Some superalloy material welding applications can be performed using a chill plate to limit the heating of the substrate material; thereby limiting the occurrence of substrate heat affects and stresses causing cracking problems.
  • this technique is not practical for many repair applications where the geometry of the parts does not facilitate the use of a chill plate.
  • FIG. 3 is a conventional chart illustrating the relative weldability of various alloys as a function of their aluminum and titanium content. Alloys such as Inconel ® 718 which have relatively lower concentrations of these elements, and consequentially relatively lower gamma prime content, are considered relatively weldable, although such welding is generally limited to low stress regions of a component. Alloys such as Inconel ® 939 which have relatively higher concentrations of these elements are generally not considered to be weldable, or can be welded only with the special procedures discussed above which increase the temperature/ductility of the material and which minimize the heat input of the process. A dashed line 80 indicates a border between a zone of weldability below the line 80 and a zone of non-weldability above the line 80.
  • the line 80 intersects 3 wt.% aluminum on the vertical axis and 6 wt.% titanium on the horizontal axis.
  • the alloys with the highest aluminum content are generally found to be the most difficult to weld.
  • the challenge to develop commercially feasible joining processes for superalloy materials continues to grow.
  • CMT cold metal transfer
  • General Electric and United Technologies have taught the use of CMT welding without substrate heating and with substrate heating respectively (Pezzutti U.S. 20130082446A1 and Rose U.S. 20130326877A1 ).
  • Rose includes pre- weld heat treatments and post-weld heat treatments of the substrate (before and after welding) in their method.
  • the CMT process was developed by Fronius International GMBH Austria and is a variation of short arc gas metal arc welding wherein the wire is caused to move toward and away from the weld pool at a relatively rapid rate (e.g. between 10-130 times /sec). With an arc established, a molten droplet forms at the end of the wire. Then forward motion of the wire to the weld pool results in a short circuit. The current rise is controlled and backward wire motion is then synchronized with short circuiting to help propel the droplet of molten filler wire to the deposit in a highly controlled manner. Low heat input, low base metal melting, small heat affected zone and little spatter results. To the knowledge of the present inventor, flux materials have not been used when welding superalloy materials with CMT processing.
  • FIGs. 1A - 1 D illustrate apparatus and steps in a known cold metal transfer process.
  • FIGs. 2A-2B illustrate a cladding process using a cored filler wire and a cold metal transfer process, in accordance with an embodiment of the present invention.
  • FIG. 3 is a prior art chart illustrating the relative weldability of various superalloys.
  • Such rods can be extruded into clean superalloy wire, but the overall process to create spools of reasonable lengths of weld wire for CMT would have been disadvantageous and practically unworkable from an economic standpoint, as it would require special equipment and be very expensive.
  • the present inventor has also recognized the use of a flux during a low heat input process (such as CMT or TIP TIG processing) helps counteract the increase in crack length observed with increasing wattage, as reported in Rush et al. In an embodiment of the present invention, the use of a flux therefore allows for increased power CMT processing without the associated increase in crack lengths.
  • the flux may serve to either (1 ) slow the cooling process, allowing for higher wattages to be employed during CMT processing, as slower cooling will reduce the stress intensities and propensity for cracking, or (2) reduce the overall heat of the CMT process, despite increases in wattage, by using a flux designed to keep the entire process cooler.
  • Heat input can be defined for arc welding as volts times amps divided by travel speed or by volume of weld metal deposited or by energy used per unit weld bead length (aka power used times arc time per unit weld bead length).
  • gas tungsten arc welding heat input ranges between about 0.5 and 1.5 kilojoules per millimeter (kJ/mm).
  • kJ/mm kilojoules per millimeter
  • conventional gas metal arc welding the range is about 0.2 to 1 .0 kJ/mm.
  • For advanced short circuiting gas metal arc welding the range is about 0.1 to 0.6 kJ/mm.
  • a heat input range of 0.05 to 0.6 kJ/mm is what is referred to as a low heat input process.
  • the parent patent application US 2014/0209577 A1 discloses a process whereby a readily extrudable cored wire having disposed therein a powdered core material may be used successfully to deposit the most difficult to weld superalloy materials. That document also discloses that the powdered core material may advantageously utilize a powdered flux material during a melting and re-solidifying process.
  • methods are disclosed for depositing a desired superalloy using a cored wire with a low heat input welding process such as cold metal transfer welding, TIP TIG, pulsed arc welding, or a low energy beam process.
  • the flux material is effective to provide energy trapping, impurity cleansing, atmospheric shielding, bead shaping, and cooling temperature control in order to accomplish crack-free joining of superalloy materials without the necessity for high temperature hot box welding or the use of a chill plate or the use of inert shielding gas. While various sub-elements of the present embodiments have been known in the welding industry for decades, the present inventors have innovatively developed a combination of steps for a superalloy cladding process that solves the long-standing problem of cracking of these materials.
  • FIG. 1A - 1 D illustrate basic apparatus and steps in a known cold metal transfer process 10.
  • a consumable electrode 12 approaches an electrically conductive substrate 14, establishing an arc 16 that melts a melt pool 18 on a surface 20 of the substrate and creates a melt drop 22 of alloy filler material on the electrode tip.
  • the electrode 12 is also progressing in a direction of welding from left to right in the figure, and a solidified deposit 24 (as discussed more fully below) is illustrated on the substrate 14.
  • FIG. 1 B the consumable electrode 12 is advanced 26 toward the melt pool 18.
  • the melt drop 22 touches the melt pool 18, extinguishing the arc and causing a short circuit.
  • FIGs. 2A-2B illustrate an additive cold metal transfer embodiment of the present invention for depositing superalloy material. Similar to the process described in FIGs. 1 A-1 D, the process of FIGs. 2A-2B utilize an oscillating feed material to deposit drops of molten filler material 22 into a weld pool 18, as described more fully below.
  • a cladding layer of superalloy material 30 is deposited onto a surface 20 of a superalloy substrate 32 using a filler or feed material in the form of electrode 31 .
  • the electrode 31 has a form of a cored wire or strip material including a hollow metal sheath 34 filled with a powdered core material 36.
  • the powdered core material 36 includes a powdered alloy material 42 and may also include a powdered flux material 38.
  • the sheath 34 and powdered core material 36 are advantageously selected such that the resulting layer of cladding material 30 has the composition of a desired superalloy material.
  • the sheath may be only an extrudable subset of elements of a composition of elements defining the desired superalloy material, and the powdered core material includes elements that complement the elements in the sheath to complete the composition of elements defining the desired superalloy material.
  • the sheath and the powdered alloy material are combined in the melt pool 18 to form a layer of cladding 30 of the desired superalloy material.
  • the flux material 38 produces a layer of slag 40 that protects, shapes and thermally insulates the layer of cladding material 30 and eliminates or minimizes the need for an inert cover gas.
  • the slag and melt pool cool and solidify together, and the slag is then removed to reveal the deposited alloy.
  • the sheath 34 is formed of a material that can be conveniently formed into a hollow shape, such as pure nickel or nickel-chromium or nickel-chromium-cobalt, and the powdered material 36 is selected such that a desired superalloy composition is formed when the filler material is melted.
  • the sheath 34 in an embodiment contains sufficient nickel (or cobalt) to achieve the desired superalloy composition, thus the solid to solid ratio of sheath verses powdered core material weights may be maintained at a ratio of 3 : 2, for example.
  • Powdered flux material 38 may be provided in the powdered core material 36 (for example 25% of the core volume) or it may be pre- placed or deposited (not shown) onto the surface 20 of the substrate 32, or the electrode 31 may be coated with flux material, or any combination of these alternatives.
  • a supplemental powdered metal material may also be added to the melt pool (not shown) by being pre-placed on the surface 20 of the substrate 32 or by being directly fed into the melt pool 18 during the step of melting.
  • an arc 16 is present between the electrode 31 and the melt pool 18.
  • the arc is extinguished when the melt drop 22 touches the melt pool 18.
  • the electrode 31 may be automatically advanced 26 toward and retracted 28 away from the melt pool 18 multiple times per second - for example at least 10 times per second in some embodiments and up to 130 times per second in some embodiments.
  • the electrode may be oscillated more than 130 times per second due to the stabilizing action of the flux 38 and slag 40. The oscillations create turbulence and forced convection in the melt pool 18 that thoroughly mix the melted sheath and core materials before solidification.
  • TIP TIG is a low heat input process utilizing a non-consumable (e.g. tungsten) electrode to melt an oscillating feed material electrode.
  • the feed material electrode 31 may be oscillated left and right, perpendicular to a progression direction of the weld seam or in other orientations in order to achieve a mixing action similar to that achieved by the process of FIGs. 2A-2B.
  • One embodiment of a filler material electrode 31 is formulated to deposit alloy 247 material as follows:
  • - sheath solid volume is about 60% of total metallic solid volume and is pure Ni;
  • - core metal powder volume is about 40% of total metallic solid volume including sufficient Cr, Co, Mo, W, Al, Ti, Ta, C, B, Zr and Hf; that when melted together and mixed with the pure nickel from the sheath, produces alloy 247 composition of nominal weight percent 8.3 Cr, 10 Co, 0.7 Mo, 10 W, 5.5 Al, 1 Ti, 3 Ta, 0.14 C, 0.015 B, 0.05 Zr and 1 .5 Hf; and
  • - core flux powder volume represents additional, largely non-metallic, wire volume possibly about equal in size to the metal powder volume and includes alumina, fluorides and silicates in a 35/30/35 ratio.
  • the mesh size range of the flux is such as to distribute uniformly within the core metal powder. Flux and metal powder may alternately be provided as composite powder particles.
  • Typical powdered prior art flux materials have particle sizes ranging from 0.5 - 2 mm, for example.
  • the powdered alloy material 42 may have a particle size range (mesh size range) of from 0.02 - 0.04 mm or 0.02 - 0.3 mm or other sub-range therein.
  • the flux material may be electrically conductive (electroslag) or not (submerged arc), and it may be chemically neutral or additive.
  • the filler material may be preheated to reduce process energy required.
  • a semi-conductive or non- conductive slag may be formed. These slags have the advantage of containing the arc within the precise weld zone, and preventing the arc from traveling or jumping laterally or axially.
  • the flux composition may include compounds which have an electrical insulative resistivity.
  • the flux material may melt to form a slag having a specific conductivity of no more than 9mho/com or between 1 and 9 mho/cm. To express electrical insulating properties, volume resistivity or dielectric strength is widely used as an index.
  • the flux material therefore includes composition(s) having a dielectric strength of at least 1 1 kV/mm.
  • the flux composition(s) disclosed are that they advantageously serve to control the arc and quiet the weld pool.
  • Embodiments include a low heat input processing wherein the oscillation rate (the rate in which the feed material is advanced and retracted from the substrate) is greater than 130 oscillations per second, and as high as 160 oscillations per second. In other embodiments, the oscillation rate is between 135-155 oscillations per second, or between 150-160 oscillations per second. Oscillation rates of lower than 130 oscillations per second may also be used.
  • Benefits to the disclosed flux is that it helps to ensure that the arc does not wander when struck. This is because the flux (and corresponding slag) is retained around the edges.
  • the use of the flux material ensures slag coverage in the trail and is sufficiently thick to assist in shaping the weld pool.
  • the use of a flux material also provides shielding thereby reducing or eliminating the need for inert or partially inert gas used in CMT processing.
  • the flux material further serves the function of cleansing impurities (scavenging tramp elements), and the slag serves to promote cooling or preserving of heat as the weld pool solidifies, as appropriate for the metal desired to be deposited.
  • the flux includes the compositions disclosed in Patent Publication US 2015/0027993, which is incorporated herein by reference.
  • carbonates such as CaC0 3 , SrC0 3 , and BaC0 3 would be particularly useful to generate CO2, which is used with CMT processing - either as a shield gas alone or combined with other inert gases such as argon or helium.
  • Metal halides may also be included to generate fluorine, chlorine, or bromine gas and to supplement metallic additions. Examples include AIF 3 and AI 2 Cl6.
  • Hydrogen halides may also be used to generate shielding gases. Metal hydrides may similarly contribute shielding gases as well as metallic additions. Examples include ⁇ 1.7, ZrH 2 , CrH, AIH 3 , and HfH 2 .
  • flux materials of the present disclosure include:
  • vectoring agent(s) 0 - 7% by weight of vectoring agent(s).
  • vectoring agent(s) 0 - 5% by weight of vectoring agent(s).
  • the flux materials of the present disclosure include: - 40% by weight of AI 2 O 3
  • the flux materials of the present disclosure include: - 40% by weight of Al 2 0 3
  • the flux materials of the present disclosure include zirconia (Zr0 2 ) and at least one metal silicate, metal fluoride, metal carbonate, metal oxide (other than zirconia), or mixtures thereof.
  • the content of zirconia is often greater than about 7.5 percent by weight, and often less than about 25 percent by weight.
  • the content of zirconia is greater than about 10 percent by weight and less than 20 percent by weight.
  • the content of zirconia is greater than about 3.5 percent by weight, and less than about 15 percent by weight.
  • the content of zirconia is between about 8 percent by weight and about 12 percent by weight.
  • the flux materials of the present disclosure include a metal carbide and at least one metal oxide, metal silicate, metal fluoride, metal carbonate, or mixtures thereof.
  • the content of the metal carbide is less than about 10 percent by weight.
  • the content of the metal carbide is equal to or greater than about 0.001 percent by weight and less than about 5 percent by weight.
  • the content of the metal carbide is greater than about 0.01 percent by weight and less than about 2 percent by weight.
  • the content of the metal carbide is between about 0.1 percent and about 3 percent by weight.
  • the flux materials of the present disclosure include at least two metal carbonates and at least one metal oxide, metal silicate, metal fluoride, or mixtures thereof.
  • the flux materials include calcium carbonate (for phosphorous control) and at least one of magnesium carbonate and manganese carbonate (for sulfur control).
  • the flux materials include calcium carbonate, magnesium carbonate and manganese carbonate.
  • Some flux materials comprise a ternary mixture of calcium carbonate, magnesium carbonate and manganese carbonate such that a proportion of the ternary mixture is equal to or less than 30% by weight relative to a total weight of the flux material. A combination of such carbonates (binary or ternary) is beneficial in most effectively scavenging multiple tramp elements.
  • Flux materials which could be used include commercially available fluxes such as those sold under the names Lincolnweld P2007, Bohler Soudokay NiCrW-412, ESAB OK 10.16 or 10.90, Special Metals NT100, Oerlikon OP76, Sandvik 50SW or SAS1 .
  • the flux particles may be ground to a desired smaller mesh size range before use.
  • Flux materials known in the art may typically include alumina, fluorides and silicates.
  • Embodiments of the processes disclosed herein may advantageously include metallic constituents of the desired cladding material, for example chrome oxides, nickel oxides or titanium oxides. Any of the currently available iron, nickel or cobalt based superalloys that are routinely used for high temperature applications such as gas turbine engines may be joined, repaired or coated with the inventive process, including those alloys mentioned above.
  • the flux may be a flux that includes a cooling agent.
  • a cooling agent may be a set of materials which participate in an endothermic process. This endothermic process may be, for example, an endothermic reaction such as an endothermic decomposition, or a heat absorptive phase change or transition from a gas to plasma. If the endothermic process is a reaction, the cooling agent may be a set of reactants added to the powdered flux material 38 before or at the time of melting which combine to form products in an endothermic reaction. Because the reaction is endothermic, it will draw heat away from the hot melt pool 18, thereby speeding the cooling process.
  • Fluxes comprised of carbonates (e.g. calcium carbonate (CaCO 3 )), would absorb heat and form oxides and gases (e.g. CaO and CO2 (and CO)) in endothermic decomposition reactions thereby both removing heat from the deposit and forming a shielding gas.
  • Ammonium nitrite may also be included in the flux as it may absorb heat and decompose to yield nitrogen (somewhat shielding) and water vapor.
  • Solid salts may also be included in the flux as they absorb heat upon melting during liquid slag formation. Also, to the extent that the laser interacts with gas molecules to form a plasma such dissociation is endothermic.
  • Another exemplar cooling agent may be a gas generating agent ("GGA") included in the powdered flux material 18.
  • GGA gas generating agent
  • This may be any substance or group of substances that rapidly form gases, such as substances that sublimate at or above room temperature, such as solid CO2 (C02( S )) or iodine (l2( S )), or a reactive material such as a carbonate which forms C0 2 .
  • the solid is injected either in the layer of powdered alloy material, or the layer of powdered slag material, or both, either at the time of melting or just before.
  • the powdered flux material's gas generating agent forms gas bubbles 36 which rise through the melt pool 30.
  • the bubbles create voids and narrow, thin channels 38 through the melt pool 30.
  • the melt pool 30 cools more quickly so as to form the layer of metallic glass 14. This is because heat is conducted away more rapidly from a thin material than a thick material.
  • the resulting pores augment the thermal insulating properties and mechanical compliance of the resulting layer of metallic glass.
  • the flux may also have properties which allow it to radiate heat.
  • the powdered flux material 38 may include metal elements having higher thermal conductivity, as higher thermal conductivity metals in the flux (and corresponding layer of slag 40) will more rapidly radiate heat away from the melt pool 18.
  • Fluxes of high silica (the metalloid oxide, S1O2) content relative to alumina (AI 2 03),or zirconia (Zr0 2 ) content may enhance heat radiation, for example at least two or three or four times the molar content of silica compared to alumina, or zirconia, or the combination of alumina and zirconia.
  • Advantages of the disclosed processes over known CMT processing include: high deposition rates and thick deposit in each processing layer due to the increased wattages that may be used, improved shielding that extends over the hot deposited metal without the need for inert gas, enhanced cleansing of the deposit of constituents that otherwise lead to solidification cracking, slag formation to shape and support the deposit, a capability to compensate for elemental losses or add alloying elements, and increases in efficiency from a reduction of the time involved in total part building.
  • Incorporation of the flux also reduces residual stresses that otherwise contribute to strain age (reheat) cracking during post weld heat treatments in one of two ways: (1 ) by using a flux which generates a thermally insulating slag to preserve heat and slow the cooling rate, or (2) by using a cooling flux to reduce the heat of the overall process, thereby reducing the overall temperature change during solidification cooling.
  • CMT cold metal transfer
  • RWF-GMAW reciprocating wire feed gas metal arc welding
  • CSC controlled short circuit
  • SKS Systems micro-mig developed by SKS Systems
  • ADP active wire process
  • Still alternate technologies that can provide the low alloy melting energy include pulsed gas metal arc welding, pulsed gas tungsten arc welding, pulsed tip tungsten inert gas welding (pulsed TIP TIG), and pulsed energy beams (including for example a laser beam, a particle beam, a charged-particle beam, a molecular beam).
  • the cold metal transfer process is advantageous because of its mechanical mixing of the melt pool by rapid repetitive dipping of the electrode tip, high deposit control and relatively low heat. In addition to welding and cladding, it can form an extensive variety of additive deposition forms and wall growth directions.
  • Tip tungsten inert gas welding may also be advantageous because of superimposed mechanical oscillation of feed wire helping to agitate the molten weld pool and promote oxide distribution therein.
  • the on/off switching of the alloy melting energy described herein includes in some embodiments switching between a first energy level (on) and a second energy level (off) that is less than 50% of the first energy level.
  • powdered alloy material and/or flux may be selected to be conductive such as to facilitate an electro-slag welding process effective to form the layer of superalloy cladding material.
  • the heat of melting is provided by an arc
  • the oxygen or carbon dioxide will react with titanium and some of the titanium will be lost as vapor or oxides during the melting process.
  • a present embodiment allows the amount of titanium included in the filler material to be in excess of the amount of titanium desired in the deposited superalloy composition to compensate for this loss.
  • the amount of titanium included in the core metal powder may be increased from 1 % to 3%.
  • alloys such as stainless steels for example
  • a cored feed material is filled with a powdered core material including powdered flux and powdered metal.
  • the powdered metal may be used to augment the composition of the sheath material to obtain a cladding material of a desired chemistry.
  • the powdered metal may include an excess of the lost material to compensate for the loss.
  • alloy 321 stainless steel sheath material is deposited under a shielding gas containing oxygen or carbon dioxide, some of the titanium from the sheath material is lost due to reaction with the oxygen or carbon dioxide.
  • the powdered core material in such an embodiment may include powdered flux including titanium compounds such as titanium oxide and powdered titanium metal to compensate for the loss, thus providing a desired alloy 321 cladding composition.
  • An advantage of using higher oscillation rates in processing is that overall processing speed is increased and it is believed that better mixing of the melted powder and sheath material is achieved.
  • the methods disclosed offer an increased processing speed for depositing alloys, and in particular, fluidity enhanced alloys and alloys with greater than 1 % silicon.
  • Repair processes for superalloy materials may include preparing the superalloy material surface to be repaired by grinding as desired to remove defects, cleaning the surface, then pre-placing or feeding a layer of powdered material containing flux material onto the surface, then traversing an energy beam across the surface to melt the powder and an upper layer of the surface into a melt pool having a floating slag layer, then allowing the melt pool and slag to solidify.
  • the melting functions to heal any surface defects at the surface of the substrate, leaving a renewed surface upon removal of the slag typically by known mechanical and/or chemical processes.
  • the sheath 34, as well as any metal contribution from the powdered core material's flux material (which may be neutral or additive), are combined in the melt pool to produce a cladding layer having a desired composition.
  • the feed material may be preheated (e.g. electrically) to reduce the required arc energy. While pre-heating of the substrate is not necessarily required to obtain acceptable results, it may be desired to apply heat to the substrate and/or to the feed material and/or the powder prior to the melting step in some embodiments, such as to increase the ductility of the substrate material and/or to reduce energy otherwise required to melt the filler. Similarly, a chill fixture could optionally be used for particular applications, which in combination with the low heat input process can minimize stresses created in the material as a result of the melting process. Furthermore, the processes described herein may negate the need for an inert shielding gas, although supplemental shielding gas may be used in some applications if preferred.
  • mixed submerged arc welding flux and alloy 247 powder was pre-placed from 2.5 to 5.5 mm depths and demonstrated to achieve crack free laser clad deposits after final post weld heat treatment.
  • Ytterbium fiber laser power levels from 0.6 up to 2 kilowatts have been used with galvanometer scanning optics making deposits from 3 to 10 mm in width at travel speeds on the order of 125 mm/min. Absence of cracking has been confirmed by dye penetrant testing and metallographic examination of deposit cross sections. It will be appreciated that alloy 247 falls within the most difficult area of the zone of non-weldability as illustrated in FIG. 3, thereby demonstrating the operability of the embodiment for a full range of superalloy compositions, including those with aluminum content of greater than 3 wt.%.

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Abstract

L'invention concerne des procédés pour faire fondre un matériau d'alimentation noyauté (31) à l'aide d'un processus à faible entrée de chaleur. Le matériau d'alimentation peut être une gaine (34) composée essentiellement de nickel pur, de nickel-chrome ou de nickel-chrome-cobalt, contenant un matériau de cœur en poudre (36) ayant un matériau d'alliage en poudre (42) et un matériau de flux en poudre (38) qui, lorsque fondus, forment un matériau de superalliage désiré. L'invention concerne également des matériaux de flux pour l'utilisation avec les procédés. Le procédé peut être un procédé de transfert de métal à froid dans lequel le matériau d'alimentation est amené à osciller à plus de 130 oscillations par seconde.
PCT/US2017/013888 2016-01-28 2017-01-18 Revêtement par flux thermique faible de superalliages utilisant un matériau d'alimentation à cœur Ceased WO2017132020A1 (fr)

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