Classifications

• • 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
  • B23K35/24—Selection of soldering or welding materials proper
  • B23K35/32—Selection of soldering or welding materials proper with the principal constituent melting at more than 1550 degrees C
• • 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
  • B23K35/24—Selection of soldering or welding materials proper
  • B23K35/30—Selection of soldering or welding materials proper with the principal constituent melting at less than 1550 degrees C
  • B23K35/3033—Ni as the principal constituent
  • B23K35/304—Ni as the principal constituent with Cr as the next major constituent
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C19/00—Alloys based on nickel or cobalt
  • C22C19/03—Alloys based on nickel or cobalt based on nickel
  • C22C19/05—Alloys based on nickel or cobalt based on nickel with chromium
  • C22C19/051—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W
  • C22C19/052—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W with the maximum Cr content being at least 40%
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C27/00—Alloys based on rhenium or a refractory metal not mentioned in groups C22C14/00 or C22C16/00
  • C22C27/06—Alloys based on chromium
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C30/00—Coating with metallic material characterised only by the composition of the metallic material, i.e. not characterised by the coating process
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S428/00—Stock material or miscellaneous articles
  • Y10S428/922—Static electricity metal bleed-off metallic stock
  • Y10S428/923—Physical dimension
  • Y10S428/924—Composite
  • Y10S428/926—Thickness of individual layer specified
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/12—All metal or with adjacent metals
  • Y10T428/12014—All metal or with adjacent metals having metal particles
  • Y10T428/12028—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, etc.]
  • Y10T428/12063—Nonparticulate metal component
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/12—All metal or with adjacent metals
  • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
  • Y10T428/12771—Transition metal-base component
  • Y10T428/12806—Refractory [Group IVB, VB, or VIB] metal-base component
  • Y10T428/12826—Group VIB metal-base component
  • Y10T428/12847—Cr-base component
  • Y10T428/12854—Next to Co-, Fe-, or Ni-base component
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/12—All metal or with adjacent metals
  • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
  • Y10T428/12771—Transition metal-base component
  • Y10T428/12861—Group VIII or IB metal-base component
  • Y10T428/12944—Ni-base component

Definitions

• This invention relates to the coating of a superalloy substrate with an oxidation and hot-corrosion resistant surface coating alloy composition comprising a nickel base alloy containing chromium and silicon which alloy will be referred to hereinafter as AME-2.
• Hot-corrosion resistance is required for applications in turbines burning natural gas or uncontaminated light distillates or in contaminated environments involving combusted diesel, heavy distillates or residual oils.
• the vacuum brazing time/temperature cycle used to apply the coating alloy to the substrate should be compatible with the normal heat treatment cycle for the substrate.
• Another object is to provide an alloy coating that melts, wets and flows uniformly at some temperature below the incipient melting point of the superalloy substrate.
• a further object is to provide an alloy which is metallurgically compatible with the substrate alloy and may be applied as a thick coating.
• the present invention relates to a coating alloy for a superalloy substrate having the following composition: Chromium 4565%, Silicon 5-1 2%, Nickel-balance. All compositions are given in weight percent.
• a nominal coating composition as proposed by applicant may comprise 45% Chromium, Silicon with the balance Nickel.
• silicon is beneficial for oxidation and hot corrosion resistance through the formation of SiO Silicon is used to control the melting and solidification behavior of the coating since the eutectic temperature in the pure Ni-Cr binary system occurs at 2450F which is too high for most nickel based superalloy substrates.
• the coating may be applied to the substrate by various methods including vacuum brazing, which is an established industrial technique.
• vacuum brazing which is an established industrial technique.
• other conventional methods of applying the coating alloy to the superalloy substrate could be used such as the slurry, aerosol spray or plasma spray plus heat treatment and transfer tape methods.
• some methods should be avoided such as the vapor deposition method which yields a coating microstructure oriented normal to the substrate surface, thus establishing potential shortcircuit diffusion paths e.g., grain boundaries, and growth defects for the introduction of corrodents such as sulphur and oxygen to the substrate.
• the resolidification structure of the subject vacuum brazed alloy is non-oriented, precluding this potential failure mode. Since the subject process involves the liquid and not the vapor state, greater segregation of the coating elements occurs.
• the present alloy takes advantage of this fact since the high chromium content produces a-Cr precipitate particles dispersed in y-solid solution nickel matrix containing a high chromium level.
• the lower melting point Ni1Si eutectic phase is equally well dispersed throughout the coating during solidification.
• a coating alloy was prepared using a nominal alloy composition comprised of 45% Chromium, 10% Silicon and the balance Nickel. Other compositions may be used falling within the range, supra.
• the substrate was prepared by mechanical abrading or by chemical cleaning plus electroplating a 0.2 to 1.0 mil layer of nickel thereon.
• the alloy used is in the form of a powder and is fabricated into a brazing transfer tape.
• the tape is comprised of 2OO +325 mesh powder, held together with about 5% of an organic binder on a plastic backing sheet.
• a template of the desired shape to fit the substrate is cut from the transfer tape. The plastic backing is removed and the tape applied to the substrate.
• the coated part is then subjected to the vacuum brazing cycle.
• the vacuum brazing cycle is controlled to permit outgassing of the binder at about 700 to 1000F, to minimize contamination of the coating and substrate.
• the optimum vacuum brazing cycle consists of heating the alloy to a temperature of about 2075F for about 5 minutes followed by argon gas cooling. Generally no finishing treatments are required, since the as-brazed coated surface yields a surface finish in the 35 to 60 microinch (RMS) range.
• the part may receive a final heat treatment to develop the mechanical properties of the subtaining brittle intermetallic compounds, such as sigma and carbides.
• the microstructure of the subject alloy contains a mixture of 'y-Ni matrix, a-Cr precipitate particles, and NizSi eutectic.
• the precise composition and morphology of these phases depend both on the starting compositions of the subject alloy powder and substrate alloy, as well as the subsequent brazing and heat treatment cycles.
• the corrosion resistance of the subject alloy is derived from the high bulk Cr content (i.e. 45%) of the coating, but more specifically, it is due to the a-Cr particles and the high Cr, 'y-Ni matrix, which constitute a very significant portion of the coated structure. Since the coating is applied in the liquid state and resolidified, elements from the substrate are easily incorporated into the coating.
• the brazing cycle time and temperature
• time and temperature can be utilized to control the morphology and composition of the coating to some extent.
• Nickel base superalloys have been coated in the temperature range 2060 to 2130F, with time-at-temperature between 2 and minutes.
• Lower brazing temperatures are not preferred due to AMB-2s melting characteristics.
• Higher brazing temperatures can be used depending upon the heating and cooling rates, the equipment used and other considerations.
• Specific superalloy substrates may even re quire higher temperatures; however, the optimum parameters for the reference alloys is 2075F for 5 minutes. In general, the higher the temperature, the shorter the time, to prevent excessive fiow, reaction, and interdiffusion with the substrate.
• One feature of the subject alloy coating in the as-coated condition is its lack of a complex diffusion zone between the coating and substrate.
• conventional aluminide coatings are characterized by a finger-like diffusion zone con-
• the non-oriented structure of the subject alloy is due to the nature of the melting and re-solidification process. Segregation of the elements and resulting precipitates is related to composition, heat input during brazing, and cooling conditions.
• Line-of-sight vapordeposited coatings such as the MCrAlYs deposited by electron beam evaporation, generally grow normal tothe substrate surface. Grain growth is, therefore, nor mal to the substrate, hence, growth defects are also oriented. Growth defects, when they occur in the subject alloy, are non-oriented solidification defects.
• Oxidation/hot-corrosion testing have been conducted under simulated gas turbine condition in a small combustion burner rig.
• a controlled atmosphere was produced by combusting doped diesel oil containing 1% S, to which artificial sea salt was mixed to produce 8 ppm Na in the combustion products.
• the rigs were run at I600F, at an air:fuel ratio of 60:1 with a gas velocity of 70 fps.
• the specimens were removed and air-blasted to room temperature every hours to simulate turbine shutdown and to promote oxide and- /or coating spallation under severe thermal cycling conditions. This is the most conditions test condition utilized to simulate a hot-corrosion operating environment.
• AMB-2 was braze-coated on IN-738 using techniques previously described, and compared to available commercial aluminide coatings applied to IN-738. Results were obtained by sectioning the specimens, and metallographically determining at 100 times magnification the maximum depth of corrosion penetration through the coating and substrate, the average bulk coating surface loss, as well as an approximation of the area percent coating remaining. The results, listed in Table I below show the clear superiority of AME-2 over conventional aluminide coatings.
• (l)RT2l-Niv;kel has: alloy ufChrum-alloy American Corp. contains l7-35'.( Al. 0l0 Cr, balance Ni and 5'71 of other incidental elements.
• pack concentration the commercial process used for applying conventional aluminide coatings, known as pack concentration, has technical and economic limitations which restrict aluminide thickness to approximately 3 mils and somewhat less on Co-base superalloys. Since pack cementation is basically a vapor deposition process, applied thickness is timedependent. AME-2, however, can be applied up to about mils thickness, with no change in the time/- temperature vacuum brazing cycle. These data in Table I show that the aluminide coatings tested were essentially fully penetrated after just 600 to 1000 hours, with virtually no coating remaining. In many cases, significant corrosion of the IN-738 substrate resulted from the destruction of the coating.
• AMB-2 can be applied in thicknesses up to about 10 mils, as stated above, with no change required in the technique or time/temperature parameters used in its application.
• AME-2 offers both a more corrosion resistant alloy composition and increased coating thickness, both of which result in a longer life.
• the coating alloy of claim 1 consisting essentially Letters Patent 9 the Umted 'f 4. of 45% chromium 10% silicon and the'balance nickel.
• An oxidation and corrosion resistant composite The alloy of Claim 1 wherein the microstructure comprising a superalloy substrate and a coating alloy Contains a mixture f 'y-Ni m trix, a-Cr precipitate parbonded thereto consisting essentially of the following tides and ;s eutectk;

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Other Surface Treatments For Metallic Materials (AREA)
• Turbine Rotor Nozzle Sealing (AREA)
• Manufacture Of Alloys Or Alloy Compounds (AREA)

Priority Applications (9)

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Cited By (16)

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Citations (5)

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• 1974
  • 1974-06-17 US US479853A patent/US3904382A/en not_active Expired - Lifetime
• 1975
  • 1975-04-28 GB GB17603/75A patent/GB1507564A/en not_active Expired
  • 1975-05-14 CA CA226,882A patent/CA1038114A/fr not_active Expired
  • 1975-06-10 IT IT24193/75A patent/IT1038831B/it active
  • 1975-06-16 DE DE19752526779 patent/DE2526779A1/de not_active Withdrawn
  • 1975-06-16 NO NO752126A patent/NO139970C/no unknown
  • 1975-06-16 JP JP7210875A patent/JPS5524497B2/ja not_active Expired
  • 1975-06-17 FR FR7518832A patent/FR2274701A1/fr active Granted
  • 1975-06-17 NL NL7507214A patent/NL7507214A/xx not_active Application Discontinuation

Patent Citations (5)

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