Classifications

• • 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
  • C23C10/00—Solid state diffusion of only metal elements or silicon into metallic material surfaces
  • C23C10/28—Solid state diffusion of only metal elements or silicon into metallic material surfaces using solids, e.g. powders, pastes
  • C23C10/34—Embedding in a powder mixture, i.e. pack cementation
• • 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
  • C22C19/053—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W with the maximum Cr content being at least 30% but less than 40%
• • 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
  • C22C19/07—Alloys based on nickel or cobalt based on cobalt
• • 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
  • Y10S428/9335—Product by special process
  • Y10S428/938—Vapor deposition or gas diffusion
• • 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
  • Y10S428/9335—Product by special process
  • Y10S428/941—Solid state alloying, e.g. diffusion, to disappearance of an original layer
• • 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
  • Y10T428/12778—Alternative base metals from diverse categories
• • 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
  • Y10T428/12931—Co-, Fe-, or Ni-base components, alternative to each other
• • 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

• ABSTRACT In the production of impact and oxidation resistant metal coatings on superalloy substrates, e.g., cobalt-base superalloys, by pack cementation, such as a nickel aluminide coating, the improvement wherein nickel is first diffusion coated onto the substrate from a pack containing a small but effective amount of sulfur as a metal transfer agent, following which the nickel coated substrate is then coated with another metal,
• This invention relates to the pack-nickelizing of heat-resistant metal substrates and, in particular, to a method of producing a hot corrosion resistant metal coating in which the metal substrate is first nickelized to form a diffusion-bonded nickel coating thereon and thereafter aluminized in a separate coating step to provide an improved protective coating containing substantial amounts of nickel aluminide which coating exhibits markedly improved impact ductility.
• a method has now been found for effecting the transfer of nickel by pack cementation onto superalloy substrates, such as cobalt-base and nickel-base alloys, while avoiding the formation of chromium-containing embrittling phases at the interface.
• superalloy substrates such as cobalt-base and nickel-base alloys
• the invention is particularly applicable to cobalt-base superalloys, it is also applicable to the coating of nickel-base alloys containing, for example, percent to 30 percent by weight of chromium where the deposit nickel dilutes the chromium at the interface to inhibit the formation of the aforementioned chromium-containing embrittling phases, such as the chromium carbides, nitrides and the like.
• Another object is to provide a method of nickelizing the substrate of cobalt-base and nickel-base superalloys preliminary to aluminizing said alloys for the production of hot corrosion resistant coatings based on nickel aluminide which exhibit markedly improved impact ductility.
• Still another object is to provide a method of nickelizing chromium-containing superalloys whereby to avoid the formation of chromium-containing embrittling phases in the subsequent production of nickel aluminide coating by aluminizing the nickelized superalloys.
• a further object is to provide a superalloy substrate, e.g., a cobalt-base superalloy, having a ductile impact and hot corrosion resistant coating diffusion bonded thereto.
• a superalloy substrate e.g., a cobalt-base superalloy
• the invention resides in a method of producing an impact resistant coating on a superalloy substrate by pack cementation wherein a layer of diffusion-bonded sulfuractivatable transfer metal e.g., nickel, is produced as a first step in the ultimate formation of the impact resistant coating.
• a layer of diffusion-bonded sulfuractivatable transfer metal e.g., nickel
• the improvement resides in providing an article of said superalloy having a solute metal, e.g., chromium, whose free energy of formation of the sulfide is higher than that of the transfer metal (e.g., higher then nickel), embedding the'article in a particulate cementation pack consisting essentially of said sulfur-activatable transfer metal mixed with an inert refractory material (e.g., alumina), the bedcontaining a small but effective amount of sulfur for effecting the transfer of said sulfur-activatable metal to the substrate of said article at an elevated diffusion coating temperature, and then heating said pack and the embedded article to an elevated diffusion coating temperature, whereby to effect diffusion coating of that article with the transfer metal, the coating being carried out while maintaining the oxygen in the pack below the partial pressure at which oxidation of sulfur to sulfur dioxide is inhibited.
• a solute metal e.g., chromium, whose free energy of formation of the sulfide is higher than that of the transfer metal (e.g.
• the oxygen is maintained at the desired partial pressure by mixing with the pack a small but effective amount of an oxygen-scavenging metal (e.g., titanium) whose free energy of formation of the oxide is at least about 1 15,000 calories per gram atom of oxygen at about 25 C.
• an oxygen-scavenging metal e.g., titanium
• the particulate nickelizing pack has a composition ranging by weight from about 5 to 60% nickel, about one-eighth to 1% titanium, about 0.002 to 0.1% of sulfur, and the balance essentially an inert refractory material e.g., such refractory oxides as alumina, magnesia, silica and the like.
• a particular pack composition is one containing approximately 40% nickel, approximately 0.2% titanium, approximately 0.02% sulfur and the balance essentially aluminum oxide.
• a typical alloy composition range is one containing by weight about 10 to 30% Cr, up to about 20% of a metal from the group consisting of Mo and W. up to about 10% of a metal from the group consisting of Cb and Ta, up to about 0.5% C, up to about 6.5 percent by weight of a metal from the group consisting of Ti and Al, the total amount of these metals not exceeding about 10%, up to about 20% Co, up to about 2% Mn, up to about 2% Si, up to about 0.1% B, up to about 1% Zr,
• a typical composition range is one containing by weight about 10 to 30% Cr, up to about 15% Ni, up to about 15% Fe, up to about 5% Cb, up to about 15% W. up to about 5% Ti and/or A1, up to about 1% Zr, up to about 1.5% C, up to about 1 or 2% of Si, up to about 2% Mn and the balance essentially at least about 45% Co.
• a well-known commercial composition is a cobalt-base alloy referred to by the designation Wl-52 containing by weight about 0.45% C, about 0.25% Mn. about 0.25% Si, about 21% Cr, about 1 1% W. about 2% Cb, about 2% Fe and the balance essentially cobalt.
• the optimum processing cycle for nickelizing the aforementioned Wl-52 alloy involves the deposition of nickel at about 9,925 F.:25 F., (about 1,0S0 C.il4 C.) by embedding an article of the alloy, e. g., an airfoil section, in a particulate pack containing by weight about 40 percent 200 mesh electrolytic nickel and 60 percent 325 mesh alumina, the mixture containing by weight about three-sixteenth percent of titanium, with the sulfur level ranging from about 0.015 to 0.05 percent.
• the primary source of the sulfur is the nickel powder. With the foregoing pack, the thickness of nickel coating ranges up to about 0.002 inch.
• the addition of ly, other oxygen scavengers may be employed so long as the free energy of formation of the oxide is at least about 1 15,000 calories per gram atom of oxygen.
• the transfer of nickel from compounds as MS, 0,5, and (NHQ S was noted to increase the pack and onto the alloy substrate is adversely affected. the quantity and depth of nickel of transfer.
• Another method of maintaining the oxygen partial forming the desired coating of nickel while avoiding the pressure to the desirable low level is to sweep out the oxygen deposition of sulfur-rich compounds, except for the formation occluded in the pack by means of a substantially oxygen-free of chromium sulfide at the surface of the substrate which is l 5 inert g such as g n n r y p g. h re i anium is easily removed by glass head honing.
• the amount of sulfur in the pack whether deliberately may range from about Vs to about 1 percent.
• a typical pack added, or whether present in the pack materials employed, for processing the alloy Wl-52 is one comprising about 40% e.g., nickel powder and/or the alumina, may range from about nickel pow the P mixture n ining about three-Six- 0.002 to 0.1 percent by weight.
• teenth percent of titanium and about 0.015 to 0.05% of sulfur The sulfur is consumed in the formation of scale and reacwith the balance essentially inert refractory oxide, e.g., alution with titanium (scavenger) and oxygen.
• the reaction mina is about of sulfur with chromium in the alloy substrate may result in three-sixteenth to about one-half percent.
• titanium sulfide Residual oxygen in the pack can react with the sulfurdioxide and with the titanium to form titanium dioxide. The preference and degree to which these reactions occur is dependent upon the relative concentration of the elements in the pack.
• the sulfur content of the pack at the lowrange results in a nickel zone in the substrate of about 0.5 mils thick (0.0005 of an inch), with about 2 to 10% nickel diffused into the surface.
• the lower the sulfur level in the pack over the small but effective range the less is the nickel transfer and the smaller the depth of diffusion.
• a nickel zone is obtained on the substrate of the alloy containing up to about 20 percent by weight of nickel as determined by microprobe analysis.
• the parts as removed from the nickelizing pack are covered with light scale which is removed by low-pressure glass bead honing.
• the scale is composed of distinct-phases of chromium sulfide with entrapped powder from the pack, the chromium sulfide ranging in composition from Cr s to Cr S,,
• the scale thickness usually averages 0.3 mils, the thickness increasing with sulfur additions and increased nickel transfer.
• lt is important that the oxygen partial pressure in the pack be maintained below a level at which oxidation ofsulfur is sub stuntiully inhibited.
• a titanium level of about three-sixteenth percent has been determined to be particularly advantageous in providing improved nickel transfer while minimizing oxidation damage during the nickelizing process cycle.
• nickelized alloys are then aluminized in a prereacted pack containing by weight 20% Cr, 3% Al, l/4% Nl-LFHF and the balance essentially alumina (-325 mesh) to yield a corrosion resistant coating of substantially improved impact ductility.
• the 0.002 to 0.0025 inch coating produced comprises nickel-cobalt aluminides containing chromium in solid solution.
• the substrate is similarly nickelized in a pack containing by weight 20% electrolytic nickel powder (200 mesh), about 0.3% titanium, about 0.02% of sulfur and the balance essentially 325 mesh alumina at a temperature of l,925 F.i25 F., for about 10 hours, following which the surface of the alloy substrate is cleaned by glass bean honing and then aluminized in the aforementioned prereacted puck at l.900F:25 F. for 20 to 30 hours to yield a corrosion resistant nickel amuminide coating (0.0025 to 0.003 inch thick) which is very highly impact and spall resistant.
• the treatment in the nickel pack causes chromium depletion in the substrate which allows for the formation ofa ductile aluminide coating during the second diffusion bonding.
• the improved ductility of the coating compared to the more brittle coatings currently used on such alloys is attributed to less chromium-rich phases within the coating and the absence of porosity at the coating substrate interface.
• the improved impact resistant coating provides a resistance to at least about 17 inch lbs. impact as compared to one-fourth inch lb. impact for the conventionally produced single step aluminide coating.
• a simple test devised to simulate the stress and temperature environment of actual turbine hardware during engine service comprises a simple bending load test in which the load is applied to a coated test bar which is subjected to an end to end temperature gradient developed by a concentrated oxyacetylene flame which is applied to the center of the test bar and the heat allowed to dissipate to the opposite ends of the bar.
• Each testpiece is cycled from maximum temperature (e.g., 2,000 P.) to black heat during a 10 minute period.
• the simple beam load is lifted and dropped three times to reproduce foreign object impact damage during service. Results have shown that the coating produced in accordance with the invention exhibits at least a 3 to 1 improvement over the conventional aluminized coating mentioned hereinabove.
• chipping and spalling of the coating occurred after 45 cycles, while in the improved coating produced in accordance with the invention, the coating was still intact after 135 cycles.
• the nickelizing pack may range by weight from about 5 to 60% nickel powder, about A; to 1% titanium, about 0.002 to 0.1% sulfur and the balance an inert refractory material, such as particulate refractory oxides, e.g., A1 MgO, SiO and the like. Examples of other oxygen scavengers are thorium, cerium, yttrium and other rare earth metals.
• the nickelizing temperature may range from about 1,500 to 2,000 F. for about 5 to 40 hours.
• a cementation pack which may be employed in the aluminizing step comprises about to 30 percent of a buffering metal (e.g., chromium), about 1 to 5% of aluminum, a small but effective amount of a halide energizer, e.g., one-quarter percent of NH FHF (such as /5 to 1 percent energizer) and the balance a particulate inert refractory material as mentioned hereinabove.
• the buffering metal aids in controlling the transfer and deposition of the aluminum. Examples of other buffering metals are nickel, iron and cobalt.
• the pack is mixed and prereacted at an elevated temperatures of, for example, 1,750 to 2,050 F. for about 1 to hours prior to use for coating and the nickelized article then aluminized at a temperature of about 1,750 to 2,050 F. for about 1 to 30 hours.
• An airfoil section made of an alloy (WI-52) comprising about 0.45% C, about 0.25% Mn, 0.25% Si, about 21% Cr, about 1 1% W. about 2% Cb, about 2% Fe and the balance essentially cobalt is embedded in a nickelizing pack containing by weight about 40% electrolytic nickel powder (-200 mesh), about 0.2% titanium powder, about 0.02% sulfur and the balance essentially alumina (-325 mesh) in a retort.
• the retort is sealed with low-melting silicate glass composition and the retort then heated in a muffle furnace to a temperature of about l,925 F.t25 F. and held at temperature for about hours.
• the retort is thereafter cooled to room temperature and the airfoil section cleaned by glass bead honing at low pressure to remove chromium sulfide scale at the surface.
• a diffused layer of nickel is obtained having an enriched zone of about 0.002 inch thick containing about 20% nickel.
• the element is similarly embedded in an aluminizing pack containing by weight 20 percent chromium mesh powder) as a buffering agent 3 percent aluminum powder (325 mesh), about one-quarter NH FHF and the balance essentially 325 mesh alumina.
• the aluminizing was carried out for 20 hours in a sealed retort to produce an extremely ductile mixed nickelcobalt aluminide coating containing chromium in solid solutron.
• a chromium-containing superalloy article em-- bedding said article in a particulate cementation pack consisting essentially of nickel powder mixed with an inert refractory material, the bed containing a small but effective amount of sulfur for effecting the transfer of said nickel to the substrate of said article at an elevated diffusion coating temperature, and
• the pack cementation bed has a composition ranging from about 5 to 60% Ni, about A; to 1% Ti, about 0.002 to O. 1% S and the balance essentially the inert refractory material.
• the nickel-coated article is aluminized by embedding it in a cementation pack containing by weight about 10 to 30% Cr, about 1 to 5% A1, a small but effective amount of a halide energizer and the balance a particulate inert refractory material, said article being then aluminized at a temperature of about l,750 to 2,050 F. for l to 30 hours.
• the superalloy is selected from the group consisting of cobalt-base alloys containing by weight about 10 to 30% Cr, up to about 15% Ni, up to about 15% Fe, up to about 5% Cb, up to about 15% percent W, up to about 5% Ti and/or Al, up to about 1% Zr, up to about 1.5% C, up to about 1 to 2% Si, up to about 2% Mn and the balance essentially 45% Co; and nickel-base alloys containing by weight about 10 to 30% Cr, up to about 20 p cent of a metal from the group consisting of Mo and W, up to about 10 percent of a metal from the group consisting of Cb and Ta, up to about 0.5% C, up to about 6.5% of a metal from the group consisting of Ti and Al, the total amount of these metals not exceeding about 10%, up to about 20% Co, up to about 2% base superalloy article containing about 10 to 30% Cr, up to about Ni, up to about 15% Fe, up to about 5% Cb
• a particulate cementation pack consisting essentially of said nickel mixed with an inert refractory material, the bed also containing a small but effective amount of sulfur for effecting transfer of nickel from the pack to the substrate of the article, and then heating said pack and the embedded article to an elevated diffusion coating temperature whereby to effect diffusion coating of said article with nickel, said coating being carried out while maintaining the oxygen in said pack at a partial pressure below which the oxidation of sulfur to sulfur oxide compounds is substantially inhibited.
• the oxygen is maintained at the desired partial pressure by mixing with said pack a small but effective amount of an oxygen-scavenging metal whose free energy of formation of the oxide is at least about 1 15,000 calories per gram atom of oxygen at about 25 C.
• the pack cementation bed has a composition ranging from about 5 to 60% Ni, about /s to 1% Ti, about 0.002 to 0.1% and the balance essentially the inert refractory material. 7
• the nickel-coated article is aluminized by embedding it in a cementation pack containing by weight about 10 to 30% Cr, about 1 to 5% A1, a small but effective amount of a halide energizer and the balance a particulate inert refractory material, the article being then aluminized at a temperature of about l,750 to 2,050 F. for l to 30 hours.

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• Mechanical Engineering (AREA)
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• Chemical Kinetics & Catalysis (AREA)
• Other Surface Treatments For Metallic Materials (AREA)
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Citations (6)

• 1970
  • 1970-06-22 US US48515A patent/US3647517A/en not_active Expired - Lifetime
• 1971
  • 1971-02-03 IL IL36129A patent/IL36129A/xx unknown
  • 1971-04-01 SE SE04224/71A patent/SE364529B/xx unknown
  • 1971-04-07 NL NL7104691.A patent/NL160338C/xx active
  • 1971-04-19 GB GB2562971*A patent/GB1307785A/en not_active Expired
  • 1971-05-27 JP JP46035918A patent/JPS5036624B1/ja active Pending
  • 1971-06-14 FR FR7121439A patent/FR2096395B1/fr not_active Expired
  • 1971-06-14 BE BE768488A patent/BE768488A/fr unknown
  • 1971-06-16 CH CH879071A patent/CH549099A/fr not_active IP Right Cessation
  • 1971-06-17 LU LU63354D patent/LU63354A1/xx unknown

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