US2763921A - Corrosion and impact resistant article and method of making same - Google Patents

Corrosion and impact resistant article and method of making same Download PDF

Info

Publication number
US2763921A
US2763921A US268146A US26814652A US2763921A US 2763921 A US2763921 A US 2763921A US 268146 A US268146 A US 268146A US 26814652 A US26814652 A US 26814652A US 2763921 A US2763921 A US 2763921A
Authority
US
United States
Prior art keywords
alloy
molybdenum
coating
chromium
max
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US268146A
Inventor
Jr Percy P Turner
Robert R Ruppender
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Northrop Grumman Space and Mission Systems Corp
Original Assignee
Thompson Products Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Thompson Products Inc filed Critical Thompson Products Inc
Priority to US268146A priority Critical patent/US2763921A/en
Application granted granted Critical
Publication of US2763921A publication Critical patent/US2763921A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

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
    • C23C24/00—Coating starting from inorganic powder
    • C23C24/08—Coating starting from inorganic powder by application of heat or pressure and heat
    • C23C24/10—Coating starting from inorganic powder by application of heat or pressure and heat with intermediate formation of a liquid phase in the layer
    • C23C24/103—Coating with metallic material, i.e. metals or metal alloys, optionally comprising hard particles, e.g. oxides, carbides or nitrides
    • C23C24/106—Coating with metal alloys or metal elements only
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B15/00—Layered products comprising a layer of metal
    • B32B15/01—Layered products comprising a layer of metal all layers being exclusively metallic
    • 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
    • Y10S29/00—Metal working
    • Y10S29/039—Spraying with other step
    • 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
    • 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
    • Y10S428/937—Sprayed metal
    • 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
    • Y10S428/939—Molten or fused coating
    • 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
    • Y10S60/00—Power plants
    • Y10S60/909—Reaction motor or component composed of specific material
    • 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
    • Y10T428/12014—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
    • Y10T428/12104—Particles discontinuous
    • 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
    • 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
    • Y10T428/12833—Alternative to or next 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

  • the present invention relates to an impact resistant articlejconsisting of a refractory metal base and an impact resistant coating.
  • molybdenum One relatively plentiful metal which exhibits good strength, toughness and creep-resistance characteristics is molybdenum.
  • molybdenum has a melting point in excess of 4500 F., it begins oxidation at temperatures as low as 900 F. The rate of formation of the molybdenum oxide increases with an increase in temperature. Since the molybdenum oxide sublimes, complete disintegration of the molybdenum body will occur in a relatively short time under conditions of high temperature oxidation.
  • Certain coating materials have the ability of forming intermetallic corrosion resistant compounds with the molybdenum surface.
  • coating materials such as silicon, aluminum, and zirconium form intermetallic compounds with molybdenum.
  • Molybdenum bodies coated with silicon for example, can withstand thousands of hours of operation above temperatures of red heat without showing any evidence of oxidation of the molybdenum base.
  • the intermetallic compounds formed at the surface of the molybdenum are usually quite brittle and liable to failure due to impact. Such impact could result during the operation of gas turbine engines in aircraft due to the presence of foreign objects, even small particles, in the gas streams of the engine. These foreign objects may be received from the outside air, or may result from chipping of the combustion tubes, or from a number of other sources. These particles pass through the turbine at extremely high velocities, on the order of several hundred feet a second. When the foreign objects strike the coated molybdenum part, fracture of the coated surface often results, thereby exposing the refractory metal body to the corrosive atmosphere of the gas stream.
  • An object of the present invention is to provide an improved impact resistant coating to a refractory metal body.
  • Another object of the present invention is to provide a brazed coating of avnickel-chromium alloy composition in the form of a relatively thin film about a corrosion resistant metal body.
  • Still another object of the present invention is to provide an improved nickel-chromium alloy composition capable of being brazed onto the surface of a refractory metal body in the form of a uniform coating.
  • Still another object of the present invention is to provide an improved method for applying impact resistant coatings to refractory metal bodies.
  • Another object of the present invention is to provide a method for brazing nickel-chromium alloy compositions onto refractory metal articles.
  • a refractory metal body is provided with an impact resistant coating by applying a coating composition consisting essentially of a liquefied matrix of a nickel chromium alloy, the matrix containing dispersed particles of a nickel-chromium alloy of higher melting point than the melting point of the matrix.
  • a mechanical mixture of two nickel-chromium alloys having differing melting points is sprayed onto the surface of the refractory article to be coated.
  • the resulting coated article is then heated to a firing temperature sufficient to just melt the lower melting a1- loy but insuflicient to melt the higher melting alloy.
  • the higher melting particles then begin to dissolve in the liquid phase, the extent of solution being dependent upon the time of treatment.
  • We have found that the best coatings under these conditions are obtained by interrupting the firing cycle before the point of complete solution of the higher melting alloy in the lower melting alloy matrix is reached.
  • the semi-fluid coating reacts with the base metal or object being coated, resulting in the formation of a small amount of higher melting alloy at theinterface which prevents or hinders the flow of the alloy coating at the given temperature.
  • the resulting coating is then uniform, tight, and integrally bonded to the base metal.
  • the coatings of the present invention can be applied directly to a refractory metal body such as molybdenum, or alloys of molybdenum containing at least molybdenum.
  • a refractory metal body such as molybdenum, or alloys of molybdenum containing at least molybdenum.
  • the alloy coatings of the present invention can also be applied to refractory metal bodies which have been treated, as by reaction with silicon, aluminum, or zirconium, to produce an outer corrosion resistant layer containing intermetallic compounds of molybdenum and the coating metal.
  • the molybdenum base may be chromized for the dual purpose of rendering the base metal more oxidation resistant, and to use the chromium as a cushion or buffer layer between the base metal and the brazed coating.
  • Chromium forms a series of solid solutions with molybdenum, but not intermet'allic compounds.
  • the brazed coating when applied to a chromized surface, is more uniform than it is when applied to bare molybdenum since the brazed layer reacts With the chromized layer and tends to eliminate uneven flow during brazing.
  • the chromizing step may be carried out by packing the article to be coated in a layer of granular aluminum oxide which is subsequently surrounded by a pack containing chromium-bearing material such as chromium or ferrochrome. Hydrogen and hydrogen-chloride gas are passed through the pack while maintaining the article at a temperature from 1800 to 2400" F.
  • the chromizing is continued for a time, usually on the order of two hours, until a chromized coating of from 0.0002 inch to 0.0004 inch is achieved.
  • the application of chromium by chromizing is definitely superior to the application of chromium by electrodeposition.
  • chromizing In chromizing, a substantial thickness of chromium can be built up, and being deposited from a vapor phase reaction, the chromium diffuses into and reacts with the molybdenum base to form a definite bond with the base metal.
  • chromium deposited from a chromizing process is more reactive than chromium deposited by other processes, and reacts with the subsequently applied brazed coatings.
  • the nickel-chromium alloys employed in the present invention preferably have analysis within the following ranges:
  • the amount of carbon in the alloy is an important consideration, as carbon tends to combine with chromium to form chromium carbide, thereby reducing the effective chromium content.
  • the reduction in effective chromium content reduces the oxidation resistance of the alloy at high temperatures.
  • the silicon in the above composition may be added as ferro-silicon, and serves to increase the high temperature resistance to oxidation.
  • the boron content of the alloy not only lowers the melting point of the alloy but also increases the fluidity of the molten alloy by decreasing its surface tension.
  • Manganese occurs as an unavoidable impurity and lowers the high temperature resistance of the alloy. The first tenths of one percent are the most' detrimental in this respect.
  • Calcium and zirconium are added to the alloy to act as deoxidizing agents. The more completely deoxided the alloy, the less susceptible it is to precipitation of oxides at the grain boundaries of the alloy. These two elements serve to increase the high temperature resistance of the alloy.
  • a preferred coating process consists in mixing two nickel-chromium alloy powders, both having a particle size of minus 325 mesh, and spraying the powdered mix- Alloy N0. 1
  • the coated article After application of the powdered metal to the surface of the refractory article, the coated article is dried to eliminate free moisture and then heated in a nonoxidizing atmosphere to braze the coating onto the corrosion resistant surface.
  • This brazing operation may be carried out in a dry hydrogen atmosphere, or under vacuum conditions, for a period up to minutes at temperatures from about 1800 to 2300 F.
  • the brazing temperature should be chosen so that it slightly exceeds the melting point of the lower melting alloy.
  • the liquid matrix reacts with the refractory metal body to form a high melting alloy at the interface between the refractory metal surface and the coating, thereby preventing or hindering the flow of the alloy coating.
  • the tenacious bond between the brazed coating and the underlying bare molybdenum, chromized molybdenum, or siliconized molybdenum, is due to this reaction between the coating and the base.
  • a reagent such as hydrofluoric acid
  • a suitable etchant consists of one part hydrofluoric acid (4555%) with two parts water, the etchant being applied for a period of from 10 to 120 seconds.
  • an etching time of about 40 seconds is used while for a chromized coating, an etching time of about 15 seconds is employed.
  • the coating should be applied so that the final thickness of the coating is within the range from 0.002 inch to 0.010 inch in thickness, with 0.0030 to 0.0040 inch thickness being an optimum range.
  • the coatings produced according to the present invention are extremely uniform, smooth and ductile. Surprisingly, the same results are not achieved when using a single alloy having a composition corresponding to the average composition of the mixture of the two alloys.
  • novel coatings of the present invention provide increased corrosion and impact resistance to refractory metal articles, making them particularly adaptable to use in high temperature environments and oxidizing conditions, such as occur in turbo-jet engines.
  • the coatings are securely bonded to the underlying refractory metal base, are extremely uniform, smooth and ductile.
  • An impact and corrosion resistant article comprising a base consisting essentially of molybdenum, and animpact resistant outer surface coating bonded to said base, said coating consisting essentially of a matrix of a nickelchromium alloy containing dispersed particles of a nickelchromium alloy having a higher melting point than said matrix, both said matrix and said particles having a composition within the following range:
  • said coating having a thickness in the range from about 0.002 inch to about 0.010 inch.
  • each of said alloys constituting substantial percentages of the total mixture, heating the resulting composite article to a temperature and for a time suflicient to render the lower melting alloy in said mixture molten, said temperature being insufiiciently high to melt the higher melting alloy of said mixture, maintaining said lower melting alloy molten until said alloy reacts with the underlying surface and dissolves some of said higher melting alloy, terminating said heating before all of said higher melting alloy is dissolved and cooling the composite article to provide a uniform, smooth coating over said molybdenum base consisting of a matrix of said lower melting alloy having dispersed therein undissolved particles of said higher melting alloy.
  • said mixture containing from 60 to 40% by weight of a higher melting alloy and from 40 to 60% by weight of a lower melting alloy, heating the resulting composite article to a temperature and for a time sufficient to render the lower melting alloy in said mixture molten, said temperature being insufficiently high to melt the higher melting alloy of said mixture, maintaining said lower melting alloy molten until said alloy reacts with the underlying surface and dissolves some of said higher melting alloy, terminating said heating before all of said higher melting alloy is dissolved and cooling the composite article to provide a uniform, smooth coating over said molybdenum base consisting of a matrix of said lower melting alloy having dispersed therein undissolved particles of said higher melting alloy.
  • each of said alloys constituting substantial percentages of the total mixture, heating the resulting composite article to a temperature and for a time sufficient to render the lower melting alloy in said mixture molten, said temperature being insufiiciently high to melt the higher melting alloy of said mixture, maintaining said lower melting alloy molten until said alloy reacts with the underlying surface and dissolves some of said higher melting V alloy, terminating said heating before all of said higher melting alloy is dissolved and cooling the composite article to provide a uniform, smooth coating over said molybdenum base consisting of a matrix of said lower melting alloy having dispersed therein undissolved particles of said higher melting alloy.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Other Surface Treatments For Metallic Materials (AREA)

Description

nited States atent. O
CORROSION AND IMPACT RESISTANT ARTICLE AND METHOD OF MAKING SAlVIE Percy P. Turner, Jr., and Robert R. Ruppender, Euclid, Ohio, assignors to Thompson Products, Inc., Cleveland, Ohio, a corporation of Ohio No Drawing. Application January 24, 1952, Serial No. 268,146
5 Claims. (Cl. 29-198) The present invention relates to an impact resistant articlejconsisting of a refractory metal base and an impact resistant coating.
The instant application is a continuation-in-part of our application, Serial No. 214,116, filed March 6, 1951, entitled Corrosion and Impact Resistant Article and Method of Making Same.
As explained in the previously identified application, the extensive development in the field of jet engines has necessitated the development of alloys for use in the manufacture of parts for such jet engines which can withstand the extremely high temperatures and oxidizing atmospheres normally present in the operation of turbojet engines. Such alloys, to function properly, must have a high strength, toughness, creep-resistance and resistance to the oxidizing gases present in the turbine engine.
One relatively plentiful metal which exhibits good strength, toughness and creep-resistance characteristics is molybdenum. However, the oxidation resistance of molybdenum and alloys containing major amounts of molybdenum is quite poor. Although molybdenum has a melting point in excess of 4500 F., it begins oxidation at temperatures as low as 900 F. The rate of formation of the molybdenum oxide increases with an increase in temperature. Since the molybdenum oxide sublimes, complete disintegration of the molybdenum body will occur in a relatively short time under conditions of high temperature oxidation.
To protect molybdenum bodies against the eflects of oxidation, it has been suggested that certain metals or metalloids be coated onto the surface of the molybdenum. Certain coating materials have the ability of forming intermetallic corrosion resistant compounds with the molybdenum surface. In particular, coating materials such as silicon, aluminum, and zirconium form intermetallic compounds with molybdenum. Molybdenum bodies coated with silicon, for example, can withstand thousands of hours of operation above temperatures of red heat without showing any evidence of oxidation of the molybdenum base.
While these intermetallic compound coatings very effectively protect the surface of the molybdenum from oxidation, the intermetallic compounds formed at the surface of the molybdenum are usually quite brittle and liable to failure due to impact. Such impact could result during the operation of gas turbine engines in aircraft due to the presence of foreign objects, even small particles, in the gas streams of the engine. These foreign objects may be received from the outside air, or may result from chipping of the combustion tubes, or from a number of other sources. These particles pass through the turbine at extremely high velocities, on the order of several hundred feet a second. When the foreign objects strike the coated molybdenum part, fracture of the coated surface often results, thereby exposing the refractory metal body to the corrosive atmosphere of the gas stream.
In our aforementioned application, we disclosed that brittle, corrosion resistant surfaces of the type described could be protected against impact by coating the surface with certain nickel-chromium alloys.
We have now found that substantially improved results can be obtained in practicing the invention described in our aforementioned application by using a plurality of nickel-chromium alloys of differing melting points, but having compositions within the ranges previously described. :More particularly, we have found that if the nickel-chromium alloy coating is applied to the surface of the refractory metal article in the form of a matrix of a liquefied nickel-chromium alloy containing dispersed particles of another nickel-chromium alloy having a higher melting point than the matrix, that a superior coating is obtained as compared with the results when a single alloy powder is used. The advantages are particularly marked with respect to the maintenance of a uniform flow of the coating materials at the brazing temperature employed to apply the nickel-chromium alloy to the surface of the refractory body, and the ability to apply thin coatings without the danger of discontinuities. 1
An object of the present invention is to provide an improved impact resistant coating to a refractory metal body.
Another object of the present invention is to provide a brazed coating of avnickel-chromium alloy composition in the form of a relatively thin film about a corrosion resistant metal body.
Still another object of the present invention is to provide an improved nickel-chromium alloy composition capable of being brazed onto the surface of a refractory metal body in the form of a uniform coating.
Still another object of the present invention is to provide an improved method for applying impact resistant coatings to refractory metal bodies.
Another object of the present invention, is to provide a method for brazing nickel-chromium alloy compositions onto refractory metal articles.
In the method of the present invention, a refractory metal body is provided with an impact resistant coating by applying a coating composition consisting essentially of a liquefied matrix of a nickel chromium alloy, the matrix containing dispersed particles of a nickel-chromium alloy of higher melting point than the melting point of the matrix.
In a preferred embodiment of the present invention, a mechanical mixture of two nickel-chromium alloys having differing melting points, both powders having a particle size on the order of minus 325 mesh, is sprayed onto the surface of the refractory article to be coated. The resulting coated article is then heated to a firing temperature sufficient to just melt the lower melting a1- loy but insuflicient to melt the higher melting alloy. Under these conditions, the higher melting particles then begin to dissolve in the liquid phase, the extent of solution being dependent upon the time of treatment. We have found that the best coatings under these conditions are obtained by interrupting the firing cycle before the point of complete solution of the higher melting alloy in the lower melting alloy matrix is reached. While this dissolution is taking place, the semi-fluid coating reacts with the base metal or object being coated, resulting in the formation of a small amount of higher melting alloy at theinterface which prevents or hinders the flow of the alloy coating at the given temperature. The resulting coating is then uniform, tight, and integrally bonded to the base metal.
The coatings of the present invention can be applied directly to a refractory metal body such as molybdenum, or alloys of molybdenum containing at least molybdenum. In addition, the alloy coatings of the present invention can also be applied to refractory metal bodies which have been treated, as by reaction with silicon, aluminum, or zirconium, to produce an outer corrosion resistant layer containing intermetallic compounds of molybdenum and the coating metal.
As another alternative, the molybdenum base may be chromized for the dual purpose of rendering the base metal more oxidation resistant, and to use the chromium as a cushion or buffer layer between the base metal and the brazed coating. Chromium forms a series of solid solutions with molybdenum, but not intermet'allic compounds. Furthermore, the brazed coating, when applied to a chromized surface, is more uniform than it is when applied to bare molybdenum since the brazed layer reacts With the chromized layer and tends to eliminate uneven flow during brazing. The chromizing step may be carried out by packing the article to be coated in a layer of granular aluminum oxide which is subsequently surrounded by a pack containing chromium-bearing material such as chromium or ferrochrome. Hydrogen and hydrogen-chloride gas are passed through the pack while maintaining the article at a temperature from 1800 to 2400" F. For the purposes of the present invention the chromizing is continued for a time, usually on the order of two hours, until a chromized coating of from 0.0002 inch to 0.0004 inch is achieved. For the purposes of this invention, the application of chromium =by chromizing is definitely superior to the application of chromium by electrodeposition. In chromizing, a substantial thickness of chromium can be built up, and being deposited from a vapor phase reaction, the chromium diffuses into and reacts with the molybdenum base to form a definite bond with the base metal. In addition, chromium deposited from a chromizing process is more reactive than chromium deposited by other processes, and reacts with the subsequently applied brazed coatings.
The nickel-chromium alloys employed in the present invention preferably have analysis within the following ranges:
Mn 1.0 max. Si 0.5 to 5.0 Fe "a 1.0to 5.5 CI 8.0 to 20.0 B 1.0 to 8.0 Ni 65 to 90 Zr 0.05 max. Ca 0.20 max. C 0.70 max.
The amount of carbon in the alloy is an important consideration, as carbon tends to combine with chromium to form chromium carbide, thereby reducing the effective chromium content. The reduction in effective chromium content reduces the oxidation resistance of the alloy at high temperatures.
The silicon in the above composition may be added as ferro-silicon, and serves to increase the high temperature resistance to oxidation.
Iron imparts fluidity to the alloy and renders it more workable. Iron may be added in the form of ferrosilicon, and this metal is also present in some of the other ingredients as an impurity.
The boron content of the alloy not only lowers the melting point of the alloy but also increases the fluidity of the molten alloy by decreasing its surface tension.
Manganese occurs as an unavoidable impurity and lowers the high temperature resistance of the alloy. The first tenths of one percent are the most' detrimental in this respect.
Calcium and zirconium are added to the alloy to act as deoxidizing agents. The more completely deoxided the alloy, the less susceptible it is to precipitation of oxides at the grain boundaries of the alloy. These two elements serve to increase the high temperature resistance of the alloy.
A preferred coating process consists in mixing two nickel-chromium alloy powders, both having a particle size of minus 325 mesh, and spraying the powdered mix- Alloy N0. 1
Alloy No. 2
The remainder of the analyses consist of unavoidable impurities.
We prefer to use powdered mixtures containing 40 to of alloy No. 1 with 60 to 40% of alloy No. 2, and specificaly about 60% alloy No. 1 and 40% alloy No. 2
After application of the powdered metal to the surface of the refractory article, the coated article is dried to eliminate free moisture and then heated in a nonoxidizing atmosphere to braze the coating onto the corrosion resistant surface. This brazing operation may be carried out in a dry hydrogen atmosphere, or under vacuum conditions, for a period up to minutes at temperatures from about 1800 to 2300 F. For the best results, we have found that the brazing temperature should be chosen so that it slightly exceeds the melting point of the lower melting alloy. Some of the discrete particles of the higher melting alloy are dissolved in the liquefied matrix, while others float in the liquid matrix. The liquid matrix reacts with the refractory metal body to form a high melting alloy at the interface between the refractory metal surface and the coating, thereby preventing or hindering the flow of the alloy coating. The tenacious bond between the brazed coating and the underlying bare molybdenum, chromized molybdenum, or siliconized molybdenum, is due to this reaction between the coating and the base.
In applying these coatings to a molybdenum surface containing an inert oxidation resistant layer, such as a silicide of molybdenum, it is advisable to etch the surface of the article with a reagent such as hydrofluoric acid to make the surface more receptive to the applied coating. A suitable etchant consists of one part hydrofluoric acid (4555%) with two parts water, the etchant being applied for a period of from 10 to 120 seconds. In the case of silicide coatings, an etching time of about 40 seconds is used while for a chromized coating, an etching time of about 15 seconds is employed.
For best results, the coating should be applied so that the final thickness of the coating is within the range from 0.002 inch to 0.010 inch in thickness, with 0.0030 to 0.0040 inch thickness being an optimum range.
The coatings produced according to the present invention are extremely uniform, smooth and ductile. Surprisingly, the same results are not achieved when using a single alloy having a composition corresponding to the average composition of the mixture of the two alloys.
From the foregoing, it will be appreciated that the novel coatings of the present invention provide increased corrosion and impact resistance to refractory metal articles, making them particularly adaptable to use in high temperature environments and oxidizing conditions, such as occur in turbo-jet engines. The coatings are securely bonded to the underlying refractory metal base, are extremely uniform, smooth and ductile.
Mn 1.0 max.
Si 0.5 to 5.0 Fe 1.0 to 5.5 Cr 8.0 to 20.0 B 1.0 to 8.0 Ni 65 to 90 Zr 0.05 max.
Ca 0.20 max. C 0.70 max.
2. An impact and corrosion resistant article comprising a base consisting essentially of molybdenum, and animpact resistant outer surface coating bonded to said base, said coating consisting essentially of a matrix of a nickelchromium alloy containing dispersed particles of a nickelchromium alloy having a higher melting point than said matrix, both said matrix and said particles having a composition within the following range:
Mn 1.0 max. Si 0.5 to 5.0 Fe 1.0 to 5.5 Cr 8.0 to 20.0 B 1.0 to 8.0 Ni 65 to 90 Zr 0.05 max. Ca 0.20 max. C 0.70 max.
said coating having a thickness in the range from about 0.002 inch to about 0.010 inch.
3. The method of increasing the corrosion resistance and impact resistance of a molybdenum base which comprises applying over said base a mixture of corrosion resistant nickel-chromium alloys of differing melting points, each of the alloys in said mixture having an analysis in the following range:
-Mn 1.0 max.
Si 0.5 to 5.0 Fe 1.0 to 5.5 Cr 8.0 to 20.0 B 1.0 to 8.0 Ni 65 to 90 Zr 0.05 max. Ca 0.20 max. C 0.70 max.
each of said alloys constituting substantial percentages of the total mixture, heating the resulting composite article to a temperature and for a time suflicient to render the lower melting alloy in said mixture molten, said temperature being insufiiciently high to melt the higher melting alloy of said mixture, maintaining said lower melting alloy molten until said alloy reacts with the underlying surface and dissolves some of said higher melting alloy, terminating said heating before all of said higher melting alloy is dissolved and cooling the composite article to provide a uniform, smooth coating over said molybdenum base consisting of a matrix of said lower melting alloy having dispersed therein undissolved particles of said higher melting alloy.
4. The method of increasing the corrosion resistance and impact resistance of a molybdenum base which comprises applying over said base a mixture of corrosion resistant nickel-chromium alloys, each of the alloys in said mixture having an analysis in the following range:
Mn 1.0 max.
Si 0.5 to 5.0 Fe 1.0 to 5.5 Cr 8.0 to 20.0 B 1.0 to 8.0 Ni 65 to Zr 0.05 max. Ca 0.20 max. C 0.70 max.
said mixture containing from 60 to 40% by weight of a higher melting alloy and from 40 to 60% by weight of a lower melting alloy, heating the resulting composite article to a temperature and for a time sufficient to render the lower melting alloy in said mixture molten, said temperature being insufficiently high to melt the higher melting alloy of said mixture, maintaining said lower melting alloy molten until said alloy reacts with the underlying surface and dissolves some of said higher melting alloy, terminating said heating before all of said higher melting alloy is dissolved and cooling the composite article to provide a uniform, smooth coating over said molybdenum base consisting of a matrix of said lower melting alloy having dispersed therein undissolved particles of said higher melting alloy.
5. The method of increasing the corrosion resistance and impact resistance of a molybdenum base Which comprises chromizing said molybdenum base, applying over the resulting chromized surface a mixture of corrosionresistant nickel-chromium alloys of differing melting points, each of the alloys in said mixture having an analysis in the following range:
Mn- 1.0 max. Si 0.5 to 5.0 Fe 1.0 to 5.5 Crn 8.0 to 20.0 B 1.0 to 8.0 Ni 65 to 90 Zr 0.05 max. Ca 0.20 max. C 0.70 max.
each of said alloys constituting substantial percentages of the total mixture, heating the resulting composite article to a temperature and for a time sufficient to render the lower melting alloy in said mixture molten, said temperature being insufiiciently high to melt the higher melting alloy of said mixture, maintaining said lower melting alloy molten until said alloy reacts with the underlying surface and dissolves some of said higher melting V alloy, terminating said heating before all of said higher melting alloy is dissolved and cooling the composite article to provide a uniform, smooth coating over said molybdenum base consisting of a matrix of said lower melting alloy having dispersed therein undissolved particles of said higher melting alloy.
References Cited in the file of this patent UNITED STATES PATENTS

Claims (1)

1. AN IMPACT AND CORROSION RESISTANT ARTICLE COMPRISING A BASE CONSISTING ESSENTIALLY OF MOLYBDENUM, AND AN IMPACT RESISTANT OUTER SURFACE COATING BONDED TO SAID BASE, SAID COATING CONSISTING ESSENTIALLY OF A MATRIX OF A NICKELCHROMIUM ALLOY CONTAINING DISPERSED PARTICLES OF A NICKELCHROMIUM ALLOY HAVING A HIGHER MELTING POINT THAN SAID MATRIX, BOTH SAID MATRIX AND SAID PARTICLES HAVING A COMPOSITION WITHIN THE FOLLOWING RANGE:
US268146A 1952-01-24 1952-01-24 Corrosion and impact resistant article and method of making same Expired - Lifetime US2763921A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US268146A US2763921A (en) 1952-01-24 1952-01-24 Corrosion and impact resistant article and method of making same

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US268146A US2763921A (en) 1952-01-24 1952-01-24 Corrosion and impact resistant article and method of making same

Publications (1)

Publication Number Publication Date
US2763921A true US2763921A (en) 1956-09-25

Family

ID=23021683

Family Applications (1)

Application Number Title Priority Date Filing Date
US268146A Expired - Lifetime US2763921A (en) 1952-01-24 1952-01-24 Corrosion and impact resistant article and method of making same

Country Status (1)

Country Link
US (1) US2763921A (en)

Cited By (22)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2837442A (en) * 1955-05-02 1958-06-03 Chromalloy Corp Methods of chromizing molybdenum tungsten and their alloys
US2924004A (en) * 1960-02-09 Refractory metal bodies
US2952904A (en) * 1957-01-15 1960-09-20 Westinghouse Electric Corp Applying protective metal coatings on molybdenum
US2983035A (en) * 1958-08-01 1961-05-09 Gen Electric Addition of carbon to nickel coatings on molybdenum
US2993678A (en) * 1955-07-21 1961-07-25 Gen Electric Coated molybdenum article
US3019516A (en) * 1959-05-13 1962-02-06 Gen Motors Corp Method of forming a protective coating on molybdenum
US3028261A (en) * 1958-04-24 1962-04-03 Chromalloy Corp Chromizing metals
US3037883A (en) * 1959-02-18 1962-06-05 Chromalloy Corp Diffusion coating of non-ferrous metals
US3044439A (en) * 1957-07-30 1962-07-17 Whitfield Lab Inc Metal coating apparatus
US3086886A (en) * 1958-06-04 1963-04-23 Schwarzkopf Dev Co Process of providing oxidizable refractory-metal bodies with a corrosion-resistant surface coating
US3117846A (en) * 1960-01-28 1964-01-14 Pfaudler Permutit Inc Multi layer difusion coatings and method of applying the same
US3230097A (en) * 1962-05-31 1966-01-18 Gen Electric Coating composition
US3231971A (en) * 1961-01-19 1966-02-01 Inland Steel Co Method of producing fusion coated metal base
US3404968A (en) * 1964-09-30 1968-10-08 Westinghouse Electric Corp Glass-to-metal seals and method for making same
US3462820A (en) * 1964-10-21 1969-08-26 United Aircraft Corp Coated cobalt alloys
US3547673A (en) * 1969-02-19 1970-12-15 Wall Colmonoy Corp Method of forming cermet-type protective coatings on heat resistant alloys
US3607369A (en) * 1968-09-11 1971-09-21 Union Carbide Corp Method for forming porous aluminum layer
US4174213A (en) * 1977-03-04 1979-11-13 Hitachi, Ltd. Highly ductile alloys of iron-nickel-chromium-molybdenum system for gas turbine combustor liner and filler metals
WO1984002483A1 (en) * 1982-12-29 1984-07-05 Sermatech Int Inc Surface modified powder metal parts and methods for making same
US10378118B2 (en) * 2013-12-11 2019-08-13 United Technologies Corporation Electroformed nickel-chromium alloy
US10669851B2 (en) 2013-12-10 2020-06-02 Raytheon Technologies Corporation Nickel-chromium-aluminum composite by electrodeposition
US10669867B2 (en) 2013-12-10 2020-06-02 Raytheon Technologies Corporation Electrodeposited nickel-chromium alloy

Citations (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1365499A (en) * 1919-10-23 1921-01-11 Gen Electric Surface-alloyed metal
US1650979A (en) * 1925-03-12 1927-11-29 Westinghouse Electric & Mfg Co Thermostatic material
GB474064A (en) * 1935-01-17 1937-10-25 Drake Mcgee & Hallsted Inc Improvements in or relating to metal surfacing
GB487263A (en) * 1937-02-12 1938-06-17 Patent Treuhand Ges Fure Elek Improvements in solders for uniting the metallic parts of vacuum devices
US2162253A (en) * 1939-04-25 1939-06-13 Grossman Cornell Joel Dental casting alloy
US2190840A (en) * 1938-05-02 1940-02-20 Driver Harris Co Corrosion resistant alloys
US2323169A (en) * 1940-02-08 1943-06-29 Rca Corp Process of plating metal bodies
US2375154A (en) * 1943-10-07 1945-05-01 Metals & Controls Corp Electric furnace
US2401040A (en) * 1942-10-05 1946-05-28 Eitel Mccullough Inc Method of making electronic tubes
US2455804A (en) * 1943-01-01 1948-12-07 Gen Electric Co Ltd Nickel chromium tungsten composite metal body and method of making same
US2520373A (en) * 1945-01-24 1950-08-29 Lockheed Aircraft Corp Turbine blade and method of making the same
US2587275A (en) * 1949-09-23 1952-02-26 Driver Harris Co Furnace element
US2697130A (en) * 1950-12-30 1954-12-14 Westinghouse Electric Corp Protection of metal against oxidation

Patent Citations (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1365499A (en) * 1919-10-23 1921-01-11 Gen Electric Surface-alloyed metal
US1650979A (en) * 1925-03-12 1927-11-29 Westinghouse Electric & Mfg Co Thermostatic material
GB474064A (en) * 1935-01-17 1937-10-25 Drake Mcgee & Hallsted Inc Improvements in or relating to metal surfacing
GB487263A (en) * 1937-02-12 1938-06-17 Patent Treuhand Ges Fure Elek Improvements in solders for uniting the metallic parts of vacuum devices
US2190840A (en) * 1938-05-02 1940-02-20 Driver Harris Co Corrosion resistant alloys
US2162253A (en) * 1939-04-25 1939-06-13 Grossman Cornell Joel Dental casting alloy
US2323169A (en) * 1940-02-08 1943-06-29 Rca Corp Process of plating metal bodies
US2401040A (en) * 1942-10-05 1946-05-28 Eitel Mccullough Inc Method of making electronic tubes
US2455804A (en) * 1943-01-01 1948-12-07 Gen Electric Co Ltd Nickel chromium tungsten composite metal body and method of making same
US2375154A (en) * 1943-10-07 1945-05-01 Metals & Controls Corp Electric furnace
US2520373A (en) * 1945-01-24 1950-08-29 Lockheed Aircraft Corp Turbine blade and method of making the same
US2587275A (en) * 1949-09-23 1952-02-26 Driver Harris Co Furnace element
US2697130A (en) * 1950-12-30 1954-12-14 Westinghouse Electric Corp Protection of metal against oxidation

Cited By (23)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2924004A (en) * 1960-02-09 Refractory metal bodies
US2837442A (en) * 1955-05-02 1958-06-03 Chromalloy Corp Methods of chromizing molybdenum tungsten and their alloys
US2993678A (en) * 1955-07-21 1961-07-25 Gen Electric Coated molybdenum article
US2952904A (en) * 1957-01-15 1960-09-20 Westinghouse Electric Corp Applying protective metal coatings on molybdenum
US3044439A (en) * 1957-07-30 1962-07-17 Whitfield Lab Inc Metal coating apparatus
US3028261A (en) * 1958-04-24 1962-04-03 Chromalloy Corp Chromizing metals
US3086886A (en) * 1958-06-04 1963-04-23 Schwarzkopf Dev Co Process of providing oxidizable refractory-metal bodies with a corrosion-resistant surface coating
US2983035A (en) * 1958-08-01 1961-05-09 Gen Electric Addition of carbon to nickel coatings on molybdenum
US3037883A (en) * 1959-02-18 1962-06-05 Chromalloy Corp Diffusion coating of non-ferrous metals
US3019516A (en) * 1959-05-13 1962-02-06 Gen Motors Corp Method of forming a protective coating on molybdenum
US3117846A (en) * 1960-01-28 1964-01-14 Pfaudler Permutit Inc Multi layer difusion coatings and method of applying the same
US3231971A (en) * 1961-01-19 1966-02-01 Inland Steel Co Method of producing fusion coated metal base
US3230097A (en) * 1962-05-31 1966-01-18 Gen Electric Coating composition
US3404968A (en) * 1964-09-30 1968-10-08 Westinghouse Electric Corp Glass-to-metal seals and method for making same
US3462820A (en) * 1964-10-21 1969-08-26 United Aircraft Corp Coated cobalt alloys
US3607369A (en) * 1968-09-11 1971-09-21 Union Carbide Corp Method for forming porous aluminum layer
US3547673A (en) * 1969-02-19 1970-12-15 Wall Colmonoy Corp Method of forming cermet-type protective coatings on heat resistant alloys
US4174213A (en) * 1977-03-04 1979-11-13 Hitachi, Ltd. Highly ductile alloys of iron-nickel-chromium-molybdenum system for gas turbine combustor liner and filler metals
WO1984002483A1 (en) * 1982-12-29 1984-07-05 Sermatech Int Inc Surface modified powder metal parts and methods for making same
US10669851B2 (en) 2013-12-10 2020-06-02 Raytheon Technologies Corporation Nickel-chromium-aluminum composite by electrodeposition
US10669867B2 (en) 2013-12-10 2020-06-02 Raytheon Technologies Corporation Electrodeposited nickel-chromium alloy
US10378118B2 (en) * 2013-12-11 2019-08-13 United Technologies Corporation Electroformed nickel-chromium alloy
US11732372B2 (en) 2013-12-11 2023-08-22 Raytheon Technologies Corporation Electroformed nickel-chromium alloy

Similar Documents

Publication Publication Date Title
US2763921A (en) Corrosion and impact resistant article and method of making same
US4382976A (en) Method of forming corrosion resistant coatings on metal articles
US3961098A (en) Coated article and method and material of coating
US3649225A (en) Composite coating for the superalloys
US3542530A (en) Nickel or cobalt base with a coating containing iron chromium and aluminum
US3754903A (en) High temperature oxidation resistant coating alloy
US4145481A (en) Process for producing elevated temperature corrosion resistant metal articles
US4086391A (en) Alumina forming coatings containing hafnium for high temperature applications
US3676085A (en) Cobalt base coating for the superalloys
US3978251A (en) Aluminide coatings
US2763920A (en) Corrosion and impact-resistant article
US3957454A (en) Coated article
US3741791A (en) Slurry coating superalloys with fecraiy coatings
US3096160A (en) Vapor diffusion coating process
US3540863A (en) Art of protectively metal coating columbium and columbium - alloy structures
EP0107508B1 (en) High temperature coating compositions
US3748110A (en) Ductile corrosion resistant coating for nickel base alloy articles
US4024294A (en) Protective coatings for superalloys
GB1579349A (en) Components resistant to corrosion at high temperatures
EP0061322A2 (en) Alloy coated metal structure having excellent resistance to high-temperature corrosion and thermal shock
US3953193A (en) Coating powder mixture
US3622402A (en) Erosion-corrosion resistant coating
US3450512A (en) Coated nickel base engine alloys
JP2934599B2 (en) High temperature corrosion resistant composite surface treatment method
US3055088A (en) Composite metal body for high temperature use