US3814673A - Process for tantalliding and niobiding base metal compositions - Google Patents

Process for tantalliding and niobiding base metal compositions Download PDF

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Publication number
US3814673A
US3814673A US00189763A US18976371A US3814673A US 3814673 A US3814673 A US 3814673A US 00189763 A US00189763 A US 00189763A US 18976371 A US18976371 A US 18976371A US 3814673 A US3814673 A US 3814673A
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United States
Prior art keywords
metal
niobium
tantalum
base metal
diffusion
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US00189763A
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English (en)
Inventor
N Cook
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GANNON UNIVERSITY ERIE
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General Electric Co
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Publication date
Priority to DE19702032645 priority Critical patent/DE2032645A1/de
Priority to FR707024656A priority patent/FR2050457B1/fr
Priority to NL7009837A priority patent/NL7009837A/xx
Application filed by General Electric Co filed Critical General Electric Co
Priority to US00189763A priority patent/US3814673A/en
Application granted granted Critical
Publication of US3814673A publication Critical patent/US3814673A/en
Assigned to GANNON UNIVERSITY ERIE, PA reassignment GANNON UNIVERSITY ERIE, PA ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: GENERAL ELECTRIC COMPANY
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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
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/54—Contact plating, i.e. electroless electrochemical plating
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D3/00—Electroplating: Baths therefor
    • C25D3/66—Electroplating: Baths therefor from melts

Definitions

  • a tantallide or niobide coating is formed on specified base metal compositions by making the base metal the cathode joined through an external electrical circuit to a tantalum or niobium anode in an electric cell having a specified fused salt electrolyte at a temperature of at least 900 C., but below the melting point of the metal composition.
  • Such a combination is a self-generating cell producing electricity, but an external E.MF. may be impressed providing the current density does not exceed amperes/cm.
  • the process is useful in making tight adherent coatings composed of tantalum or niobium and the base metal on the surface of the substrate.
  • This invention relates to a method for metalliding a based metal composition. More particularly, this invention is concerned with a process for tantalliding and niobiding a base metal composition in a fused salt bath.
  • tantalum and niobium can be electrodeposited at 650 C. to 850 C. on certain metal compositions to form a firmly adherent layer of tantalum or niobium joined to the metal composition by a metal-tometal bond by electrodeposition in a fused salt bath.
  • This method also requires that the molten fluorides must contain at least one of the fluorides of the group potassium, rubidium, or cesium.
  • the tantalum or niobium metal is employed as the anode and is immersed in a fused salt bath composed essentially of a member of the class consisting of the alkali metal fluorides of lithium and sodium and mixtures thereof and mixtures of the alkali metal fluorides with magnesium, calcium, strontium or barium fluoride and containing from 0.01-5 mole percent of tantalum or niobium fluoride.
  • the cathode employed is the base metal upon which the diffusion coating is to be made.
  • a combination is an electric cell in which an electric current will be generated when an electrical connection, which is external to the fused bath, is made between the base metal cathode and the anode.
  • the metal of the anode dissolves in the fused salt bath and the metal ions are discharged at the surface of the base metal cathode where they form a deposit of tantalum or niobium which immediately diffuses into and reacts with the base metal to form a metallide coating.
  • the alkali metal fluorides which can be used in accordance with the process of this invention includes the fluorides of lithium and sodium, the mixtures thereof.
  • Lithium fluoride is preferred, however, because of its lower reactivity at temperatures above 850 C. Eutectic mixtures of lithium and sodium fluoride can often be used, however, especially at the lower operating temperatures of the process.
  • Mixtures of the all lithium and sodium alkali metal fluorides with magnesium, calcium, strontium, or barium fluoride can also be employed as components of the molten salts in the process of this invention.
  • Magnesium fluoride does not always function as an inert component, however, since it sometimes permits the incorporation of small amounts of magnesium in the diflfusion coating, and this is not always desirable.
  • the chemical composition of the fused salt bath is critical for optimum metalliding results.
  • the starting salt should be as anhydrous and free of all impurities as is possible or should be easily dried or purified by simply heating during the fusion step.
  • the process must be carried out in the substantial absence of oxygen since oxygen interferes with the process by forming tantalum or niobium oxides and thereby preventing a coherent dififusiou coating of tantalum or niobium from being formed on the base metal cathode.
  • the process can be carried out in an inert gas atmosphere.
  • substantial absence of oxygen it is meant that neither atmospheric oxygen nor oxides of metals are present in the fused salt bath.
  • the best results are obtained by starting With reagent grade salts and by carrying out the process in an inert gas atmosphere, for example, in an atmosphere of argon, helium, neon, krypton or xenon.
  • T antallided and niobided diffusion coatings can be made on some metal surfacessuch as nickel and iron into which tantalum and niobium readily difiusein the presence of considerable oxygen content in the salt, i.e., a few parts-per-thousand, but the surfaces are usually dull and microscopically rough due to surface oxidation. Such coatings usually need to be slightly thicker than the bright smooth coatings to give comparable corrosion resistances. In the diffusion of tantalum into metals such as chromium and complex alloys where diffusion is slow, it is much more desirable and often critical that the oxide content of the baths be extremely low.
  • the oxygen can be removed from the fused salt bath by employing a carbon anode and running the bath as an electrolytic cell to remove the oxides and oxygen by means of the carbon anode.
  • a carbon anode and running the bath as an electrolytic cell to remove the oxides and oxygen by means of the carbon anode.
  • the last traces of oxygen and oxides can be removed from the fused salt bath by maintaining the fused salt bath under an inert atmosphere and placing in the bath, strips or chips of tantalum or niobium for a period of time until the strips or chips upon removal from the bath showed no evidence of pitting or other deterioration of the glossy, shiny surface of the metal due to the reaction of the tantalum or niobium with oxygen.
  • Such strips of metal can also be used as electrodes and will usually speedup the scavenging of the oxygen from the salt melt.
  • the base metals which can be tantallided or niobided, in accordance with the process of this invention includes the metals having atomic numbers of 23-29, 41-46 and 73-79 inclusive. These metals are, for example, vanadium, chromium, manganese, iron, cobalt, nickel, copper, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, tantalum, tungsten, rhenium, iridium, platinum and gold.
  • Alloys of these metals with each other or alloys containing these metals as the major constituent, that is, over 50 mole percent, alloyed with other metals as a minor constituent, that is less than 50 mole percent, can also be metallided in accordance with our process, providing the melting point of the resulting alloy is not lower than the temperature at which the used salt bath is being operated.
  • an electric current will flow through the circuit without any applied electromotive force.
  • the anode acts by dissolving in the fused salt bath to produce electrons and the metal ions.
  • the electrons flow through the external circuit formed by the conductor, and the metal ions migrate through the fused salt bath to the base metal cathode to be metallided, where the electrons discharge the metal ions, forming a metallide coating.
  • the amount of current can be measured with an ammeter which enables one to readily calculate the amount of metal being deposited on the base metal cathode and being converted to the metallided layer. Knowing the area of the article being plated, it is possible to calculate the thickness of the metallide coating formed, thereby permitting accurate control of the process to obtain any desired thickness of the metallide layer.
  • the total current density should not exceed 10 amperes/cm.
  • the tantalum or niobium deposition rate exceeds the diffusion rate and the base metal cathode becomes coated with a plate of tantalum or niobium.
  • the diffusion rate of tantalum and niobium into the cathode article varies from one material to another, with temperature, and with the thickness of the coating being formed, there is always a variation in the upper limits of the current densities that may be employed.
  • T the deposition rate of the iding agent must always be adjusted so as not to exceed the diffusion rate of the iding agent into the substrate material if high efliciency and high quality diffusion coatings are to be obtained.
  • the maximum current density for good tantalliding or niobiding is 10 amperes/cmfi, when operating within the preferred temperature ranges of this disclosure. Higher current densities can sometimes be used to form coatings with tantalum and niobium but in addition to the formation of a metallide coating, plating of the iding agent occurs over the diffusion layer.
  • Very low current densities (0.01-0.l amp/cm?) are often employed when diffusion rates are correspondingly low, and when very dilute surface solutions or very thin coatings are desired.
  • the composition of the diffusion coating can be changed by varying the current density, producing under one condition a composition suitable for one application and under another condition a composition suitable for another application.
  • current densities to form good quality tantallide or niobide coatings fall between 0.2 and 4.0 amperes per cm. for the preferred temperature ranges of this disclosure.
  • the source for example, a
  • measuring instruments such as voltmeters, ammeters, resistances, timers, etc., may be included in the external circuit to aid in the control of the process.
  • the coated metal compositions prepared by our process have a wide variety of uses. They can be used to protect reaction vessels and apparatus from chemical attack, electro-chemical corrosion, and anodic oxidation, to make gears, bearings, and other articles reqiuring hard, wear-resistant surfaces, and to prevent corrosion at high temperatures on gas turbine material, heating elements etc. Other uses will be readily apparent to those skilled in the art as well as other modifications and variations of the present invention in light 'of the above teachings.
  • tantalide and niobide designate any solid solutions or alloys of tantalum and nobium and the base regardless of whether the base metal does or does not form an intermetallic compound with tantalum and niobium in definite stoichiometric proportions which can be represented by a chemical formula.
  • K TaF- potassium fluorotantalate salt
  • a A" diameter tantalum rod (anode) was immersed into the salt and clean-up of salt impurities was accomplished by immersing nickel screens'(cathodes -50 cm. each) in the salt at 900 C. and electrolyzing at 4 amps for 15 minutes. After 10 amp-hours of electrolysis coulombic etficiencies (based on reduction of Ta+ to Ta) approaching 100% were realized.
  • the expanded nickel screen containing 6.5 mg. Ta/cm. was incorporated as an air cathode current collector in a phosphoric acid matrix fuel cell operating at 15 0 C.
  • the tantallided screen exhibited excellent electrochemical corrosion resistance for the 111 hour test period as a current collector material, i.e. the screen performed as well as a gold screen current collector in the same type fuel cell.
  • the three remaining tantallided screens containing 7.1, 12.0 and 15.0 mg. Ta/cm. were incorporated as air cathode current collectors in a sulfonic acid solid polymer electrolyte fuel cell operating at 60 C.
  • the tantallided screens exhibited excellent electrochemical corrosion resistance for 450 hours as current collector materials, i.e., the screens performed as well as a gold screen current collector int he same type fuel cell.
  • EXAMPLE V Strips of 1020 mild steel, 4340 tool steel and Carpenter 20 Cb-3 (50 cm. in area) were tantillided at 1080" C. and -.050 to +0.1 volts (anode polarity), with the following results.
  • tantallided 1020 mild steel, 4340 tool steel, and Carpenter 20 Cb-3 stainless steel were subjected to anodic electrochemical corrosion in 1.5 N H 80 at 80 C., the tantalided 1020 and 4340 steels had marginal corrosion resistance, but the tantallided Carpenter 20 Cb-3 exhibited excellent corrosion resistance comparable to the cororsion resistance of tantallided expanded nickel screens from Example III.
  • niobium anode can be substituted for the tantalum anode and KzNbFq for the KgTaFq in the lithium fluoride bath and the cell operated as given in the above ex amples to give niobium diffusion'coatings on the various base metal cathodes discussed above.
  • metal composition is an alloy of nickel and cobalt.
  • the metal composition is an alloy of nickel and copper.

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  • Chemical & Material Sciences (AREA)
  • Electrochemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Electroplating And Plating Baths Therefor (AREA)
US00189763A 1969-07-02 1971-10-15 Process for tantalliding and niobiding base metal compositions Expired - Lifetime US3814673A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
DE19702032645 DE2032645A1 (de) 1969-07-02 1970-07-01 Verfahren zur Herstellung von Diffusionsuberzugen aus Tantal oder Niob auf Metallen oder Metallegierungen
FR707024656A FR2050457B1 (cg-RX-API-DMAC7.html) 1969-07-02 1970-07-02
NL7009837A NL7009837A (cg-RX-API-DMAC7.html) 1969-07-02 1970-07-02
US00189763A US3814673A (en) 1969-07-02 1971-10-15 Process for tantalliding and niobiding base metal compositions

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US83840969A 1969-07-02 1969-07-02
US83863669A 1969-07-02 1969-07-02
US00189763A US3814673A (en) 1969-07-02 1971-10-15 Process for tantalliding and niobiding base metal compositions

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US3814673A true US3814673A (en) 1974-06-04

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US (1) US3814673A (cg-RX-API-DMAC7.html)
DE (1) DE2032645A1 (cg-RX-API-DMAC7.html)
FR (1) FR2050457B1 (cg-RX-API-DMAC7.html)
NL (1) NL7009837A (cg-RX-API-DMAC7.html)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3930060A (en) * 1972-05-04 1975-12-30 Toyoda Chuo Kenkyusho Kk Method for forming a carbide layer of a V-a group element of the periodic table on the surface of an iron, ferrous alloy or cemented carbide article
US3940848A (en) * 1973-02-15 1976-03-02 Siemens Aktiengesellschaft Method for the manufacture of tubular conductors
US4432839A (en) * 1981-06-18 1984-02-21 Diamond Shamrock Corporation Method for making metallided foils
US4662998A (en) * 1985-12-12 1987-05-05 The United States Of America As Represented By The Secretary Of The Navy Electrodeposition of refractory metal silicides
US20110132769A1 (en) * 2008-09-29 2011-06-09 Hurst William D Alloy Coating Apparatus and Metalliding Method
CN104790001A (zh) * 2015-04-13 2015-07-22 南京理工大学 一种中碳CrNiMo钢表面熔盐镀钽涂层的制备方法

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US311828A (en) * 1885-02-03 Centrifugal reel
US2828251A (en) * 1953-09-30 1958-03-25 Horizons Titanium Corp Electrolytic cladding process
FR1385594A (fr) * 1963-02-18 1965-01-15 Union Carbide Corp Dépôt électrolytique de métaux réfractaires
FR1544319A (fr) * 1966-11-10 1968-10-31 Gen Electric Procédé de traitement superficiel d'un métal ou alliage par le titane

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3930060A (en) * 1972-05-04 1975-12-30 Toyoda Chuo Kenkyusho Kk Method for forming a carbide layer of a V-a group element of the periodic table on the surface of an iron, ferrous alloy or cemented carbide article
US3940848A (en) * 1973-02-15 1976-03-02 Siemens Aktiengesellschaft Method for the manufacture of tubular conductors
US4432839A (en) * 1981-06-18 1984-02-21 Diamond Shamrock Corporation Method for making metallided foils
US4662998A (en) * 1985-12-12 1987-05-05 The United States Of America As Represented By The Secretary Of The Navy Electrodeposition of refractory metal silicides
US20110132769A1 (en) * 2008-09-29 2011-06-09 Hurst William D Alloy Coating Apparatus and Metalliding Method
EP2329063A4 (en) * 2008-09-29 2012-03-21 William D Hurst APPARATUS FOR FORMING AN ALLOY COATING AND METHOD FOR METALLURATION
CN104790001A (zh) * 2015-04-13 2015-07-22 南京理工大学 一种中碳CrNiMo钢表面熔盐镀钽涂层的制备方法

Also Published As

Publication number Publication date
FR2050457A1 (cg-RX-API-DMAC7.html) 1971-04-02
NL7009837A (cg-RX-API-DMAC7.html) 1971-01-05
FR2050457B1 (cg-RX-API-DMAC7.html) 1973-07-13
DE2032645A1 (de) 1971-01-14

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Owner name: GANNON UNIVERSITY ERIE, PA

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:GENERAL ELECTRIC COMPANY;REEL/FRAME:004261/0009

Effective date: 19830826