US3413142A - Process of cooling diffusion coated metal articles in liquid sodium metal - Google Patents

Process of cooling diffusion coated metal articles in liquid sodium metal Download PDF

Info

Publication number
US3413142A
US3413142A US472657A US47265765A US3413142A US 3413142 A US3413142 A US 3413142A US 472657 A US472657 A US 472657A US 47265765 A US47265765 A US 47265765A US 3413142 A US3413142 A US 3413142A
Authority
US
United States
Prior art keywords
bath
coating
quenching
sodium
metal
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
US472657A
Other languages
English (en)
Inventor
Charles H Lemke
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.)
EIDP Inc
Original Assignee
EI Du Pont de Nemours and Co
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 EI Du Pont de Nemours and Co filed Critical EI Du Pont de Nemours and Co
Priority to US472657A priority Critical patent/US3413142A/en
Priority to NL6609454A priority patent/NL6609454A/xx
Priority to CH1004066A priority patent/CH473234A/de
Priority to BE683999D priority patent/BE683999A/xx
Priority to FR69620A priority patent/FR1486863A/fr
Priority to GB31933/66A priority patent/GB1127424A/en
Priority to DE19661521447 priority patent/DE1521447B2/de
Priority to NO163935A priority patent/NO115793B/no
Application granted granted Critical
Publication of US3413142A publication Critical patent/US3413142A/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
    • C23C10/00—Solid state diffusion of only metal elements or silicon into metallic material surfaces
    • C23C10/18—Solid state diffusion of only metal elements or silicon into metallic material surfaces using liquids, e.g. salt baths, liquid suspensions
    • C23C10/20—Solid state diffusion of only metal elements or silicon into metallic material surfaces using liquids, e.g. salt baths, liquid suspensions only one element being diffused
    • C23C10/22—Metal melt containing the element to be diffused

Definitions

  • ABSTRACT OF THE DISCLOSURE In an alloy diffusion coating process wherein a metal article is immersed in a molten bath containing a metal transfer agent such as calcium, strontium, barium, magnesium and lithium and at least one metal diffusing element, the coated article is quenched in molten sodium below 300 C.
  • a metal transfer agent such as calcium, strontium, barium, magnesium and lithium
  • An inert gaseous atmosphere can be used throughout the process.
  • This invention relates to a process for applying coatings to metal surfaces. More particularly, this invention relates to an improvement in a liquid-to-solid diffusion coating process in which the coated article is rapidly quenched from an elevated temperature.
  • High velocity gas streams and fluidized solids beds have proved to be marginally effective and, in order to achieve sufficiently rapid cooling, require the use of expensive and complex equipment. Also, the fluidized solids methods of quenching require handling and recovery of large volumes of expensive inert gases if staining is to be avoided.
  • an object of this invention to provide a process which permits quenching of alloy diffusion coated metal articles which have quantities of transfer agent on their surfaces without explosion hazards. It is another object to provide a process whereby the quenching medium does not rapidly degrade and does not contribute carbon to the coating. It is a further object of the invention to provide a process whereby the coated article can be rapidly cooled without producing stains on the surface. A still further object of the invention is to provide a quenching stystem which will not impair the corrosion resistance of the coatings.
  • a diffusion coated metal article is removed from a molten coating bath with a coating of the bath material on its surface and immersed, while at a temperature above the boiling point of liquid sodium, in a quenching bath containing liquid sodium metal.
  • the liquid sodium metal rapidly quenches the coated article.
  • the sodium metal remains stable with little or no reaction with the transfer agent which adheres to the article to be quenched and with little vaporization of the sodium metal which might be expected at the elevated temperature of the coated article.
  • sodium oxide and sodium hydroxide either or both of which is always found floating on the surface of molten sodium which has been handled without extreme measures being taken to exclude air, does not react violently with the transfer agent.
  • the article when cleaned of sodium and transfer agent is essentially free of stains.
  • a coating bath containing a transfer agent and one or more diffusing elements is heated to the desired processing temperature. This temperature will be between about 900 C. and the melting point of the article to be coated.
  • a second bath containing liquid sodium metal is prepared and preferably maintained at a temperature between about C. and 300 C. although higher temperatures may be used.
  • the metal article to be coated is immersed in the molten coating bath for a predetermined period of time during which the diffusing element alloys with the base metal.
  • the coated metal article is then removed from the coating bath and quickly transferred to the quenching bath. The time of transfer is so controlled that the article remains at a temperature above the boiling point of sodium metal until the moment of immersion in the quenching bath.
  • the optimum temperatures and time of transfer to the quenching bath will depend on such factors as the relative size (mass) of the article and the amount of material in the quenching bath. Preferably, the transfer time is not greater than about 60 seconds, with about l030 seconds generally being preferred.
  • the amount of quenchant in the bath should be sufficient to cool the coated article to a temperature below about 350 C. before any significant migration of undesirable elements, such as carbon, occurs within the coated article.
  • the time of quenching should generally be in the range from about 1 to 3 seconds.
  • the transfer agents particularly calcium, remove carbon from the alloyed portion of the coated article.
  • the transfer agents By rapid quenching in the sodium containing bath, migration of carbon from the substrate to the diffusion coating is prevented.
  • Articles coated and quenched by the process of this invention may be readily cleaned after removal from the quenching bath.
  • the use of organic solvents and abrasives is not required.
  • Residual sodium remaining on the quenched article may be removed by steam or high velocity water sprays. Any transfer agent remaining on the surface is then easily removed by washing with water or dilute acid solutions such as 20% nitric acid or 15% acetic acid.
  • an inert atmosphere of argon is preferred; however, other gases such as helium, hydrogen, and an argon-nitrogen mixture may be used.
  • the operation may, of course, be carried out in air; however, if air is used, the process should be carefully monitored to detect any unusual build-up of sodium oxide or sodium hydroxide in the quenching bath.
  • the preferred quenching bath used in this invention is liquid sodium metal.
  • combinations of the sodium metal with other alkali metals such as potassium, cesium and rubidium may be used. If combinations of the metals are used, it is preferred that sodium constitute a major portion of the bath.
  • the process is particularly suitable for quenching the diffusion coated low and medium carbon steels as well as various alloys which contain, for example, zirconium, titanium, vanadium, columbium, etc.
  • Suitable substrates are disclosed in the US. patents previously mentioned.
  • diffusing elements including such elements as nickel, manganese, cobalt, zinc, molybdenum, niobium and aluminum which may be present alone or in combination in the coating bath.
  • various diluents for the transfer agent may be used in the coating bath.
  • the transfer agent represent a significant liquid phase in the coating bath.
  • a preferred transfer agent is calcium, however, barium, strontium, magnesium and lithium may be used.
  • the transfer agent must be present in an amount sufiicient to wet the surface of the article in order to effect diffusion of the diffusing element into the surface of the article and to provide a superficial coating of the transfer agent on the article as it is removed from the coating bath.
  • a practical lower limit for most coating operations will be about 10% by weight of the coating bath.
  • Preferably, to about 97% by weight of one or more of the transfer agents is used.
  • the thicknesses of the coatings formed on the articles were determined by standard metallographic examination or in the case of chrornium-containing coatings on iron by dissolving away the substrate with concentrated nitric acid and measuring the unsupported coating film with :a suitable micrometer.
  • the composition of the surface coatings was determined by X-ray fluorescence and, in the case of carbon, by a combustion/conductimetric method. This latter analysis was made with a Leco condimetric carbon analyzer, manufactured by the Leco Corp., St. Joseph, Mo. This appara- 4 tus and method of using it is well known to those skilled in the art.
  • the CASS test (copper/acetic acid salt spray test) referred to in the examples was carried out in accordance with the ASTM B3 6861T procedure.
  • a molten bath was prepared in a heated iron crucible.
  • the bath contained about 93% calcium, 1.5% calcium nitride, 4.5% chromium and minor amounts of calcium oxide, nickel, aluminum and other elements commonly found in commercial calcium.
  • the crucible was positioned in an enclosure into which argon gas was introduced.
  • Panels, 2.5" x 5", prepared from low carbon, cold rolled basic oxygen furnace steel, mils thick, (nominal 0.05 %0.08% carbon content) were immersed in the coating bath for nine minutes with the bath being maintained at a temperature of 1140 C. At the end of the nine minute period, they were removed from the coating bath. A coating of the transfer agent was present on the panels.
  • the panels were transferred through the argon atmosphere to quenching tanks which were maintained at temperatures in a 60-160 C. range.
  • the time of transfer varied from 2 to 40 seconds with the temperature of the panels being about 900-1l00 C. at the time they were immersed in the quenching bath, depending on the length of transfer time.
  • the quenching medium was liquid sodium .at a temperature of 160 C.
  • a hydrocarbon oil at 78130 C. Hydrocarbon Oil, A. F. Holden Co., Milford, Mich.
  • a silicon oil at 60120 C. Silicon Oil #710, Dow-Corning 00., Midland, Mich. was used. After quenching, the panels were cleaned by one of the following methods:
  • the cleaned panels were buffed lightly to develop a satisfactory surface luster and were then passivated by treating them for about 4 minutes at F. in a 20% by weight nitric acid solution containing 2% by weight of Na Cr O
  • the panels were then subjected to the CASS accelerated corrosion test.
  • the coating were analyzed for chromium content by X-ray fluorescence.
  • the coating thicknesses were measured by observing a metallographically polished and etched cross-sectioned sample with a metallograph fitted with a calibrated micrometer eyepiece. Examination of the coatings after cleaning showed the panels quenched in sodium to be bright and free from stains whereas those quenched in silicon oil and hydrocarbon oil had stains ranging from gray to black.
  • Table 1 The data relating to coating characteristics and CASS test results for the samples are set forth in Table 1 which follows:
  • Example II The experiments of Example I were repeated except that the panels were removed from the coating bath and transferred through air to the quenching baths. The time of transfer from the coating bath to the quenching baths was varied. Liquid sodium and the hydrocarbon oil described in Example I were used as the quenching media. The average chromium content and coating thickness for the two groups of panels were as follows:
  • EXAMPLE HI Panels of mild steel (nominal 0.05%0.08% carbon content) 2.5" X 4 X 0.1" thick were heated in a calcium bath and quenched using the quench systems described in Table 4 which follows. The time required to cool the interior of the sample was measured by embedding a thermocouple in a hole drilled into the interior of the sample.
  • a coating bath prepared in an iron crucible, contained 150 grams of barium and 5 grams of cobalt powder. The bath was stirred and surrounded by an argon atmosphere. An iron sample (0.0025% carbon) 3" X 4 X .02" was immersed in the bath for one hour at 1100 C. The sample was removed from the bath and quickly transferred through the argon atmosphere to a sodium quenching bath which was maintained at about 125 C. After cooling, the sample was removed from the bath and cleaned with water containing dilute (10%) nitric acid. The surface of the sample was bright and the sample contained about cobalt at the surface.
  • a coating bath was prepared in a molybdenum crucible containing 90 grams of strontium and 10 grams of powdered nickel. The bath was stirred and surrounded by an argon atmosphere. A sample of iron (0.0025 carbon) was immersed in the bath for 15 minutes at 1100 C. The sample was removed from the bath and quickly transferred through the argon atmosphere to a sodium quenching bath which was maintained at C. After cooling, the sample was removed from the bath and cleaned with water containing dilute (10%) nitric acid. The surface of the sample was bright and the sample contained about 55% nickel at the surface.
  • EXAMPLE VI A coating bath was prepared in an iron crucible containing 100 grams of magnesium and 10 grams of chromium. The bath was heated to 1100 C. and agitated by a mechanical stirrer. The bath was protected by an argon atmosphere. A mild steel coupon (0.05% carbon) 4" x 1 X .06 was immersed in the bath for two hours. The coupon was withdrawn and quickly transferred to a sodium quenching bath which was maintained at C. After cooling, the coupon was cleaned with water containing dilute (10%) nitric acid. The surface of the coupon was bright and contained 22% chromium.
  • EXAMPLE VII A coating bath containing 100 grams of lithium and one gram of chromium was prepared in a carbon steel crucible. A mild steel coupon (0.05 carbon) was immersed in the bath for 30 minutes at 1100 C. The coupon was withdrawn from the bath and quickly transferred to a sodium quenching bath. After cleaning with water containing dilute (10%) nitric acid, the surface was shiny and bright and had a concentration of 28 to 30% chromium. The coating was stripped from its substrate in concentrated nitric acid and found to be highly ductile.
  • EXAMPLE VIII A coating bath containing calcium, calcium nitride and chromium powder was prepared in a heated iron crucible and protected from atmospheric contamination by a loosefitting lid and a continuous purge of argon gas fed into the top of the crucible.
  • the calcium nitride of the bath was varied from 2% to 24% during the tests, and the chromium content of the bath was maintained at a suitable level by replenishing additions made immediately after the treatment of each panel.
  • the coating bath temperature was maintained at 1140'- 1150 C. during the tests, and the test panels of 2.5" X 5 X 0.090 thick low carbon, basic oxygen furnace steel (0.0 8% nominal carbon content) were coated for nine minutes. At the end of the coating period the panels were transferred to the quench medium through air with the time of transfer varying from 5 to 25 seconds.
  • EXAMPLE X An alloy coating bath of molten calcium and powdered chromium metal was prepared as described in Example I, and steel panels were treated in this bath at 1140 C. for nine minutes. SAE 1008 steel panels, 90 mils thick of the panels.
  • Example 7 The panels. were transferred through an argon atmosphere to the quench medium in times varying from 3 to 60 seconds as reported in Table 7. All of the test panels were mechanically bufied before treatment in the coating bath. After coating and quenching, they Were cleaned as described in Example I, mechanically bufied to heighten the luster of the finish, passivated as described in Example I, and then subjected to tests for determination of the properties of the coatings; One set of samples was quenched in sodium, and another in the hydrocarbon oil described in Example I. The data obtained are set forth in Table 7.
  • the process of this invention may be advantageously used in other diffusion coating applications where coatings or properties of the coated articles are improved by rapid quench.
  • this process bright, stain-free surfaces are obtained.
  • the hazards of explosion due to violent reaction of the transfer agents with water are avoided.
  • surface staining and the tendency to carbonize the diffusion coated surface resulting from the use of oils is avoided.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Chemical Treatment Of Metals (AREA)
  • Preventing Corrosion Or Incrustation Of Metals (AREA)
  • Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
  • Other Surface Treatments For Metallic Materials (AREA)
US472657A 1965-07-16 1965-07-16 Process of cooling diffusion coated metal articles in liquid sodium metal Expired - Lifetime US3413142A (en)

Priority Applications (8)

Application Number Priority Date Filing Date Title
US472657A US3413142A (en) 1965-07-16 1965-07-16 Process of cooling diffusion coated metal articles in liquid sodium metal
NL6609454A NL6609454A (enrdf_load_stackoverflow) 1965-07-16 1966-07-06
CH1004066A CH473234A (de) 1965-07-16 1966-07-11 Diffusionsbeschichtungsverfahren
BE683999D BE683999A (enrdf_load_stackoverflow) 1965-07-16 1966-07-12
FR69620A FR1486863A (fr) 1965-07-16 1966-07-15 Procédé de revêtement à diffusion liquide-solide pour appliquer des revêtements sur des surfaces métalliques
GB31933/66A GB1127424A (en) 1965-07-16 1966-07-15 Improvements in or relating to diffusion coating of metal articles
DE19661521447 DE1521447B2 (de) 1965-07-16 1966-07-15 Verfahren zur diffusionsbeschichtung von metallerzeugnissen
NO163935A NO115793B (enrdf_load_stackoverflow) 1965-07-16 1966-07-15

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US472657A US3413142A (en) 1965-07-16 1965-07-16 Process of cooling diffusion coated metal articles in liquid sodium metal

Publications (1)

Publication Number Publication Date
US3413142A true US3413142A (en) 1968-11-26

Family

ID=23876416

Family Applications (1)

Application Number Title Priority Date Filing Date
US472657A Expired - Lifetime US3413142A (en) 1965-07-16 1965-07-16 Process of cooling diffusion coated metal articles in liquid sodium metal

Country Status (7)

Country Link
US (1) US3413142A (enrdf_load_stackoverflow)
BE (1) BE683999A (enrdf_load_stackoverflow)
CH (1) CH473234A (enrdf_load_stackoverflow)
DE (1) DE1521447B2 (enrdf_load_stackoverflow)
GB (1) GB1127424A (enrdf_load_stackoverflow)
NL (1) NL6609454A (enrdf_load_stackoverflow)
NO (1) NO115793B (enrdf_load_stackoverflow)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3494805A (en) * 1967-03-22 1970-02-10 Atomic Energy Commission Method of inhibiting the corrosion of tantalum by liquid lithium at high temperatures
US3497379A (en) * 1967-12-27 1970-02-24 Du Pont Process for improving the corrosion resistance of alloy diffusion coated metal articles
US3524752A (en) * 1967-08-01 1970-08-18 Du Pont Addition of nitrogen gas to atmosphere in alloy diffusion coating
US3547685A (en) * 1968-08-21 1970-12-15 Atomic Energy Commission Method of inhibiting the corrosion of tantalum by liquid lithium
US3770488A (en) * 1971-04-06 1973-11-06 Us Air Force Metal impregnated graphite fibers and method of making same
US4398967A (en) * 1979-09-11 1983-08-16 Devan Jackson H Method for inhibiting alkali metal corrosion of nickel-containing alloys
DE3523003A1 (de) * 1985-06-27 1987-01-02 Schmetz Kg Verfahren zur oberflaechenbeschichtung von metallen
WO2002070774A1 (de) * 2001-03-05 2002-09-12 GWP Gesellschaft für Werkstoffprüfung mbH Verfahren zum härten von metallischen werkstücken

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2797173A (en) * 1954-05-06 1957-06-25 John D Keller Method of and apparatus for annealing and coating steel sheets
US3184331A (en) * 1963-12-16 1965-05-18 Du Pont Process of diffusion coating
US3184292A (en) * 1964-07-08 1965-05-18 Du Pont Process and composition for diffusion coating refractory metals and product produced thereby
US3261712A (en) * 1965-03-15 1966-07-19 Du Pont Process for diffusion coating metals
US3294498A (en) * 1963-09-24 1966-12-27 Du Pont Cr-fe diffusion coating ferrous metal substrate
US3342628A (en) * 1964-05-14 1967-09-19 Du Pont Alloy diffusion process

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2797173A (en) * 1954-05-06 1957-06-25 John D Keller Method of and apparatus for annealing and coating steel sheets
US3294498A (en) * 1963-09-24 1966-12-27 Du Pont Cr-fe diffusion coating ferrous metal substrate
US3184331A (en) * 1963-12-16 1965-05-18 Du Pont Process of diffusion coating
US3342628A (en) * 1964-05-14 1967-09-19 Du Pont Alloy diffusion process
US3184292A (en) * 1964-07-08 1965-05-18 Du Pont Process and composition for diffusion coating refractory metals and product produced thereby
US3261712A (en) * 1965-03-15 1966-07-19 Du Pont Process for diffusion coating metals

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3494805A (en) * 1967-03-22 1970-02-10 Atomic Energy Commission Method of inhibiting the corrosion of tantalum by liquid lithium at high temperatures
US3524752A (en) * 1967-08-01 1970-08-18 Du Pont Addition of nitrogen gas to atmosphere in alloy diffusion coating
US3497379A (en) * 1967-12-27 1970-02-24 Du Pont Process for improving the corrosion resistance of alloy diffusion coated metal articles
US3547685A (en) * 1968-08-21 1970-12-15 Atomic Energy Commission Method of inhibiting the corrosion of tantalum by liquid lithium
US3770488A (en) * 1971-04-06 1973-11-06 Us Air Force Metal impregnated graphite fibers and method of making same
US4398967A (en) * 1979-09-11 1983-08-16 Devan Jackson H Method for inhibiting alkali metal corrosion of nickel-containing alloys
DE3523003A1 (de) * 1985-06-27 1987-01-02 Schmetz Kg Verfahren zur oberflaechenbeschichtung von metallen
WO2002070774A1 (de) * 2001-03-05 2002-09-12 GWP Gesellschaft für Werkstoffprüfung mbH Verfahren zum härten von metallischen werkstücken

Also Published As

Publication number Publication date
BE683999A (enrdf_load_stackoverflow) 1966-12-16
DE1521447B2 (de) 1971-05-06
DE1521447A1 (de) 1969-07-24
NL6609454A (enrdf_load_stackoverflow) 1967-01-17
CH473234A (de) 1969-05-31
NO115793B (enrdf_load_stackoverflow) 1968-12-02
GB1127424A (en) 1968-09-18

Similar Documents

Publication Publication Date Title
US3184331A (en) Process of diffusion coating
US4913980A (en) Corrosion resistant coatings
US3413142A (en) Process of cooling diffusion coated metal articles in liquid sodium metal
Aoki et al. Low temperature gas carburising for austenitic stainless steels: the NV-Pionite process
US3261712A (en) Process for diffusion coating metals
US3403988A (en) Chromized metal substrate
US3184292A (en) Process and composition for diffusion coating refractory metals and product produced thereby
Harrison et al. The gaseous carburisation of austenitic steels
US3467545A (en) Alloy diffusion coating process
Sereda et al. Modification of the surface of copper alloys with aluminum in the conditions of self-propagating high-temperature synthesis
US3620816A (en) Method of diffusion coating metal substrates using molten lead as transport medium
US2926111A (en) Method of forming a protective coating on ferrous metal surfaces
Bahadur Structural studies of calorized coatings on mild steel
US3232594A (en) Corrosion resistant apparatus for conversion coating of metals
US3481769A (en) Alloy diffusion coating process
US3377195A (en) Diffusion coating for metals
US3524752A (en) Addition of nitrogen gas to atmosphere in alloy diffusion coating
NO163935B (no) Vippebeslag for kombinasjonssofa.
US3397092A (en) Corrosion-resistant coatings
US3236684A (en) Alloy diffusion coating process
Kocabaş et al. Effect of plasma nitriding time on surface properties of hard chromium electroplated AISI 1010 steel
JPS622628B2 (enrdf_load_stackoverflow)
WO2005075698A1 (en) Metal dusting resistant stable-carbide forming alloy surfaces
US3497379A (en) Process for improving the corrosion resistance of alloy diffusion coated metal articles
JP2824174B2 (ja) 耐水素吸収性に優れたチタン材