WO2008124238A2 - Accélérateurs de diffusion pour cémentation à basse température - Google Patents

Accélérateurs de diffusion pour cémentation à basse température Download PDF

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Publication number
WO2008124238A2
WO2008124238A2 PCT/US2008/056558 US2008056558W WO2008124238A2 WO 2008124238 A2 WO2008124238 A2 WO 2008124238A2 US 2008056558 W US2008056558 W US 2008056558W WO 2008124238 A2 WO2008124238 A2 WO 2008124238A2
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WO
WIPO (PCT)
Prior art keywords
workpiece
low temperature
altered
surface layer
metal
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Application number
PCT/US2008/056558
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English (en)
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WO2008124238A3 (fr
Inventor
Sunniva R. Collins
William H. Glime
Gary W. Henrich
Andrew P. Marshall
Gerhard H. Schiroky
Peter C. Williams
George R. Vraciu
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Swagelock Company
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.)
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Publication date
Application filed by Swagelock Company filed Critical Swagelock Company
Priority to US12/530,799 priority Critical patent/US20100037991A1/en
Publication of WO2008124238A2 publication Critical patent/WO2008124238A2/fr
Publication of WO2008124238A3 publication Critical patent/WO2008124238A3/fr

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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
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/02—Pretreatment of the material to be coated
    • 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
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
    • C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
    • C23C8/20—Carburising
    • C23C8/22—Carburising of ferrous surfaces
    • 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
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
    • C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
    • C23C8/24—Nitriding
    • C23C8/26—Nitriding of ferrous surfaces
    • 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
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
    • C23C8/28—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases more than one element being applied in one step
    • C23C8/30—Carbo-nitriding
    • C23C8/32—Carbo-nitriding of ferrous surfaces

Definitions

  • Case hardening is a widely used industrial process for enhancing the surface hardness of shaped metal articles.
  • the workpiece is contacted with a gaseous carbon compound at elevated temperature whereby carbon atoms liberated by decomposition of the carbon compound diffuse into the workpiece' s surface.
  • Hardening occurs through the reaction of these diffused carbon atoms with one or more metals in the workpiece thereby forming distinct chemical compounds, i.e. carbides, followed by precipitation of these carbides as discrete, extremely hard, crystalline particles in the metal forming the workpiece's surface.
  • Stickels "Gas Carburizing", pp 312 to 324, Volume 4, ASM Handbook, ⁇ 1991, ASM International.
  • this invention in one embodiment provides a low temperature carburized stainless steel product having an altered surface layer which (a) contains an increased concentration of carbon atoms relative to the base metal from which the product is made, (b) is harder than the base metal from which the product is made, (c) is free of carbide precipitates, and (d) contains an increased concentration of at least one promoter element selected from Mo, Ni, Cr, Ti, V and Nb relative to the base metal from which the product is made.
  • this invention in a broader embodiment provides a metal product produced by subjecting a metal workpiece to a low temperature diffusion-based surface treatment to produce an altered surface layer containing an increased concentration of a diffusing element in an amount sufficient to alter the properties of the metal forming the surface layer, the altered surface layer also being free of precipitates of compounds of the diffusing element, wherein the altered surface layer further contains an increased concentration of at least one promoter element capable of enhancing the rate at which the diffusing element diffuses into the surface of the workpiece to be altered during the low temperature diffusion-based surface treatment.
  • this invention further provides a process for enhancing the rate at which a diffusing element diffuses into the surface of a metal workpiece in a low temperature diffusion-based surface treatment to produce an altered surface layer containing an increased concentration of the diffusing element in an amount sufficient to alter the properties of the metal forming the surface layer, the altered surface layer also being free of precipitates of compounds of the diffusing element, the process comprising treating the workpiece to increase the concentration of at least one promoter element in the surface to be altered, the promoter element being capable of enhancing the rate at which the diffusing element diffuses into the surface of the workpiece to be altered during the low temperature diffusion-based surface treatment.
  • this invention also provides a process for altering the physical properties of the surface layer of a metal workpiece by a low temperature diffusion-based surface treatment in which the metal workpiece is contacted with a gas containing a diffusing element at a treatment temperature which is high enough to cause the diffusing element to diffuse into the workpiece surfaces thereby producing an altered surface layer, the treatment temperature also being low enough to prevent formation of precipitates of compounds of the diffusing element, wherein the workpiece is treated to increase the concentration of at least one promoter element in the surface to be altered, the promoter element being capable of enhancing the rate at which the diffusing element diffuses into the surface of the workpiece to be altered during the low temperature diffusion-based surface treatment.
  • low temperature carburization of a workpiece surface is accomplished faster by impregnating the surface with a diffusion promoter prior to or during the low temperature carburization process.
  • the primary focus of this invention is on the low temperature carburization of iron-, nickel- and cobalt-based alloys, especially stainless steel.
  • elemental carbon diffuses into the metal matrix forming the workpiece without formation of carbide precipitates.
  • Low temperature carburization normally produces an outermost oxide surface layer on the workpiece being treated about 20-30 ran thick. See, Japan 9-71853 (Kokai 9-71853). Depending on the carburizing conditions, this outermost oxide surface layer may also be covered with soot. In addition, under this oxide surface layer, an extremely thin outer surface layer of the metal may contain a small amount of carbide precipitates, especially if the low temperature carburization conditions are too severe. See, U.S. 5,556,483, U.S. 5,593,510 and U.S. 5,792,282. In order for the workpiece to exhibit an attractive metallic appearance, this soot and outermost oxide surface layer must be removed.
  • this extremely thin outermost metal surface layer must also be removed in order for the workpiece to exhibit good corrosion resistance, at least if this outermost metal surface layer contains carbide precipitates. Therefore, as a practical matter, these unwanted by-products of the low temperature carburization process (i.e., the soot, oxide surface layer, and thin outermost metal layer containing carbide precipitates, if any) are removed before the workpiece is used.
  • reference to a workpiece surface layer which is "free of carbide precipitates" or which is made “without formation of carbide precipitates” refers to the carbon-hardened surface layer remaining after the unwanted by-products of the low temperature carburization process (i.e., the soot, oxide surface layer, and thin outermost metal layer containing carbide precipitates, if any) are removed.
  • low temperature carburization is carried out in the same way as done in the past by contacting the workpiece with a carburizing gas at an elevated temperature for a time sufficient to produce in the primary surface layer of the workpiece (i.e. the surface layer of the workpiece after the unwanted by-products of the low temperature carburization process are removed) an elevated amount of elemental carbon without formation of carbide precipitates.
  • the carburization temperature will normally be no greater than about 500° C, although higher temperatures can be used by following the modified approach described in commonly assigned U.S. 6,547,888.
  • carburization will normally last 20-50 hours, although longer or shorter processing times can be used.
  • a primary surface layer typically about 20-50 ⁇ thick and normally containing about 2-15 atomic %, more typically about 5-10 atomic % or even 9-12 atomic % atomic carbon will be obtained.
  • This invention concentrates on low temperature carburization of iron-, nickel- and cobalt-based alloys, hi this context, an alloy which is "based" on a particular metal means that the alloy contains at least 35% of that metal.
  • this invention is also applicable to other analogous low temperature diffusion-based surface treatments as well.
  • atomic carbon diffuses interstitially into the workpiece surfaces, i.e., carbon atoms travel through the spaces between the metal atoms without significant substitutional diffusion of the metal atoms. Because the processing temperature is low, these carbon atoms form a solid solution with the metal atoms of the workpiece surfaces. They do not react with these metal atoms to form other compounds.
  • Low temperature carburization is therefore different from normal carburization carried out at higher temperatures in which the carbon atoms react to form carbide precipitates, i.e., specific metal compounds such as M 23 C 6 (e.g., Cr 23 C 6 Or chromium carbide), M 5 C 2 and the like, arranged in the form of discrete phases separate and apart from the metal matrix in which they are contained.
  • specific metal compounds such as M 23 C 6 (e.g., Cr 23 C 6 Or chromium carbide), M 5 C 2 and the like, arranged in the form of discrete phases separate and apart from the metal matrix in which they are contained.
  • the present invention is applicable to all such low temperature diffusion-based surface treatments. That is to say, the speed or rate at which each of these low temperature diffusion-based surface treatments can be carried out can be enhanced by adopting the principles of this invention.
  • this invention is described here in terms of low temperature carburization for convenience, this invention also applies to such other analogous processes as well. Enhancing Diffusion
  • Alloys M152 (S32550), AM355 and 17-4 PH (S 17400) also contain 2-5% Ni, 2-3% Mo, or both, which indicates that these additional alloying elements, i.e., the Ni and Mo, promote the rate at which low temperature carburization of these alloys occurs.
  • Cr, Ti, V and Nb have also been observed to impart a similar promoting effect on the ability of certain other iron-based alloys to respond to low temperature carburization. Accordingly, recognition of this phenomenon is taken advantage of in this invention by treating a workpiece made from such an alloy, prior to or during the low temperature carburization process, to cause one or more of these "promoter elements" to be taken up by and diffuse into the workpiece surface.
  • the low temperature carburization when carried out, it can be completed faster (and/or a thicker hardened surface can be achieved in the same amount of time) than would otherwise occur, because the promoter element facilitates diffusion of carbon into the metal matrix of the workpiece surface.
  • the amount of promoter element that should be added to the workpiece surfaces to promote the low temperature diffusion-based surface treatment varies depending on the composition of the workpiece being treated and the particular promoter element chosen. For example, it has been found that the addition of about 0.5-5 wt.% Mo, Ni, Cr, Ti, V and/or Nb significantly enhances the rate with which elemental carbon is taken up by iron- based workpieces. However, greater or lesser amounts will still achieve some benefits and still can be used. For example, amounts as low as 0.1 wt.% and as high as 5 wt.% can be used. Additions on the order of 0.3 to 2.0 wt.% are more common.
  • routine experimentation can be used to determine the optimal amounts of particular promoter elements to use on particular alloys. Similar amounts of promoter elements are believed appropriate for non-iron-based alloys, it being understood that routine experimentation may be helpful for determining the appropriate amounts of particular promoter elements to use on these alloys as well.
  • the primary focus of this invention is on the low temperature carburization of iron-based alloys, especially stainless steels and the like.
  • Alloys 440C (S44004) and 410 (S41000) mentioned above are particularly interesting. However, it is also applicable to other low temperature diffusion based processes as well.
  • Ni and Mo are believed to be helpful in promoting the diffusion process.
  • V and Nb are believed to be helpful in promoting the diffusion process.
  • Such promoting elements can be used singly or in combination.
  • the AISI 400 series stainless steels such as Alloy 410, Alloy 416 and Alloy 440C, which contain far less nickel, are difficult to process by standard low temperature carburization due to a low acceptance of carbon.
  • These alloys can be processed with particular advantage according to this invention, since the presence of additional amounts of diffused nickel according to this invention will significantly enhance the rate at which diffusion of carbon into these alloys occurs.
  • duplex steels which are composed of ferritic regions rich in Cr but poor in Ni as well as austenitic regions with moderate Cr content but rich in Ni, can be processed with advantage by this invention, since the addition of a suitable diffusing agent such as Ni to the steel as a whole will allow its ferritic regions to carburize more easily. Alloys 2205 and 2507 are good examples of such duplex steels.
  • the speed or rate at which a low temperature diffusion-based surface treatment of a metal workpiece can be completed (and/or the thickness of the altered surface layer obtained can be increased) by impregnating the surface with a diffusion promoter prior to or during the low temperature carburization process can be done by any process or technique which will increase the concentration of the promoter element in the surface of the workpiece which is to be altered by the low temperature diffusion-based surface treatment. In other words, this can be done by any process or technique which increases the concentration of the promoter element in the surface of the workpiece prior to the start of the low temperature diffusion-based surface treatment.
  • the workpiece can be coated with a layer of the promoter element by any known coating technique and then heated to elevated temperature to drive the promoter element into the workpiece surface.
  • a workpiece made from an iron-based alloy can be provided with a coating of the promoter element by electroplating, electroless plating techniques, plasma coating, dipping in molten metal, painting with a paint containing the promoter element, or any other technique which will provide a layer of the promoter element in contact with the workpiece surfaces.
  • the promoter element will be present in elemental form, although it can also be present in the form of a compound which decomposes to yield the promoter element at the conditions employed for driving the promoter element into the workpiece surfaces.
  • the coated workpiece can be heated to elevated temperature, e.g., 1,000° C (1832° F) or more, to drive the promoter element from the coating into the workpiece.
  • elevated temperature e.g., 1,000° C (1832° F) or more
  • a modification of this technique based on ALD (atomic layer deposition) in which the workpiece is subjected to repeated iterations of deposition and diffusion can also be used.
  • promoter elements can diffuse into metal surfaces.
  • gas phase diffusion processes analogous to the low temperature diffusion-based process described above can be used, i.e., diffusion-based processes in which the promoter element, or a compound capable of decomposing to yield this element, is contacted with the workpiece surface in the form of a gas.
  • the so-called GE Metalliting process in which the workpiece is contacted with a molten bath of a fluoride salt containing the promoter element can be used.
  • a workpiece previously treated to make its surface porous can be impregnated with the promoter element, or a compound capable of decomposing to yield this element, and then heated to elevated temperature to promote diffusion of this element into its surfaces.
  • examples of techniques that can be used for making the workpiece surface porous include contact with hot, concentrated HCl, aqua regia or the like, mechanical abrasion, anodizing the workpiece, and growing a porous oxide layer the workpiece surface in the manner described in the Background Section above (i.e., by exposing the surface to oxygen or a compound capable of liberating oxygen under the conditions encountered by the workpiece).
  • impregnation of the workpiece with the promoter element will be done prior to the start of the low temperature diffusion based surface treatment.
  • impregnation can also be done during the low temperature diffusion based surface treatment, for example, by interrupting (i.e.
  • the workpiece is impregnated with a promoter element such that the altered surface layer in the metal product ultimately produced by the low temperature diffusion based surface treatment, in addition to containing an increased concentration of the diffusing element responsible for altering the properties of this surface layer, further contains an increased concentration of at least one promoter element capable of enhancing the rate at which this diffusing element diffuses into the workpiece surface layer.
  • the invention described here differs from that prior practice in that, in this invention, more than incidental diffusion of nickel or other promoter elements is involved.
  • the amount of promoter element which diffuses into the workpiece surfaces is greater than the incidental amount of nickel atoms that may have diffused into the workpiece surfaces in that earlier technology. Therefore, it will be appreciated that reference in this document to an "increased concentration of promoter element" in the surface layer of the metal product produced by this invention means an increase over and above the incidental increase that might occur in that earlier technology as a by-product of the low temperature diffusion based surface treatment.
  • Some metals form coherent protective oxide coating layers essentially instantaneously upon contact with air.
  • a good example is aluminum and its alloys, which form coherent protective coating layers of aluminum oxide.
  • Another example is stainless steel, which forms a coherent protective coating layer of chromium oxide.
  • These protective coherent oxide coating layers are impervious to most materials, including the diffusing elements typically used in most low temperature diffusion-based processes. Accordingly, these workpieces are typically "activated" before or simultaneously with the diffusion-based surface treatment to make this coating permeable to the diffusing element being used.
  • Activation is normally done by treatment with a halogen-containing gas such as F 2 , Cl 2 , HCl, HF, NF 3 and the like.
  • a halogen-containing gas such as F 2 , Cl 2 , HCl, HF, NF 3 and the like.
  • Treatment with acids in liquid form particularly aqueous compositions of strong acids, such as aqueous HCl, H 2 SO 4 , HNO 3 , aqua regia and the like can also be used.
  • Activating can be also be done mechanically, for example, by sawing, scraping or sanding the workpiece to expose the "native" metal of the surface being treated.
  • activating can also be done electrochemically, i.e., by contacting the metal with an electrolyte and subjecting the metal to a sufficient electric potential to cause anodic decomposition.
  • the workpiece being treated by this invention is made from a metal which does not form such a coherent protective oxide coating, no special pretreatment or other procedures is needed for causing the selected promoter element to diffuse into the workpiece surfaces.
  • this metal does form a coherent protective oxide coating, some form of activation may be necessary depending on the approach used for supplying the promoter element and/or driving the diffusing element into the workpiece surfaces.
  • the GE Metalliting process in which the workpiece is contacted with a molten bath of a fluoride salt containing the promoter element will also depassivate most protective, coherent oxide coatings. So in many instances, no special activation or pretreatment is required for practicing this invention.
  • the workpiece can be pretreated to depassivate this oxide coating before the promoter element is applied, or at least before the workpiece is treated to drive a previously-applied promoter element into its surfaces.
  • This pretreatment can be done in the same way as described above for activating the workpiece in traditional low temperature diffusion based surface treatments such as, for example, by contact with a halogen-containing gas or strong acid, by mechanically exposing the workpiece's native metal, or electrochemically. Once this is done, the workpiece can be subjected to the particular coating/diffusion approach selected for diffusing the promoter element into the workpiece surface. Normally, this will be done without exposing the activated workpiece to the atmosphere to avoid repassivating the previously-depassivated surfaces.
  • the metal products produced by earlier low temperature diffusion-based processes include an altered surface layer containing an increased concentration, relative to the "native" metal from which the workpiece is made, of a diffusing element in an amount sufficient to alter the properties of the metal forming the surface layer. Nonetheless, this altered surface layer is still free of precipitates of compounds formed from the diffusing element.
  • a stainless steel workpiece is low temperature carburized, an altered surface layer is obtained which is not only free of chromium carbide precipitates but, in addition, exhibits greater hardness due to the presence of the diffused carbon atoms.
  • the surface of the workpiece which is subjected to the low temperature diffusion-based process further includes an increased concentration of at least one promoter element capable of enhancing the rate at which the diffusing element diffuses into the workpiece's surfaces.
  • the amount of this increase is greater than any incidental increase that may have occurred as a by-product of the low temperature carburization process described in U.S. 2006/0090817 A in which the workpiece is activated by means of an electroless nickel coating.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)

Abstract

Le processus de cémentation à basse température de la surface d'une pièce peut être accélérée par imprégnation de ladite surface au moyen d'un accélérateur avant ou pendant ledit processus.
PCT/US2008/056558 2007-04-05 2008-03-12 Accélérateurs de diffusion pour cémentation à basse température WO2008124238A2 (fr)

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Application Number Priority Date Filing Date Title
US12/530,799 US20100037991A1 (en) 2007-04-05 2008-03-12 Diffusion promoters for low temperature case hardening

Applications Claiming Priority (4)

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US92193507P 2007-04-05 2007-04-05
US60/921,935 2007-04-05
US93106407P 2007-05-21 2007-05-21
US60/931,064 2007-05-21

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WO2008124238A2 true WO2008124238A2 (fr) 2008-10-16
WO2008124238A3 WO2008124238A3 (fr) 2009-08-06

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US20130186520A1 (en) * 2012-01-20 2013-07-25 Swagelok Company Concurrent flow of activating gas in low temperature carburization
US9212416B2 (en) 2009-08-07 2015-12-15 Swagelok Company Low temperature carburization under soft vacuum

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Publication number Priority date Publication date Assignee Title
US9212416B2 (en) 2009-08-07 2015-12-15 Swagelok Company Low temperature carburization under soft vacuum
US10156006B2 (en) 2009-08-07 2018-12-18 Swagelok Company Low temperature carburization under soft vacuum
US10934611B2 (en) 2009-08-07 2021-03-02 Swagelok Company Low temperature carburization under soft vacuum
US20130186520A1 (en) * 2012-01-20 2013-07-25 Swagelok Company Concurrent flow of activating gas in low temperature carburization
JP2015507096A (ja) * 2012-01-20 2015-03-05 スウエイジロク・カンパニー 低温浸炭における活性化ガスの同時流
US9617632B2 (en) * 2012-01-20 2017-04-11 Swagelok Company Concurrent flow of activating gas in low temperature carburization
US10246766B2 (en) 2012-01-20 2019-04-02 Swagelok Company Concurrent flow of activating gas in low temperature carburization
US11035032B2 (en) 2012-01-20 2021-06-15 Swagelok Company Concurrent flow of activating gas in low temperature carburization

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