US20070204934A1 - Method for Activating Surface of Metal Member - Google Patents

Method for Activating Surface of Metal Member Download PDF

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US20070204934A1
US20070204934A1 US10/586,626 US58662605A US2007204934A1 US 20070204934 A1 US20070204934 A1 US 20070204934A1 US 58662605 A US58662605 A US 58662605A US 2007204934 A1 US2007204934 A1 US 2007204934A1
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gas
furnace
hcn
treatment
metal
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Kaoru Hoshino
Makoto Miyashita
Takashi Kawamura
Toshiko Totsuka
Hiroshi Eiraku
Kuniji Yashiro
Takumi Kurosawa
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Parker Netsushori Kogyo KK
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Parker Netsushori Kogyo KK
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    • 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
    • C23C8/28—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
    • 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

  • the invention of the present application relates to a method for the pretreatment of a metal member to activate a surface of the metal member before applying diffusion treatment such as nitriding or carburizing to the metal member.
  • gas nitriding or gas carburizing that forms a nitrided layer or carburized layer in a surface of a metal member is widely applied primarily to members made of iron-based material.
  • Such a chloride is placed together with a metal member in a treatment furnace and is heated there. By this heating, the chloride is decomposed to form HCl, and the thus-formed HCl decomposes a passivated film on a surface of the metal member to activate the surface so that diffusion treatment such as nitriding or carburizing as a next step is assured.
  • a metal member by such a chloride results in the erosion of a furnace wall made of bricks or a metal by HCl formed through decomposition, and in gas nitriding or gas softnitriding, HCl so formed reacts with ammonia as atmosphere gas to form ammonium chloride, which not only deposits in the furnace or an exhaust system to cause troubles but also remains on the surface of the metal member (work) to induce reductions in the corrosion resistance and fatigue strength of the member.
  • an activation method of the surface of a metal member with a compound of fluorine which belongs to the same halogen group, NF 3 has been put into practical use in recent years (for example, Patent Document 1).
  • NF 3 is decomposed to form fluorine, and the thus-formed fluorine converts a passivated film on the surface of the metal member into a fluoride film to activate the surface of the metal member.
  • the activation method of the surface of the metal member with the fluorine compound (NF 3 ) requires sophisticated treatment for the detoxification of NF 3 and HF contained in effluent gas, which prevents the wide-spread adoption of the method.
  • the ammonia gas nitriding method disclosed in Patent Document 2 reductively activates a passivated film on a surface of a high-chromium alloy steel member by forming reducing radicals and CO at the surface of the alloy steel member through the pyrolysis of acetone.
  • acetone is pyrolyzed on the heated surface of the high-chromium alloy steel member in accordance with the below-described formula (1) so that reducing radicals and CO are formed at the surface of the high-chromium alloy steel member. 2(CH 3 )CO ⁇ 2CH 3 .+CO (1)
  • An oxide film (MO) on the surface of the metal member is reduced in accordance with the following formula (2): 5MO+2CH 3 . ⁇ 5M+2CO+3H 2 O (2)
  • the HCN formed in accordance with the formula (4) reduces the passivated film on the surface of the high-chromium alloy steel member in accordance with the following formula: Cr 2 O 3 +6HCN ⁇ 2Cr(CN) 3 +3H 2 O (5)
  • the Cs and Ns in the resulting Cr(CN) 3 diffuse into the surface of the high-chromium alloy steel member, and contribute to carburizing and nitriding so that no residue is formed on the surface of the member.
  • the chromium chloride remains on the surface of the member, and acts as a causative substance for the corrosion of the member.
  • Patent Document 2 is good in that it has theoretically solved the problems of the chloride-dependent activation method for a surface of a metal member as disclosed in Patent Document 1. Nonetheless, the method disclosed in Patent Document 2 is accompanied by a drawback that the use of acetone, which is liquid at normal temperature and pressure, requires facilities for the introduction of acetone vapor and the difficult flow rate control of acetone makes it hard to obtain a metal member having an evenly-activated surface.
  • the present inventors have struggled to develop a method that makes use of a compound, which is gaseous at normal temperature and pressure, in place of acetone involving the problems in handling, leading to the completion of the present invention.
  • the present invention provides:
  • a method for activating a surface of a metal member which comprises heating a mixed gas of a carbon donor compound, which is gaseous at normal temperature and pressure, and ammonia as essential components to at least 300° C. in a metal-made heating furnace to form HCN under catalyticaction of the metal member, a metal-made inner wall of the furnace or a metal-made jig in the thus-heated mixed gas, and causing the thus-formed HCN to act on the surface of the metal member.
  • carbon donor compound is at least one compound selected from acetylene, ethylene, propane, butane and carbon monoxide.
  • metal-made inner wall of the heating furnace or the metal-made jig contains at least one metal selected from Fe, Ni, Co, Cu, Cr, Mo, Nb, V, Ti and Zr.
  • a passivated film on a surface of a high-alloy steel member makes it difficult to apply diffusion treatment, such as gas nitriding or gas carburizing, that forms a nitrided layer, carburized layer or carbonitrided layer on the surface of the steel member.
  • diffusion treatment such as gas nitriding or gas carburizing
  • an activating treatment method is provided for the surface of the metal member. This method is not accompanied by problems of conventional activation treatment with a halide, such as furnace deposits, furnace wall erosion and effluent gas detoxification treatment, and is useful as pretreatment for diffusion treatment.
  • the passivated surface of the high-alloy steel member can be activated by using a gas commonly employed in gas heat treatment, and forming HCN gas in a heating furnace while making use of catalytic action of the steel member or a surface of the furnace.
  • CH 3 (methyl radicals) formed by the pyrolysis of acetone in the formula ( 1 ) reduce an oxide film on a surface of a metal member.
  • the CO formed in the above-described formula (1) and (2) reacts with ammonia as atmosphere gas on the metal surface to form HCN.
  • HCN acts on the metal oxide film in accordance with the above-described formula (5).
  • the CH 3 . formed by the pyrolysis of acetone and HCN (the reaction product of CO, the other pyrolyzate, with ammonia as atmosphere gas) are similar to each other in their action on the passivated film.
  • the present inventors therefore, presumed that the existence of both CH 3 . and HCN would be a sufficient condition for the activation of the surface of a high-chromium alloy steel member but would not absolutely be a necessary condition. Paying attention to HCN, the present inventors, therefore, endeavored to develop a method for the formation of HCN on a metal surface and also to ascertain effects of HCN for the activation of the surface of a metal member.
  • HCN-forming reactions between ammonia and the above-mentioned carbon-containing compounds can be expressed by the following formulas, respectively: NH 3 +CO ⁇ HCN+H 2 O (7) 2NH 3 +2CO 2 ⁇ 2HCN+H 2 O+O 2 (8) 2NH 3 +C 2 H 2 ⁇ 2HCN+3H 2 (9) 2NH 3 +C 2 H 4 ⁇ 2HCN+4H 2 (10) 3NH 3 +C 3 H 8 ⁇ 3HCN+7H 2 (11) 4NH 3 +C 4 H 10 ⁇ 4HCN+9H 2 (12)
  • RX gas means a gas, which is formed by mixing substantially equal chemical equivalents of a hydrocarbon gas (for example, propane gas, butane gas, or natural gas) and air and causing them to decompose in a catalyst layer maintained at 1,000° C., contains CO and H 2 (N 2 ) as a primary component and small amounts of CO 2 and H 2 O, and is widely used as a nitriding gas.
  • a hydrocarbon gas for example, propane gas, butane gas, or natural gas
  • the CO contained in NH 3 :RX gas 1:1 by molar ratio, a typical composition for gas softnitriding, amounts to about 10% in terms of volume percentage.
  • HCN which is required for the activation of a surface of a metal member, is therefore presumed to exist sufficiently in a gas softnitriding furnace.
  • CO gas When CO gas is selected as a carbon donor compound for the activation of a surface of a metal member, it is thus desired to use CO gas singly instead of RX gas. Because the amount of CO gas required to be injected in the present invention is as little as 1/10 (by volume) or so of a gas softnitriding atmosphere, the effects of H 2 O and CO 2 in RX gas are reduced so that RX gas may be used as a CO source in some instances.
  • the activating effect for the surface of the alloy steel member in the present invention is attributed to HCN.
  • the above-described activating effect is dependent on the concentration of HCN in the furnace atmosphere.
  • the concentration of HCN can appropriately be in a range of from 100 to 30,000 mg/m 3 .
  • the above-described activating effect cannot be expected.
  • the above-described activating effect is saturated, resulting not only in an economical disadvantage but also in the occurrence of sooting (the formation of carbon in the furnace) by pyrolysis of the carbon donor compound. Therefore, HCN concentrations outside the above-described range are not preferred.
  • the dew point of the furnace atmosphere gas may preferably be 5° C. or lower. If the dew point is higher than 5° C., the metal surface activated by HCN gas is re-oxidized with H 2 O in the atmosphere and accordingly, is passivated back again.
  • the method according to the present invention is also advantageous from the environmental standpoint in that as explained in the reaction formula (5), the HCN attributed to the activation of the surface of the metal member is absorbed into the member and attributes to the nitriding and carburizing of the member to leave no residue on the surface of the member and the HCN discharged as effluent gas without any contribution to the reaction can be readily burned and detoxified in an ammonia combustion facility arranged as an attachment for the nitriding facility to obviate any new additional facility.
  • a further advantage of the present invention is that the time of nitriding treatment can be shortened owing to the smooth progress of the steps in the nitriding treatment process.
  • Gas nitriding of a metal member is generally conducted in such a schedule as will be described below.
  • the metal member is set in a furnace, and subsequent to vacuum purging or nitrogen gas replacement of the air in the furnace, the temperature is raised to a nitriding temperature of the metal member and is then maintained constantly at the temperature, both while introducing the nitriding atmosphere gas (NH 3 +N 2 ) at a rate as much as 1 to 10 times the internal volume of the furnace per hour.
  • the internal pressure of the furnace is maintained at atmospheric pressure+0.5 kPa or so by a pressure control valve, and the force-out effluent gas is caused to burn and decompose in an effluent gas combustion facility.
  • Patent Document 1 According to the method disclosed in Patent Document 1 and making use of the fluorine-based gas, it is necessary, subsequent to the introduction of the fluorine-based gas and the activation treatment of the member, to exhaust the fluorine-based gas and then to introduce the nitriding atmosphere gas into the furnace as disclosed in the examples of the specification of Japanese Patent No. 2,501,925.
  • the carbon donor compound is introduced into the nitriding atmosphere gas during the step in which the metal member is heated to the nitriding treatment temperature.
  • HCN is formed to activate the surface of the metal member, and the subsequent termination of the introduction of the carbon donor compound makes it possible to advance directly to the nitriding step.
  • the treatment time of the nitriding step is substantially shortened, thereby making it possible to fundamentally eliminate the re-oxidation phenomenon of the surface of the metal member which has until now remained as a problem in the conventional treatment upon advancing from the activation step to the nitriding step.
  • the inner wall can preferably be made of metal. Even if the inner wall is not made of metal, the present invention can still be practiced provided that the metal member to be treated acts as a catalyst for the formation of HCN or a jig adapted to hold the metal member within the furnace is made of metal.
  • the metal that makes up the metal-made inner wall, metal member or jig may preferably contain, for example, one or more metals selected from Fe, Ni, Co, Cu, Cr, Mo, Nb, V, Ti and Zr.
  • these metal members are held by suitable jigs and are subjected to surface activation treatment in a manner known per se in the art.
  • the surface treatment gases to be fed into the furnace are the carbon donor compound, which is gaseous at normal temperature and pressure, and ammonia, which are fed from their own gas cylinders into the furnace.
  • the nitriding atmosphere gas (ammonia alone, ammonia+nitrogen gas, or ammonia+nitrogen gas+hydrogen gas) is introduced into the furnace to establish a reducing atmosphere.
  • heating is initiated, followed by the introduction of the carbon donor compound useful in the present invention.
  • the ammonia gas and carbon donor compound form HCN under the catalytic action of the metal surface when they are heated to 300° C. or higher in the furnace.
  • the ratio of the flow rate of ammonia as a nitriding atmosphere gas to that of the introduced carbon donor compound should be controlled within a range of from 1:0.0001 to 1:0.1. If the flow rate of the carbon donor compound is so low that the flow rate ratio becomes smaller than 1:0.0001, HCN is formed too little to bring about its activating effect. If the flow rate of the carbon donor compound is so high that the flow rate ratio becomes greater than 1:0.1, on the other hand, the activating effect is saturated to result in an economical disadvantage.
  • the carbon donor compound is composed of one or more gaseous compounds selected from acetylene, ethylene, propane, butane and carbon monoxide as described above, and can be fed into the treatment furnace concurrently with the ammonia-containing gas as mentioned above. It is preferred for the efficient utilization of the carbon donor compound to initiate the introduction of the carbon donor compound at the time point that the temperature of the ammonia-containing gas within the furnace has reached about 300° C. To raise the concentration of the carbon donor compound in the furnace atmosphere at such an early stage as permitting shortening the treatment time, however, it is desired to introduce the carbon donor compound at the same time as the initiation of heating and to assure the formation of HCN from the initial stage.
  • FIG. 1 shows a Muffle furnace 1 , an outer shell 2 of the Muffle furnace, a heater 3 , an internal container (retort) 4 , a gas inlet pipe 5 , an exhaust pipe 6 , a motor 7 , a fan 8 , a metal-made jig 9 , a gas guide cylinder 10 , an inverted funnel 11 , a vacuum pump 12 , an effluent gas combustion facility 13 , a carbon donor compound gas cylinder 14 , an ammonia gas cylinder 15 , a nitrogen gas cylinder 16 , a hydrogen gas cylinder 17 , a flow rate meter 18 , and a gas control valve 19 .
  • Effluent gas from the furnace was branched off to have a portion of the effluent gas absorbed in a 2 wt. % aqueous solution of caustic soda, and an analysis was performed for HCN. From the analysis results of the HCN-absorbed solution, the average HCN concentration in the furnace atmosphere during the acetylene gas injection period was 8,000 mg/m 3 . Some of the SUS304 specimens were weighed to determine a weight increase after the nitriding treatment. As a result, the weight increase was determined to be 20 g/m 2 . Some of the SUS304 specimens were cut, and their cut surfaces were polished, etched with Marble's solution, and then observed under an optical microscope.
  • Nitrided layers of 50- ⁇ m uniform thickness were found to be formed (a 500 ⁇ micrograph is shown in FIG. 2 ). Some of the remaining specimens were measured for surface hardness at 5 points by a Vickers hardness tester. All the values (Hv) distributed between 1,200 and 1,250.
  • SUS304 plates were set in the Muffle furnace employed in Example 1, NH 3 gas and N 2 gas were fed at flow rates of 200 L/H, respectively, and the furnace atmosphere was heated from room temperature to 550° C. in 75 minutes. At the time point that the atmosphere temperature had reached 100° C. in the course of the heating (at the 18 th minute after the initiation of the heating), an injection of propane gas was tinitiated at 5 L/hr. After heated to 550° C., the atmosphere temperature was maintained for 2 hours. At that time point, the injection of propane gas was terminated and instead, NH 3 gas and N 2 gas were then fed at 550° C. for 4 hours to allow nitriding to proceed. Subsequently, the heating was stopped and N 2 gas alone was continuously fed to cool down the furnace. When the atmosphere temperature had dropped to 100° C, or lower, the specimens were taken out of the furnace.
  • Effluent gas from the furnace was branched off to have a portion of the effluent gas absorbed in a 2 wt. % aqueous solution of caustic soda, and an analysis was performed for HCN. From the analysis results of the HCN-absorbed solution, the average HCN concentration in the furnace atmosphere during the propane gas injection period was 400 mg/m 3 .
  • Some of the SUS304 specimens were weighed to determine a weight increase after the nitriding treatment. As a result, the weight increase was determined to be 18 g/m 2 .
  • Some of the SUS304 specimens were cut, and their cut surfaces were polished, etched with Marble's solution, and then observed under an optical microscope. Nitrided layers of 45- ⁇ m uniform thickness were found to be formed. Some of the remaining specimens were measured for surface hardness at 5 points by a Vickers hardness tester. All the values (Hv) distributed between 1,200 and 1,250.
  • SUS304 plates were set in the Muffle furnace employed in Example 1, NH 3 gas and N 2 gas were fed at flow rates of 200 L/H, respectively, and the furnace atmosphere was heated from room temperature to 550° C. in 75 minutes. At the time point that the atmosphere temperature had reached 100° C. in the course of the heating (at the 18 th minute after the initiation of the heating), an injection of CO gas was initiated at 5 L/hr. After heated to 550° C., the atmosphere temperature was maintained for 2 hours. At that time point, the injection of CO gas was terminated and instead, NH 3 gas and N 2 gas were then fed for 4 hours to allow nitriding to proceed. Subsequently, the heating was stopped and N 2 gas alone was continuously fed at 550° C. to cool down the furnace. When the atmosphere temperature had dropped to 100° C. or lower, the specimens were taken out of the furnace.
  • Effluent gas from the furnace was branched off to have a portion of the effluent gas absorbed in a 2 wt. % aqueous solution of caustic soda, and an analysis was performed for HCN. From the analysis results of the HCN-absorbed solution, the average HCN concentration in the furnace atmosphere during the CO gas injection period was 1,000 mg/m 3 .
  • Some of the SUS304 specimens were weighed to determine a weight increase after the nitriding treatment. As a result, the weight increase was determined to be 18 g/m 2 .
  • Some of the SUS304 specimens were cut, and their cut surfaces were polished, etched with Marble's solution, and then observed under an optical microscope. Nitrided layers of 45- ⁇ m uniform thickness were found to be formed. Some of the remaining specimens were measured for surface hardness at 5 points by a Vickers hardness tester. All the values (Hv) distributed between 1,200 and 1,250.
  • SUS304 plates were set in the Muffle furnace employed in Example 1, NH 3 gas and N 2 gas were fed at flow rates of 200 L/H, respectively, and the furnace atmosphere was heated from room temperature to 550° C. in 75 minutes. At the time point that the atmosphere temperature had reached 100° C. in the course of the heating (at the 18 th minute after the initiation of the heating), an injection of C 2 H 4 gas was initiated at 5 L/hr. After heated to 550° C., the atmosphere temperature was maintained for 2 hours. At that time point, the injection of C 2 H 4 gas was terminated and instead, NH 3 gas and N 2 gas were then fed at 550° C. for 4 hours to allow nitriding to proceed. Subsequently, the heating was stopped and N 2 gas alone was continuously fed to cool down the furnace. When the atmosphere temperature had dropped to 100° C. or lower, the specimens were taken out of the furnace.
  • Effluent gas from the furnace was branched off to have a portion of the effluent gas absorbed in a 2 wt. % aqueous solution of caustic soda, and an analysis was performed for HCN. From the analysis results of the HCN-absorbed solution, the average HCN concentration in the furnace atmosphere during the C 2 H 4 gas injection period was 1,200 mg/m 3 .
  • Some of the SUS304 specimens were weighed to determine a weight increase after the nitriding treatment. As a result, the weight increase was determined to be 18 g/m 2 .
  • Some of the SUS304 specimens were cut, and their cut surfaces were polished, etched with Marble's solution, and then observed under an optical microscope. Nitrided layers of 45- ⁇ m uniform thickness were found to be formed. Some of the remaining specimens were measured for surface hardness at 5 points by a Vickers hardness tester. All the values (Hv) distributed between 1,200 and 1,250.
  • SUS304 plates were set in the Muffle furnace employed in Example 1, NH 3 gas and N 2 gas were fed at flow rates of 200 L/H, respectively, and the furnace atmosphere was heated from room temperature to 550° C. in 75 minutes. At the time point that the atmosphere temperature had reached 100° C. in the course of the heating (at the 18 th minute after the initiation of the heating), an injection of C 4 H 10 gas was initiated at 5 L/hr. After heated to 550° C., the atmosphere temperature was maintained for 2 hours. At that time point, the injection of C 4 H 10 gas was terminated and instead, NH 3 gas and N 2 gas were then fed at 550° C. for 4 hours to allow nitriding to proceed. Subsequently, the heating was stopped and N 2 gas alone was continuously fed to cool down the furnace. When the atmosphere temperature had dropped to 100° C. or lower, the specimens were taken out of the furnace.
  • Effluent gas from the furnace was branched off to have a portion of the effluent gas absorbed in a 2 wt. % aqueous solution of caustic soda, and an analysis was performed for HCN. From the analysis results of the HCN-absorbed solution, the average HCN concentration in the furnace atmosphere during the C 4 H 10 gas injection period was 600 mg/m 3 .
  • Some of the SUS304 specimens were weighed to determine a weight increase after the nitriding treatment. As a result, the weight increase was determined to be 18 g/m 2 .
  • Some of the SUS304 specimens were cut, and their cut surfaces were polished, etched with Marble's solution, and then observed under an optical microscope. Nitrided layers of 45- ⁇ m uniform thickness were found to be formed. Some of the remaining specimens were measured for surface hardness at 5 points by a Vickers hardness tester. All the values (Hv) distributed between 1,200 and 1,250.
  • SUS304 plates were set in the Muffle furnace employed in Example 1, NH 3 gas and N 2 gas were fed at flow rates of 200 L/H, respectively, and the furnace atmosphere was heated from room temperature to 550° C. in 75 minutes. After heated to 550° C., the atmosphere temperature was maintained for 6 hours. NH 3 gas and N 2 gas were continuously fed to allow nitriding to proceed. Subsequently, the heating was stopped and N 2 gas alone was continuously fed to cool down the furnace. When the atmosphere temperature had dropped to 100° C. or lower, the specimens were taken out of the furnace.
  • Effluent gas from the furnace was branched off to have a portion of the effluent gas absorbed in a 2 wt. % aqueous solution of caustic soda, and an analysis was performed for HCN. From the analysis results of the HCN-absorbed solution, HCN was not detected at all, thereby ascertaining that HCN did not exist at all in the furnace atmosphere.
  • Some of the SUS304 specimens were weighed to determine a weight increase after the nitriding treatment. As a result, the weight increase was determined to be 10 g/M 2 .
  • Some of the SUS304 specimens were cut, and their cut surfaces were polished, etched with Marble's solution, and then observed under an optical microscope.
  • Nitrided layers of uneven thicknesses of from 8 to 18 ⁇ m were found to be formed (a 500 ⁇ micrograph is shown in FIG. 3 ). Some of the remaining specimens were measured for surface hardness at 5 points by a Vickers hardness tester. The values (Hv) considerably varied from 500 to 1,100, and their absolute values were found to be lower compared with the corresponding values of the examples.
  • a passivated film on a surface of a high-alloy steel member makes it difficult to apply diffusion treatment, such as gas nitriding or gas carburizing, that forms a nitrided layer, carburized layer or carbonitrided layer on the surface of the steel member.
  • diffusion treatment such as gas nitriding or gas carburizing
  • an activating treatment method is provided for the surface of the metal member. This method is not accompanied by problems of conventional activation treatment with a halide, such as furnace deposits, furnace wall erosion and effluent gas detoxification treatment, and is useful as pretreatment for diffusion treatment.
  • the passivated surface of the high-alloy steel member can be activated by using a gas commonly employed in gas heat treatment, and forming HCN gas in a heating furnace while making use of catalytic action of the steel member or a surface of the furnace.
  • FIG. 1 A diagram illustrating the construction of a treatment furnace useful in the present invention.
  • FIG. 2 A micrograph of a cut surface of a specimen of Example 1.
  • FIG. 3 A micrograph of a cut surface of a specimen of Comparative Example 1.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
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  • Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
US10/586,626 2004-01-20 2005-01-19 Method for Activating Surface of Metal Member Abandoned US20070204934A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
JP2004012328 2004-01-20
JP2004-012328 2004-01-20
PCT/JP2005/000607 WO2005068679A1 (fr) 2004-01-20 2005-01-19 Procede d'activation de surface d'un element metallique

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CN102168269A (zh) * 2011-03-16 2011-08-31 广州有色金属研究院 一种催渗等离子氮碳共渗与氮碳化钛复合膜层的制备方法
US8961711B2 (en) 2010-05-24 2015-02-24 Air Products And Chemicals, Inc. Method and apparatus for nitriding metal articles
US9617632B2 (en) 2012-01-20 2017-04-11 Swagelok Company Concurrent flow of activating gas in low temperature carburization

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EP2278038A1 (fr) 2009-07-20 2011-01-26 Danmarks Tekniske Universitet (DTU) Procédé d'activation d'un article de métal passif ferreux ou non ferreux préalable à la carburation, à la nitruration et/ou à la nitrocarburation
KR101245564B1 (ko) * 2011-05-06 2013-03-20 주식회사 삼락열처리 스테인레스강, 내열강 및 고합금강에 대한 가스질화방법
TWI548778B (zh) * 2014-02-11 2016-09-11 國立臺灣大學 不銹鋼表面處理方法及不銹鋼處理系統
JP6357042B2 (ja) * 2014-07-18 2018-07-11 株式会社日本テクノ ガス軟窒化方法およびガス軟窒化装置
JP6516238B2 (ja) * 2015-03-30 2019-05-22 日鉄ステンレス株式会社 オーステナイト系ステンレス鋼及びその製造法
TWI798885B (zh) 2020-11-18 2023-04-11 日商帕卡熱處理工業股份有限公司 金屬構件之處理方法及處理裝置

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US20110030849A1 (en) * 2009-08-07 2011-02-10 Swagelok Company Low temperature carburization under soft vacuum
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
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CN102168269A (zh) * 2011-03-16 2011-08-31 广州有色金属研究院 一种催渗等离子氮碳共渗与氮碳化钛复合膜层的制备方法
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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CN1910303A (zh) 2007-02-07
WO2005068679A1 (fr) 2005-07-28
CN1910303B (zh) 2010-05-12
EP1707646B1 (fr) 2009-08-12
KR100858598B1 (ko) 2008-09-17
EP1707646A4 (fr) 2008-09-03
JP4861703B2 (ja) 2012-01-25
JPWO2005068679A1 (ja) 2007-12-27
KR20060114368A (ko) 2006-11-06
DE602005015934D1 (de) 2009-09-24

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