EP0637637B1 - Procédé de nitruration de pièces en métal ferreux, à résistance améliorée à la corrosion - Google Patents

Procédé de nitruration de pièces en métal ferreux, à résistance améliorée à la corrosion Download PDF

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Publication number
EP0637637B1
EP0637637B1 EP94401694A EP94401694A EP0637637B1 EP 0637637 B1 EP0637637 B1 EP 0637637B1 EP 94401694 A EP94401694 A EP 94401694A EP 94401694 A EP94401694 A EP 94401694A EP 0637637 B1 EP0637637 B1 EP 0637637B1
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EP
European Patent Office
Prior art keywords
bath
parts
current
nitriding
articles
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
EP94401694A
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German (de)
English (en)
French (fr)
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EP0637637A1 (fr
Inventor
Hocine Hadj-Rabah
Jean-Paul Terrat
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.)
Centre Stephanois de Recherches Mecaniques Hydromecanique et Frottement SA
Original Assignee
Centre Stephanois de Recherches Mecaniques Hydromecanique et Frottement SA
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Publication of EP0637637A1 publication Critical patent/EP0637637A1/fr
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Classifications

    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • 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
    • C23C8/40—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 liquids, e.g. salt baths, liquid suspensions
    • C23C8/42—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 liquids, e.g. salt baths, liquid suspensions only one element being applied
    • C23C8/48—Nitriding
    • C23C8/50—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
    • C23C8/40—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 liquids, e.g. salt baths, liquid suspensions
    • C23C8/52—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 liquids, e.g. salt baths, liquid suspensions more than one element being applied in one step
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D21/00—Processes for servicing or operating cells for electrolytic coating
    • C25D21/12—Process control or regulation
    • C25D21/14—Controlled addition of electrolyte components

Definitions

  • the invention relates to a process for nitriding ferrous metal parts, giving them increased resistance to corrosion, in which the parts are treated by immersion for a suitable period in a bath of molten salts essentially consisting of cyanates and carbonates of alkali metals.
  • Salt baths capable of diffusing metalloids, essentially nitrogen and possibly carbon and sulfur, have long been known in the surface layers of parts made of ferrous metals to improve their resistance to wear and seizure.
  • cyanide salt baths the toxicity of which created difficulties in processing, baths were used, the active element of which was the cyanate ion CNO - essentially, the cations being alkali metals which jointly provide sufficiently low chemical stability and melting point.
  • Patent documents FR-A-2 171 993 and FR-A-2 271 307 describe such baths, in which the presence of lithium among the alkali metals, and of sulfur species in small quantities, led to nitrided layers of improved quality.
  • FR-A-2 271 307 further describes a method for keeping the cyanide content of nitriding baths based on alkali metal cyanates and carbonates at a very low value. This process consists in adding sulfur species to said bath so as to have a sulfur content of between 10 and 1000 ppm and also adding a substance comprising in its formula a carboxyl group.
  • DE-B-1 177 899 describes the cathodic polarization, within the framework of a nitriding by mixed bath comprising a high percentage of cyanides (30 to 60%) and cyanates, of the object to be treated in order to improve the adhesion of the layer formed, not the formation of an additional layer of oxide.
  • nitrided parts can be improved considerably by immersing them for at least 10 minutes in baths of oxidizing salts composed in particular of a mixture of nitrates and hydroxides of alkali metals, temperatures between 360 and 500 ° C.
  • oxidizing salts composed in particular of a mixture of nitrates and hydroxides of alkali metals, temperatures between 360 and 500 ° C.
  • the patent document FR-A-2 525 637 in particular, describes a salt bath composed of nitrates, hydroxides and alkali carbonates, with a small amount of an oxygenated salt of alkali metal whose redox potential, relative to the reference electrode hydrogen is less than or equal to -1 volts.
  • This bath which also requires blowing air to keep the bath at dissolved oxygen saturation, and limiting the content of solid particles, leads to substantial increases in corrosion resistance.
  • the invention provides a process for nitriding ferrous metal parts, giving them increased resistance to corrosion, in which the parts are treated by immersion for an appropriate period in a bath of molten salts consisting essentially of alkali metal cyanates and carbonates, and containing an amount of at least one sulfur species, characterized in that, during their immersion in the bath, the parts are brought, with respect to a counterelectrode immersed in the bath, to a potential positive electric current such that a substantial current crosses the bath of the parts at the counterelectrode, and the content of cyanides formed in secondary reaction is maintained at a value less than 6%.
  • the bath is contained in a metal crucible forming a counterelectrode.
  • the extent and shape of the crucible favors electric field configurations in the bath of molten salts which regularize the current density on the parts, and decrease the current density on the counterelectrode and therefore reduce the importance of secondary redox phenomena at the salt bath / crucible wall interface.
  • the average current passing through the bath is kept substantially constant during the treatment of the parts. It has in fact been found that the properties of the layers formed on the parts by the treatment vary as a function of the current density which creates them. The results can therefore, be reproducible only if the current must be kept constant during treatment.
  • the current density values are in the range of 300 to 800 A / m 2 , the preferred range being 450 to 550 A / m 2 . If we use the unit (except standards), classic in industrial electrochemistry, of current density, that is to say A / dm 2 , the ranges are from 3 to 8 A / dm 2 , better 4,5-5, 5 A / dm 2 .
  • the bath temperatures being, conventionally in the range 450 ° -650 ° C, and better still 550-600 ° C.
  • the treatment duration ranges from 10 to 150 min., The most effective durations ranging from 30 to 100 min.
  • the bath contains at least one sulfur species, in an amount such that the S 2- content of the bath is between 1 and 6 ppm.
  • the preferred baths have a composition corresponding substantially to the compositions according to FR-A-2 171 993, with, more precisely the following anionic and cationic contents: NOC - CO 3 2- K + Na + Li + 30 to 45% 15 to 25% 20 to 30% 15 to 25% 0.5 to 5%
  • FR-A-2 271 307 it is preferred, in accordance with FR-A-2 271 307, to maintain the bath substantially at its original composition by additions of regenerating agents, and to homogenize it, the homogeneity being preferably obtained by blowing in air.
  • thermochemical nitriding process For the study and development of the process according to the invention, the tests were carried out while trying to vary only one parameter at a time. Given that, compared to known nitriding processes, the contribution of the invention consisted in making a process cooperate electrochemical to a thermochemical nitriding process, without knowing a priori the interactions that could occur between these two processes, we chose to keep the thermochemical parameters, bath composition and temperature fixed, and to vary the electrochemical parameters, current density and amount of electrical charge passing through the bath.
  • this charge quantity parameter is equivalent, at constant current density, to the time of current flow in the bath, which is also a thermochemical parameter.
  • the operation was carried out in a metal crucible containing 400 kg of molten salts in accordance with FR-A-2 171 993, heated in operation to 570 ° C.
  • the chemical composition was kept constant according to the teachings of FR-A-2 271 307 by periodic metered addition of regenerating salts and potassium sulfide. Air was blown into the crucible for the purpose of homogenization, at a flow rate of 250 l / min.
  • Periodic filtration ensured that the rate of suspended solids was kept at a suitable value.
  • test pieces were plates 100 x 100 mm in surface (2 dm 2 for both sides) and 1 mm thick, made of XC38 steel, which were fixed to a metal bar mounted insulated across the 'upper opening of the crucible.
  • a direct current source consisting of a potentiostat capable of delivering up to 10 amps, adjustable and stabilized, either in voltage or in current, was connected by one pole to the crucible and by the other to the supply bar of current where the part is fixed.
  • the plate-shaped parts were degreased with trichlorethylene vapor; leaving the bath after the treatments, the pieces were cooled for 2 min. with calm ambient air (to avoid thermal shocks), then rinse with hot water (> 60 ° C) for 10 minutes, the water being stirred by blowing air, then drying with hot air.
  • the current passing through the bath was therefore increased in stages between series of tests.
  • the current will be expressed in current density, which is a substantially invariant parameter for the transposition of dimension of parts.
  • the active surface of the parts was 2 dm 2 .
  • test pieces were subjected to corrosion tests. These were carried out according to two methods; measurement of corrosion potential in deaerated 3% NaCl solution; and determination of the duration of exposure to normalized salt spray before the appearance of traces of corrosion. It will be noted that, for these tests, the edges of the plates were protected by a varnish, to avoid that anomalies in the surface state in the immediate vicinity of sharp angles do not disturb the tests.
  • the dense gray layer has already started to form after a treatment of 30 minutes. At 60 minutes it is comparable to that obtained at 90 minutes at 4 A / dm 2 . It then continues to grow, but begins to become porous at 120 minutes while the deep white layer shows signs of degradation.
  • the corrosion resistance tests corroborated those of the first series of tests, namely that the parts whose formed layers comprise a dense gray layer have a corrosion resistance much higher than that of the nitrided layers without intervention.
  • current and which is in the range of corrosion resistance obtained by a treatment with oxidizing salts bath after the conventional nitriding treatment without current.
  • the bath of oxidizing salts is, for example, a bath in accordance with FR-A-2 525 637.
  • the active nitriding component in molten salt baths analogous to those of the present invention is the cyanate anion CNO - , which, by disproportionation under the effect of temperature, and oxidation, releases highly reactive nascent nitrogen, capable of diffusing into the ferrous substrate.
  • the nitrided layer degrades and becomes porous over its entire thickness, which leads to a reduction in the resistance to corrosion and to wear of the treated parts.
  • the nitriding / oxidation treatment was carried out under the conditions of Example 1, under a current density of 5 A / dm 2 , respectively for 30 minutes (mark A) and for 60 minutes (mark B). Sliders treated for 90 minutes without current intervention (reference C) according to the teachings of FR-A-2 171 993 were used in comparison.
  • parts A (5 A / dm 2 , 30 minutes) behave a little better than parts B (5 A / dm 2 , 60 minutes); taking into account the dispersions conventionally recorded in the dry friction tests, the difference is not significant, however. In any event, the comparison pieces C have clearly more unfavorable behaviors.
  • the current flowing through the bath does not appear necessary for the current flowing through the bath to be a strict direct current, and could be a non-filtered unidirectional current, or a pulsed current.
  • the surface condition of the parts, as well as the composition of the surface layers, would be favorable for the attachment of a varnish or a wax, beneficial for certain applications.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Electrochemistry (AREA)
  • Automation & Control Theory (AREA)
  • Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
  • Preventing Corrosion Or Incrustation Of Metals (AREA)
  • Superconductors And Manufacturing Methods Therefor (AREA)
EP94401694A 1993-08-06 1994-07-22 Procédé de nitruration de pièces en métal ferreux, à résistance améliorée à la corrosion Expired - Lifetime EP0637637B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9309706A FR2708623B1 (fr) 1993-08-06 1993-08-06 Procédé de nitruration de pièces en métal ferreux, à résistance améliorée à la corrosion.
FR9309706 1993-08-06

Publications (2)

Publication Number Publication Date
EP0637637A1 EP0637637A1 (fr) 1995-02-08
EP0637637B1 true EP0637637B1 (fr) 1997-03-26

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP94401694A Expired - Lifetime EP0637637B1 (fr) 1993-08-06 1994-07-22 Procédé de nitruration de pièces en métal ferreux, à résistance améliorée à la corrosion

Country Status (14)

Country Link
US (1) US5518605A (pt)
EP (1) EP0637637B1 (pt)
JP (1) JP3056951B2 (pt)
KR (1) KR100294861B1 (pt)
CN (1) CN1054890C (pt)
AT (1) ATE150802T1 (pt)
BR (1) BR9403000A (pt)
CA (1) CA2129061C (pt)
DE (1) DE69402272T2 (pt)
ES (1) ES2099552T3 (pt)
FR (1) FR2708623B1 (pt)
MY (1) MY117886A (pt)
PL (1) PL177659B1 (pt)
TW (1) TW315389B (pt)

Families Citing this family (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2731232B1 (fr) * 1995-03-01 1997-05-16 Stephanois Rech Procede de traitement de surfaces ferreuses soumises a des sollicitations elevees de frottement
FR2733015B1 (fr) * 1995-04-11 1997-07-04 Valeo Systemes Dessuyage Procede de fabrication d'une vis de butee d'arbre, et vis de butee d'arbre, notamment pour moteur electrique
DE19832404C1 (de) * 1998-07-18 1999-10-21 Houghton Durferrit Gmbh Verfahren zur elektrolytischen Erzeugung von Cyanid in Nitrocarburierschmelzen
FR2783291B1 (fr) 1998-09-16 2000-12-08 Stephanois Rech Mec Organes de guidage glissants, lubrifies a la graisse, a bas coefficient de frottement et a duree de vie amelioree
JP4487340B2 (ja) * 1999-07-21 2010-06-23 日本精工株式会社 転がり軸受用保持器の製造方法
FR2812888B1 (fr) * 2000-08-14 2003-09-05 Stephanois Rech Mec Procede de traitement superficiel de pieces mecaniques soumise a la fois a l'usure et a la corrosion
TW557330B (en) * 2000-11-29 2003-10-11 Parker Netsushori Kogyo Kk Improved salt bath nitrogenating method for corrosion-resistant iron material and iron units
DE10126937C2 (de) * 2001-06-01 2003-11-27 Federal Mogul Burscheid Gmbh Gleitringdichtung mit einer Oxid-Nitrid-Verbundschicht
US6746546B2 (en) * 2001-11-02 2004-06-08 Kolene Corporation Low temperature nitriding salt and method of use
JP3748425B2 (ja) * 2002-09-04 2006-02-22 パーカー熱処理工業株式会社 耐食性を強化された金属部材の塩浴窒化方法
DE10355005B4 (de) * 2002-11-29 2005-12-01 Koenig & Bauer Ag Zylinder einer Druckmaschine mit mindestens einem in ihrem Ballen angeordneten Kanal und Verfahren zu ihrer Herstellung
JP2005126752A (ja) * 2003-10-22 2005-05-19 Nippon Parkerizing Co Ltd 表面硬度と高耐食性が付与された自動車用足回り部材
US8203095B2 (en) * 2006-04-20 2012-06-19 Materials & Electrochemical Research Corp. Method of using a thermal plasma to produce a functionally graded composite surface layer on metals
IT1391946B1 (it) * 2008-11-18 2012-02-02 Race Spa T Guida lineare e metodo per produrla.
KR101290896B1 (ko) * 2011-10-13 2013-07-29 중앙대학교 산학협력단 산질화를 이용한 내식성 금속 및 내식성 향상을 위한 금속 표면 개질 방법
CN103122446A (zh) * 2013-02-02 2013-05-29 大连经济技术开发区圣洁真空技术开发有限公司 定量钛氮化碳氮共渗技术
CN104233424B (zh) * 2014-09-30 2017-01-25 长沙理工大学 金属表面碳氮共渗处理的方法
JP7062529B2 (ja) * 2018-06-15 2022-05-06 住友電気工業株式会社 窒化鉄材の製造方法

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DE608257C (de) * 1931-06-09 1935-01-19 Degussa Verfahren zur Haertesteigerung von Eisen, Stahl und deren Legierungen durch Zementieren bzw. Nitrieren
DE1177899B (de) * 1961-04-13 1964-09-10 Degussa Verfahren zum Nitrieren von Metallen, insbesondere von Eisen und Eisenlegierungen, in alkalicyanid- und alkalicyanathaltigen Salzbaedern
FR1408988A (fr) * 1963-08-02 1965-08-20 Applic Des Traitements De Surf Procédé de production, sur des pièces en métal ferreux, d'une couche superficielle présentant une grande résistance à l'usure et au grippage
GB1020534A (en) * 1963-08-02 1966-02-23 Ici Ltd Improvements in the production of a wear-resistant surface on ferrous metal parts
DE1255438B (de) * 1965-04-28 1967-11-30 Degussa Verfahren zum Nitrieren und/oder Carbonitrieren von Metallen, besonders von Eisen und Eisenlegierungen, in alkalicyanid- und alkalicyanathaltigen Salzschmelzbaedern
BE795015A (fr) * 1972-02-18 1973-05-29 Stephanois Rech Mec Procede de traitement de pieces metalliques ferreuses pour augmenter leur resistance a l'usure et au grippage
FR2171993A1 (en) * 1972-02-18 1973-09-28 Stephanois Rech Surface treating ferrous metals - with molten salt bath contg carbonate, cyanate, lithium, potassium, and sodium ions
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Also Published As

Publication number Publication date
FR2708623B1 (fr) 1995-10-20
CN1054890C (zh) 2000-07-26
MY117886A (en) 2004-08-30
JPH0762522A (ja) 1995-03-07
TW315389B (pt) 1997-09-11
BR9403000A (pt) 1995-04-11
DE69402272T2 (de) 1997-10-02
KR100294861B1 (ko) 2001-09-17
ATE150802T1 (de) 1997-04-15
CA2129061C (fr) 2000-12-12
CA2129061A1 (fr) 1995-02-07
PL177659B1 (pl) 1999-12-31
PL304555A1 (en) 1995-02-20
KR950006019A (ko) 1995-03-20
EP0637637A1 (fr) 1995-02-08
FR2708623A1 (fr) 1995-02-10
CN1099811A (zh) 1995-03-08
DE69402272D1 (de) 1997-04-30
JP3056951B2 (ja) 2000-06-26
US5518605A (en) 1996-05-21
ES2099552T3 (es) 1997-05-16

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