EP0931849B1 - Procédé de protection directe contre l'usure-corrosion de pièces métalliques - Google Patents

Procédé de protection directe contre l'usure-corrosion de pièces métalliques Download PDF

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Publication number
EP0931849B1
EP0931849B1 EP98203391A EP98203391A EP0931849B1 EP 0931849 B1 EP0931849 B1 EP 0931849B1 EP 98203391 A EP98203391 A EP 98203391A EP 98203391 A EP98203391 A EP 98203391A EP 0931849 B1 EP0931849 B1 EP 0931849B1
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EP
European Patent Office
Prior art keywords
steel
layer
nitrogen
corrosion
metallic
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
EP98203391A
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German (de)
English (en)
Other versions
EP0931849A3 (fr
EP0931849A2 (fr
Inventor
Pietro Cerutti
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.)
T.T.N. S.P.A.
Original Assignee
Material Service Holding SA
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Filing date
Publication date
Application filed by Material Service Holding SA filed Critical Material Service Holding SA
Publication of EP0931849A2 publication Critical patent/EP0931849A2/fr
Publication of EP0931849A3 publication Critical patent/EP0931849A3/fr
Application granted granted Critical
Publication of EP0931849B1 publication Critical patent/EP0931849B1/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
    • C23C8/06—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
    • C23C8/34—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 more than one step

Definitions

  • the present invention refers to a process suitable to give a direct protection against the wear corrosion of metallic pieces, in particular without producing polluting materials.
  • the French patent 2 672 059 shows, as known and available systems or treatments for increasing the corrosion resistance of metallic pieces, salt baths or environments with an oxidising ionised atmosphere (plasma-ionic environments), in particular at page 2 of the description.
  • plasma-ionic environments oxidising ionised atmosphere
  • the barrier is obtained by dipping the metallic parts to be treated in liquid salt baths containing carbonates - nitrides - hidroxides and oxygenated alcali metals (for the oxidation phase).
  • the morphology of the so obtained protective layers is not compact enough because of the high level of porosity (up to 50%). Said porosity currently requires, to obtain a perfect insulation, a saturation with polymeric resins or waxes in order to close said porosity; otherwise preferred paths are present which will start the corrosion.
  • thermochemical means can not realise a thickness with a defined and constant chemical composition.
  • Said protection means are particularly weak and inefficient for corrosion protection in aqueous environment containing salts, for protection during dipping in solutions of melted light alloys and said protection means have a very low wettability associated to layers which have been subjected to hardening through nitride precipitation.
  • JP-A-56058963 discloses a surface treatment of a steel material involving a nitrification step in NH 3 at 450-600°C for 1-10h and a second step carried out in an oxidising atmosphere in the presence of superheated steam at 450 to 550°C.
  • JP-A-01079362 teaches a surface hardening, pollution free process comprising the formation of a soft-nitrated surface under non-oxidative conditions, followed by a gaseous oxidation treatment.
  • the United Stated patent No. 2,343,418 describes a method of making propeller blades for aircraft which comprises nitriding the outer surfaces of the blade by heating, subjecting to a gas treatment and then treating the blade with gas and air at a suitable stabilised temperature for a time sufficient to produce a non-reflecting oxidised surface on the nitrided outside of the blade.
  • EP-A-0299625 discloses a method for producing a black wear and corrosion resistant finish by the steps of forming an epsilon iron nitride or carbonitride layer, bringing the component to gas oxidation temperature and oxidising by a gaseous medium to form a dense black coating and carrying out a surface finish treatment.
  • US-patent No. 4,496, 410 discloses a method for producing a corrosion resistant non-alloy steel component comprising the steps of nitriding a non alloy steel component and producing an epsilon iron nitride surface layer thereon, and heat treating the component in an oxidising atmosphere to provide an oxide-rich surface layer and then quenching the component into an oil/water emulsion with the component at a temperature such that nitrogen is retained in solid solution in the ferric matrix of the steel microstructure.
  • the purpose of the present invention is to define a process which can solve the above mentioned technical problems.
  • Said purpose, according to the present invention is achieved by realising a process suitable to give a direct protection against the wear corrosion of metallic pieces as disclosed by claim 1 in the following claims.
  • a pure magnetite layer as it will be shown in details hereinafter, will be realised for at least the first 3-5 ⁇ m on the surface of a metallic piece to be treated, as for instance on a tool steel or on a hadened and tempered steel and on low-alloy steel as well as on sheet steel.
  • the process suitable to give a direct protection against the corrosion of metallic pieces according to the present invention is an innovative gaseous process. This fact allows to eliminate any geometric and/or dimensional restriction since the convection puts the reacting agents in contact with the entire surface of the piece to be treated for protection.
  • the invention allows the application of a layer of iron oxide, Fe 3 O 4 , even on parts with a vertical length of up to 10 meters or with 2.5 meter diameter.
  • the process residual gases are directed to a post-combustor which releases only N 2 - H 2 - O 2 in totally neutral gases into the environment.
  • the surface layer produced through the invention process has a nitrogen diffusion area with a maximum depth of 0.1 mm. Said diffusion has to have a nitrogen weight % lower than 2%, said percentage being different in function of the steel type of the piece to be treated.
  • the nitrogen during this phase, is diffused through the grain edge and fills. the vacancies or the vacant areas formed by imperfections of the crystal lattice. As an alternative, the nitrogen atoms are trapped in the free interstitial gaps of the surface of the piece to be treated.
  • the temperature of this first phase of the process is comprised between 480 - 505°C for hardened and tempered steel, and between 500 - 525°C for tool steel.
  • the nitrogen weight % decreases while going towards the inner portion of the surface and it becomes almost zero at depth over 0.1 mm.
  • the duration of this first phase is no more than 10 hours.
  • layers of 2-4 ⁇ m thick iron oxide Fe 3 O 4 are formed at temperatures comprised between 505 and 545°C, said layers contain oxygen weight % between 25% and 30%.
  • a very important factor is the stability of the above oxygen content inside the steel structure and inside the entire so obtained thickness.
  • the transition from the layer below is realised through a sudden decrease of the oxygen percentage from 25-30% to zero on a maximum depth of about 1 ⁇ m.
  • the integration of a layer with a high level of chemical stability which makes the compound stable in a steel matrix previously hardened by a nitrogen diffusion of about 0.1 mm, makes available a barrier and insulation effect of a protective film directly from inside the steel. It is like having two different compounds integrated one into the other and exerting a mutually consolidating action. In fact, the steel supports and makes compact the oxide, while the oxide protects and insulates the steel.
  • the magnetite repellence towards all the liquid solutions is generally given by the compactness and by the compression level of the outer layers.
  • Said compression is due to the difference between the lattice structure of the oxide and the iron cell (body-centered cubic lattice).
  • the surface clearly compresses the lower layers; in this way, if the brittleness of these layers is not so high to cause cracks and flakings, we will obtain a mechanical closing action against any outside corrosive environment or alloying solution or light alloy mixtures (Al, Pb, brass).
  • magnetite has the following more interesting characteristics in order to assure the protection from environment corrosion and/or from melted metals:
  • This invention has produced the realisation of a magnetite layer in a gaseous environment, said realisation converts a 2-4 ⁇ m thick layer previously hardened through nitrogen diffusion into oxide.
  • the process of the invention is realised through a systematic and continuous control of the process parameters in function of the chemical analysis of a differential quantum-meter GDS versus the depth associated with more sporadic controls with X-rays.
  • a further parameter to be taken into account is the ratio between the linear thermal expansion coefficients of the oxide and of the metal contiguous thereto.
  • FeO/Fe goes to 1.25 at temperatures up to 1000°C and to a 1.03 value for Fe 2 O 3 /Fe.
  • thermochemical means used up to now have a chemical composition of the layer quite different from the one which is defined by an oxygen weight % comprised between 21 and 25% and constant over the first 4-5 ⁇ m as in the present invention.
  • the process of the invention produces this barrier which has a chemical identity with a defined and constant composition without changes into a transition composition with the base metal.
  • X38CrMoV5.1 steel samples have been treated by diffusion during a first phase for 10 hours at a 525°C temperature.
  • the first nitrogen diffusion phase has been stopped and, during a second phase, an oxygen containing atmosphere has been introduced for 5-6 hours at a 545°C temperature.
  • said bar had been treated with a known method, as for instance the one according to the French patent 2 672 059, said bar would have been subjected to a salt bath for 10 hours.
  • the oxidation according to the present invention does not jeopardise the previously acquired characteristics in terms of wear and seizing strength; on the contrary, especially in reference to this last feature, the oxidation greatly improves the friction and the plasticity coefficient of the hardened layers, thanks to the morphology of the hexagonal crystal lattice.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
  • Preventing Corrosion Or Incrustation Of Metals (AREA)
  • Other Surface Treatments For Metallic Materials (AREA)
  • Physical Vapour Deposition (AREA)
  • Compounds Of Iron (AREA)
  • Heat Treatment Of Sheet Steel (AREA)

Claims (5)

  1. Procédé adapté pour donner une protection directe contre la corrosion de frottement des pièces métalliques dans laquel chaque pièce métallique est soumise à la nitruration avec une production ultérieure et intégrée d'une couche de magnétite (Fe3O4), dans lequel ladite pièce métallique, pendant une première phase,
       est traitée dans un environnement gazeux avec de l'azote diffusé à une température située entre 480 - 525°C et pendant une durée n'excédant pas dix heures,
       jusqu'à ce que ladite pièce métallique atteigne un pourcentage en poids d'azote n'excédant pas environ 4% dans une couche de diffusion de ladite pièce métallique.
       et, pendant une seconde phase, une fois que l'alimentation en azote est terminée, la pièce métallique est traitée dans un environnement oxydant gazeux à une température situés entre 505°C et 545°C, de sorte
       qu'une couche de magnétite soit formée, laquelle est répartie sur la surface de ladite pièce métallique avec une épaisseur de 3-5 µm et le gradient de transition entre la couche de Fe3O4 (O2 = 25-30%) et la couche de diffusion d'azote (O2 ≅ environ 0%) est inférieurs ou égale à 1 µm afin de garantir l'identité chimique des deux zones ayant une action anticorrosive et anti-usure complémentaire et intégrée.
  2. Procédé selon la revendication 1, caractérisé en ce que ladite couche de magnétite (Fe3O4) contient de l'oxygène entre 25 et 30% en poids.
  3. Procédé selon la revendication 1 ou 2, caractérisé en ce que ledit pourcentage en poids de N2 est d'environ 4% pour l'aluminium ou le chrome contenant de l'acier.
  4. Procédé selon la revendication 1 ou 2, caractérisé en ce que le pourcentage en poids de N2 est d'environ 2% pour les aciers trempés et revenus et pour les aciers faiblement alliés.
  5. Procédé selon l'une quelconque des revendications 1 à 4, caractérisé en ce qu'il comprend une activation mécanique de surface et de nettoyage préliminaire des pièces métalliques à un état avancé d'usage.
EP98203391A 1998-01-26 1998-10-09 Procédé de protection directe contre l'usure-corrosion de pièces métalliques Expired - Lifetime EP0931849B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ITMI980131 1998-01-26
IT98MI000131A IT1298200B1 (it) 1998-01-26 1998-01-26 Procedimento per conferire una protezione diretta contro la corrosione ad usura a pezzi metallici

Publications (3)

Publication Number Publication Date
EP0931849A2 EP0931849A2 (fr) 1999-07-28
EP0931849A3 EP0931849A3 (fr) 2000-08-02
EP0931849B1 true EP0931849B1 (fr) 2003-05-28

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP98203391A Expired - Lifetime EP0931849B1 (fr) 1998-01-26 1998-10-09 Procédé de protection directe contre l'usure-corrosion de pièces métalliques

Country Status (5)

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EP (1) EP0931849B1 (fr)
AT (1) ATE241711T1 (fr)
DE (1) DE69815051T2 (fr)
ES (1) ES2201405T3 (fr)
IT (1) IT1298200B1 (fr)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2003129213A (ja) 2001-10-16 2003-05-08 Honda Motor Co Ltd 窒化処理鋼の製造方法
DE102011078171A1 (de) 2011-06-28 2013-01-03 Robert Bosch Gmbh Verfahren zum Aufbringen einer korrosionsfesten und verschleißfesten Schicht auf einem Metallteil
KR101630561B1 (ko) * 2012-04-03 2016-06-14 히타치 긴조쿠 고구코 가부시키가이샤 주조용 부재 및 그 제조 방법, 다이캐스팅용 슬리브, 및 다이캐스팅 장치
DE102014210571A1 (de) * 2014-06-04 2015-12-17 Robert Bosch Gmbh Bauteilelement einer Baugruppe und Herstellungsverfahren dafür

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2343418A (en) * 1941-01-02 1944-03-07 Aviat Corp Method of making propeller blades
JPS5658963A (en) * 1979-10-20 1981-05-22 Kiyoichi Ogawa Method and device for nitrified-layer stabilizing vapor coating processing
US4496401A (en) * 1981-10-15 1985-01-29 Lucas Industries Corrosion resistant steel components and method of manufacture thereof
GB2208658B (en) * 1987-07-17 1992-02-19 Lucas Ind Plc Manufacture of corrosion resistant steel components
JPS6479362A (en) * 1987-09-22 1989-03-24 Isuzu Motors Ltd Method and device for surface hardening
CA2016843A1 (fr) * 1990-05-15 1991-11-15 Michel J. Korwin Procede de fabrication d'un constitutant anticorrosion a base d'alliage de fer
JP3142689B2 (ja) * 1993-06-29 2001-03-07 株式会社神戸製鋼所 疲労強度の優れたばね

Also Published As

Publication number Publication date
IT1298200B1 (it) 1999-12-20
ES2201405T3 (es) 2004-03-16
DE69815051T2 (de) 2004-04-08
ATE241711T1 (de) 2003-06-15
EP0931849A3 (fr) 2000-08-02
DE69815051D1 (de) 2003-07-03
ITMI980131A1 (it) 1999-07-26
EP0931849A2 (fr) 1999-07-28

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