EP0931849A2 - Verfahren zum direktem Schutz gegen Verschleiss-Korrosion von metallischen Gegenständen - Google Patents

Verfahren zum direktem Schutz gegen Verschleiss-Korrosion von metallischen Gegenständen Download PDF

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Publication number
EP0931849A2
EP0931849A2 EP98203391A EP98203391A EP0931849A2 EP 0931849 A2 EP0931849 A2 EP 0931849A2 EP 98203391 A EP98203391 A EP 98203391A EP 98203391 A EP98203391 A EP 98203391A EP 0931849 A2 EP0931849 A2 EP 0931849A2
Authority
EP
European Patent Office
Prior art keywords
corrosion
nitrogen
steel
layer
metallic piece
Prior art date
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Granted
Application number
EP98203391A
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English (en)
French (fr)
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EP0931849A3 (de
EP0931849B1 (de
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.)
Ttn SpA
Original Assignee
Material Service Holding SA
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Filing date
Publication date
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Publication of EP0931849A3 publication Critical patent/EP0931849A3/de
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Publication of EP0931849B1 publication Critical patent/EP0931849B1/de
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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.
  • the purpose of the present invention is to define a process which can solve the above mentioned technical problems.
  • 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 hardened 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)
EP98203391A 1998-01-26 1998-10-09 Verfahren zum direktem Schutz gegen Verschleiss-Korrosion von metallischen Gegenständen Expired - Lifetime EP0931849B1 (de)

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 true EP0931849A2 (de) 1999-07-28
EP0931849A3 EP0931849A3 (de) 2000-08-02
EP0931849B1 EP0931849B1 (de) 2003-05-28

Family

ID=11378697

Family Applications (1)

Application Number Title Priority Date Filing Date
EP98203391A Expired - Lifetime EP0931849B1 (de) 1998-01-26 1998-10-09 Verfahren zum direktem Schutz gegen Verschleiss-Korrosion von metallischen Gegenständen

Country Status (5)

Country Link
EP (1) EP0931849B1 (de)
AT (1) ATE241711T1 (de)
DE (1) DE69815051T2 (de)
ES (1) ES2201405T3 (de)
IT (1) IT1298200B1 (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1437423A4 (de) * 2001-10-16 2007-04-18 Honda Motor Co Ltd Verfahren zur herstellung von nitrierstahl
WO2015185253A1 (de) * 2014-06-04 2015-12-10 Robert Bosch Gmbh Bauteilelement einer baugruppe und herstellungsverfahren dafür
JPWO2013150855A1 (ja) * 2012-04-03 2015-12-17 日立金属工具鋼株式会社 鋳造用部材及びその製造方法、ダイカスト用スリーブ、並びにダイカスト装置

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102011078171A1 (de) 2011-06-28 2013-01-03 Robert Bosch Gmbh Verfahren zum Aufbringen einer korrosionsfesten und verschleißfesten Schicht auf einem Metallteil

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 (en) * 1990-05-15 1991-11-15 Michel J. Korwin Thermochemical treatment of machinery components for improved corrosion resistance
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

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1437423A4 (de) * 2001-10-16 2007-04-18 Honda Motor Co Ltd Verfahren zur herstellung von nitrierstahl
US7326306B2 (en) 2001-10-16 2008-02-05 Honda Giken Kogyo Kabushiki Kaisha Method for producing nitriding steel
JPWO2013150855A1 (ja) * 2012-04-03 2015-12-17 日立金属工具鋼株式会社 鋳造用部材及びその製造方法、ダイカスト用スリーブ、並びにダイカスト装置
WO2015185253A1 (de) * 2014-06-04 2015-12-10 Robert Bosch Gmbh Bauteilelement einer baugruppe und herstellungsverfahren dafür

Also Published As

Publication number Publication date
DE69815051D1 (de) 2003-07-03
IT1298200B1 (it) 1999-12-20
ITMI980131A1 (it) 1999-07-26
ATE241711T1 (de) 2003-06-15
ES2201405T3 (es) 2004-03-16
EP0931849A3 (de) 2000-08-02
DE69815051T2 (de) 2004-04-08
EP0931849B1 (de) 2003-05-28

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