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
  • C23C8/10—Oxidising

Definitions

• the invention relates to a protective layer for an aluminum-containing alloy for use at high temperatures, in particular at temperatures up to 1400 ° C.
• the invention further relates to methods for producing such protective layers on aluminum-containing alloys.
• the resistance is based on the formation of a dense and slowly growing aluminum oxide layer, which forms on the material surfaces (alloys) when used at high temperatures.
• This protective cover layer which is based on a selective oxidation of the alloying element aluminum, only occurs if the aluminum content in the alloy is sufficiently high, e.g. B. at least about 8 wt .-% in Fe-Al or Ni-Al alloys and at least about 3 wt .-% in Fe-Cr-Al or Ni-Cr-A alloys.
• the alloy element aluminum present in the alloy is regularly used up.
• the consumption per unit of time is generally proportional to the oxide growth rate and therefore increases with increasing temperature, since the oxide growth rate (k in cm 2 per second) increases with increasing temperature.
• the total aluminum reservoir in an alloy containing aluminum increases in proportion to the wall thickness of a corresponding component. With one shift or film as a component, the thickness typically corresponds to the layer thickness, for a wire as a component, for example, the diameter.
• t B typical times (t B ) until the end of the service life of components made of FeCrAl alloys (commercial names, for example KANHAL AF or ALUCHROM YHF) as a function of temperature and wall thickness are known from the literature. For example - for 1 mm wall thickness at 1200 ° C, about 10000 h, for 0.05 mm wall thickness at 1100 ° C about 700 h. for 0.05 mm wall thickness at 1200 ° C about 80 h,
• the growth rate (k) of the oxide layer disadvantageously shows a clear deviation from the above-mentioned temperature dependency.
• This deviation occurs particularly in the initial stage (eg up to about 100 h) of the oxidation stress.
• the reason for this deviation lies in the fact that at temperatures around 800 ° C it is not the ⁇ -Al 2 0 3 (hexagonal structure; corundum lattice) formed at high temperatures (at and above 1000 ° C), but rather metastable Al 2 0 3 modifications, in particular ⁇ - or ⁇ -Al 2 0 3 .
• These last-mentioned oxide modifications are distinguished by significantly higher growth rates than the ⁇ -Al 2 0 3 .
• the initially high growth rate of the oxide layer can disadvantageously exhaust the existing, very small aluminum reservoir in just a few hours. This regularly leads to the complete destruction of the component.
• the actual lifespan is thus orders of magnitude smaller than would be expected due to the extrapolation of the growth rates of the ⁇ -Al 2 0 3 layers at high temperatures (1000 to 1200 ° C).
• the above-mentioned alloys are therefore not suitable for use in the thin-walled components mentioned, for example car catalysts, gas burners or filter systems.
• the object of the invention is to provide a process in which aluminum-containing alloys form an oxidic cover layer predominantly composed of ⁇ -Al 2 O 3 at a temperature of more than 800 ° C., in particular in the initial stage of the oxidation, and so on have significantly improved long-term behavior.
• the object of the invention is achieved by a method for the treatment of aluminum-containing alloys for high-temperature use according to the main claim.
• Advantageous embodiments of the method can be found in the claims referring back to it.
• the treatment according to the invention is based on the fact that the presence of other, i.e. H. not containing aluminum
• the non-aluminum-containing oxides act on the surface of the alloy like nucleating agents, which promote the formation of the -Al 2 0 3 modification in particular at temperatures above 800 ° C. This effect advantageously occurs right at the start of the oxidation of the alloy at operating temperatures, so that the harmful formation of metastable aluminum oxides is regularly prevented from the start.
• Suitable examples of such oxides which have an advantageous effect on the surface are in particular Ni oxides, Fe oxides, Cr oxides and Ti oxides.
• the oxides can be applied to the surfaces of the components made of the metallic, aluminum-containing alloys mentioned by various methods or can also be produced.
• an oxide layer is formed on the surface of the alloy, which predominantly does not consist of an aluminum oxide.
• the Surface layer has further, non-aluminum-containing oxides with a content of at least 20%, and in particular of more than 50%.
• the surface layer of the alloy is understood to mean a region close to the surface up to a thickness of 1000 nm. It has been found in the context of the invention that the mode of action of the non-aluminum-containing oxides on the surface of the alloy also occurs with layer thicknesses of only a few nm.
• the dashed lines show the layer thickness of an oxide layer formed on the surface of a corresponding alloy when ⁇ -Al 2 0 3 is exclusively formed at the corresponding temperatures versus time (both in arbitrary units). After an initially somewhat steeper initial course of the growth rate, the growth rate then remains almost constant, which leads to an almost linear increase in the layer thickness for longer times. Overall, the layer thickness that is formed is higher the higher the corresponding operating temperature.
• the layer thickness is also indicated by a solid line initial formation of metastable aluminum oxides and subsequent formation of ⁇ -Al 2 0 3 entered.
• the comparison shows the significantly higher growth rate of metastable aluminum oxides, especially in the early stages. In the further course, the growth rate then remains almost constant, so that an almost linearly increasing layer thickness also forms over time.
• Ni oxide, Fe oxide, Cr oxide or even Ti oxide with a preferred thickness of 5 to 1000 nm is applied to the surface of a component made of an aluminum-containing alloy by vapor deposition.
• the coating method mentioned corresponds to the prior art.
• a metallic layer made of Fe, Ni, Cr or Ti is first applied to the surface of a component made of an aluminum-containing alloy by means of customary coating processes up to a thickness of 5 to 1000 nm.
• customary coating processes up to a thickness of 5 to 1000 nm.
• vapor deposition, cathode sputtering, galvanic coating are mentioned as suitable methods of application.
• the metals mentioned were converted into the corresponding oxides in an oxygen-containing atmosphere.
• a component made of an aluminum-containing alloy is treated in a chloride- and / or fluoride-containing solution or in a gas atmosphere in which such a solution is located.
• a suitable solution is, for example, a 10% NaCl solution in water. This treatment takes place at room temperature or at a slightly elevated temperature, approx. 80 ° C instead.
• an Fe- or Ni-containing oxide and / or hydroxide is formed on the surface of the component, depending on the alloy base.
• the hydroxide which may be present is converted into the desired Fe oxide (Fe 2 0 3 ) or Ni oxide (NiO).
• a component is first exposed to a temperature of 750 ° C for a period of a few minutes to five hours.
• an oxide containing Fe or Ni was preferably formed on the surface.

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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)
• Other Surface Treatments For Metallic Materials (AREA)
• Physical Vapour Deposition (AREA)
• Manufacture Of Alloys Or Alloy Compounds (AREA)

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• 2004
  • 2004-01-21 DE DE102004002946A patent/DE102004002946A1/de not_active Withdrawn
  • 2004-11-20 US US10/586,089 patent/US7850791B2/en not_active Expired - Fee Related
  • 2004-11-20 CN CNB2004800408091A patent/CN100569990C/zh not_active Expired - Fee Related
  • 2004-11-20 EP EP04802781A patent/EP1706518B1/de not_active Expired - Lifetime
  • 2004-11-20 WO PCT/DE2004/002570 patent/WO2005071132A1/de not_active Ceased
  • 2004-11-20 AT AT04802781T patent/ATE554195T1/de active
  • 2004-11-20 JP JP2006549845A patent/JP4636389B2/ja not_active Expired - Lifetime

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