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
  • C23C8/08—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
  • C23C8/16—Oxidising using oxygen-containing compounds, e.g. water, carbon dioxide
• • 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

Definitions

• the invention relates to a method for increasing the thermal shock resistance of the oxide layer and thus improving the oxidation behavior of heating conductor materials.
• the metallic materials contain 3 to 10% aluminum, 10 to 25% chromium, and one or more reactive elements from the series silicon and / or zirconium and / or hafnium and / or titanium with less than 5% and / or one or more elements from the group of rare earths with less than 0.3% and / or alkaline earth metals with 0.001 to 1% from the group Mg, Ba, Ca, Sr, Be as well as the trace elements usual in steels, the rest iron and / or Nickel and / or cobalt.
• the oxide layer produced is rough, so that it can advantageously also serve as an adhesive base for further coatings, for example also for use as a catalyst support.
• metallic alloys of the type M Cr Al X and the type M Cr Al ZX with M as iron and / or cobalt and / or nickel as the base and X small additions by weight of highly reactive elements such as Y, Zr, Ti, Ce, Sm, Hf, La, Th, U, V, W, Ta, Nb, Mo, Gd, Si, Mg, Ca and Z as one element or its oxide from the series of X, but a different one than that chosen for X.
• highly reactive elements such as Y, Zr, Ti, Ce, Sm, Hf, La, Th, U, V, W, Ta, Nb, Mo, Gd, Si, Mg, Ca and Z as one element or its oxide from the series of X, but a different one than that chosen for X.
• Y, Zr, Ti, Ce, Sm, Hf, La, Th, U, V, W, Ta, Nb, Mo, Gd, Si, Mg, Ca and Z as one element or its oxide from the series of
• Shell-shaped oxides can be produced in a known manner from these using special heat treatments on the surface of metallic materials.
• whisker-shaped oxides can be produced from ferritic steels which contain more than 0.002% of rare earths if they are subjected to long-term oxidation in preferably dry air at about 900 to 930 ° C.
• a similar prior art is also described in GB-PS 2 063 723.
• the disadvantage of this technique is the need to add rare earths to increase the adhesive strength of the different types of oxide layers of the alloy of the metal. Rare earths are not only expensive, they also react with oxygen, impurities and the crucible materials in the course of the manufacturing process of the semi-finished product, so that high losses occur.
• the invention has for its object to provide a method with which the adhesive strength of the oxide layer of heat-resistant steels containing chromium and aluminum is improved, in such a way that a reduction or elimination of rare earths in Material is made possible for many applications.
• the object is achieved in that the materials or components made of the materials are first heated in an oxygen-free atmosphere with recrystallization in their surface zone (thermal etching).
• the materials can then preferably be oxidized in an oxygen in a bound form and only containing a maximum of 1% free molecular oxygen.
• the oxide layer should consist of more than 96% aluminum oxide.
• the atmosphere may consist of hydrogen-water vapor mixtures or a mixture thereof with carbon dioxide and carbon monoxide, e.g. reducing flue gas.
• Carbon dioxide which is as low in oxygen as possible, is preferably used, from which a carbon dioxide-carbon monoxide mixture forms during the oxidation.
• Step 2) first forms a thin layer of almost pure aluminum oxide. It is achieved that in the case of semi-finished products and components whose use temperature is, for example, approximately 700 to 950 ° C., the further oxygen uptake is considerably slowed down.
• Steps 2) and 3) can also be carried out with the help of the weakly reducing flue gas, e.g. an acetylene burner.
• the weakly reducing flue gas e.g. an acetylene burner.
• the heating conductor materials contain small amounts of zirconium, titanium or hafnium. Preferably 0.1 to 0.2% zirconium and titanium (0.1 to 0.15%) are used. A further improvement is achieved if rare earths or alkaline earth metals are present in the starting alloy. In this way, the problematic use of rare earths can often be avoided.
• the process can be carried out with a suitable vacuum furnace in combination with the oxidizing treatment in reducing flue gases.
• a two-chamber vacuum oven is preferably used in the production of components that have a large specific surface area - such as catalyst supports, which consist of wound or stacked, embossed foils - in which a chamber for high-temperature treatment in a vacuum and the other is used for oxidation using chemically bound oxygen.
• the process can thus be carried out in a single cycle.

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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)
• Catalysts (AREA)
• Conductive Materials (AREA)

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• 1988
  • 1988-02-12 DE DE3804359A patent/DE3804359C1/de not_active Expired
• 1989
  • 1989-01-14 EP EP89100624A patent/EP0327831A3/fr not_active Ceased
  • 1989-02-09 US US07/308,211 patent/US4969960A/en not_active Expired - Fee Related

Patent Citations (6)

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