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
  • C23C30/00—Coating with metallic material characterised only by the composition of the metallic material, i.e. not characterised by the coating process
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/12—All metal or with adjacent metals
  • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
  • Y10T428/12771—Transition metal-base component
  • Y10T428/12861—Group VIII or IB metal-base component
  • Y10T428/12937—Co- or Ni-base component next to Fe-base component
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/12—All metal or with adjacent metals
  • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
  • Y10T428/12771—Transition metal-base component
  • Y10T428/12861—Group VIII or IB metal-base component
  • Y10T428/12944—Ni-base component

Definitions

• the invention relates to a high-temperature protective layer according to the preamble of claim 1.
• Such high-temperature protective layers are mainly used where it is necessary to protect the base material of components made of heat-resistant steels and / or alloys that are used at temperatures above 600 ° C.
• high-temperature protective layers are intended to slow down or completely prevent the effects of high-temperature corrosion, especially of sulfur, oil ash, oxygen, alkaline earths and vandium.
• Such high-temperature protective layers are designed so that they can be applied directly to the base material of the component to be protected.
• High-temperature protective layers are of particular importance for components of gas turbines. They are mainly applied to rotor blades and guide vanes as well as to heat accumulation segments in gas turbines.
• An austenitic material based on nickel, cobalt or iron is preferably used to manufacture these components.
• nickel superalloys in particular are used as the base material.
• Components that are intended for gas turbines are provided, for example, with protective layers that are formed by an alloy that contains nickel, cobalt, chromium, aluminum and yttrium.
• the aluminum content of these alloys is relatively high, while the chromium content is quite low, which leads to poor corrosion resistance. This is solely due to the low chromium content.
• Protective layers which are made from the abovementioned alloys have the property that, under operating conditions, in particular when they are exposed to a temperature of more than 900 °, they form an aluminum oxide-containing cover layer on their surface.
• the yttrium contained in the alloy results in a certain adhesive strength of the aluminum oxide cover layer on the protective layer.
• the structure of these protective layers consists of a matrix in which an aluminum-containing phase is embedded. Progressive oxidation leads to a rapid depletion of aluminum near the surface. This leads to an increased susceptibility of the protective layers to corrosion.
• the invention has for its object to show a high-temperature protective layer which has a low oxidation rate, is corrosion-resistant, and is additionally adapted to the base materials of the components even at high temperatures.
• the adhesive strength of the metallic oxide layer that forms, in particular the aluminum oxide cover layer that is formed is increased by adding silicon, and the corrosion resistance of the high-temperature protective layer is thereby significantly increased.
• Adding zirconium and silicon to such an alloy increases the resistance to oxidation and corrosion, and the chromium content can be kept very high.
• the amount of zirconium added to the alloy is 0.2 to 2% by weight, preferably 1% by weight, based on the total weight of the alloy.
• the low solubility of zirconium in an alloy based on nickel leads to the elimination of zirconium-rich phases.
• Such an alloy can optionally be used with a very small amount of yttrium, for example 0.1 to 1% by weight, based on the total weight of the alloy or without yttrium.
• tantalum added to the alloy is present in solution in the matrix. Preferably 0.5 to 3, preferably 1% by weight of tantalum is added to the alloy. If tantalum is added, it may not be necessary to add silicon. Corrosion-resistant protective layers are, however, achieved particularly well if silicon is added to the alloy in addition to the tantalum. If necessary, small additions of titanium can be added to the alloy. However, the amount should only be between 0.1 and 2% by weight based on the total weight of the alloy.
• the additions of silicon, silicon and zirconium or silicon and tantalum enable the alloy to have a very large chromium, aluminum and cobalt content.
• the chromium content can be between 18 and 27% by weight, the cobalt content up to 20% by weight and the aluminum content up to 12% by weight, based on the total weight of the alloy.
• the amounts of chromium, aluminum and cobalt can also be selected to be lower. This enables a very good adaptation to the nickel-containing base material of the components.
• oxide dispersion hardened alloys, from which many components to be protected are also made.
• the protective layer is compatible with these alloys even at very high temperatures.
• a particularly advantageous high-temperature protective layer which has very good oxidation and corrosion resistance, is formed by an alloy which contains 18 to 25% by weight of chromium, 7 to 12% by weight of aluminum, 0.5 to 3% by weight of silicon, 0 , 5 to 1 wt.% Yttrium and 3 to 15 wt.% Cobalt, and the rest of which consists of nickel.
• This alloy can have additions of titanium in amounts of between 0.1 and 2% by weight.
• the above weight data refer to the total weight of the alloy.
• An alloy modified with tantalum by which the adhesive strength of the self-forming aluminum oxide top layer is particularly favored, preferably contains 18 to 25% by weight of chromium, 7 to 12% by weight of aluminum, 0.5 to 3% by weight of silicon, 0.5 up to 1 wt% yttrium, 1 wt% tantalum, 3 to 15 wt% cobalt.
• the rest of the alloy is nickel. This alloy also permits the addition of titanium in amounts between 0.1 and 2% by weight, should this addition be necessary.
• composition of an alloy for forming the high-temperature protective layer in which the yttrium can optionally be dispensed with, preferably has 18 to 27% by weight of chromium, 8 to 12% by weight of aluminum, 0.5 to 3% by weight of silicon, 1% by weight, zirconium, 5 to 20% by weight of cobalt and a proportion of nickel which forms the remaining constituent of the alloy. All weight data in the alloy compositions shown above relate to the respective total weight of the alloy.
• a high-temperature protective layer which is formed from this alloy, has a chromium-rich, aluminum-poorer matrix with a high volume fraction of an aluminum-rich phase, as well as further precipitations with a high zirconium and silicon proportion.
• All of the alloys described here are suitable for the formation of a high-temperature protective layer. Regardless of which of the alloys described above they are formed, an aluminum oxide cover layer is formed in each case under operating conditions on these protective layers, which are not removed even at temperatures that are greater than 900 ° C.
• the gas turbine component to be coated is made of an austenitic material, in particular a nickel superalloy.
• the component is first chemically cleaned and then roughened with a sandblast.
• the component is coated under vacuum using the plasma spraying process.
• An alloy is used for the coating, which contains 18 to 25% by weight of chromium, 7 to 12% by weight of aluminum, 0.5 to 3% by weight of silicon, 0.5 to 1% by weight of yttrium and 3 to 15% by weight.
• the rest of the alloy consists of nickel.
• an alloy which contains 18 to 27% by weight of chromium, 8 to 12% by weight of aluminum, 0.5 to 3% by weight of silicon, 1% by weight of zirconium and 5 to 20% by weight of cobalt has, the remaining portion of the alloy is nickel.
• the plasma spraying process can also be used to apply an alloy which contains 18 to 25% by weight of chromium, 7 to 12% by weight of aluminum, 0.5 to 3% by weight of silicon, 0.5 to 1% by weight of yttrium, 1% by weight. % Tantalum and 3 to 15% by weight cobalt has, the remaining portion of the alloy consists of nickel.
• the material forming the alloy is in powder form and preferably has a grain size of 45 ⁇ m.
• the component is heated to 800 ° C. using the plasma.
• the alloy is applied directly to the base material of the component. Argon and hydrogen are used as the plasma gas.
• the component is subjected to a heat treatment. This takes place in a high vacuum annealing furnace. A pressure of less than 5x10 ⁇ 3 Torr is maintained in it. After reaching the vacuum, the furnace is heated to a temperature of 1100 ° C. The above temperature is held for about 1 hour with a tolerance of about +/- 4 ° C. The heating of the furnace is then switched off. The coated and heat-treated component is slowly cooled in the oven. Its production is finished after cooling.

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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)
• Coating By Spraying Or Casting (AREA)
• Other Surface Treatments For Metallic Materials (AREA)
• Turbine Rotor Nozzle Sealing (AREA)

Applications Claiming Priority (2)

Publications (3)

Family

ID=6298672

Family Applications (1)

Country Status (4)

Cited By (8)

Families Citing this family (9)

Family Cites Families (16)

• 1986
  • 1986-04-15 DE DE19863612568 patent/DE3612568A1/de not_active Withdrawn
• 1987
  • 1987-04-01 EP EP87104785A patent/EP0241807B1/fr not_active Expired - Lifetime
  • 1987-04-01 DE DE8787104785T patent/DE3771546D1/de not_active Expired - Lifetime
  • 1987-04-14 JP JP62090013A patent/JP2574287B2/ja not_active Expired - Lifetime
• 1988
  • 1988-12-29 US US07/291,355 patent/US4909984A/en not_active Expired - Lifetime

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