Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/56—Electroplating: Baths therefor from solutions of alloys
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
  • C25D11/02—Anodisation
  • C25D11/04—Anodisation of aluminium or alloys based thereon
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
  • C25D5/48—After-treatment of electroplated surfaces
  • C25D5/50—After-treatment of electroplated surfaces by heat-treatment

Definitions

• the subject of the present invention is a coated workpiece, which has improved temperature resistance, as well as the provision a method for its production.
• Titanium or titanium alloys low density in combination with high strength, as well as having mechanical strength, only a certain temperature resistance exhibit.
• the maximum Temperature at which no impairment of the workpiece occurs at approx. 500 ° C. If the temperature exceeds this value, oxidation of the Workpiece made of titanium or titanium alloy instead. The workpiece becomes unusable.
• This oxidative degradation is not limited to titanium or titanium alloys instead, but also with all other workpieces from z.
• titanium it has been proven to aluminum layers on the Apply titanium material.
• the aluminum layer applied on the titanium workpiece is heated to a temperature that allows a intermetallic phase from the originally existing aluminum layer with the underlying workpiece of titanium or a titanium alloy becomes.
• This alloy layer shows an increased temperature resistance of about 650 - 700 ° C. Since the surface layer thus formed is very hard and brittle, it is not possible such a workpiece in a subsequent treatment step mechanically deform. It would immediately damage the temperature-stable Surface layer occur.
• WO 02/058923 it is proposed on a titanium sheet roll-coat an aluminum layer.
• the roll cladding becomes at a high temperature of about 500 ° C, a thin aluminum foil on applied to a titanium sheet or a titanium foil. Due to the high processing temperatures the aluminum layer adheres to the titanium sheet.
• This thermal treatment forms a corrosion protective coating that is made a titanium / aluminum alloy. By exposing this surface layer with oxygen, it is converted into a titanium-aluminum mixed oxide layer.
• a disadvantage of the process described in WO 02/058923 is that if the titanium sheet are provided on both sides with an aluminum layer should be applied to both sides of the titanium sheet, this aluminum layer got to. This requires a very high operational effort as either a second station must be present in the Walzplattierstrom, with a second Aluminum layer can be applied, or it is necessary that the Titanium sheet passes through the Walzplattierstrom twice.
• a disadvantage of the described In addition, process is only sheets or foils with an aluminum layer can be provided to from these sheets below To produce molded components. It is not possible, a three-dimensionally designed Workpiece by roll-cladding with an aluminum layer to provide.
• the present invention thus has the object, the disadvantages of the prior art overcome.
• the technical task of the present Invention is in particular the provision of a coated Workpiece, which has a superior high-temperature resistance, as well the provision of a process for the preparation of the coated Workpieces.
• geometrically complex and large workpieces be provided with a protective layer which is homogeneous on the workpiece is distributed.
• the method used for this purpose should be simpler and cheaper be.
• the substrate is the step a) electrically conductive. It is further preferred that the substrate of step a) a metallic substrate and / or a metallized substrate.
• the metallic one Substrate and / or metallized substrate may contain one or more metals, which are preferably transition metals.
• the substrate is selected from the group of Substrates containing the metals magnesium, zinc, tin, titanium, iron, nickel, Chromium, vanadium, tungsten, molybdenum, manganese, cobalt and mixtures thereof and / or alloys thereof.
• Preferred substrates include substrates Titanium, titanium alloys, stainless steel, chromium-nickel alloys, and / or nickel-base alloys.
• the galvanic deposition of the layer (s) (of step a) can be done with any galvanic process, which is known in the art is.
• the layer which is applied in step a), from a non-aqueous electrolyte or from an aqueous electrolyte be applied.
• the layer of step a) is preferably selected from aluminum, Magnesium, tin and mixtures thereof and / or alloys thereof.
• the layer contains an aluminum / magnesium alloy and / or an aluminum / tin alloy.
• the first applied on the substrate layer contains preferably metals selected from the group iron, iron and nickel, tin and nickel, nickel, cobalt, copper, chromium, molybdenum, vanadium or alloys the aforementioned metals.
• the first applied on the substrate layer contains preferably metals selected from the group iron, iron and nickel, tin and nickel, nickel, cobalt, copper, chromium, molybdenum, vanadium or alloys the aforementioned metals.
• the outer layer selected from aluminum, magnesium, tin and mixtures the same and / or alloys thereof applied.
• the layer or the outer layers of a layer structure contains an aluminum / magnesium alloy, it is preferred that the Layer 1 - 80% by weight of magnesium, more preferably 2 - 50% by weight of magnesium, more preferably 3 to 40% by weight of magnesium and most preferably 4 to Contains 30% by weight of magnesium.
• the layer or the outer layers of a layer structure contains an aluminum / tin alloy, it is preferred that the layer 1 - 80% by weight of tin, more preferably 2 to 50% by weight of tin, even more preferred 3 to 30% by weight of tin and most preferably 4 to 25% by weight of tin.
• Each layer applied in step a) preferably has one Layer thickness of 0.1 ⁇ m - 100 ⁇ m.
• the layer thickness is 0.5 ⁇ m to 70 ⁇ m, more preferably 1 ⁇ m-50 ⁇ m, preferably 2 ⁇ m-40 ⁇ m, more preferably 3 ⁇ m-30 ⁇ m, more preferably 4 ⁇ m-28 ⁇ m and most preferably 5 ⁇ m-25 ⁇ m.
• the layer or one of the layers of step a) consists of a aqueous electrolytes can be electrodeposited, so as possible Electrolytes solutions of the aforementioned metals are used. Especially The metals can be used as halides, sulfates, sulfonates or fluoroborates available. The electrolytes may contain other additives, such as. B. complexing Substances.
• non-aqueous Electrolyte When the layer or one of the layers of step a) is non-aqueous Electrolyte is electrodeposited, so it is possible to use all non-aqueous To use electrolytes that are known in the art.
• Possible Electrolytes contain compounds of the aforementioned metals.
• the metals are preferably in the form of halides which are reacted with ethers, in particular diethyl ether can be complexed.
• the metals as acetylacetonates (acac) are present.
• a layer in step a) it is possible for a layer to have a Layer containing aluminum / magnesium, aluminum or a layer containing Aluminum / tin is to use every electrolyte that the professional is common.
• the electrolyte preferably contains organoaluminum compounds of the general formula (I) and (II): M [(R 1 ) 3 Al- (H-Al (R 2 ) 2 ) n -R 3 ] Al (R 4 ) 3 wherein n is 0 or 1, M is sodium or potassium and R 1 , R 2 , R 3 , R 4 may be the same or different, wherein R 1 , R 2 , R 3 , R 4 is a C 1 -C 4 Alkyl group and a halogen-free, aprotic solvent is used as the solvent for the electrolyte.
• the electrolyte used may be a mixture of the complexes K [AlEt 4 ], Na [AlEt 4 ] and AlEt 3 .
• the molar ratio of the complexes to AlEt 3 is preferably 1: 0.5 to 1: 3 and more preferably 1: 2.
• the electrolytic deposition of the layer can be carried out using a soluble anode containing the metals intended for deposition, be performed.
• This anode can either be intended for deposition contain mentioned metals as a metal alloy or it can be several soluble anodes of the respective pure metals are used. If one Layer containing an aluminum / magnesium alloy deposited should, so it is possible, a soluble aluminum and a likewise soluble magnesium anode or an anode made of an aluminum / magnesium alloy to use.
• the electrolytic coating of a non-aqueous electrolyte is preferably carried out at a temperature of 80 - 105 ° C.
• Prefers is a temperature of the plating bath of 91 - 100 ° C.
• the substrate is before in step a) the layer is applied galvanically, one the electric current applied conductive layer.
• the electric current conducting layer can with any method applied to the substrate, which the person skilled in the art is known.
• the electric current conducting layer is through Metallization applied to the substrate.
• step b) of the method according to the invention the temperature and / or the duration of the heat treatment chosen so that at least in the border region between the substrate and the applied layer of step a) an alloy, containing metal of the surface layer of the substrate and metal and / or metal alloys of the deposited layer is formed.
• the temperature and / or the duration of the heat treatment chosen so that they on the properties of the substrate and the specific coating applied are coordinated.
• this temperature is preferably ⁇ 650 ° C.
• the heat treatment generally forms on the surface of the coated workpiece an intermetallic phase at which the in step a) applied layer either partially or continuously in the intermetallic Phase is converted.
• the coated substrate below / along to temper the liquidus line of the resulting material mixture.
• the liquidus line is the melting temperature of the material mixture formed in dependence of the specific composition.
• aluminum layer is applied to a titanium substrate, the proportion of aluminum is first in the surface layer 100%.
• the heat treatment will be form a titanium-aluminum alloy which has a specific melting point Has. Now if the temperature during the heat treatment is chosen so that just reached the melting point of the alloy formed, or scarce is below, so this heat treatment is as a heat treatment below / along to understand the liquidus line of the resulting material mixture.
• the heat treatment of the coated Substrate is carried out so that on the surface of the coated Substrates a liquid phase is formed.
• a liquid phase is formed.
• the heat treatment can be carried out under a protective gas atmosphere.
• a protective gas is used, which with the coated material does not react.
• the protective gas is a Noble gas, e.g. Argon.
• the heat treatment takes place in a protective gas atmosphere.
• the heat treatment also done in air.
• the temperature of the heat treatment of step b) is preferably between 400 ° C and 1000 ° C, more preferably between 450 ° C and 900 ° C and most preferably between 500 ° C and 800 ° C.
• the duration of the heat treatment of step b) can be between one second and 10 hours. It is preferably between 1 minute and 5 hours, and most preferably between 2 minutes and 3 hours. Alternatively, it is possible that the heat treatment of step b) then takes place, when the workpiece is installed at its destination. So it is possible that z. As a motor element or turbine element during its first use is heated so that the diffusion of the surface layer of the substrate with the applied layer takes place.
• the layer undergo further treatment.
• the treatment may be an anodic oxidation, which preferably is the anodizing of the layer.
• Such a treatment is an option if in step a) a layer containing aluminum was applied.
• the coated used in the process of the present invention Workpiece is preferably a rack goods, a bulk goods, a Continuous product or a molding.
• the coated workpiece is a Wire, a sheet metal, a screw, a nut, a concrete anchorage, a machine component, an engine, an engine part or a turbine blade.
• Workpieces have excellent long-term resistance to thermal Stress. They show during repeated heating and cooling cycles, that, due to the temperature load, over a long period of time no Corrosion of the workpiece occurs.
• the coated show Workpieces improved resistance to oxidation or other corrosive High temperature influences, in which the uncoated workpiece, ie the substrate already begins to corrode.
• a coated titanium substrate shows accordingly the present invention, if it is z.
• a temperature stability in the range from 750 - 1000 ° C.
• the coated substrates of the present invention are opposite those of the prior art significantly more temperature-resistant.
• the galvanic Procedures to obtain highly pure layers are germs that pass through Impurity, not present in the layer.
• form highly pure diffusion layers which due to the high purity of a improved stability, above all, have improved temperature stability.
• Another advantage of the method of the present invention is that it is more cost effective compared to the prior art methods is.
• the galvanic application of a layer is cheaper than z. B. the Plasma spraying.
• Another advantage is that both by the plasma spraying as z.
• chemical vacuum deposition or physical vacuum deposition the substrate is more thermally stressed. This leads in particular geometrically complex substrates to a thermal distortion of the workpiece.
• the thermal load of the workpiece in step a) significantly lower. hereby it is possible to produce coated workpieces with lower manufacturing tolerances which has significant advantages in subsequent operation, e.g. turbine blade causes. Furthermore, lower manufacturing tolerances at thermally highly loaded coated workpieces an increased level of safety.
• the workpieces produced by the method of the present invention such as B. Turbine blades when installed in a gas turbine, higher safety margins compared to the turbine blades of the State of the art.
• a sheet metal of the size 5 x 25 x 1 mm made of titanium becomes by galvanic deposition from a non-aqueous electrolyte with a layer of aluminum with provided a layer thickness of 12 microns.
• the titanium sheet provided with a layer of aluminum is heated in an oven to the temperature indicated in Table 1. The temperature is maintained for the period indicated in Table 1. Subsequently, the coated titanium sheet is removed from the oven and cooled in an air atmosphere. The furnace is either exposed during the alloying process with ambient air or with the protective gas argon. number Heating speed temperature hold time cooling down the atmosphere A Fast 700 ° C 5 min air cooling Surroundings B Fast 700 ° C 5 min. air cooling argon C Slowly 650 ° C 30 min air cooling argon
• the coated titanium sheets numbered A, B and C are heated in an oven to the temperature indicated in Table 2. After the holding time shown in Table 1, the material sample is taken out of the oven, cooled, and the corrosion of the coated titanium sheet is visually evaluated. This shows that the applied layer excellent corrosion resistance, even at very high temperatures, such. B. causes 900 ° C. An uncoated titanium sheet would be permanently damaged by oxidation at temperatures above 650 ° C. Even with a hold time of 384 hours at 700 ° C, no appreciable corrosion of the coated titanium sheet occurs.
• a titanium sheet which according to produced by the process of the present invention, improved corrosion resistance having.
• the so coated workpieces are opposite those of the prior art significantly more corrosion resistant.
• the Corrosion resistance at elevated temperatures significantly improved.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Other Surface Treatments For Metallic Materials (AREA)

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Cited By (7)

Citations (7)

• 2003
  • 2003-11-14 EP EP03026218A patent/EP1533401A1/fr not_active Withdrawn

Patent Citations (7)

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