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
  • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
  • C23C4/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
• • 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
  • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
  • C23C4/04—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the coating material
  • C23C4/06—Metallic material
  • C23C4/073—Metallic material containing MCrAl or MCrAlY alloys, where M is nickel, cobalt or iron, with or without non-metal elements
• • 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
  • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
  • C23C4/12—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the method of spraying
  • C23C4/134—Plasma spraying
• • 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
  • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
  • C23C4/12—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the method of spraying
  • C23C4/137—Spraying in vacuum or in an inert atmosphere
• • 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
  • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
  • C23C4/18—After-treatment

Definitions

• the invention relates to the field of metals and alloys, and more particularly to the field of nickel alloys.
• the invention relates to a method for repairing monocrystalline materials, which are frequently used for components subject to high temperatures, such as the blades of stationary gas turbines or aircraft turbines.
• Kazuhoro et al. m a method known with which a defective turbine blade can be repaired.
• no epitaxial growth takes place on the monocrystalline substrate, as a result of which a polycrystalline microstructure is produced which does not regularly have the mechanical properties of the original substrate.
• US Pat. No. 5,732,467 A1 describes a method for repairing cracks in the outer surfaces of components which have a superalloy with a directionally oriented microstructure.
• the process described therein coats and seals the outer surfaces of directionally solidified and monocrystalline structures by coating the defective region using a high speed oxy-fuel process (also referred to herein as HVOF) followed by hot isostatic pressing of the corresponding component.
• HVOF high speed oxy-fuel process
• HVOF hot isostatic pressing
• the fracture site must be capable of being able to be welded and at the same time allowing an orientation direction of the newly applied material which has the same orientation as the rest of the material. For this purpose, a temperature gradient is needed, which supports the orientation orientation.
• the laser beam buildup welding described here is, in principle, a suitable method for correspondingly welding such break points due to its specific process parameters, such as small local energy input and controlled material input.
• the challenges of this process are to achieve a perfect single-crystalline, crack-free area, since only a small amount of unstable energy distribution can regularly produce polycrystalline areas.
• process parameters may result in consistent epitaxial growth on a single crystalline substrate, for example, where the ratio between the Temperature gradient in the weld zone and the solidification rate is higher than a material-dependent threshold.
• the temperature of the melt decides whether a heterogeneous nucleation or epitaxial growth occurs.
• the document shows that directional solidification has also been observed during plasma spraying.
• the object of the invention is to provide a repair method for single-crystalline materials, in particular for single-crystal stationary turbine blades and / or aircraft turbines, in which the added material has largely the same microstructure and crystal orientation as the material to be repaired.
• the object of the invention is achieved by a method for repair of monocrystalline materials according to the main claim.
• epitaxial growth can be generated on a monocrystalline material (substrate) by the method of vacuum plasma spraying.
• the material to be repaired typically comprises a metallic alloy, in particular a nickel-base alloy or also a cobalt-base alloy.
• plasma spraying is understood to mean a coating process which is carried out with the aid of a plasma and is not based on plasma polymerization.
• vacuum spraying means a coating process which is carried out by atmospheric oxygen in a vacuum chamber at a pressure of 1 to 200 mbar in order to avoid the oxidation of the coating material.
• a coating material in the optimal case, the same material is used from which the substrate material consists. Since the components to be repaired, such as blades of stationary gas turbines and / or aircraft turbine blades, are generally materials subjected to high temperatures, suitable coating materials are, in particular, all high-temperature metallic alloys or superalloys.
• the known high-temperature alloys currently include predominantly solid and high-strength nickel-based alloys or cobalt-base alloys.
• superalloys are generally metallic materials of complex composition (iron, nickel, platinum, chromium or cobalt-based with additions of elements Co, Ni, Fe, Cr, Mo, W, Re, Ru, Ta, Nb, Al, Ti, Mn , Zr, C and B) for high temperature applications. They are usually tinder and high heat resistant. They can be produced both by melting metallurgy and by powder metallurgy.
• the polycrystallinity of thermally sprayed metallic layers can be suppressed by spraying an at least similar alloy as that of the monocrystalline substrate material onto the heated and polished substrate surface under greatly reduced pressure and in an argon atmosphere .
• the term "identical" means that the proportion of alloying elements of the substrate and the layer is only slightly different and that after heat treatment they have a nearly identical microstructure.
• the temperatures of the substrate are so high that the solidification rate of the molten powder particles is greatly reduced, but the melting temperature of the substrate is not reached.
• substrate temperatures between 700 ° C and temperatures just below the melting temperature of the substrate used, d. H.
• d. H For example, 50 ° C below the melting temperature of the substrate set.
• the solidification rate can not be accurately measured in this process adversely, but it should preferably be less than 100 mm / s.
• Nucleation does not take place anywhere within the deposited layer at this condition, but advantageously directly at the substrate surface where it aligns with the predetermined orientation of the single crystal of the substrate. An epitaxial growth of the deposited layer on the substrate is thus possible.
• the heating of the area of the substrate to be repaired by a meander movement of a plasma torch without powder promotion takes place over the surface of the substrate.
• the substrate can be heated in various ways: electrically, inductively or by electromagnetic radiation.
• the entire substrate is advantageously heated to at least 700 ° C., advantageously to at least 800 ° C., preferably even to approximately 1100 ° C.
• the substrate itself is indeed heated, but not up to temperatures at which the substrate melts.
• the powder melted in the plasma theoretically strikes a solid, polished substrate surface, nucleates there and can thus advantageously solidify in the same crystal orientation.
• a melting of the surface of the substrate locally by a few ⁇ can not be excluded.
• This process step is clearly distinguishable from hitherto known repair methods, such as, for example, welding methods using a laser, in which the substrate itself is often also melted at least on the surface to be repaired.
• a vacuum plasma spray system with powder delivery system and a device for heating a substrate (component) to temperatures of about 700 ° C. to 1300 ° C. are preferably required.
• the area to be repaired on the component should preferably be polished.
• the repair process of the damaged component usually begins with the removal of the bondcoat and Topcoats the thermal barrier coating by hydrofluoric acid, also called stripping (English), if such are present on the substrate material.
• the critical damage is identified and regularly removed, ground and polished by a machining process. Grinding can be done, for example, with abrasive paper of grain size: 320, 640, 1200 and 4000.
• the subsequent polishing can be done with a diamond suspension on a soft cloth, for example, first a suspension with diamond particles having an average particle size of about 3 ⁇ and then a suspension with diamond particles having an average particle size of about 1 prn is used.
• a light microscope is suitable for checking the polished substrate surface.
• the treated substrate surface should be free from scratches.
• the masking of the undamaged areas of the substrate takes place.
• the removed area can be rebuilt by the inventive method.
• Layer thicknesses of about 10 pm up to several mm can be realized.
• the layer thickness during a single run over / spraying of the plasma torch can be set individually and results from the robot speed in connection with the powder feed rate.
• the entire layer thickness is regularly realized by repeated driving over / spraying. For example, a one-time transition results in a layer thickness of approximately 25 ⁇ m.
• the layer can be built arbitrarily thick.
• an excessively high application rate during the single transition should not be carried out, since otherwise it can disadvantageously lead to increased pore formation. A polish between the individual transitions is not necessary.
• the application of several layers is possible according to the invention, provided that between the applications of the layers in each case a polishing of the corresponding surface. This may be necessary, for example, if after a first repair and inspection of an area further repair appears necessary. In this respect, the repaired substrate can then be polished again and used for further repair.
• the applied layer is usually very stress-free due to the high application temperature, there is no physical limit for a maximum layer thickness that can be applied by the method according to the invention.
• a layer thickness range of a few pm up to about 5 mm can be achieved by the method.
• a post-processing and possibly a restoration of the original component dimensions and a heat treatment for example in the form of solution annealing and precipitation annealing.
• a new thermal barrier coating can be applied again and, if necessary, new cooling holes can be drilled.
• the inventive method thus advantageously offers the possibility to offset defective and discarded single-crystal blades in a new condition.
• the optimal process parameters can be determined by means of some preliminary tests by a specialist.
• CET models and / or microstructure diagrams already exist, for example for CMSX-4® [5] (see FIG. 1), which can be used.
• the temperature to be set is alloy-specific.
• the additional further heating by the plasma jet is necessary so that an oxidation of the surface is suppressed.
• the hydrogen contained in the plasma jet creates reducing conditions.
• the desired temperatures should be as high as possible, so a temperature of 50 K below the melting temperature is desirable.
• the temperature difference to the remaining substrate / component should be as low as possible, since the area to be repaired should advantageously have the most homogeneous possible temperature distribution.
• a high substrate temperature usually has an advantageous effect on the formation of residual stresses. Residual stresses can disadvantageously lead to spalling of the previously applied layer. The higher the substrate temperature, the lower the resulting residual stresses.
• An inhomogeneous temperature distribution of the component during the injection process would increase the susceptibility to residual stresses in the entire component.
• the essential difference in the method according to the invention is the additional external heating of the substrate. Only with this it is possible the desired microstructure with the superior mechanical properties of the monocrystalline alloys and to achieve minimum residual stresses. A heating of the component only by the introduced energy of the plasma would be sufficient in contrast.
• FIG. 2 schematically shows a solidification model for the method described.
• the molten powder particles hit the heated surface of the sample at the speed v p .
• the temperature near the substrate is below the melting temperature.
• There the dendrites and the interdendritic area are already frozen. Above it lies a transitional area in which the solidification front lies and the dendrites form.
• the interdental area has not yet solidified.
• the molten particles hit the substrate.
• the temperature is above the melting temperature.
• CMSX-4 ® is a registered trademark for a single crystal (SC) alloy of the firm Cannon-Muskegon, MI (USA).
• ERBO / 1 is a second generation single crystal nickel based superalloy from Doncasters Precision Casting, Bochum (Germany). Table 1 :
• substrate samples measuring 32 mm ⁇ 20 mm ⁇ 2.5 mm and a hole with a diameter of 1 mm and a length of 10 mm are produced from ERBO-1 plates by means of spark erosion.
• FIG. 3 shows the sample geometry used here.
• the substrate samples are ground and polished.
• the surface was first treated successively with 320, 640, 1200 grit paper and finally with 4000 grit.
• the subsequent polishing was carried out by means of a saturated with a diamond suspension soft cloth.
• a cloth was used with a suspension with diamond particles having an average particle size of about 3 ⁇ and polished the surface circular.
• a further cloth with a suspension with diamond particles having a mean particle size of about 1 ⁇ m was used and the surface was polished again.
• An insulated SiN flat heater 2 with a power of 1000 W allows the heating of the sample 4 up to 1 100 ° C in a vacuum, preferably at 1 to 200 mbar.
• a SiC heat plate 3 On the heater 2 is a SiC heat plate 3, which ensures a more constant temperature of the sample.
• the heater 2, the heat-conducting plate (SiC) 3 and the sample 4 are surrounded by a prepared insulation 1, 5, which reduces the convection.
• the application of the sprayed layer or of the layers takes place via an opening in the diaphragm 6.
• the temperature is controlled by a controller and by the temperature measurement in the sample with a thermocouple. Both the cables of the thermocouple and the power cable of the heater are placed separately by means of implementation in the vacuum chamber.
• the powder feeder Sulzer Metco Powder Feeder Twin-120-V is filled with CMSX-4 ® powder with spherical particles with a mean geometric particle diameter of 25 - 60 pm.
• the mean particle size was determined by means of laser diffraction with the Horiba LA-950V2 device from Retsch.
• the powder having a mean particle diameter of 38.53 mm for example, the D 10 value to 27.70 ⁇ , the D 50 value to 39.77 ⁇ and the Dg 0 value to 55.27 ⁇ .
• the powder was previously stored for 2 hours at 150 ° C. This step is for removing water in the powder.
• the sample heater is activated first. From a temperature of approx. 300 ° C, the plasma flame of the F4 - VB from Oerlinkon Metco supports the heating of the substrate surface until the coating temperature of approx. 900 ° C is reached.
• the plasma gas contained in the argon containing plasma gas (plasma gas: 50 NLPM argon and 9 NLPM hydrogen) thereby provides for reducing conditions.
• the oxygen contained in the argon can be selectively oxidized without this reacts with the substrate surface and disadvantageously forms an oxide layer.
• the parameters selected for the coating can be found in Table 2.
• solution heat treatment may be necessary in order to reduce any inhomogeneities in the structure of the coating which may be present.
• the aforementioned heat treatment can advantageously be carried out under pressure with a hot isostatic press (HIP).
• HIP hot isostatic press
• the pressure-assisted heat treatment regularly reduces pores in the microstructure.
• Solution annealing 1300-1315 ° C in protective atmosphere for 6 hours followed by cooling from 150-400 ° C / min to about 800 ° C.
• Elimination annealing 1 140 ⁇ 10 ° C for 4 hours, then 870 ⁇ 10 ° C for 16 hours in a controlled atmosphere.
• FIGS. 5a and 5b are scanning electron micrographs of transverse sections of the samples treated in this way, which show directional solidification on the monocrystalline substrate.
• FIG. 5a shows the monocrystalline substrate onto which the repair layer has been injected.
• the columnar structure of the grains in the polycrystalline layer is an indication of directional solidification.
• an area with a similar gray color as the substrate is noticeable. This means due to the crystal orientation contrast in the backscattered electron image of the scanning electron microscope, the same crystal orientation for substrate and layer in this same-colored area.
• Figure 5b represents a higher magnification of this range.
• no oxide is present. This is very important for the nucleation of the molten powder on the substrate.
• the dark ⁇ '-precipitates in the ⁇ matrix can be recognized.
• FIG. 6a and 6b show scanning electron micrographs of cross sections of the same sample, which was first solution-annealed after the coating with the parameters listed above and then precipitation annealed.
• FIG. 6a shows the transition region from the monocrystalline substrate to the repair layer.
• the white dashed line marks the former interface.
• the repair layer has only a slightly increased pore density, which would disappear by a pressure-assisted heat treatment by means of HIP.
• the smaller black dots indicate Al 2 0 3 inclusions, which were caused by slight oxidation of the spray material.
• the porosity in the sprayed layer is determined by the application rate resulting from the powder feed rate and the robot speed. As the order rate decreases, the layer's viscosity is also reduced. Furthermore, it was found that the size of the solidified grains depends on the powder size used. Thus, the size of the directionally solidified grains increases with higher particle diameters.
• the quality of the argon should be improved with respect to the oxygen content.
• Another reason for the formation of an oxide layer could be an unfavorable robot movement during the injection process. This should preferably be adjusted so that the sample does not leave the area of influence of the plasma torch. If there is no nucleation on the polished surface of the area to be repaired, although no oxide layer is present, the temperature of the workpiece to be repaired must be increased.
• Kazuhiro Ogawa and Dowon Seo (201 1). Repair of Turbine Blades Using Cold Spray Technique Advances in Gas Turbine Technology Ernesto Benini (Ed.), InTech, DOI: 10.5772 / 23623. Available from: https://www.intechopen.com/books/advances-in-gas-turbine-technology / repair-of-turbine-blades-using-cold-spray-technique.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Plasma & Fusion (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Coating By Spraying Or Casting (AREA)
• Turbine Rotor Nozzle Sealing (AREA)
• Crystals, And After-Treatments Of Crystals (AREA)
• Other Surface Treatments For Metallic Materials (AREA)

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• 2017
  • 2017-10-26 DE DE102017009948.0A patent/DE102017009948A1/de not_active Withdrawn
• 2018
  • 2018-10-04 WO PCT/DE2018/000281 patent/WO2019080951A1/de unknown
  • 2018-10-04 US US16/649,994 patent/US20200216942A1/en not_active Abandoned
  • 2018-10-04 CN CN201880062701.4A patent/CN111373068A/zh active Pending
  • 2018-10-04 PL PL18796582T patent/PL3701060T3/pl unknown
  • 2018-10-04 EP EP18796582.7A patent/EP3701060B1/de active Active
  • 2018-10-04 ES ES18796582T patent/ES2886226T3/es active Active

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