EP3266902B1 - Oxide film removal method - Google Patents
Oxide film removal method Download PDFInfo
- Publication number
- EP3266902B1 EP3266902B1 EP16792573.4A EP16792573A EP3266902B1 EP 3266902 B1 EP3266902 B1 EP 3266902B1 EP 16792573 A EP16792573 A EP 16792573A EP 3266902 B1 EP3266902 B1 EP 3266902B1
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- EP
- European Patent Office
- Prior art keywords
- oxide film
- oxide
- metal
- removing method
- superalloy
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- 238000000034 method Methods 0.000 title claims description 62
- 229910000601 superalloy Inorganic materials 0.000 claims description 107
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 83
- 239000002253 acid Substances 0.000 claims description 50
- 239000010953 base metal Substances 0.000 claims description 46
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 42
- 229910052751 metal Inorganic materials 0.000 claims description 42
- 239000002184 metal Substances 0.000 claims description 42
- 229910052759 nickel Inorganic materials 0.000 claims description 41
- 238000010438 heat treatment Methods 0.000 claims description 34
- 229910052782 aluminium Inorganic materials 0.000 claims description 15
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 15
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 claims description 14
- 238000004140 cleaning Methods 0.000 claims description 8
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 6
- 239000010941 cobalt Substances 0.000 claims description 5
- 229910017052 cobalt Inorganic materials 0.000 claims description 5
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 5
- 229910044991 metal oxide Inorganic materials 0.000 claims description 5
- 150000004706 metal oxides Chemical class 0.000 claims description 5
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 4
- 239000010936 titanium Substances 0.000 claims description 4
- 229910052719 titanium Inorganic materials 0.000 claims description 4
- 239000007789 gas Substances 0.000 description 31
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 28
- 229910000480 nickel oxide Inorganic materials 0.000 description 19
- GNRSAWUEBMWBQH-UHFFFAOYSA-N oxonickel Chemical compound [Ni]=O GNRSAWUEBMWBQH-UHFFFAOYSA-N 0.000 description 19
- 239000000463 material Substances 0.000 description 14
- QDOXWKRWXJOMAK-UHFFFAOYSA-N dichromium trioxide Chemical compound O=[Cr]O[Cr]=O QDOXWKRWXJOMAK-UHFFFAOYSA-N 0.000 description 13
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 7
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 6
- FBAFATDZDUQKNH-UHFFFAOYSA-M iron chloride Chemical compound [Cl-].[Fe] FBAFATDZDUQKNH-UHFFFAOYSA-M 0.000 description 6
- 238000005219 brazing Methods 0.000 description 5
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 5
- 238000002474 experimental method Methods 0.000 description 4
- 239000007788 liquid Substances 0.000 description 4
- 231100000331 toxic Toxicity 0.000 description 4
- 230000002588 toxic effect Effects 0.000 description 4
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 3
- 238000004833 X-ray photoelectron spectroscopy Methods 0.000 description 3
- 229910045601 alloy Inorganic materials 0.000 description 3
- 239000000956 alloy Substances 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 3
- 238000001514 detection method Methods 0.000 description 3
- 229910017604 nitric acid Inorganic materials 0.000 description 3
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 239000003638 chemical reducing agent Substances 0.000 description 2
- 229910052593 corundum Inorganic materials 0.000 description 2
- 230000008034 disappearance Effects 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 238000005498 polishing Methods 0.000 description 2
- 229910001845 yogo sapphire Inorganic materials 0.000 description 2
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 1
- 208000025599 Heat Stress disease Diseases 0.000 description 1
- 229910021578 Iron(III) chloride Inorganic materials 0.000 description 1
- 229910000428 cobalt oxide Inorganic materials 0.000 description 1
- IVMYJDGYRUAWML-UHFFFAOYSA-N cobalt(ii) oxide Chemical compound [Co]=O IVMYJDGYRUAWML-UHFFFAOYSA-N 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- -1 fluoride ions Chemical class 0.000 description 1
- 150000004820 halides Chemical class 0.000 description 1
- 231100000086 high toxicity Toxicity 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 229910000040 hydrogen fluoride Inorganic materials 0.000 description 1
- RBTARNINKXHZNM-UHFFFAOYSA-K iron trichloride Chemical compound Cl[Fe](Cl)Cl RBTARNINKXHZNM-UHFFFAOYSA-K 0.000 description 1
- 238000000053 physical method Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Images
Classifications
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- 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
- C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
- C23F1/00—Etching metallic material by chemical means
- C23F1/10—Etching compositions
- C23F1/14—Aqueous compositions
- C23F1/16—Acidic compositions
- C23F1/28—Acidic compositions for etching iron group metals
-
- 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
- C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
- C23F1/00—Etching metallic material by chemical means
-
- 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
- C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
- C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
- C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
- C23G1/10—Other heavy metals
-
- 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
- C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
- C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
- C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
- C23G1/12—Light metals
- C23G1/125—Light metals aluminium
-
- 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
- C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
- C23G5/00—Cleaning or de-greasing metallic material by other methods; Apparatus for cleaning or de-greasing metallic material with organic solvents
Definitions
- the present invention relates to an oxide film removing method, and especially, to a method of removing an oxide film formed in a superalloy surface.
- Components of an aircraft engine, a turbine, a plant and so on are sometimes used in a high-temperature environment or a high stress environment. It is known that a part used in the high-temperature environment or the high stress environment is formed of a superalloy material.
- Patent Literature 1 discloses a method of cleaning a metal product.
- the method described in Patent Literature 1 contains removing the surface oxide of the superalloy part by using halide.
- Patent Literature 2 discloses a method of cleaning and repairing a superalloy article.
- the method described in Patent Literature 2 contains reducing an oxide in a crack of the superalloy part by using gaseous active fluoride ions.
- Patent Literature 3 discloses a method in place of fluoride ion cleaning.
- the method described in Patent Literature 3 contains expanding a narrow crack, removing a part of metal oxide with an acid solution, and removing a part of the metal oxide by cleaning in a high-temperature vacuum atmosphere or a high-temperature hydrogen atmosphere.
- An object of the present invention is to provide an oxide film removing method that can effectively remove an oxide film in a superalloy surface without using a highly toxic gaseous fluoride.
- An oxide film removing method in some embodiments is a method of removing an oxide film formed in a surface of a superalloy part that contains a first metal as a base metal and a second metal different from the first metal.
- the oxide film contains oxide of the base metal and oxide of the second metal.
- the oxide film removing method includes arranging the superalloy part inside a heating chamber; preparing a reduction gas atmosphere or a vacuum atmosphere inside the heating chamber; reducing the oxide of the base metal of an oxide film to the base metal by heating the inside of the heating chamber in a condition that the reduction gas atmosphere or the vacuum atmosphere is maintained; and carrying out acid processing to apply acid solution to the superalloy part after the reduction.
- the acid processing includes: dissolving the base metal; and separating the oxide of the second metal left without being reduced through the reduction from the superalloy part together with the dissolved base metal.
- the acid processing may not be carried out before the reduction.
- the base metal may be nickel or cobalt.
- the oxide of the second metal is a metal oxide in which thermodynamic stability is higher than that of the oxide of the base metal.
- the second metal may contain at least one of aluminum, titanium, and chrome.
- the second metal may contain aluminum.
- the acid solution may contain hydrochloric acid.
- the superalloy part may have a crack, and the oxide film may contain an oxide film formed in a surface of the crack.
- the method may not contain expanding a crack physically.
- the oxide film removing method can be provided in which the oxide film in the superalloy surface can be effectively removed without using a highly toxic gaseous fluoride.
- Superalloy means alloy usable (in other words, sustainable in strength) in a high temperature environment (e.g. 800 °C or above).
- a “base metal” means a metal component with the highest content (weight %) of the metal components contained in alloy.
- FIG. 1 is a sectional view schematically showing an example of a superalloy part 1.
- the superalloy part 1 contains a base material 10 and an oxide film 20.
- the oxide film 20 is formed by, for example, exposing the superalloy part 1 to air (oxygen) under the high-temperature environment. Note that a boundary between the base material 10 and the oxide film 20 is clearly illustrated in FIG. 1 . However, in actual, the boundary between the base material 10 and the oxide film is not always definite.
- the base material 10 is superalloy that contains base metal and second metal.
- the base metal is nickel and the second metal is aluminum.
- the oxide film 20 contains the oxide of base metal and the oxide of second metal.
- the oxide of base metal is nickel oxide (e.g. NiO).
- the oxide of second metal is aluminum oxide (e.g. Al 2 O 3 ).
- a region 22 where nickel oxide is rich is schematically shown by a symbol of a white triangle.
- a region 24 where aluminum oxide is rich is schematically shown by a symbol of a white circle.
- FIG. 2 is a sectional view schematically showing the superalloy part 1 after nickel oxide is reduced to nickel.
- FIG. 2 a region 32 where nickel has become rich through the reduction is schematically shown by a symbol of black triangle. Note that although not illustrated to FIG. 2 , nickel oxide that exists in the region 24 where aluminum oxide is rich has also been reduced to nickel.
- aluminum oxide is a compound that is stable thermodynamically, the state of oxide is maintained even if the aluminum oxide is arranged in the high-temperature reduction gas atmosphere or the high-temperature vacuum atmosphere. Therefore, the aluminum oxide is difficult to be reduced more than the nickel oxide.
- the region 32 where nickel is rich is dissolved with the hydrochloric acid solution (more specifically, nickel in the region where nickel is rich is dissolved by the hydrochloric acid solution). Also, the hydrochloric acid solution enters a cavity (or a passage) formed through the dissolving of nickel. As a result, nickel in a region other than the region 32 where nickel is rich (for example, nickel in the region 24 where aluminum oxide is rich) is also dissolved by the hydrochloric acid solution.
- FIG. 3 is a sectional view schematically showing the superalloy part 1 during application of the hydrochloric acid solution.
- the region 32 where nickel is rich disappears through the dissolution and a cavity 42 (or a passage) is formed.
- a smaller cavity 43 is formed from the cavity 42. Due to existence of the cavity 42 and the cavity 43, bonding force between a portion of the oxide film 20 and another portion of the oxide film 20, and bonding force between the oxide film 20 and the base material 10 are reduced.
- FIG. 4 is a sectional view schematically showing the superalloy part 1 during the application of hydrochloric acid solution, and showing the state after a time passed from the state shown in FIG. 3 .
- the aluminum oxide or the region 24 where aluminum oxide is rich
- the superalloy part 1 or the base material 10
- the dissolved nickel due to the reduction of bonding force between the oxide film 20 and the base material 10.
- the cavity 42 or cavity 43 as shown in FIG. 3 is difficult to be formed, since the nickel oxide is difficult to be dissolved with the hydrochloric acid solution more than nickel.
- the oxide of base metal is reduced to the base metal before the application of hydrochloric acid solution, the cavity 42 or cavity 43 as shown in FIG. 3 is easy to be formed.
- the aluminum oxide that is difficult to be reduced becomes able to be separated from the superalloy part 1 (or the base material 10).
- the base metal is nickel
- the base metal is not limited to nickel.
- the base metal may be cobalt.
- the second metal contained in the superalloy part 1 is aluminum has been described.
- the second metal is not limited to aluminum.
- the second metal may be chrome or titanium.
- the second metal may contain at least one of aluminum, titanium, and chrome.
- the second metal may contain aluminum and chrome.
- the acid solution is hydrochloric acid solution.
- the acid solution is not limited to the hydrochloric acid solution, and is optional.
- the acid solution may be an acid solution of whatever kind if the acid solution can dissolve the base metal.
- the acid solution may be mixed acid (for example, the mixed acid of hydrochloric acid and nitric acid).
- FIG. 5 is a sectional view schematically showing an example of the superalloy part 1.
- the oxide film 20 is formed in the surface of the superalloy part 1.
- the oxide film 20 may be formed in the whole surface of the superalloy part 1 and may be formed in a part of the surface of the superalloy part 1.
- the superalloy part 1 is a superalloy part that has a crack 3.
- the oxide film 20 is formed in the surface of crack 3, too.
- the base metal of the superalloy part 1 is nickel.
- a first metal with the highest content weight% is, for example, nickel.
- the superalloy part 1 may be a nickel-based superalloy part (in other words, the superalloy part in which the content of the nickel is 50 weight% or above).
- aluminum may be contained as the alloy component in the superalloy part 1.
- the second metal that is different from the first metal is, for example, aluminum.
- the oxide of base metal (e.g. nickel) and the oxide of second metal (e.g. aluminum) are contained in the oxide film in the surface of superalloy part 1.
- FIG. 6 is a sectional view schematically showing an example of the reduction processing device 5.
- the reduction processing device 5 includes, for example, a main unit section 51, a door 52, a heater 53, a temperature sensor 54, a controller 55, a gas supply pipe 56, a first valve 57, a gas discharge pipe 58, and a second valve 59.
- the main unit section 51 accommodates the superalloy part 1 as an object to be processed.
- the door 52 opens and closes an opening of the main unit section 51.
- the main unit section 51 and the door 52 functions as a heating chamber 50 when the superalloy part 1 is to be reduction processed (more specifically, a heating sealed chamber).
- the heater 53 is a device for heating the heating chamber 50.
- the heater 53 is a device for heating the heating chamber or the superalloy part 1 arranged in the heating chamber.
- the temperature sensor 54 is a sensor to measure a temperature in the heating chamber or a temperature of the superalloy part 1. Data acquired by the temperature sensor 54 is sent to the controller 55.
- the controller 55 controls the heater 53 based on the data received from the temperature sensor 54. By controlling the heater 53 by the controller 55, the temperature in the heating chamber or the temperature of the superalloy part 1 is maintained in a desired temperature.
- the gas supply pipe 56 is used to supply reduction gas into the heating chamber 50.
- the first valve 57 is arranged in the passage of gas supply pipe 56 and opens and closes the passage.
- the reduction gas is hydrogen gas. Note that when the reduction processing device 5 is a device which carries out the reduction processing in a vacuum atmosphere, the gas supply pipe 56 and the first valve 57 may be omitted.
- the gas discharge pipe 58 is used to discharge air (gas) from the heating chamber 50.
- the gas discharge pipe 58 is connected with a vacuum pump (not illustrated).
- the second valve 59 is arranged in the passage of gas discharge pipe 58 and opens and closes the passage.
- FIG. 7 is a sectional view schematically showing an example of the acid processing device 6.
- the acid processing device 6 has a liquid bath 60.
- Acid solution 62 is filled in the liquid bath 60.
- the superalloy part 1 as the object to be processed is arranged in the liquid bath 60.
- FIG. 8 is a flow chart showing the procedure of removing the oxide film.
- the superalloy part 1 that contains nickel (first metal) as the base metal and aluminum (second metal different from nickel) is arranged in the heating chamber 50.
- the oxide film 20 is formed in the surface of the superalloy part 1. Also, the oxide film 20 contains nickel oxide (the oxide of base metal) and aluminum oxide (the oxide of second metal).
- a reduction gas atmosphere or a vacuum atmosphere is prepared in the heating chamber 50.
- the gas in the heating chamber 50 is first discharged through the gas discharge pipe 58. After that, the reduction gas is supplied into the heating chamber 50 through the gas supply pipe 56.
- the reduction gas is hydrogen (H 2 ) gas.
- the grade of hydrogen gas to be supplied into the heating chamber 50 is, for example, G1 equivalent (in other words, the purity of hydrogen gas is 99.99999 volume % or above).
- the reduction gas is the hydrogen gas, for example, the dew point in the heating chamber 50 after introduction of the reduction gas is equal to or less than -80 °C.
- the gas in the heating chamber 50 is discharged through the gas discharge pipe 58.
- the pressure in the heating chamber 50 is lowered to 10 -3 Pa or below.
- a third step S3 is a reduction step of reducing the oxide of base metal to the base metal.
- the inside of the heating chamber 50 is heated in the condition that the reduction gas atmosphere or the vacuum atmosphere is maintained.
- the temperature in the heating chamber is maintained at, for example, 800 °C or above, 1000 °C or above, 1100 °C or above (especially, in case of the vacuum atmosphere), or 1200 °C or above.
- the temperature in the heating chamber is maintained below the melting point of superalloy that configures the superalloy part.
- the heating processing time is, for example, from 15 minutes to 24 hours, from 30 minutes to 24 hours, or from 60 minutes to 24 hours.
- the temperature in the heating chamber is 1000 °C or above and the melting point of superalloy or below, and the heating processing time is from 30 minutes or above to 300 minutes or below.
- the third step S3 As the reduction step, nickel oxide (the oxide of base metal) is reduced to nickel (the base metal) of the oxide contained in the surface oxide film of the superalloy part 1.
- the superalloy part 1 is taken out from the heating chamber 50.
- a fourth step S4 is an acid processing step.
- the acid solution is applied to the superalloy part 1.
- the application of acid solution to the superalloy part 1 is carried out by, for example, immersing the superalloy part 1 in the acid solution 62 in the liquid bath 60.
- the acid solution contains hydrochloric acid. This is because nickel has a high solubility to the hydrochloric acid.
- Iron chloride (III) FeCl 3
- Iron chloride (III) reinforces oxidizability of the hydrochloric acid.
- nitric acid may be contained in the acid solution.
- the acid solution may be a solution that contains the hydrochloric acid, the iron chloride (III) and the nitric acid.
- the temperature of acid solution is, for example, 10 °C or above and 40 °C or below, 10 °C or above and 30 °C or below, or 20 °C or above and 30 °C or below.
- the processing time of the acid processing step (in other words, a time during which the superalloy part 1 is immersed in the acid solution) is, for example, 20 minutes or above to 180 minutes or below, 30 minutes or above to 180 minutes or below, 40 minutes or above to 180 minutes or below.
- nickel (the base metal) that exists in the surface of the superalloy part 1 is dissolved by the acid solution.
- nickel (the base metal) generated from nickel oxide (the oxide of base metal) in the oxide film 20 by the reduction step is dissolved by the acid solution.
- the aluminum oxide (the oxide of second metal) left without being reduced at the reduction step is separated from the superalloy part 1 together with the dissolved base metal.
- the superalloy part 1 is taken out from the acid solution and washed (e.g. with water).
- the oxide film 20 is effectively removed from the superalloy part 1 through the above steps.
- the superalloy part 1 processed by the above steps is a superalloy part having a crack 3.
- the oxide film 20 is formed in the surface of the crack 3, too.
- a physical method such as polishing cannot be sometimes applied.
- the oxide film removing method in the present embodiment is effective.
- a step of physically expanding the crack 3 by the polishing and so on is unnecessary.
- the crack 3 may be repaired, after the oxide film removing method in the present embodiment is executed (in other words, after execution the above-mentioned first to fourth steps).
- the repair of the crack 3 is executed by filling a brazing material into the crack 3.
- the brazing material the brazing material having the base metal of the superalloy part 1 as a main component can be used.
- the base metal of the superalloy part 1 is nickel, nickel-based brazing material is used, and when the base metal of the superalloy part 1 is cobalt, cobalt-based brazing material can be used.
- the superalloy part 1 may be a superalloy part which has been used in the high-temperature environment of equal to or more than 800 °C.
- the crack and so on is easy to be caused due to heat fatigue in the superalloy part which has been used in the high-temperature environment.
- the oxide film in the surface of the superalloy part has a low solubility to the acid solution due to the exposure to the high-temperature environment. Therefore, it is sometimes difficult to remove the oxide film only by the acid processing. In such a case, the oxide film removing method in the present embodiment is effective.
- Aluminum oxide, titanium oxide or chrome oxide may be contained in the oxide film 20 in the surface of the superalloy part 1.
- the aluminum oxide, the titanium oxide and the chrome oxide are oxides difficult to reduce, compared with the nickel oxide.
- the aluminum oxide, the titanium oxide and the chrome oxide are not reduced by the reduction step of the above-mentioned third step. Therefore, when the aluminum oxide, the titanium oxide or the chrome oxide is contained in the oxide film 20 in the surface of the superalloy part 1, the oxide film removing method in the present embodiment is effective in which the acid processing step is executed after the reduction step.
- thermodynamic stability of the metal oxide is Al 2 O 3 > TiO 2 > Cr 2 O 3 > CoO > NiO in descending order at 1200 °C. Therefore, generally, the reduction is difficult in the order of the aluminum oxide, the titanium oxide, the chrome oxide, the cobalt oxide, and the nickel oxide.
- the strong reducer of gaseous fluoride e.g. HF gas
- the gaseous fluoride has high toxicity.
- the gaseous fluoride sometimes gives damage to the boundary between crystals of the superalloy.
- the superalloy part sometimes corrodes due to the gaseous fluoride remained after reduction processing.
- a special facility is necessary for the application of the gaseous fluoride.
- the oxide film removing method in the present embodiment it is possible to remove the aluminum oxide and so on without reducing it. For this reason, it is possible to avoid and reduce the use of the strong reducer such as the gaseous fluoride.
- FIG. 9A to FIG. 9C are experiment data showing the effectivity of the oxide film removing method in the present embodiment.
- FIG. 9A is a graph showing the analysis result.
- the horizontal axis shows a depth (nanometer) from the surface of the superalloy sample, and the vertical axis shows detection strength (the number of detected photoelectrons).
- nickel oxide, aluminum oxide and chrome oxide are formed in the surface of the superalloy sample (the region from 0 nm to 1600 nm in depth from the surface of the sample). Also, it could be found that metal nickel exists hardly in the region from 0 nm to 800 nm in depth from the surface of the sample.
- FIG. 9B is a graph showing the analysis result.
- the horizontal axis shows a depth (nanometer) from the surface of the superalloy sample
- the vertical axis shows detection strength (the number of detected photoelectrons).
- metal nickel exists in the region from 0 nm to 800 nm in depth from the surface of the sample.
- the nickel oxide existing in the region from 0 nm to 800 nm in depth from the surface of the sample was reduced to metal nickel.
- nickel oxide since nickel oxide was hardly observed in the region from 800 nm to 1600 nm in depth from the surface of the sample, the nickel oxide that had existed in the region from 800 nm to 1600 nm in depth from the surface of the sample has also been reduced to metal nickel.
- the nickel oxide which is the oxide of base metal was effectively reduced but aluminum oxide and chrome oxide were not effectively reduced.
- FIG. 9C is a graph showing the analysis result.
- the horizontal axis shows a depth (nanometer) from the surface of the superalloy sample, and the vertical axis shows detection strength (the number of detected photoelectrons).
- the oxide film was formed when the superalloy part was exposed to air (oxygen) under the high-temperature environment.
- the oxide film becomes difficult to dissolve by the acid when the oxide film is exposed to air in the high-temperature environment. Therefore, the reduction processing is executed before the acid processing, in order to remove the oxide film effectively.
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Description
- The present invention relates to an oxide film removing method, and especially, to a method of removing an oxide film formed in a superalloy surface.
- Components of an aircraft engine, a turbine, a plant and so on are sometimes used in a high-temperature environment or a high stress environment. It is known that a part used in the high-temperature environment or the high stress environment is formed of a superalloy material.
- In case of repairing the superalloy part, it is known that an oxide film in the surface of the superalloy part is removed as a pre-process. As the oxide film removing process, the fluoride ion cleaning (FIC) is well-known. However, it is known that hydrogen fluoride gas and so on used for the fluoride ion cleaning is highly toxic.
- As the related technique,
Patent Literature 1 discloses a method of cleaning a metal product. The method described inPatent Literature 1 contains removing the surface oxide of the superalloy part by using halide. - Also,
Patent Literature 2 discloses a method of cleaning and repairing a superalloy article. The method described inPatent Literature 2 contains reducing an oxide in a crack of the superalloy part by using gaseous active fluoride ions. - Also,
Patent Literature 3 discloses a method in place of fluoride ion cleaning. The method described inPatent Literature 3 contains expanding a narrow crack, removing a part of metal oxide with an acid solution, and removing a part of the metal oxide by cleaning in a high-temperature vacuum atmosphere or a high-temperature hydrogen atmosphere. -
- [Patent Literature 1]
JP H07-91662B - [Patent Literature 2]
US 4,098,450A - [Patent Literature 3]
US 2011/0120972A1 - An object of the present invention is to provide an oxide film removing method that can effectively remove an oxide film in a superalloy surface without using a highly toxic gaseous fluoride.
- This object and other objects and profits of the present invention could be easily confirmed from the following description and the attached drawings.
- An oxide film removing method in some embodiments is a method of removing an oxide film formed in a surface of a superalloy part that contains a first metal as a base metal and a second metal different from the first metal. The oxide film contains oxide of the base metal and oxide of the second metal.
- The oxide film removing method includes arranging the superalloy part inside a heating chamber; preparing a reduction gas atmosphere or a vacuum atmosphere inside the heating chamber; reducing the oxide of the base metal of an oxide film to the base metal by heating the inside of the heating chamber in a condition that the reduction gas atmosphere or the vacuum atmosphere is maintained; and carrying out acid processing to apply acid solution to the superalloy part after the reduction. The acid processing includes: dissolving the base metal; and separating the oxide of the second metal left without being reduced through the reduction from the superalloy part together with the dissolved base metal.
- In the oxide film removing method, the acid processing may not be carried out before the reduction.
- In the oxide film removing method, the base metal may be nickel or cobalt.
- In the oxide film removing method, the oxide of the second metal is a metal oxide in which thermodynamic stability is higher than that of the oxide of the base metal.
- In the oxide film removing method, the second metal may contain at least one of aluminum, titanium, and chrome.
- In the oxide film removing method, the second metal may contain aluminum.
- In the oxide film removing method, the acid solution may contain hydrochloric acid.
- In the oxide film removing method, the superalloy part may have a crack, and the oxide film may contain an oxide film formed in a surface of the crack.
- In the oxide film removing method, the method may not contain expanding a crack physically.
- In the oxide film removing method, the method may not contain a fluoride ion cleaning process.
- According to the present invention, the oxide film removing method can be provided in which the oxide film in the superalloy surface can be effectively removed without using a highly toxic gaseous fluoride.
-
- [
FIG. 1 ]
FIG. 1 is a sectional view schematically showing an example of a superalloy part. - [
FIG. 2 ]
FIG. 2 is a sectional view schematically showing the superalloy part after nickel oxide is reduced to nickel. - [
FIG. 3 ]
FIG. 3 is a sectional view schematically showing thesuperalloy part 1 during application of hydrochloric acid solution. - [
FIG. 4 ]
FIG. 4 is a sectional view schematically showing thesuperalloy part 1 during application of hydrochloric acid solution. - [
FIG. 5 ]
FIG. 5 is a sectional view schematically showing an example of the superalloy part. - [
FIG. 6 ]
FIG. 6 is a sectional view schematically showing an example of a reduction processing device. - [
FIG. 7 ]
FIG. 7 is a sectional view schematically showing an example of an acid processing device. - [
FIG. 8 ]
FIG. 8 is a flow chart showing a procedure of removing an oxide film. - [
FIG. 9A ]
FIG. 9A shows an experiment result showing the effectivity of an oxide film removing method according to an embodiment. - [
FIG. 9B ]
FIG. 9B shows the experimental result showing the effectivity of the oxide film removing method according to the embodiment. - [
FIG. 9C ]
FIG. 9C shows the experimental result showing the effectivity of the oxide film removing method according to the embodiment. - Hereinafter, an oxide film removing method according to an embodiment will be described with reference to the attached drawings.
- In this Specification, "Superalloy" means alloy usable (in other words, sustainable in strength) in a high temperature environment (e.g. 800 °C or above).
- In this Specification, a "base metal" means a metal component with the highest content (weight %) of the metal components contained in alloy.
- As an example, a method of removing an oxide film formed in the surface of a superalloy part that contains nickel (Ni) as a base metal and aluminum (Al) will be described.
-
FIG. 1 is a sectional view schematically showing an example of asuperalloy part 1. Thesuperalloy part 1 contains abase material 10 and anoxide film 20. Theoxide film 20 is formed by, for example, exposing thesuperalloy part 1 to air (oxygen) under the high-temperature environment. Note that a boundary between thebase material 10 and theoxide film 20 is clearly illustrated inFIG. 1 . However, in actual, the boundary between thebase material 10 and the oxide film is not always definite. - The
base material 10 is superalloy that contains base metal and second metal. In an example shown inFIG. 1 , the base metal is nickel and the second metal is aluminum. - The
oxide film 20 contains the oxide of base metal and the oxide of second metal. In the example shown inFIG. 1 , the oxide of base metal is nickel oxide (e.g. NiO). Also, the oxide of second metal is aluminum oxide (e.g. Al2O3). InFIG. 1 , aregion 22 where nickel oxide is rich (in other words, a region where the concentration of nickel oxide is relatively high) is schematically shown by a symbol of a white triangle. Also, inFIG. 1 , aregion 24 where aluminum oxide is rich (in other words, the region where the concentration of aluminum oxide is relatively high) is schematically shown by a symbol of a white circle. - When the
superalloy part 1 shown inFIG. 1 is arranged in a high temperature reduction gas atmosphere or a high temperature vacuum atmosphere, nickel oxide is reduced to nickel.FIG. 2 is a sectional view schematically showing thesuperalloy part 1 after nickel oxide is reduced to nickel. - In
FIG. 2 , aregion 32 where nickel has become rich through the reduction is schematically shown by a symbol of black triangle. Note that although not illustrated toFIG. 2 , nickel oxide that exists in theregion 24 where aluminum oxide is rich has also been reduced to nickel. - On the other hand, since aluminum oxide is a compound that is stable thermodynamically, the state of oxide is maintained even if the aluminum oxide is arranged in the high-temperature reduction gas atmosphere or the high-temperature vacuum atmosphere. Therefore, the aluminum oxide is difficult to be reduced more than the nickel oxide.
- When hydrochloric acid solution to the
superalloy part 1 shown inFIG. 2 is applied, theregion 32 where nickel is rich is dissolved with the hydrochloric acid solution (more specifically, nickel in the region where nickel is rich is dissolved by the hydrochloric acid solution). Also, the hydrochloric acid solution enters a cavity (or a passage) formed through the dissolving of nickel. As a result, nickel in a region other than theregion 32 where nickel is rich (for example, nickel in theregion 24 where aluminum oxide is rich) is also dissolved by the hydrochloric acid solution. -
FIG. 3 is a sectional view schematically showing thesuperalloy part 1 during application of the hydrochloric acid solution. Referring toFIG. 3 , it is understood that theregion 32 where nickel is rich disappears through the dissolution and a cavity 42 (or a passage) is formed. Also, it could be understood that a smaller cavity 43 (or a passage) is formed from thecavity 42. Due to existence of thecavity 42 and thecavity 43, bonding force between a portion of theoxide film 20 and another portion of theoxide film 20, and bonding force between theoxide film 20 and thebase material 10 are reduced. -
FIG. 4 is a sectional view schematically showing thesuperalloy part 1 during the application of hydrochloric acid solution, and showing the state after a time passed from the state shown inFIG. 3 . Referring toFIG. 4 , it could be understood that the aluminum oxide (or theregion 24 where aluminum oxide is rich) is separated from the superalloy part 1 (or the base material 10) together with the dissolved nickel, due to the reduction of bonding force between theoxide film 20 and thebase material 10. - Note that even if the hydrochloric acid solution is applied to the superalloy part shown in
FIG. 1 , thecavity 42 orcavity 43 as shown inFIG. 3 is difficult to be formed, since the nickel oxide is difficult to be dissolved with the hydrochloric acid solution more than nickel. On the other hand, in the present embodiment, since the oxide of base metal is reduced to the base metal before the application of hydrochloric acid solution, thecavity 42 orcavity 43 as shown inFIG. 3 is easy to be formed. As a result, as shown inFIG. 4 , the aluminum oxide that is difficult to be reduced becomes able to be separated from the superalloy part 1 (or the base material 10). - In an example shown in
FIG. 1 to FIG. 4 , it is possible to effectively separate and remove the oxide film in the surface of superalloy part without using gaseous fluoride having strong toxic. - In the example shown in
FIG. 1 to FIG. 4 , a case that the base metal is nickel has been described. However, the base metal is not limited to nickel. For example, the base metal may be cobalt. - In the example shown in
FIG. 1 to FIG. 4 , a case that the second metal contained in thesuperalloy part 1 is aluminum has been described. However, the second metal is not limited to aluminum. The second metal may be chrome or titanium. Alternatively, the second metal may contain at least one of aluminum, titanium, and chrome. For example, the second metal may contain aluminum and chrome. - In the example shown in
FIG. 1 to FIG. 4 , a case that acid solution is hydrochloric acid solution has been described. However, the acid solution is not limited to the hydrochloric acid solution, and is optional. The acid solution may be an acid solution of whatever kind if the acid solution can dissolve the base metal. Also, the acid solution may be mixed acid (for example, the mixed acid of hydrochloric acid and nitric acid). - Referring to
FIG. 5 to FIG. 8 , the oxide film removing method according to an embodiment will be described in detail. -
FIG. 5 is a sectional view schematically showing an example of thesuperalloy part 1. Theoxide film 20 is formed in the surface of thesuperalloy part 1. Theoxide film 20 may be formed in the whole surface of thesuperalloy part 1 and may be formed in a part of the surface of thesuperalloy part 1. - For example, the
superalloy part 1 is a superalloy part that has acrack 3. In the example shown inFIG. 5 , theoxide film 20 is formed in the surface ofcrack 3, too. - For example, the base metal of the
superalloy part 1 is nickel. In other words, of the metal components contained in thesuperalloy part 1, a first metal with the highest content weight% is, for example, nickel. Thesuperalloy part 1 may be a nickel-based superalloy part (in other words, the superalloy part in which the content of the nickel is 50 weight% or above). For example, aluminum may be contained as the alloy component in thesuperalloy part 1. In other words, of the metal components contained in thesuperalloy part 1, the second metal that is different from the first metal is, for example, aluminum. - The oxide of base metal (e.g. nickel) and the oxide of second metal (e.g. aluminum) are contained in the oxide film in the surface of
superalloy part 1. -
FIG. 6 is a sectional view schematically showing an example of the reduction processing device 5. The reduction processing device 5 includes, for example, amain unit section 51, adoor 52, aheater 53, atemperature sensor 54, acontroller 55, agas supply pipe 56, afirst valve 57, agas discharge pipe 58, and asecond valve 59. - The
main unit section 51 accommodates thesuperalloy part 1 as an object to be processed. Thedoor 52 opens and closes an opening of themain unit section 51. Themain unit section 51 and thedoor 52 functions as aheating chamber 50 when thesuperalloy part 1 is to be reduction processed (more specifically, a heating sealed chamber). - The
heater 53 is a device for heating theheating chamber 50. In other words, theheater 53 is a device for heating the heating chamber or thesuperalloy part 1 arranged in the heating chamber. Thetemperature sensor 54 is a sensor to measure a temperature in the heating chamber or a temperature of thesuperalloy part 1. Data acquired by thetemperature sensor 54 is sent to thecontroller 55. Thecontroller 55 controls theheater 53 based on the data received from thetemperature sensor 54. By controlling theheater 53 by thecontroller 55, the temperature in the heating chamber or the temperature of thesuperalloy part 1 is maintained in a desired temperature. - The
gas supply pipe 56 is used to supply reduction gas into theheating chamber 50. Thefirst valve 57 is arranged in the passage ofgas supply pipe 56 and opens and closes the passage. For example, the reduction gas is hydrogen gas. Note that when the reduction processing device 5 is a device which carries out the reduction processing in a vacuum atmosphere, thegas supply pipe 56 and thefirst valve 57 may be omitted. - The
gas discharge pipe 58 is used to discharge air (gas) from theheating chamber 50. For example, thegas discharge pipe 58 is connected with a vacuum pump (not illustrated). Thesecond valve 59 is arranged in the passage ofgas discharge pipe 58 and opens and closes the passage. -
FIG. 7 is a sectional view schematically showing an example of theacid processing device 6. For example, theacid processing device 6 has a liquid bath 60.Acid solution 62 is filled in the liquid bath 60. Thesuperalloy part 1 as the object to be processed is arranged in the liquid bath 60. - Next, referring to
FIG. 8 , a procedure of removing the oxide film will be described.FIG. 8 is a flow chart showing the procedure of removing the oxide film. - At a first step S1, the
superalloy part 1 that contains nickel (first metal) as the base metal and aluminum (second metal different from nickel) is arranged in theheating chamber 50. - Note that the
oxide film 20 is formed in the surface of thesuperalloy part 1. Also, theoxide film 20 contains nickel oxide (the oxide of base metal) and aluminum oxide (the oxide of second metal). - At a second step S2, a reduction gas atmosphere or a vacuum atmosphere is prepared in the
heating chamber 50. - When preparing the reduction gas atmosphere, the gas in the
heating chamber 50 is first discharged through thegas discharge pipe 58. After that, the reduction gas is supplied into theheating chamber 50 through thegas supply pipe 56. For example, the reduction gas is hydrogen (H2) gas. When the reduction gas is hydrogen gas, the grade of hydrogen gas to be supplied into theheating chamber 50 is, for example, G1 equivalent (in other words, the purity of hydrogen gas is 99.99999 volume % or above). When the reduction gas is the hydrogen gas, for example, the dew point in theheating chamber 50 after introduction of the reduction gas is equal to or less than -80 °C. - Alternatively, when the vacuum atmosphere should be prepared, the gas in the
heating chamber 50 is discharged through thegas discharge pipe 58. For example, through the discharge, the pressure in theheating chamber 50 is lowered to 10-3 Pa or below. - A third step S3 is a reduction step of reducing the oxide of base metal to the base metal. At the third step S3, the inside of the
heating chamber 50 is heated in the condition that the reduction gas atmosphere or the vacuum atmosphere is maintained. The temperature in the heating chamber is maintained at, for example, 800 °C or above, 1000 °C or above, 1100 °C or above (especially, in case of the vacuum atmosphere), or 1200 °C or above. Also, the temperature in the heating chamber is maintained below the melting point of superalloy that configures the superalloy part. The heating processing time is, for example, from 15 minutes to 24 hours, from 30 minutes to 24 hours, or from 60 minutes to 24 hours. For example, the temperature in the heating chamber is 1000 °C or above and the melting point of superalloy or below, and the heating processing time is from 30 minutes or above to 300 minutes or below. - By executing the third step S3 as the reduction step, nickel oxide (the oxide of base metal) is reduced to nickel (the base metal) of the oxide contained in the surface oxide film of the
superalloy part 1. After the third step S3 is executed, thesuperalloy part 1 is taken out from theheating chamber 50. - A fourth step S4 is an acid processing step. At the fourth step S4, the acid solution is applied to the
superalloy part 1. The application of acid solution to thesuperalloy part 1 is carried out by, for example, immersing thesuperalloy part 1 in theacid solution 62 in the liquid bath 60. - When the base metal is nickel, it is desirable that the acid solution contains hydrochloric acid. This is because nickel has a high solubility to the hydrochloric acid. Iron chloride (III) (FeCl3) may be contained in the acid solution. Iron chloride (III) reinforces oxidizability of the hydrochloric acid. Alternatively or additionally, nitric acid may be contained in the acid solution. For example, the acid solution may be a solution that contains the hydrochloric acid, the iron chloride (III) and the nitric acid.
- The temperature of acid solution is, for example, 10 °C or above and 40 °C or below, 10 °C or above and 30 °C or below, or 20 °C or above and 30 °C or below.
- The processing time of the acid processing step (in other words, a time during which the
superalloy part 1 is immersed in the acid solution) is, for example, 20 minutes or above to 180 minutes or below, 30 minutes or above to 180 minutes or below, 40 minutes or above to 180 minutes or below. - Through execution of the fourth step S4 as the acid processing step, nickel (the base metal) that exists in the surface of the
superalloy part 1 is dissolved by the acid solution. In other words, nickel (the base metal) generated from nickel oxide (the oxide of base metal) in theoxide film 20 by the reduction step is dissolved by the acid solution. - Also, by execution of the fourth step S4 as the acid processing step, the aluminum oxide (the oxide of second metal) left without being reduced at the reduction step is separated from the
superalloy part 1 together with the dissolved base metal. After the execution of the fourth step S4, thesuperalloy part 1 is taken out from the acid solution and washed (e.g. with water). - The
oxide film 20 is effectively removed from thesuperalloy part 1 through the above steps. - Note that the
superalloy part 1 processed by the above steps is a superalloy part having acrack 3. In an example shown inFIG. 5 , theoxide film 20 is formed in the surface of thecrack 3, too. For removal of the oxide film in the surface ofcrack 3, a physical method such as polishing cannot be sometimes applied. In such a case, the oxide film removing method in the present embodiment is effective. When the oxide film removing method in the present embodiment is used, a step of physically expanding thecrack 3 by the polishing and so on is unnecessary. - When the
superalloy part 1 to be processed by the above steps is a superalloy part having thecrack 3, thecrack 3 may be repaired, after the oxide film removing method in the present embodiment is executed (in other words, after execution the above-mentioned first to fourth steps). For example, the repair of thecrack 3 is executed by filling a brazing material into thecrack 3. For example, as the brazing material, the brazing material having the base metal of thesuperalloy part 1 as a main component can be used. For example, when the base metal of thesuperalloy part 1 is nickel, nickel-based brazing material is used, and when the base metal of thesuperalloy part 1 is cobalt, cobalt-based brazing material can be used. - For example, the
superalloy part 1 may be a superalloy part which has been used in the high-temperature environment of equal to or more than 800 °C. The crack and so on is easy to be caused due to heat fatigue in the superalloy part which has been used in the high-temperature environment. Also, the oxide film in the surface of the superalloy part has a low solubility to the acid solution due to the exposure to the high-temperature environment. Therefore, it is sometimes difficult to remove the oxide film only by the acid processing. In such a case, the oxide film removing method in the present embodiment is effective. - Aluminum oxide, titanium oxide or chrome oxide may be contained in the
oxide film 20 in the surface of thesuperalloy part 1. The aluminum oxide, the titanium oxide and the chrome oxide are oxides difficult to reduce, compared with the nickel oxide. The aluminum oxide, the titanium oxide and the chrome oxide are not reduced by the reduction step of the above-mentioned third step. Therefore, when the aluminum oxide, the titanium oxide or the chrome oxide is contained in theoxide film 20 in the surface of thesuperalloy part 1, the oxide film removing method in the present embodiment is effective in which the acid processing step is executed after the reduction step. - Note that the thermodynamic stability of the metal oxide is Al2O3 > TiO2 > Cr2O3 > CoO > NiO in descending order at 1200 °C. Therefore, generally, the reduction is difficult in the order of the aluminum oxide, the titanium oxide, the chrome oxide, the cobalt oxide, and the nickel oxide.
- To remove the aluminum oxide and so on, the strong reducer of gaseous fluoride (e.g. HF gas) is sometimes used. However, the gaseous fluoride has high toxicity. Also, the gaseous fluoride sometimes gives damage to the boundary between crystals of the superalloy. Moreover, the superalloy part sometimes corrodes due to the gaseous fluoride remained after reduction processing. In addition, a special facility is necessary for the application of the gaseous fluoride. On the other hand, according to the oxide film removing method in the present embodiment, it is possible to remove the aluminum oxide and so on without reducing it. For this reason, it is possible to avoid and reduce the use of the strong reducer such as the gaseous fluoride.
-
FIG. 9A to FIG. 9C are experiment data showing the effectivity of the oxide film removing method in the present embodiment. - In the experiment, a superalloy sample was used in which the base metal was nickel and aluminum and chrome were contained. In case of experiment, first, the superalloy sample was oxidized in the atmosphere.
- The surface state of the superalloy sample after the oxidation was analyzed by using an X-ray photoelectron spectroscopy.
FIG. 9A is a graph showing the analysis result. In the graph ofFIG. 9A , the horizontal axis shows a depth (nanometer) from the surface of the superalloy sample, and the vertical axis shows detection strength (the number of detected photoelectrons). - Referring to
FIG. 9A , it could be found that nickel oxide, aluminum oxide and chrome oxide are formed in the surface of the superalloy sample (the region from 0 nm to 1600 nm in depth from the surface of the sample). Also, it could be found that metal nickel exists hardly in the region from 0 nm to 800 nm in depth from the surface of the sample. - Next, the superalloy sample after the above-mentioned oxidation is reduced at the above-mentioned third step S3. The state of the surface of the superalloy sample after the reduction is analyzed by using the X-ray photoelectron spectroscopy.
FIG. 9B is a graph showing the analysis result. In the graph ofFIG. 9B , the horizontal axis shows a depth (nanometer) from the surface of the superalloy sample, and the vertical axis shows detection strength (the number of detected photoelectrons). - Referring to
FIG. 9B , it could be found that aluminum oxide and chrome oxide exist in the surface section of the superalloy sample (the region from 0 nm to 1600 nm in depth from the surface of the sample). In other words, it could be found that aluminum oxide and chrome oxide are not too much reduced in the reduction processing. - Also, referring to
FIG. 9B , it could be found that metal nickel exists in the region from 0 nm to 800 nm in depth from the surface of the sample. In other words, it could be found that the nickel oxide existing in the region from 0 nm to 800 nm in depth from the surface of the sample was reduced to metal nickel. Also, it could be found that since nickel oxide was hardly observed in the region from 800 nm to 1600 nm in depth from the surface of the sample, the nickel oxide that had existed in the region from 800 nm to 1600 nm in depth from the surface of the sample has also been reduced to metal nickel. - As mentioned above, it was proved that at the reduction step in the present embodiment, the nickel oxide which is the oxide of base metal was effectively reduced but aluminum oxide and chrome oxide were not effectively reduced.
- Next, the superalloy sample after the above-mentioned reduction processing is acid processed at the above-mentioned fourth step S4. The state of the surface of the superalloy sample after acid processing is analyzed by using the X-ray photoelectron spectroscopy.
FIG. 9C is a graph showing the analysis result. In the graph ofFIG. 9C , the horizontal axis shows a depth (nanometer) from the surface of the superalloy sample, and the vertical axis shows detection strength (the number of detected photoelectrons). - Referring to
FIG. 9C , it could be found that aluminum oxide and chrome oxide exist hardly in the surface (the region from 0 nm to 1600 nm in depth from the surface of the superalloy sample). It is found from the above fact that the oxide films that had existed in the surface of the superalloy sample after the reduction processing have disappeared after the acid processing. Note that the aluminum oxide is insoluble to the acid solution. Therefore, the disappearance of the oxide film is inferred not to be caused by the dissolving of aluminum oxide. It is inferred that the disappearance of the oxide film is caused as the result that nickel in the oxide film dissolved so that aluminum oxide (and chrome oxide) lost a base to combine with the superalloy sample. - As mention above, it was proved that the oxide film was removed effectively by executing the acid processing after the reduction processing.
- Note that the oxide film was formed when the superalloy part was exposed to air (oxygen) under the high-temperature environment. The oxide film becomes difficult to dissolve by the acid when the oxide film is exposed to air in the high-temperature environment. Therefore, the reduction processing is executed before the acid processing, in order to remove the oxide film effectively.
Claims (10)
- An oxide film removing method of removing an oxide film formed in a surface of a superalloy part that contains a first metal as a base metal and a second metal different from the first metal, the oxide film containing oxide of the base metal and oxide of the second metal,
the oxide film removing method comprising:arranging the superalloy part inside a heating chamber;preparing a reduction gas atmosphere or a vacuum atmosphere inside the heating chamber;reducing the oxide of the base metal of the oxide film to the base metal by heating the inside of the heating chamber in a condition that the reduction gas atmosphere or the vacuum atmosphere is maintained; andcarrying out acid processing to apply acid solution to the superalloy part after the reduction,wherein the acid processing comprises:dissolving the base metal; andseparating the oxide of the second metal left without being reduced through the reduction, from the superalloy part together with the dissolved base metal. - The oxide film removing method according to claim 1, wherein the acid processing is carried out after the reduction.
- The oxide film removing method according to claim 1 or 2, wherein the base metal is nickel or cobalt.
- The oxide film removing method according to any one of claims 1 to 3, wherein the oxide of the second metal is a metal oxide in which thermodynamic stability is higher than that of the oxide of the base metal.
- The oxide film removing method according to any one of claims 1 to 4, wherein the second metal contains at least one of aluminum, titanium, and chrome.
- The oxide film removing method according to claim 5, wherein the second metal contains aluminum.
- The oxide film removing method according to any one of claims 1 to 6, wherein the acid solution contains hydrochloric acid.
- The oxide film removing method according to any one of claims 1 to 7, wherein the superalloy part has a crack, and
wherein the oxide film contains an oxide film formed in a surface of the crack. - The oxide film removing method according to claim 8, wherein the method does not contain expanding a crack physically.
- The oxide film removing method according to any one of claims 1 to 9, wherein the method does not contain a fluoride ion cleaning process.
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US4188237A (en) * | 1978-02-02 | 1980-02-12 | University Of Dayton | Method for cleaning metal parts with elemental fluorine |
US4405379A (en) * | 1980-02-06 | 1983-09-20 | University Of Dayton | Method for cleaning metal parts |
US4729799A (en) * | 1986-06-30 | 1988-03-08 | United Technologies Corporation | Stress relief of single crystal superalloy articles |
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JP2002146449A (en) * | 2000-11-02 | 2002-05-22 | Toyota Motor Corp | Method for regenerating hydrogen storage alloy |
US20050035085A1 (en) * | 2003-08-13 | 2005-02-17 | Stowell William Randolph | Apparatus and method for reducing metal oxides on superalloy articles |
EP1559485A1 (en) * | 2004-01-30 | 2005-08-03 | Siemens Aktiengesellschaft | Method for removing a layer |
US20110120972A1 (en) * | 2009-11-20 | 2011-05-26 | Meyer Tool, Inc. | Replacement process for fluoride ion cleaning |
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- 2016-04-27 WO PCT/JP2016/063267 patent/WO2016181848A1/en active Application Filing
- 2016-04-27 US US15/572,368 patent/US20180135186A1/en not_active Abandoned
- 2016-04-27 EP EP16792573.4A patent/EP3266902B1/en active Active
- 2016-04-27 ES ES16792573T patent/ES2773110T3/en active Active
- 2016-04-27 CA CA2982720A patent/CA2982720C/en active Active
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Also Published As
Publication number | Publication date |
---|---|
JP2016211039A (en) | 2016-12-15 |
WO2016181848A1 (en) | 2016-11-17 |
EP3266902A1 (en) | 2018-01-10 |
JP6508823B2 (en) | 2019-05-08 |
EP3266902A4 (en) | 2018-02-14 |
CA2982720A1 (en) | 2016-11-17 |
US20180135186A1 (en) | 2018-05-17 |
CA2982720C (en) | 2020-07-21 |
ES2773110T3 (en) | 2020-07-09 |
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