WO2023218390A1 - Chemical solution suitable for polishing niobium and alloys thereof by plasma electropolishing - Google Patents
Chemical solution suitable for polishing niobium and alloys thereof by plasma electropolishing Download PDFInfo
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- WO2023218390A1 WO2023218390A1 PCT/IB2023/054867 IB2023054867W WO2023218390A1 WO 2023218390 A1 WO2023218390 A1 WO 2023218390A1 IB 2023054867 W IB2023054867 W IB 2023054867W WO 2023218390 A1 WO2023218390 A1 WO 2023218390A1
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- Prior art keywords
- composition
- plasma
- electropolishing
- mass concentration
- polishing
- Prior art date
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- 229910045601 alloy Inorganic materials 0.000 title claims description 9
- 239000000956 alloy Substances 0.000 title claims description 9
- 238000005498 polishing Methods 0.000 title abstract description 17
- 239000010955 niobium Substances 0.000 title description 13
- 229910052758 niobium Inorganic materials 0.000 title description 9
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 title description 8
- 239000000126 substance Substances 0.000 title description 7
- 238000000034 method Methods 0.000 claims abstract description 33
- 229910052751 metal Inorganic materials 0.000 claims abstract description 32
- 239000002184 metal Substances 0.000 claims abstract description 32
- 239000000203 mixture Substances 0.000 claims abstract description 32
- 230000008569 process Effects 0.000 claims abstract description 30
- 150000003839 salts Chemical class 0.000 claims abstract description 21
- 239000000243 solution Substances 0.000 claims description 16
- 239000007864 aqueous solution Substances 0.000 claims description 10
- PQXKHYXIUOZZFA-UHFFFAOYSA-M lithium fluoride Inorganic materials [Li+].[F-] PQXKHYXIUOZZFA-UHFFFAOYSA-M 0.000 claims description 10
- 150000002739 metals Chemical class 0.000 claims description 8
- LDDQLRUQCUTJBB-UHFFFAOYSA-N ammonium fluoride Chemical compound [NH4+].[F-] LDDQLRUQCUTJBB-UHFFFAOYSA-N 0.000 claims description 6
- 229910017971 NH4BF4 Inorganic materials 0.000 claims description 5
- 229910052735 hafnium Inorganic materials 0.000 claims description 5
- 229910052715 tantalum Inorganic materials 0.000 claims description 5
- 229910052719 titanium Inorganic materials 0.000 claims description 5
- NMGYKLMMQCTUGI-UHFFFAOYSA-J diazanium;titanium(4+);hexafluoride Chemical compound [NH4+].[NH4+].[F-].[F-].[F-].[F-].[F-].[F-].[Ti+4] NMGYKLMMQCTUGI-UHFFFAOYSA-J 0.000 claims description 3
- 229910019975 (NH4)2SiF6 Inorganic materials 0.000 claims 1
- 229910019985 (NH4)2TiF6 Inorganic materials 0.000 claims 1
- 229910020440 K2SiF6 Inorganic materials 0.000 claims 1
- 229910020491 K2TiF6 Inorganic materials 0.000 claims 1
- 229910007549 Li2SiF6 Inorganic materials 0.000 claims 1
- 229910004883 Na2SiF6 Inorganic materials 0.000 claims 1
- 229910052726 zirconium Inorganic materials 0.000 claims 1
- 238000007517 polishing process Methods 0.000 abstract description 2
- -1 ammonium tetrafluoroborate Chemical compound 0.000 description 9
- PUZPDOWCWNUUKD-UHFFFAOYSA-M sodium fluoride Chemical compound [F-].[Na+] PUZPDOWCWNUUKD-UHFFFAOYSA-M 0.000 description 9
- 239000010936 titanium Substances 0.000 description 9
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 6
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 5
- 239000002253 acid Substances 0.000 description 5
- 150000007513 acids Chemical class 0.000 description 5
- 230000008901 benefit Effects 0.000 description 5
- NROKBHXJSPEDAR-UHFFFAOYSA-M potassium fluoride Chemical compound [F-].[K+] NROKBHXJSPEDAR-UHFFFAOYSA-M 0.000 description 5
- VBJZVLUMGGDVMO-UHFFFAOYSA-N hafnium atom Chemical compound [Hf] VBJZVLUMGGDVMO-UHFFFAOYSA-N 0.000 description 4
- 239000011698 potassium fluoride Substances 0.000 description 4
- VSZWPYCFIRKVQL-UHFFFAOYSA-N selanylidenegallium;selenium Chemical compound [Se].[Se]=[Ga].[Se]=[Ga] VSZWPYCFIRKVQL-UHFFFAOYSA-N 0.000 description 4
- 235000013024 sodium fluoride Nutrition 0.000 description 4
- 239000011775 sodium fluoride Substances 0.000 description 4
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 description 4
- 238000011282 treatment Methods 0.000 description 4
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 4
- DDFHBQSCUXNBSA-UHFFFAOYSA-N 5-(5-carboxythiophen-2-yl)thiophene-2-carboxylic acid Chemical compound S1C(C(=O)O)=CC=C1C1=CC=C(C(O)=O)S1 DDFHBQSCUXNBSA-UHFFFAOYSA-N 0.000 description 3
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 3
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 3
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 3
- KVBCYCWRDBDGBG-UHFFFAOYSA-N azane;dihydrofluoride Chemical compound [NH4+].F.[F-] KVBCYCWRDBDGBG-UHFFFAOYSA-N 0.000 description 3
- 229910052796 boron Inorganic materials 0.000 description 3
- 239000003792 electrolyte Substances 0.000 description 3
- 238000007254 oxidation reaction Methods 0.000 description 3
- 229910052720 vanadium Inorganic materials 0.000 description 3
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 2
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 2
- 229910001257 Nb alloy Inorganic materials 0.000 description 2
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 2
- RXCBCUJUGULOGC-UHFFFAOYSA-H dipotassium;tetrafluorotitanium;difluoride Chemical compound [F-].[F-].[F-].[F-].[F-].[F-].[K+].[K+].[Ti+4] RXCBCUJUGULOGC-UHFFFAOYSA-H 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 231100001261 hazardous Toxicity 0.000 description 2
- 229910052744 lithium Inorganic materials 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- QPJSUIGXIBEQAC-UHFFFAOYSA-N n-(2,4-dichloro-5-propan-2-yloxyphenyl)acetamide Chemical compound CC(C)OC1=CC(NC(C)=O)=C(Cl)C=C1Cl QPJSUIGXIBEQAC-UHFFFAOYSA-N 0.000 description 2
- 229910017604 nitric acid Inorganic materials 0.000 description 2
- LXPCOISGJFXEJE-UHFFFAOYSA-N oxifentorex Chemical compound C=1C=CC=CC=1C[N+](C)([O-])C(C)CC1=CC=CC=C1 LXPCOISGJFXEJE-UHFFFAOYSA-N 0.000 description 2
- 235000003270 potassium fluoride Nutrition 0.000 description 2
- JTDPJYXDDYUJBS-UHFFFAOYSA-N quinoline-2-carbohydrazide Chemical compound C1=CC=CC2=NC(C(=O)NN)=CC=C21 JTDPJYXDDYUJBS-UHFFFAOYSA-N 0.000 description 2
- 238000006722 reduction reaction Methods 0.000 description 2
- 229910052708 sodium Inorganic materials 0.000 description 2
- 239000011734 sodium Substances 0.000 description 2
- 229910001369 Brass Inorganic materials 0.000 description 1
- 229910001069 Ti alloy Inorganic materials 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- 238000001994 activation Methods 0.000 description 1
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 1
- 239000010951 brass Substances 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000005238 degreasing Methods 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 230000036541 health Effects 0.000 description 1
- 238000002203 pretreatment Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000012266 salt solution Substances 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 235000011149 sulphuric acid Nutrition 0.000 description 1
- 238000002604 ultrasonography Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
- C25F3/00—Electrolytic etching or polishing
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
- C25F3/00—Electrolytic etching or polishing
- C25F3/16—Polishing
- C25F3/22—Polishing of heavy metals
- C25F3/26—Polishing of heavy metals of refractory metals
Definitions
- the invention relates to a composition for plasma electropolishing of metal surfaces and to the related electropolishing process using said composition.
- said composition consists of an aqueous solution of soluble salts of hydrofluoric, boron hydrofluoric, fluorosilicic, or hexafluorotitanic acids, and to the related plasma electropolishing process.
- the present invention relates to the plasma electropolishing process of metal surfaces.
- the present invention relates to a plasma electropolishing process using an aqueous solution of soluble salts of hydrofluoric, Boron hydrofluoric, fluorosilicic, or hexafluorotitanic acids.
- the present invention refers to the composition of the polishing solution and to the optimal process parameters to be applied to the plasma electropolishing process for metal surfaces such as Titanium (Ti), Zirconium (Zr), Hafnium (Hf), Vanadium (Va), Niobium (Nb), Tantalum (Ta), or from alloys of said metals.
- metal surface polishing is carried out with processes of chemical or electrochemical nature.
- the piece to be treated is immersed in a concentrated aqueous solution of plural acids whose action allows to remove a superficial layer of metal, preferably acting on asperities present and decreasing their roughness.
- the piece to be treated is immersed in a concentrated aqueous solution of several acids, and connected to the positive pole of an electric circuit, thereby acting as the anode of an electrolytic cell.
- a second metallic electrode immersed in the same solution, faced to the piece to be treated and at a suitable distance from the latter (usually of the order of tens of cm), acts as the cathode.
- Applying a potential difference between anode and cathode triggers an oxidation reaction on the metal of the piece to be treated, partially dissolving it into the solution. Said oxidation reaction occurs preferentially at asperities of the metal surface, which are then dissolved to a greater extent and smoothed.
- PEP plasma electropolishing
- plasma electrolytic polishing PEP
- PEP plasma electrolytic polishing
- the process is industrially known and applied for various metals and alloys, such as Chrome-Cobalt-Molybdenum, stainless steel, and brass, for which polishing formulas are available; whereas it is not used for treatment on Niobium and its alloys.
- metals and alloys such as Chrome-Cobalt-Molybdenum, stainless steel, and brass, for which polishing formulas are available; whereas it is not used for treatment on Niobium and its alloys.
- only one formula for Niobium plasma electropolishing is known [Y. Aliakseyeu, A. Bubulis, V.
- Object of the present invention is to provide a composition of the polishing solution and optimal process parameters to be applied to the plasma electropolishing process plasma for the treatment of metal surfaces of Titanium (Ti), Zirconium (Zr), Hafnium (Hf), Vanadium (Va), Niobium (Nb), Tantalum (Ta), or from alloys of said metals, such as to obtain better results compared to the traditional electropolishing techniques.
- the present invention generally refers to the composition of a solution to be used in the plasma electropolishing process of metal surfaces. More particularly, the invention relates to an aqueous solution of soluble salts of hydrofluoric, boron hydrofluoric, fluorosilicic, or hexafluorotitanic acids, and the use of said solution in the related plasma electropolishing process of metal surfaces.
- object of the present invention is the plasma electropolishing process using said composition.
- said plasma electropolishing process relates to metal surfaces consisting of at least one of the following metals: Titanium (Ti), Zirconium (Zr), Hafnium (Hf), Vanadium (V), Niobium (Nb), Tantalum (Ta), or alloys of said metals.
- Figure 1 schematic description of the plasma electropolishing process: 1 - surface to be treated, 2 -composition for plasma electropolishing, 3 -second metallic member, 4- positive pole, 5 - negative pole, 6 - voltage generator.
- surface to be polished it is meant any one item exhibiting an exposed metal surface whose roughness has to be reduced; by “anode” it is meant the electrode of an electrochemical cell which undergoes an oxidation reaction, and by “cathode” the electrode in which a reduction reaction takes place.
- a composition of salts soluble in aqueous solution is made, to be used in a plasma electropolishing process of metal surfaces as defined in claim 1.
- composition of salts in aqueous solution comprising at least one salt selected from the following two groups, respectively:
- B Sodium fluoride, NaF; potassium fluoride, KF; lithium fluoride, LiF; sodium hexafluorosilicate, NajSiFs; lithium hexafluorosilicate, LizSiFs; potassium hexafluorosilicate, KaSiFs; sodium hexafluorotitanate, NajTiFs; potassium hexafluorotitanate, KjTiFs, lithium hexafluorotitanate, LiaTiFs-
- the mass concentration of the salts selected in group A is from 1.0% to 5.0%, and the mass concentration of the salts selected in group B is from 0.5% to 3.0%.
- the salt selected in group A is ammonium fluoride (NH4F) with a mass concentration of 3.0% and the salt selected in group B is sodium fluoride (NaF) with a mass concentration of 1.0%
- the salt selected in group A is ammonium hydrogen difluoride ((NF jHFz) with a mass concentration of 2.5% and the salt selected in group B is potassium fluoride (KF) with a mass concentration of 1.0%
- the salt selected in group A is ammonium tetrafluoroborate, NH4BF4 with a mass concentration of 3.0% and the salt selected in group B is lithium fluoride (LiF) with a mass concentration of 0.5%.
- the composition of the described solution is used in the plasma electropolishing process of metal surfaces consisting of at least one of the following metals: Titanium (Ti), Zirconium (Zr), Hafnium (Hf), Vanadium (Va), Niobium (Nb), Tantalum (Ta), or alloys of said metals.
- said plasma electropolishing process comprises the steps of: a) Placing the surface to be polished 1 in contact with the composition 2; b) Placing at least one further metal element 3 in contact with the same composition, so that electrical contact between all metal surfaces through the same composition is ensured; c) Connecting the surface to be polished 1 to the positive pole 4 and the other elements 3 to the negative pole 5 of a voltage generator 6, so that the surface to be polished acts as the anode of an electrochemical cell; d) Setting the temperature of the composition so that it is between 60°C and 95°C; e) Applying a continuous potential difference between the two electrodes between 200 V and 400 V.
- the potential difference applied between the two electrodes is 300 V while the temperature of the solution is maintained at 85°C.
- Object of the present invention is to provide a composition for plasma electropolishing of metal surfaces, and the related electropolishing process using said composition, such as to overcome the limitations of the known art.
- An advantage of the present invention compared to the known art is the rate at which the desired treatment is carried out; in fact, the process according to the invention proves to be 10 times faster than the conventional electropolishing process and about 3.5 times faster than chemical polishing.
- a further advantage of the present invention is the greater efficiency compared to the known art; in fact, the polishing effect of the treated surface is obtained with the removal of lesser amounts of material compared to the known processes.
- compositions subject-matter of the present invention which by consisting of solutions at lower concentrations prove to be less hazardous for the environment and the operators' health compared to those used in the known art.
- a further advantage of the invention is the ability to remove contaminating elements from the surface to be treated by virtue of the higher power employed for area unit, thereby avoiding the need to apply pre-treatments commonly used in the conventional electropolishing and chemical polishing processes: (degreasing, ultrasound cleaning, activation, polishing).
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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)
- ing And Chemical Polishing (AREA)
Abstract
The invention refers to the electrochemical polishing process of metal surfaces known as plasma electropolishing, plasma electrolytic polishing (PEP), using a salt-based solution. The present invention dwells on the ideal composition of the polishing solution and on the optimal process parameters in order to obtain better results compared to the traditional electropolishing techniques.
Description
CHEMICAL SOLUTION SUITABLE FOR POLISHING NIOBIUM AND ALLOYS THEREOF BY PLASMA ELECTROPOLISHING
Technical field of the Invention
The invention relates to a composition for plasma electropolishing of metal surfaces and to the related electropolishing process using said composition. In particular, said composition consists of an aqueous solution of soluble salts of hydrofluoric, boron hydrofluoric, fluorosilicic, or hexafluorotitanic acids, and to the related plasma electropolishing process.
Known art
The present invention relates to the plasma electropolishing process of metal surfaces. In particular, the present invention relates to a plasma electropolishing process using an aqueous solution of soluble salts of hydrofluoric, Boron hydrofluoric, fluorosilicic, or hexafluorotitanic acids. More particularly, the present invention refers to the composition of the polishing solution and to the optimal process parameters to be applied to the plasma electropolishing process for metal surfaces such as Titanium (Ti), Zirconium (Zr), Hafnium (Hf), Vanadium (Va), Niobium (Nb), Tantalum (Ta), or from alloys of said metals.
Typically, metal surface polishing is carried out with processes of chemical or electrochemical nature.
In chemical polishing, the piece to be treated is immersed in a concentrated aqueous solution of plural acids whose action allows to remove a superficial layer of metal, preferably acting on asperities present and decreasing their roughness.
In the electrochemical process, called electropolishing or electrolytic polishing, the piece to be treated is immersed in a concentrated aqueous solution of several acids, and connected to the positive pole of an electric circuit, thereby acting as the anode of an electrolytic cell. A second metallic electrode, immersed in the same solution, faced to the piece to be treated and at a suitable distance from the latter (usually of the order of tens of cm), acts as the cathode. Applying a potential difference between anode and cathode triggers an oxidation reaction on the metal of the piece to be treated, partially dissolving it into the solution. Said oxidation reaction occurs preferentially at asperities of the metal surface, which are then dissolved to a greater extent and smoothed. The overall effect is a reduction of piece roughness.
With reference to Nb or Nb alloy surfaces, the solutions used for chemical polishing consist of 46% hydrofluoric acid (HF), 85% phosphoric acid (H3PO4) and 56% nitric acid (HNO3) mixed together i n a 1 : 2 : 1 vo l u m e rat i o, re s p ect ive l y . The solutions for electropolishing instead consist of 46% hydrofluoric acid (HF) and 98% sulfuric acid (H2SO4) mixtures in a 1:9 volume ratio. The typical time required to remove 200 pm of thickness of the material is between 6 and 10 hours, the voltage applied generally is from 5 V to 20 V.
An alternative approach is the so-called plasma electropolishing, or plasma electrolytic polishing (PEP), which is different from traditional electropolishing owing to the regime of higher voltages, from 200 V to 400 V, enabling faster processing times and the use of diluted solutions. PEP, in fact, uses diluted aqueous solutions of salts enabling to abate the generation of hazardous gases. The process is industrially known and applied for various metals and alloys, such as Chrome-Cobalt-Molybdenum, stainless steel, and brass, for which polishing formulas are available; whereas it is not used for treatment on Niobium and its alloys. In the literature, only one formula for Niobium plasma electropolishing is known [Y. Aliakseyeu, A. Bubulis, V. Minchenya, A. Korolyov, V. Niss, and R. Kandrotaite Janutiene, 'Plasma Electrolyte Polishing of Titanium and Niobium Alloys in Low Concentrated Salt Solution Based Electrolyte', mech, vol. 27 , no. 1, pp. 88-93, Feb. 2021, doi: 10.5755/j02.mech.25044] using a solution containing exclusively NH4F.
Despite the advantages of plasma electropolishing compared with the described polishing methods, singling out parameters of electrolyte composition and ideal conditions of time and current to be applied to the treatment still remains challenging.
Object of the present invention is to provide a composition of the polishing solution and optimal process parameters to be applied to the plasma electropolishing process plasma for the treatment of metal surfaces of Titanium (Ti), Zirconium (Zr), Hafnium (Hf), Vanadium (Va), Niobium (Nb), Tantalum (Ta), or from alloys of said metals, such as to obtain better results compared to the traditional electropolishing techniques.
Summary of the Invention
The present invention generally refers to the composition of a solution to be used in the plasma electropolishing process of metal surfaces. More particularly, the invention relates to
an aqueous solution of soluble salts of hydrofluoric, boron hydrofluoric, fluorosilicic, or hexafluorotitanic acids, and the use of said solution in the related plasma electropolishing process of metal surfaces.
Object of the invention is the composition of an aqueous solution of soluble salts to be used in a plasma electropolishing process of metal surfaces; said solution comprising at least one salt selected from the following two groups, respectively:
A. Ammonium fluoride, NH4F; ammonium hydrogen difluoride, (NH^HFz; ammonium tetrafluoroborate, NH4BF4; ammonium hexafluorosilicate, (NF hSiFg; ammonium hexafluorotitanate, (NF hTiFg;
B. Sodium fluoride, NaF; potassium fluoride, KF; lithium fluoride, LiF; sodium hexafluorosilicate, NajSiFs; lithium hexafluorosilicate, LizSiFs; potassium hexafluorosilicate, KaSiFs; sodium hexafluorotitanate, NajTiFs; potassium hexafluorotitanate, KjTiFs, lithium hexafluorotitanate, LiaTiFs; moreover, object of the present invention is the plasma electropolishing process using said composition. In particular, said plasma electropolishing process relates to metal surfaces consisting of at least one of the following metals: Titanium (Ti), Zirconium (Zr), Hafnium (Hf), Vanadium (V), Niobium (Nb), Tantalum (Ta), or alloys of said metals.
Brief description of the figures
Figure 1: schematic description of the plasma electropolishing process: 1 - surface to be treated, 2 -composition for plasma electropolishing, 3 -second metallic member, 4- positive pole, 5 - negative pole, 6 - voltage generator.
Detailed description of the Invention
In the description of the present invention, by "surface to be polished" it is meant any one item exhibiting an exposed metal surface whose roughness has to be reduced; by "anode" it is meant the electrode of an electrochemical cell which undergoes an oxidation reaction, and by "cathode" the electrode in which a reduction reaction takes place.
According to the present invention, a composition of salts soluble in aqueous solution is made, to be used in a plasma electropolishing process of metal surfaces as defined in claim 1.
For a better understanding of the present invention a preferred embodiment is presently described, purely by way of a non-limiting example.
Composition of salts in aqueous solution comprising at least one salt selected from the following two groups, respectively:
A. Ammonium fluoride, NH4F; ammonium hydrogen difluoride, (NH^HFz; ammonium tetrafluoroborate, NH4BF4; ammonium hexafluorosilicate, (NF hSiFg; ammonium hexafluorotitanate, (NF hTiFg;
B. Sodium fluoride, NaF; potassium fluoride, KF; lithium fluoride, LiF; sodium hexafluorosilicate, NajSiFs; lithium hexafluorosilicate, LizSiFs; potassium hexafluorosilicate, KaSiFs; sodium hexafluorotitanate, NajTiFs; potassium hexafluorotitanate, KjTiFs, lithium hexafluorotitanate, LiaTiFs-
According to an aspect of the invention the mass concentration of the salts selected in group A is from 1.0% to 5.0%, and the mass concentration of the salts selected in group B is from 0.5% to 3.0%.
In a preferred embodiment of the invention, the salt selected in group A is ammonium fluoride (NH4F) with a mass concentration of 3.0% and the salt selected in group B is sodium fluoride (NaF) with a mass concentration of 1.0%
In a second preferred embodiment of the invention, the salt selected in group A is ammonium hydrogen difluoride ((NF jHFz) with a mass concentration of 2.5% and the salt selected in group B is potassium fluoride (KF) with a mass concentration of 1.0%
In a third preferred embodiment of the invention, the salt selected in group A is ammonium tetrafluoroborate, NH4BF4 with a mass concentration of 3.0% and the salt selected in group B is lithium fluoride (LiF) with a mass concentration of 0.5%.
Advantageously, according to the invention, the composition of the described solution is used in the plasma electropolishing process of metal surfaces consisting of at least one of the following metals: Titanium (Ti), Zirconium (Zr), Hafnium (Hf), Vanadium (Va), Niobium (Nb), Tantalum (Ta), or alloys of said metals.
With reference to Figure 1, according to an aspect of the invention, said plasma electropolishing process comprises the steps of: a) Placing the surface to be polished 1 in contact with the composition 2; b) Placing at least one further metal element 3 in contact with the same composition, so that electrical contact between all metal surfaces through the same composition is ensured; c) Connecting the surface to be polished 1 to the positive pole 4 and the other elements 3 to the negative pole 5 of a voltage generator 6, so that the surface
to be polished acts as the anode of an electrochemical cell; d) Setting the temperature of the composition so that it is between 60°C and 95°C; e) Applying a continuous potential difference between the two electrodes between 200 V and 400 V. Advantageously, according to the invention, the potential difference applied between the two electrodes is 300 V while the temperature of the solution is maintained at 85°C.
Object of the present invention is to provide a composition for plasma electropolishing of metal surfaces, and the related electropolishing process using said composition, such as to overcome the limitations of the known art.
An advantage of the present invention compared to the known art is the rate at which the desired treatment is carried out; in fact, the process according to the invention proves to be 10 times faster than the conventional electropolishing process and about 3.5 times faster than chemical polishing.
A further advantage of the present invention is the greater efficiency compared to the known art; in fact, the polishing effect of the treated surface is obtained with the removal of lesser amounts of material compared to the known processes.
Another advantage relates to the compositions subject-matter of the present invention, which by consisting of solutions at lower concentrations prove to be less hazardous for the environment and the operators' health compared to those used in the known art.
A further advantage of the invention is the ability to remove contaminating elements from the surface to be treated by virtue of the higher power employed for area unit, thereby avoiding the need to apply pre-treatments commonly used in the conventional electropolishing and chemical polishing processes: (degreasing, ultrasound cleaning, activation, polishing).
Claims
1. Composition for a plasma electropolishing process of metal surfaces comprising an aqueous solution of at least one salt selected from the following two groups, respectively:
A. NH4F, (NH4)HF2, NH4BF4, (NH4)2SiF6, (NH4)2TiF6
B. NaF, KF, LiF, Na2SiF6, Li2SiF6, K2SiF6, Na2TiF6, K2TiF6, Li2TiF6
2. Composition according to the preceding claim, wherein the mass concentration of the salt selected in group A is between 1.0% and 5.0%, and the mass concentration of the salt selected in group B is between 0.5% and 3.0%.
3. Composition, according to the preceding claims, consisting of NH4F in a mass concentration of 3.0% and NaF in a mass concentration of 1.0%.
4. Composition, according to the preceding claims, consisting of (NH4)HF2 in a mass concentration of 2.5% and KF in a mass concentration of 1.0%.
5. Composition, according to the preceding claims, consisting of NH4BF4 in a mass concentration of 3.0% and LiF in a mass concentration of 0.5%.
6. Plasma electropolishing process of metal surfaces using the composition according to one of the preceding claims, comprising the steps of: a) Placing the surface to be polished (1) in contact with the composition (2); b) Placing at least one further metal element (3) in contact with the same composition, so that electrical contact between all metal surfaces through the same composition is ensured; c) Connecting the surface to be polished (1) to the positive pole (4) and the other elements (3) to the negative pole (5) of a voltage generator (6), so that the surface to be polished acts as the anode of an electrochemical cell; d) Setting the temperature of the composition so that it is between 60°C and 95°C. e) Applying a continuous potential difference between the two electrodes between 200 V and 400 V.
7. Process according to the preceding claim wherein the metal surface comprises at least one of: Ti, Zr, Hf, Va, Nb, Ta, or an alloy of said metals.
8. Process, according to the preceding claim wherein the potential difference applied between the two electrodes is 300 V.
9. Process, according to the preceding claim wherein the temperature of the solution is maintained at 85°C.
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| RU2373306C2 (en) * | 2007-06-25 | 2009-11-20 | ООО "НПП Уралавиаспецтехнология" | Method of multistage electrolyte-plasma polishing of products made of titanium and titanium alloys |
| RU2715396C1 (en) * | 2019-09-10 | 2020-02-27 | федеральное государственное бюджетное образовательное учреждение высшего образования "Уфимский государственный авиационный технический университет" | Method for electric polishing of gte blade of alloyed steel and device for its implementation |
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2023
- 2023-05-11 WO PCT/IB2023/054867 patent/WO2023218390A1/en unknown
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| RU2373306C2 (en) * | 2007-06-25 | 2009-11-20 | ООО "НПП Уралавиаспецтехнология" | Method of multistage electrolyte-plasma polishing of products made of titanium and titanium alloys |
| RU2715396C1 (en) * | 2019-09-10 | 2020-02-27 | федеральное государственное бюджетное образовательное учреждение высшего образования "Уфимский государственный авиационный технический университет" | Method for electric polishing of gte blade of alloyed steel and device for its implementation |
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| Title |
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| ALIAKSEYEU Y ET AL: "Plasma electrolyte polishing of titanium and niobium alloys in low concentrated salt solution based electrolyte", MECHANIKA 20210224 KAUNO TECHNOLOGIJOS UNIVERSITETAS LTU, vol. 27, no. 1, 24 February 2021 (2021-02-24), pages 88 - 93, DOI: 10.5755/J02.MECH.25044 * |
| DATABASE COMPENDEX [online] ENGINEERING INFORMATION, INC., NEW YORK, NY, US; 24 February 2021 (2021-02-24), ALIAKSEYEU Y ET AL: "Plasma electrolyte polishing of titanium and niobium alloys in low concentrated salt solution based electrolyte", XP002809816, Database accession no. E20211210102891 * |
| HUANG YU ET AL: "Principle, process, and application of metal plasma electrolytic polishing: a review", THE INTERNATIONAL JOURNAL OF ADVANCED MANUFACTURING TECHNOLOGY, SPRINGER, LONDON, vol. 114, no. 7-8, 7 April 2021 (2021-04-07), pages 1893 - 1912, XP037455793, ISSN: 0268-3768, [retrieved on 20210407], DOI: 10.1007/S00170-021-07012-7 * |
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