US3749656A - Method of making an article having a hard and ornamental coating - Google Patents

Method of making an article having a hard and ornamental coating Download PDF

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Publication number
US3749656A
US3749656A US00133382A US3749656DA US3749656A US 3749656 A US3749656 A US 3749656A US 00133382 A US00133382 A US 00133382A US 3749656D A US3749656D A US 3749656DA US 3749656 A US3749656 A US 3749656A
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United States
Prior art keywords
tantalum
carbide
coating
workpiece
coated
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Expired - Lifetime
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US00133382A
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English (en)
Inventor
A Hara
S Yazu
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Sumitomo Electric Industries Ltd
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Sumitomo Electric Industries Ltd
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D13/00—Electrophoretic coating characterised by the process
    • C25D13/02—Electrophoretic coating characterised by the process with inorganic material

Definitions

  • the method comprises providing a dispersion of fine powders of tantalum or tantalum compound or mixed fine powders of the same with other materials in water, aqueous medium or organic solvent, applying a direct current voltage to the surface of a workpiece to be coated to thus cause electrophoretic deposition of the fine powders thereon, heating the coated surface at high temperatures in vacuum or in a reducing or inert atmosphere and thereby forming a coating layer consisting mainly of tantalum carbide.
  • This invention relates to articles having an ornamental coating which is golden colored, beautiful and hard so that it is hardly scratched and to a method of making such articles.
  • Gold platings have a beautiful and gold lustre, but are soft and readily scratched.
  • WC-Co cemented carbides called non-scratch, have been used for ornaments, for example, watch frames.
  • Electrophoretic deposition has been put to practical use, for example, in coating a surface with an aqueous paint by electrodeposition using water as a dispersing medium or in electrodepositing fine powder of alumina on a heater of electronic tube. Furthermore, the utilization of electrophoretic deposition has been proposed as disclosed in Japanese patent publication No. 8951/1963, US. Pat. No. 3,171,192 and Journal of the Electrochemical Society vol. 109, No. 10, pp. 923-927.
  • the feature of the method of forming a coating according to the invention consists in providing a dispersion of fine powders of tantalum or tantalum compounds or mixed fine powders of the same with other materials in water, aqueous medium or organic solvent, immersing a workpiece to be coated as one electrode in said dispersion, applying a direct current voltage of several ten to several hundred volts to said workpiece to thus cause electrophoretic deposition of the fine powders thereon, heating the coated surface at high temperatures in vacuum or in a reducing or inert atmosphere and thereby forming a coating layer consisting mainly of tantalum carbide.
  • the materials to be coated according to the invention include cemented carbides such as tungsten carbide-cobalt and tungsten carbide-cobalt with titanium carbide, tantalum carbide, molybdenum carbide, hafnium carbide, zirconium carbide, chromium carbide and/or vanadium carbide, high melting point metals such as tungsten and molybdenum, steels such as stainless steel and carbon steel, cermets and pure iron.
  • cemented carbides such as tungsten carbide-cobalt and tungsten carbide-cobalt with titanium carbide, tantalum carbide, molybdenum carbide, hafnium carbide, zirconium carbide, chromium carbide and/or vanadium carbide, high melting point metals such as tungsten and molybdenum, steels such as stainless steel and carbon steel, cermets and pure iron.
  • tantalum or a tantalum compound besides tantalum carbide for example, tantalum hydride or tantalum oxide
  • the material to be coated contains carbon
  • the composition of the thus obtained coating layer comprises tantalum carbide as a main component and a transition metal such as iron group metal or copper as a binder metal.
  • a transition metal such as iron group metal or copper
  • this binder metal exceeds 50%, the hardness lowers to a large extent. Thus it is desired to hold the binder metal less than 50%.
  • carbides besides tantalum carbide, borides and nitrides may be contained therein as far as they do not deteriorate the beautiful color of tantalum carbide.
  • Preparation of the above mentioned dispersion of tantalum or tantalum compound may be carried out, as occasion demands, with addition of a small amount of a colloidal ion forming material, for example, alginates such as sodium, calcium, magnesium and ammonium alginates, nitrates such as aluminum nitrate, and sulfates to a dispersing medium, in particular, water or aqueous dispersing medium.
  • a tantalum containing electrodeposited film excellent in adhesiveness can be obtained at a low voltage of several ten volts. An amount of about 0.05% based on the dispersing medium is sufficient.
  • the alginate added to a dispersing medium is dissociated into alginate ion and metal ion, the alginate ion adhering to tantalum or tantalum compound, for example, tantalum hydride fine grains followed by electrophoresis to the surface of a workpiece to be coated as anode.
  • the alginate tends to deposit. During the same time, it becomes a colloid and acts as a paste to strengthen the electrodepositing effect as well as an adhesive between the workpiece and fine powder.
  • a film of uniform thickness can be formed on parts of complex shape or sharp angle and the thickness of the electrodeposited film can be freely controlled, for example, ranging from several microns to several hundred microns.
  • the coating layer consisting of the electrodeposited fine powder sinters densely and adheres strongly to the base member during the next heating treatment.
  • tantalum carbide fine powder an alloying or solid solution making reaction with the surface layer of a workpiece to be coated takes place intimately, whilst, in the case of using tantalum or tantalum compound fine powder besides tantalum carbide, a carbonization reaction with previously mixed carbon, diffused carbon from a workpiece to be coated or carbon in atmosphere proceeds.
  • the base member is of cemented carbides, in particular, its binder metal for example, cobalt moves during heating like capilarity and, consequently, the coating layer containing the moved binder metal is obtained.
  • a material to be the binder metal may previously be electrodeposited.
  • the metal penetrates through tantalum carbide by capilarity, liquid phase sintering taking place, even if the powder to be electrodeposited contains no binder metal.
  • a metal capable of forming a low melting point liquid phase with tantalum carbide may previously be plated onto a workpiece.
  • Example 1 Tantalum carbide powder of -200 mesh was ballmilled by wet process for 3 hours and dried. g. of the resulting powder was taken and dispersed in a mixed solution of 50 ml. of methylene chloride, 30 ml. of isopropyl alcohol and 20 ml. of nitromethane. 0.1 g. of prolamin was added thereto and stirred for 3 hours.
  • a nickel plate was used as anode and an insert (12.7 mm. square, 4.8 mm. thickness) of K20 cemented carbides (WC-7% Co) was held by a narrow copper wire as cathode. 200 volts direct current at milliamperes was applied across the electrodes for 60 seconds to effect electrophoresis. The thus coated insert was then dried in the air and held at 1350 C. for 1 hour in a vacuum furnace mm. Hg).
  • the resulting coating layer was a uniform and completely dense layer of about 100 microns, which gave a beautiful golden color when lapped.
  • Example 2 A commercially sold tantalum hydride powder of 325 mesh was ball-milled by wet process for 15 hours to obtain a colloidal powder of tantalum hydride. 15 g. of the resulting powder was taken and dispersed in 300 ml. of water. Moreover, I g. of powdered sodium alginate was dissolved in 500 ml. of water to prepare a solution and 10 ml. of this solution was added to the dispersion with agitation. A copper plate was used as cathode and an insert (12.7 mm. square, 4.8 mm. thickness) of K20 cemented carbides (WC-7% Co) was held by a narrow copper wire as anode.
  • K20 cemented carbides WC-7% Co
  • the resulting coating layer was a uniform layer of about 60 microns, which gave a beautiful golden color when lapped. X-ray diffraction showed nothing on the surface of the insert but the diffraction figure of tantalum carbide.
  • Example 3 A commercially sold tantalum hydride powder of 325 mesh was mixed with 5% of Cobalt powder and 6.2% of carbon powder and ball-milled by wet process for 24 hours to obtain a colloidal mixed powder.
  • a workpiece of molybdenum was used as anode in place of K20 cemented carbides and subjected to electrodeposition under the similar condition to that of Example 2. The thus coated workpiece was then dried in the air and held at 1350 C. for 30 minutes in a hydrogen furnace.
  • the resulting coating layer was a uniform layer of about 50 microns in thickness, which gave a beautiful gold color when lapped.
  • Example 4 Tantalum carbide powder of -200 mesh and 10% of electrolytic copper powder of mesh were ball-milled by wet process for 24 hours.
  • the colloidal mixed powder was subjected to electrodeposition to a workpiece of carbon steel (0.30% carbon) used as cathode in place of K20 cemented carbides under the similar condition to that of Example 1.
  • the thus coated workpiece was then dried in the air and heated at 1150 C. for 20 minutes in a hydrogen furnace.
  • the resulting coating layer was lapped to thus give a beautiful golden color.
  • a method of making articles having a hard and attractive, golden colored-coating comprising dispersing a fine powder of tantalum carbide in a liquid medium selected from the group consisting of water, an aqueous medium and an organic solvent, immersing a workpiece of WC-base cemented carbides in the dispersion, applying a direct current voltage to the surface of said workpiece to cause electrophoretic deposition of the fine powder of tantalum carbide thereupon, removing the thuscoated workpiece from the dispersion and heating the coated surface at high temperatures in a vacuum or in a reducing or inert atmosphere, thereby forming a coating layer of tantalum carbide on the surface of the workp1ece.
  • said workpiece consists of tungsten carbide-cobalt with at least one member selected from the group consisting of titanium carbide, tantalum carbide, molybdenum carbide, hafnium carbide, zirconium carbide, chromium carbide and vanadium carbide.

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  • Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Other Surface Treatments For Metallic Materials (AREA)
  • Electroplating And Plating Baths Therefor (AREA)
  • Powder Metallurgy (AREA)
US00133382A 1970-04-20 1971-04-12 Method of making an article having a hard and ornamental coating Expired - Lifetime US3749656A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP45032950A JPS5215605B1 (de) 1970-04-20 1970-04-20

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US3749656A true US3749656A (en) 1973-07-31

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JP (1) JPS5215605B1 (de)
CH (1) CH521864A (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2011007019A1 (es) * 2009-07-15 2011-01-20 Fundacion Cidetec Procedimiento para la obtención de un recubrimiento cerámico mediante deposición electroforética
US9896384B2 (en) 2014-06-17 2018-02-20 University Of Utah Research Foundation Methods of sintering dense zeta-phase tantalum carbide

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2011007019A1 (es) * 2009-07-15 2011-01-20 Fundacion Cidetec Procedimiento para la obtención de un recubrimiento cerámico mediante deposición electroforética
US9896384B2 (en) 2014-06-17 2018-02-20 University Of Utah Research Foundation Methods of sintering dense zeta-phase tantalum carbide

Also Published As

Publication number Publication date
CH521864A (de) 1972-04-30
DE2119154A1 (de) 1971-11-04
JPS5215605B1 (de) 1977-05-02
DE2119154B2 (de) 1977-03-10

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