Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D15/00—Electrolytic or electrophoretic production of coatings containing embedded materials, e.g. particles, whiskers, wires
  • C25D15/02—Combined electrolytic and electrophoretic processes with charged materials
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D3/00—Electroplating: Baths therefor
  • C25D3/02—Electroplating: Baths therefor from solutions
  • C25D3/56—Electroplating: Baths therefor from solutions of alloys
  • C25D3/562—Electroplating: Baths therefor from solutions of alloys containing more than 50% by weight of iron or nickel or cobalt

Definitions

• the invention relates to a method for coating workpieces, in which an alloy containing at least phosphorus and nickel is deposited from an electrolyte to form a functional, in particular corrosion-resistant and wear-resistant, metallic coating.
• the invention further relates to a cover in this regard.
• metallic coatings are primarily used for the functional coating of workpieces in order to take account of the stress mechanisms that occur during intended use by means of suitable surface properties, such as hardness, wear resistance, friction or thermal and chemical resistance.
• Protective coatings of this type are usually produced by electroplating.
• electrolytic deposition in which electrocrystallization takes place
• electroless metal deposition which is a simple immersion process without an external power source and anodes. In both processes, metal deposition can be applied to both metallic and non-metallic workpiece surfaces. Due to the high degree of contour accuracy during the deposition, the electroless deposition is used in particular when very tight tolerances have to be observed for workpieces with complex geometries.
• the electrolytic deposition is subject to clear limits because of the geometry-dependent distribution of local cathode current densities.
• it is therefore known to deposit polyalloys with a higher phosphorus content with the base metal nickel without external current.
• a nickel-cobalt-phosphor coating alloyed with the addition of cobalt in proportions of 0.5 to 1.5% by weight with a phosphorus content between 10 and 13% by weight increased the residual compressive stress and contributes to the measurable hardness.
• the phosphorus content in the alloy matrix has a significant influence on the passivation properties of a metallic coating. For example, corrosion tests showed that an improvement
• Corrosion resistance at phosphorus contents of 14 to 21 wt .-% can be achieved.
• a disadvantage of the deposition of metal coatings without external current, however, is that such high phosphorus contents cannot be achieved due to the lack of imprinted reaction mechanisms.
• the invention is based on the object of specifying a method for coating workpieces which, with a substantially higher installation rate of elemental phosphorus, enables increased wear resistance and hardness as well as improved corrosion-protective effect.
• a coating in this regard is to be specified.
• This object is achieved according to the invention in a method of the type mentioned at the outset by electrolytically depositing an at least quaternary alloy with the components nickel, cobalt, tungsten and phosphorus as a coating.
• Such a method enables an incorporation rate of phosphorus into the metallic coating of between 1 4 and 21% by weight due to the electrolytic deposition and the associated forced reductive reaction system at the interface between the electrolyte and the workpiece.
• the invention is also based on the surprising finding that the common cathodic deposition of nickel, cobalt, tungsten and phosphorus forms an alloy coating which is distinguished by a high level of corrosion resistance and wear resistance. It is particularly advantageous, depending on the functional use of the coating, to cathodically deposit an alloy with at least one further component, preferably made of tin, lead, molybdenum, rhenium or vanadium, as a metal deposit. In this way, for example, a temperature resistance, solderability, magnetic permeability or a suitable coefficient of friction that meets the respective requirements can be achieved.
• non-metallic particles preferably carbides or carbide mixed crystals
• Boron, silicon, tungsten, vanadium and / or titanium carbide is advantageously used for this purpose. It is also advantageous if particles with a grain size of 0.1 to 1.5 ⁇ m are used for this purpose. Alternatively, ultrafine particles with diameters in the nanometer range or particles with a grain size of more than 1.5 ⁇ m can also be used, depending on the desired surface layer properties.
• the particles are incorporated in different concentrations over the course of the thickness of the coating.
• the particles are added to the electrolyte as a disperse phase and are incorporated in the alloy deposit during the electrodeposition.
• This installation is mainly due to adsorption, electrostatic attraction and mechanical inclusion.
• the particles are expediently kept suspended in the electrolyte by moving the galvanic bath. In a manner known per se, for example by stirring or blowing air into the bath, it is possible to keep the particles in suspension.
• additional coloring pigments preferably made of titanium dioxide, are incorporated, so that self-colored coatings result which ensure high light and weather resistance.
• a corrosion-resistant and wear-resistant coating is also proposed according to the invention, which can be produced in particular by the method described above and is essentially composed of a composition
• a metallic coating is formed by galvanic alloy deposition, which is composed of 0.5 to 2.0% by weight of tungsten, 1.0 to 2.0% by weight of cobalt, 15 to 20% by weight of phosphorus and a remainder Proportion of nickel.
• the metallic matrix of this alloy deposit also has embedded non-metallic particles made of tetraborecarbide. These were built into the coating near the cathode during mechanical crystallization, adsorption or electrostatic attraction.
• the tetraborarbide is in the form of a in the electrolyte used for the deposition suspended fine powder, the particles having a grain size of 0.1 to 1.5 ⁇ m.
• the particles are kept in suspension in the electrolyte in uniform concentration.
• a differently concentrated installation of the particles over the course of the thickness of the coating can be brought about by a suitable change in the bath movement.
• the coating formed in this way has a total of 30 to 39% by volume of incorporated tetraborecarbide.
• the coating Due to the interaction of the components nickel, cobalt, tungsten, phosphorus and boron carbide, the coating has a high resistance to both acid and alkaline corrosion media as well as oxidizing acids.
• the salt spray test according to DIN 50 021 used for the corrosion test showed exposure for more than 485 h with a thickness of the coating of 60 ⁇ m and a base material made of steel for more severe conditions with the addition of copper chloride.
• the cover thus fulfills the requirements of RAL-RG 660 for level 4/4 hydraulics in mine construction.
• the coating is also characterized by high wear resistance. With an average roughness depth of approx. 2 to 3 ⁇ m, the wear resistance was determined according to TABER using test criteria that wear out abrasions. For this purpose, friction rollers of the type CS-1 0 with a bearing load of 9.81 N were used. After 100,000 revolutions, the coating reached an average wear value of 2.71 mg / 1000 revolutions, in particular from the diagram in the drawing showing the course of the determined wear removal values according to TA BER in mg 1000 revolutions above the revolutions U. can be seen. The running-in behavior of the friction rollers was not taken into account. The wear value determined is below the abrasion resistance of max.

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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)
• Electroplating Methods And Accessories (AREA)
• Electroplating And Plating Baths Therefor (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Paints Or Removers (AREA)

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Publications (2)

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• 1998
  • 1998-09-01 EP EP98116503A patent/EP0984082A1/fr not_active Withdrawn
• 1999
  • 1999-08-28 ES ES99968252T patent/ES2233099T3/es not_active Expired - Lifetime
  • 1999-08-28 US US09/786,300 patent/US6635165B1/en not_active Expired - Lifetime
  • 1999-08-28 EP EP99968252A patent/EP1117856B1/fr not_active Expired - Lifetime
  • 1999-08-28 DE DE59911058T patent/DE59911058D1/de not_active Expired - Lifetime
  • 1999-08-28 WO PCT/EP1999/006358 patent/WO2000012782A1/fr active IP Right Grant
  • 1999-08-28 AT AT99968252T patent/ATE282099T1/de not_active IP Right Cessation

Non-Patent Citations (1)

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