Method For Producing Heavy Highly Adhesive Protective Coatings on Valve-Metal Parts By Micro-Arc Oxidation

Inactive Publication Date: 2008-11-20
NIKIFOROV ALEKSEJ ALEKSANDROVICH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0009]FIG. I shows a picture of an installation that explains realization of the method claimed. The installation for producing protective coatings on valve-metal parts or alloys thereof by micro-arc oxidation comprises a metal bath I with an electrolyte 2, in which a part 5 is mounted on a current-conductive holder 3 with an electroinsulating coating 4 at the air-electrolyte interface, said part being connected to one of the terminals of a power source 6, another one—to the metal bath I.

Problems solved by technology

The main defects of the known method are an insufficient thickness of the obtainable coating and a low adhesion of the coating to a base material, which is explained by the fact that the thickness of said coating is linearly increased as a voltage is raised and what is more the rate of film growth begins reducing abruptly (up to 5 mcm / hr) on achievement of certain thickness (60-70 mcm in the example cited).
Besides, the further slow growth of a protective film on a part is not accompanied by improvement of its adhesion to the base material.

Method used

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  • Method For Producing Heavy Highly Adhesive Protective Coatings on Valve-Metal Parts By Micro-Arc Oxidation
  • Method For Producing Heavy Highly Adhesive Protective Coatings on Valve-Metal Parts By Micro-Arc Oxidation

Examples

Experimental program
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Effect test

example i

[0012]A coating was applied to an aluminium alloy, D16 grade, in an electrolyte containing 2 g / l KOH (caustic potash) and 9 g / l water glass. The time of coating was 20 min at the temperature of the electrolyte of 20° C. and a current density of 20 A / dm2. The holder was an aluminium wire.

[0013]The thickness of a coating thus obtained was:

[0014]22 mcm for an unprotected holder;

[0015]47 mcm for a protected holder.

example 2

[0016]A coating was applied to an aluminium alloy, D16 grade in an electrolyte containing 2 g / l KOH (caustic potassium) and 9 g / l water glass. The time of coating was 150 min at the temperature of the electrolyte of 20° C. and a current density of 20 A / dm2. The holder was an aluminium wire.

[0017]The thickness of a coating thus obtained was:

[0018]108 mcm for an unprotected holder;

[0019]223 mcm for a protected holder.

[0020]Thus, the claimed method allows one to substantially raise a voltage on the holder of a part and to increase the thickness of an obtainable coating more than twice. On check of adhesion of the coating to a base material, separation of the coating occurred not at the lower boundary of a protective film, as in the case of the prototype, but on the base material.

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Abstract

The invention relates to electrochemistry, in particular to anodizing parts made of valve metals such as aluminium, titanium, tantalum etc and alloys thereof and can be used for producing solid heat-resistant and wear-resistant coatings for mechanical engineering. A method consists in placing a part in an electrolyte on a current-conductive holder coated with an insulating material, producing a working voltage between said part and electrolyte and raising the voltage until a micro-arc discharge is originated on the part surface. The holder of the part is externally coated with, an electroinsulating material at the air-electrolyte interface. The technical result of the invention is to produce by micro-arc oxidation heavy protective coatings which exhibit a high-hardness, have a low friction factor and a high adhesion to a base material on the parts made of the valve metals or alloys thereof.

Description

FIELD OF THE INVENTION[0001]The invention relates to electrochemistry, in particular to anodizing parts made of valve metals such as aluminium, titanium, tantalum etc and alloys thereof and can be used for producing solid heat-resistant and wear-resistant coatings for mechanical engineering.PRIOR ART[0002]Known is a method of micro-arc oxidation of valve metals taken as a prototype (cf. A. N. Novikov “Repair of parts of aluminium and alloys thereof”, Orel, the Orel State Agricultural Academy, 1997, pp. 32-33), which comprises placing a part in an electrolyte on a current-conductive holder, producing a working voltage between said part and said electrolyte, raising the voltage until a micro-arc discharge is originated on the part surface. To avoid forming a protective film on said part or suspension portions not to be oxidized, special removable fluoroplastic or capralon jackets are manufactured to cover same on application of coatings.[0003]The known method of micro-arc oxidation ma...

Claims

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Application Information

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IPC IPC(8): C25D11/00C25D11/02
CPCC25D11/026C25D11/005
Inventor NIKIFOROV, ALEKSEJ ALEKSANDROVICH
Owner NIKIFOROV ALEKSEJ ALEKSANDROVICH
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