| Method of producing corundum layer on metal parts -> Monitor Keywords |
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  Method of producing corundum layer on metal partsRelated Patent Categories: Electrolysis: Processes, Compositions Used Therein, And Methods Of Preparing The Compositions, Electrolytic Coating (process, Composition And Method Of Preparing Composition), Forming Nonmetal Coating Using Specified Waveform Other Than Pure Dc Or 60 Hz Sine Wave Ac (e.g., Anodic Oxide Coating, Etc.)The Patent Description & Claims data below is from USPTO Patent Application 20060207884. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] The present invention relates to an electrochemical process of application of coatings, and can be used in machine construction, instrument making, and medicine. [0002] Methods of forming protective or decorative ceramic coatings on aluminum and their alloys are known. They are disclosed for example in U.S. Pat. Nos. 3,956,080; 4,082,626; 4,659,440; 5,275,713 and use an anodic process with application of direct current and voltage up to 600 v for obtaining ceramic coatings with high corrosion resistance and adhesion. They however have the disadvantage that the ceramic coating is formed slowly and has low hardness. [0003] In U.S. Pat. No. 5,147,515 in order to apply coatings, electrophoresis is utilized with a electrolyte formed by colloid aqueous solutions of silicates or water-insoluble salts with high concentration, where ceramic particles are in suspended state. Direct current is used, which has a wave shape and preferably a rectangular shape, with a gradual increase of voltage from 50 to 200 v. Such coating can have a thickness up to 700 micron, high hardness, wear resistance and resistance to corrosion. The disadvantage of such coatings is a non-uniform thickness of the coating, high roughness of the surface, and low cyclical resistance to thermal shock, and also low adhesion. [0004] U.S. Pat. No. 5,616,229 discloses the use of a wave electrical current as a current source, with a wave shape in form of a tooth, with voltage approximately 700 volt which is provided by a capacitor block with a total capacity 375 microfarad. In order to accelerate the process of forming the coating, salts of metals are added to the electrolyte. However, the addition of metal salts leads to an increase of the layer on the surface of the part and to a change of at least its size and increase of surface roughness. With the use of the capacitor block with a total capacity of 375 microfarad, it is possible to obtain coatings on small parts with the surface up to 0.1 dm.sup.2. [0005] U.S. Pat. No. 5,720,866 discloses the use of direct current in first and second phases, and the use of alternating current with superposition of direct current or with alternating square anodic pulses and square cathodic pulses with reduced amplitude in third phase, while in fourth phase the magnitude and frequency of cathodic pulses is reduced and the magnitude of anodic pulses is increased. [0006] The existing methods can be further improved SUMMARY OF THE INVENTION [0007] Accordingly, it is an object of the present invention to provide a method of forming a corundum surface layer on metal parts, which is a further improvement of the existing methods. [0008] More particularly, it is an object of the present invention to provide a corundum layer on a surface of parts composed of metals Al, Ti, Ta, Mg, steel and their alloys, with the use of an electrochemical method in a mode of anodic-cathodic, galvano-plasma treatment in alkali electrolytes, for obtaining heat resistant, wear resistant, erosion-resistant, and corrosion-resistant surfaces of parts. [0009] It is also an object of the present invention to reduce a time of formation of a corundum layer, to reduce time of application of a coating, to increase resistance of parts to a thermal shock, and to provide erosion resistance. [0010] In accordance with the present invention the above mentioned objectives are achieved by the use of an wave alternating current which has a gradual increase of voltage between a cathode and an anode to 1000-1800 volt, preferably to 1800 volt. [0011] The inventive method can be performed with a changing time of anodic and cathodic pulses of voltage, executed in three modes. [0012] First mode is a cathodic mode, in which time and amplitude of a cathodic pulse of voltage is increased and amplitude and time of anodic pulse of voltage is reduced. This mode is used for removal of metallic admixtures, fusible compounds and oxides from the surface layer of a part. Second mode is an anodic-cathodic mode, in which time of action and amplitude of anodic pulse of voltage is increased, and time of action and amplitude of a cathodic pulse of voltage is reduced. This mode is provided for formation of a corundum layer without changes in dimensions of the part. Third mode is an anodic-pulse mode, in which time and amplitude of anodic pulse of voltage is increased with a subsequent pause. This mode is used for accelerated formation of a corundum layer of a great thickness (up to 1 mm) with low porosity and high adhesion. [0013] The treatment can be performed in an alkali electrolyte with an optimal concentration, with maintaining a ratio between alkali, liquid glass, catalyst and filler 1:2:0,2:2. The part which is immersed into the electrolyte can be fixed on an aluminum anode which can be arranged on an ultrasound vibrator. A renewed and cold electrolyte can be supplied into a zone of arc discharges with a speed of movement along a surface of the part from 100 to 1000 mm/sec. [0014] The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS [0015] FIG. 1 is a view showing a cathodic mode with an asymmetric pulse of voltage of the method in accordance with the present invention; [0016] FIG. 2 is a view showing an anodic-cathodic mode with an asymmetric pulse of voltage and increased time of an anodic pulse, of the inventive method; [0017] FIG. 3 is a view showing an anodic mode with an increased time of an anodic pulse of voltage and a pause, of the method in accordance with the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS [0018] In order to provide a corundum surface layer on a part in accordance with the present invention, a cathode composed of stainless steel or titanium alloy is introduced into an electrolytic bath, or a housing of the bath can be composed of these materials. A metal part is then introduced as an anode into the electrolytic bath, preferably it is arranged on a suspension of for example aluminum alloy with an outside insulation from electrolyte, and mounted in an ultrasound vibrator, to subject the part to ultrasound vibrations for obtaining a surface with low roughness. [0019] The electrolyte can be composed of a solution in a distilled water of NaOH, KOH, NaAlO.sub.2, KAlO.sub.2, Na .sub.2SiO.sub.3, K.sub.2SiO.sub.3, Na .sub.6P.sub.6O.sub.12, K.sub.6P.sub.6O.sub.12, KMNO.sub.4, Al.sub.2O.sub.3, fine powders of oxides, carbides and nitrides in required combination and concentration, depending on required properties of a corundum layer and a metal of the metal part. A ratio between alkali, liquid glass, catalyst and filler is selected to be 1:1:0.2:2. [0020] A wave electric current is then turned on, which can be an asymmetric current, and voltage between the cathode and the anode is increased substantially to 1000-1,800 volt. This provides an exceptionally intense and efficient formation of the corundum layer on the metal part. Continue reading... Full patent description for Method of producing corundum layer on metal parts Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Method of producing corundum layer on metal parts patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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