Method for electrolytically depositing a ceramic coating on a metal, electrolyte for such electrolytic ceramic coating method, and metal member

Abstract

A method of electrolytic ceramic coating for metals, in which there can be obtained a coating film that even when it is thin, exhibits high hardness, excellent abrasion resistance and excellent toughness and that even when applied to a slide material without polishing, has low offensiveness to the mate material. As such a method, there is provided a method of electrolytic ceramic coating for metals, comprising carrying out electrolysis with the use of a metal as a positive electrode in an electrolyte containing a zirconium compound so that a ceramic coating is formed on the surface of the metal.

1 . A method for electrolytically depositing a ceramic coating on a metal wherein an electrolytic treatment is conducted by using the metal as an anode in an electrolyte containing a zirconium compound to thereby form a ceramic coating on a surface of the metal.  
     
     
         2 . The method for electrolytically depositing a ceramic coating on a metal according to  claim 1  wherein the zirconium compound is a water soluble zirconium compound.  
     
     
         3 . The method for electrolytically depositing a ceramic coating on a metal according to  claim 2  wherein the water soluble zirconium compound is a zirconium carbonate compound.  
     
     
         4 . The method for electrolytically depositing a ceramic coating on a metal according to  claim 1  wherein the electrolyte is at a pH of at least 8.0.  
     
     
         5 . The method for electrolytically depositing a ceramic coating on a metal according to  claim 1  wherein the electrolyte further contains a water soluble phosphorus compound.  
     
     
         6 . The method for electrolytically depositing a ceramic coating on a metal according to  claim 5  wherein the water soluble phosphorus compound is a condensed phosphate.  
     
     
         7 . The method for electrolytically depositing a ceramic coating on a metal according to  claim 1  wherein the electrolyte further contains an ion and/or an oxide of at least one metal selected from the group consisting of titanium, yttrium, calcium, magnesium, scandium, and cerium.  
     
     
         8 . The method for electrolytically depositing a ceramic coating on a metal according to  claim 1  wherein the electrolyte further contains poorly soluble particles of at least one member selected from the group consisting of oxide, hydroxide, phosphate, and carbonate.  
     
     
         9 . The method for electrolytically depositing a ceramic coating on a metal according to  claim 1  wherein the electrolytic treatment is carried out by a direct current electrolysis or a bipolar electrolysis using a voltage waveform in which an AC component is superposed on a DC component.  
     
     
         10 . The method for electrolytically depositing a ceramic coating on a metal according to  claim 1  wherein the electrolytic treatment is conducted by using a voltage waveform in which at least one pulse wave selected from the group consisting of rectangular wave, sine wave, and triangular wave having a duty ratio of up to 0.5 is superposed on a DC or AC component.  
     
     
         11 . The method for electrolytically depositing a ceramic coating on a metal according to  claim 9  wherein the maximum value of the voltage waveform is at least 400 V.  
     
     
         12 . The method for electrolytically depositing a ceramic coating on a metal according to  claim 1  wherein the electrolytic treatment is conducted under glow discharge and/or arc discharge caused on the surface of the metal used as the anode.  
     
     
         13 . The method for electrolytically depositing a ceramic coating on a metal according to  claim 1  wherein the metal is a valve metal or its alloy.  
     
     
         14 . An electrolyte for use in electrolytic deposition of a ceramic coating on a metal, containing water, a zirconium compound, and at least one member selected from the group consisting of alkali metal ion, ammonium ion, and organic alkali.  
     
     
         15 . The electrolyte for use in electrolytic deposition of a ceramic coating on a metal according to  claim 14  wherein the zirconium compound is a water soluble zirconium compound.  
     
     
         16 . The electrolyte for use in electrolytic deposition of a ceramic coating on a metal according to  claim 15  wherein the water soluble zirconium compound is a zirconium carbonate compound.  
     
     
         17 . The electrolyte for use in electrolytic deposition of a ceramic coating on a metal according to  claim 14  wherein the electrolyte is at a pH of at least 8.0.  
     
     
         18 . The electrolyte for use in electrolytic deposition of a ceramic coating on a metal according to  claim 14  wherein the electrolyte further contains a water soluble phosphorus compound.  
     
     
         19 . The electrolyte for use in electrolytic deposition of a ceramic coating on a metal according to  claim 18  wherein the water soluble phosphorus compound is a condensed phosphate.  
     
     
         20 . The electrolyte for use in electrolytic deposition of a ceramic coating on a metal according to  claim 14  wherein the electrolyte further contains an ion and/or an oxide of at least one metal selected from the group consisting of titanium, yttrium, calcium, magnesium, scandium, and cerium.  
     
     
         21 . The electrolyte for use in electrolytic deposition of a ceramic coating on a metal according to  claim 14  wherein the electrolyte further contains poorly soluble particles of at least one member selected from the group consisting of oxide, hydroxide, phosphate, and carbonate.  
     
     
         22 . The electrolyte for use in electrolytic deposition of a ceramic coating on a metal according to  claim 14  wherein the electrolyte is used for electrolytically depositing a ceramic coating on a valve metal or its alloy.  
     
     
         23 . A metal member comprising a metal substrate and a hard coating on the metal substrate, wherein: 
 the hard coating comprises an amorphous layer which is composed of an amorphous oxide containing a metal element constituting the metal substrate and zirconium, and zirconium oxide microcrystals dispersed in the amorphous oxide.    
     
     
         24 . A metal member comprising a metal substrate and a hard coating on the metal substrate, wherein: 
 the hard coating comprises a crystalline layer on the metal substrate and an amorphous layer on the crystalline layer, with the crystalline layer containing crystals of oxide of a metal element constituting the metal substrate, and the amorphous layer being composed of an amorphous oxide containing the metal element constituting the metal substrate and zirconium, and zirconium oxide microcrystals dispersed in the amorphous oxide.    
     
     
         25 . The metal member according to  claim 24  wherein the crystalline layer further contains zirconium oxide microcrystals dispersed along a grain boundary and/or in a grain of the crystals of oxide of the metal element constituting the metal substrate.  
     
     
         26 . The metal member according to  claim 23  wherein concentration distribution of the zirconium in the hard coating is such that the zirconium concentration gradually reduces from the surface of the hard coating toward the metal substrate.  
     
     
         27 . The metal member according to  claim 23  wherein, when the hard coating is analyzed by X ray diffractometry, relative peak intensity on (111) plane of tetragonal zirconium oxide and/or cubic zirconium oxide is equal to or higher than relative peak intensity of the main peak of the oxide of the metal element constituting the metal substrate.  
     
     
         28 . The metal member according to  claim 23  wherein, when the hard coating is analyzed by X ray diffractometry, proportion of volume of monoclinic zirconium oxide to the total of volume of the tetragonal zirconium oxide and/or the cubic zirconium oxide and volume of the monoclinic zirconium oxide is up to 0.5.  
     
     
         29 . The metal member according to  claim 23  wherein microcrystals of the tetragonal zirconium oxide and/or the cubic zirconium oxide have an average grain diameter of 0.25 to 500 nm.  
     
     
         30 . The metal member according to  claim 23  wherein a phosphorus oxide is present on the surface of the hard coating and/or at the interface of the hard coating with the metal substrate.  
     
     
         31 . The metal member according to  claim 23  wherein the hard coating further contains at least one element selected from the group consisting of yttrium, calcium, cerium, scandium, magnesium, and titanium.  
     
     
         32 . The metal member according to  claim 23  wherein the metal element constituting the metal substrate is a valve metal or its alloy.  
     
     
         33 . A metal member according to produced by the method for electrolytically depositing a ceramic coating on a metal according to  claim 1.