CA1052317A - Electrolytic formation of group va carbide on an iron, ferrous alloy or cemented carbide article - Google Patents
Electrolytic formation of group va carbide on an iron, ferrous alloy or cemented carbide articleInfo
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- CA1052317A CA1052317A CA170,290A CA170290A CA1052317A CA 1052317 A CA1052317 A CA 1052317A CA 170290 A CA170290 A CA 170290A CA 1052317 A CA1052317 A CA 1052317A
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- article
- carbide
- layer
- molten bath
- group element
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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
- C25D9/00—Electrolytic coating other than with metals
- C25D9/04—Electrolytic coating other than with metals with inorganic materials
- C25D9/08—Electrolytic coating other than with metals with inorganic materials by cathodic processes
Abstract
ABSTRACT OF THE DISCLOSURE:
A method for forming a carbide layer of a V-a group element of the Periodic Table on the surface of an iron, ferrous alloy or cemented carbide article in a treating molten bath, comprising preparing the treating molten bath composed of boric acid or a borate and a V-a group element, immersing the article in the treating molten bath and applying an electric current to the treating molten bath with said article being used as the cathode, thereby forming, a very hard carbide layer of said V-a group element of the surface of said article. The method of this invention can form quickly a uniform and dense carbide layer on the surface of the article and can be carried out in the open air.
A method for forming a carbide layer of a V-a group element of the Periodic Table on the surface of an iron, ferrous alloy or cemented carbide article in a treating molten bath, comprising preparing the treating molten bath composed of boric acid or a borate and a V-a group element, immersing the article in the treating molten bath and applying an electric current to the treating molten bath with said article being used as the cathode, thereby forming, a very hard carbide layer of said V-a group element of the surface of said article. The method of this invention can form quickly a uniform and dense carbide layer on the surface of the article and can be carried out in the open air.
Description
~SZ3~7 This invention relates to a method for forming a carbi-de layer of a V-a group element of the ~eriodic Table on the su.face of an iron, ferrous alloy or cemented carbide article, and more particularly it relates to the formation of the carbide layer on the surface of the article immersed in a treating molten bath. The iron ferrous alloy or cemented carbide article with the carbide layer formed thereof has a greatly improved hardness, wear resistance and machinability.
There have been reported several kinds of methods for coating or forming a metallic carbide layer on the surface of metallic articles~ We have pxeviously developed a method for forming a carbide layer of a V-a group element on the surface of metallic article in a treating molten bath consisting of boric acid or a borate and a metal powder containing a V-a group element (Canadian Patent N. 935 074). The method can ~orm ~ a uniform carbide layer and is highly productive and cheap.
The carbide of a V-a group element, such as vanadium carbide (VC), niobium carbide (~b) and tantalum carbide (TaC) has a very high hardness ranging from Hv 2000 to Hv 3000. Therefore, the carbide layer formed represents a high value of hardness and a superior resistance performance against wear and is thus highly suitable for the surface treatment of moulds such as dies and punches, tools such as pinchers and screwdrivers, parts for many kinds of tooling machines, automobile parts to be subjected to wear.
Further, the carbide of a V-a group element is much harder and less reactive with iron or steel at a high temperature than the tungsten carbide forming cemented carbide is. Therefore, the formation of the carbide layer of a V-a group element on the surface of a cutting tool made of cemented carbide increases greatly the durability of the tool.
The method mentioned above, however, takes a relatively - 1 - ~
~05~3~7 long time for forming a practically acceptable thick carbide layer of a V-a group element.
Therefore, it is the pxincipal object of the present invention to provide an improved method for forming a carbide layer of a V-a group element on the surface of an iron, ferrous alloy or cemented carbide article in a treating molten bathO
It is another object of this invention to provide a method ~or forming quickly a metallic carbide layer with denseness and uniformity on the surface of the article.
It is still another object of this invention to provide a method for forming a metallic carbide layer on the surface of the article by applying an electric current to the article.
It is a still further object of this invention to provide a method for forming a carbide layer, which is safe and simple in practice and less expensive.
The above objects are obtained in a method which ccmprises the steps of:
preparing a treating molten bath composed of molten boric acid or a borate and a substance containing a V-a group element of the Periodic Table in a vessel, immersing the article containing at least 0.05% by weight of carbon into the treating molten bath, applying an electric current to the treating molten bath through said article being used as the cathode for depositing the V-a group element on the surface of the article and for forming the carbide layer of said V-a group element with the carbon contained within said article on the surface of said article and taking said article out of the trca-ting molten bath.
A description now follows of specific embodiments in connection with the accompanying drawings, in which:
~i 1~5'~3~7 Figs. 1 to 4 are photomicrographs showing vanadium car-bide layers on carbon tool steel, which are formed according to Example l;
Fig. 5 to 7 are graphs obtained in Example 1 by X-ray micro analyzer and showing the contents of the components forming the carbide layers;
Fig. 8 is a graph obtained in Example 1 and showing the effect of the current density applied to the article treated on the thickness of khe layer formed;.
" 1~5'~317 Fig. 9 is a photomicro~raph showing a niobium carbide layer on carbon tool steel, which is forned according to Example
There have been reported several kinds of methods for coating or forming a metallic carbide layer on the surface of metallic articles~ We have pxeviously developed a method for forming a carbide layer of a V-a group element on the surface of metallic article in a treating molten bath consisting of boric acid or a borate and a metal powder containing a V-a group element (Canadian Patent N. 935 074). The method can ~orm ~ a uniform carbide layer and is highly productive and cheap.
The carbide of a V-a group element, such as vanadium carbide (VC), niobium carbide (~b) and tantalum carbide (TaC) has a very high hardness ranging from Hv 2000 to Hv 3000. Therefore, the carbide layer formed represents a high value of hardness and a superior resistance performance against wear and is thus highly suitable for the surface treatment of moulds such as dies and punches, tools such as pinchers and screwdrivers, parts for many kinds of tooling machines, automobile parts to be subjected to wear.
Further, the carbide of a V-a group element is much harder and less reactive with iron or steel at a high temperature than the tungsten carbide forming cemented carbide is. Therefore, the formation of the carbide layer of a V-a group element on the surface of a cutting tool made of cemented carbide increases greatly the durability of the tool.
The method mentioned above, however, takes a relatively - 1 - ~
~05~3~7 long time for forming a practically acceptable thick carbide layer of a V-a group element.
Therefore, it is the pxincipal object of the present invention to provide an improved method for forming a carbide layer of a V-a group element on the surface of an iron, ferrous alloy or cemented carbide article in a treating molten bathO
It is another object of this invention to provide a method ~or forming quickly a metallic carbide layer with denseness and uniformity on the surface of the article.
It is still another object of this invention to provide a method for forming a metallic carbide layer on the surface of the article by applying an electric current to the article.
It is a still further object of this invention to provide a method for forming a carbide layer, which is safe and simple in practice and less expensive.
The above objects are obtained in a method which ccmprises the steps of:
preparing a treating molten bath composed of molten boric acid or a borate and a substance containing a V-a group element of the Periodic Table in a vessel, immersing the article containing at least 0.05% by weight of carbon into the treating molten bath, applying an electric current to the treating molten bath through said article being used as the cathode for depositing the V-a group element on the surface of the article and for forming the carbide layer of said V-a group element with the carbon contained within said article on the surface of said article and taking said article out of the trca-ting molten bath.
A description now follows of specific embodiments in connection with the accompanying drawings, in which:
~i 1~5'~3~7 Figs. 1 to 4 are photomicrographs showing vanadium car-bide layers on carbon tool steel, which are formed according to Example l;
Fig. 5 to 7 are graphs obtained in Example 1 by X-ray micro analyzer and showing the contents of the components forming the carbide layers;
Fig. 8 is a graph obtained in Example 1 and showing the effect of the current density applied to the article treated on the thickness of khe layer formed;.
" 1~5'~317 Fig. 9 is a photomicro~raph showing a niobium carbide layer on carbon tool steel, which is forned according to Example
2, Fig. 10 is a graph obtained in Example 2 by X-ray micro analyzer and showing the contents of the components forming the niobium carbide layer;
Fig. 11 to 13 are photomicrographs showing vanadium carbide layers on carbon tool steels, which are formed according to Example 3;
10Fig. 14 is a photomicrograph showing a vanadium carbide layer formed on carbon tool steel according to Example 4, Fig. 15 and 16 are graphs obtained in Example 6 and showing the effect of the current density applied to the article treated on the thickness of the layer form~d;
Fig. 17 is a photomicrograph snowing a van~di~n carblde layer formed on carbon tool steel according to Example 6, F_g. 18 is a graph obtained in Example 6 b~ ~-ray micr~, analyzer and showing the contents of the components formlng the vanadium carbide layer, ~oFig. 19 is a phot~mierograph showing a vanadlum oarbide layer formed on carbon tool steel according to Example 7;
Fig. 20 is a photomicrograph showing a niobium carbide layer formed on carbon tool steel according to Example 9, Figs. 21 and 22 are photomicrographs showing vanadium carbide layers fo~med on carbon tool steel according to Example 11 Fig. 23 is an X-ray diffraction chart of the vanadium carbide layer formed on cemented carbide according to ~xample 12;
Fig. 24 is a photomicrograph showing a vanadium carbide layer formed on cemented carbide according to Example 14, 30Fig. 25 is a photomicrographic showing a niobium layer formed or. cemented carbide according to Example~15, Fig. 26 is a photomicrograph showing a rliobium carbide l~Z3~7 layer formed on cemented carbide according to Example 16, Fig. 27 is an X-ray diffraction chart of the niobium carbide layer formed on cemented carbide according to Example 16~
Broadly, the present invention ls directed to an improve-ment of the method for forming a carbide layer of an iron,ferrous alloy or cemented carbide article in a treating molten bath and is characterized in that the treating bath is composed of boric acid or a borate and a V-a group element of the Periodic Table dissolved therein and in that the article immersed in the treat-ing molten bath is treated with an electric current for deposit-ing the V-a group element on the surface of the article. The element deposited reacts with the carbon contained within the article and forms the carbide layer of the V-a group element on thè surface of the article. The method of the present invention comprises preparing a treating molten bath containing a molten boric acid or a borate and a V-a group element, immersing an iron, ferrous alloy or cemented carbide article in the treating molten bath, applying an electric current to the treating molten bath with the article being used as the cathode for forming the carbide layer of the V-a group element on the surface of the article.
The electric current deposits the V-a group element dissolved in the treating molten bath on the surface of the article and accelerates the formation of the carbide layer of the V-a grou~ element on the surface of the articleO ~he voltage of the electric current is relatively low. It is not necessary for said voltage to be enough high -for electrolysing the molten boric acid or borate in the treating molten bath. In order to accelerate the formation of the carbide layer of a V-a group element on the surface of the article, a relatively high voltage (in other words, a relatively large current density of the cathode3 may be employed. In that case, large current density deposits a reduced boron on the surface of the article together b ~ 4 ~Q5Z3~'7 with a V-a group element and the boron reacts with a part of the V-a group element. I'hereforç, the carbide layer of the V-a group element comes to include a small amount oE a boride of a V-a group element such as vanadium boride (VB2), niobium boride (NbB2) and tantalum boride (TaB2), and in some cascs,the boride layer of a V-a group element is formed on the carbide layer of a V~a group element. Said boride of a V-a group element has been known to have a much higher hardness than that of the carbide of a V-a group element. Also said boride has a good wear resistance and corrosion resistance against chemical reagent and molten metal.
Therefore, the boride layer of a V a group element formed and the carbide layer containing the boride work as well as the carbide layer of a V-a group element. However, with a too large current density, the amount of boron brought Qn the surface is too much and prevents a V-a group element from reaching onto the surface of the article. Said boron ~ forms boride such as iron boride and cobalt boride with metals of the mother material of the article. Therefore, a too large current density o~ the anode is not good.
The critical current density of the cathode composed of the article to be treated depends on the substance including a V-a group element in the treating molten bath. For example, in the treating molten bath containing the oxide of a V-a group element, a relatively large current density, 15 A/cm , can be applied for forming the carbide layer of a V-a group element on the surface of the article. In the treating molten bath containing the chlori-de of a V-a group element, the upper limit of the current density for forming the carbide layer of a V-a group element is 3 A/cm2.
The practical lower limit of the current density of the cathode is 0.01 A/cm . ~aowever, when the treating molten bath includes the oxide of V-a group element, more than 0.1 A/cm2 is preferable.
The treating molten bath used in the present invention ¢~*
~S'~3~7 is composed of a molten bo~ic acid or a borate and a substance containing a V-a group element. As said substance, the metals of a V-a group element, alloys containing a V-a g~oup element, the oxide and chloride of a V-a gxoup element such as V203, V205, VOCL2, NaV03, Na2VO~, NH~V02, Nb205, Ta205, VC13, VCl~, NbC14, TaC15, can be used. In order to prepare the treating molten bath, the powder of said substance is introduced in the molten boric acid or borate or the powder of said substance and the powder of said boric acid or borate are mixed together and then the mixture is heated up to its fusing state. By another method, a block of said metals or alloys immersed in the bath as the anode and is anodically dissolved in the molten boric acid or borate for preparing the treating molten bath.
Borate such as sodium borate (borax) (Na2B~07), potassium borate,boric acid and the like and the mixture thereof can be used.
The boric acid and borate have a functlon to dissolve a metallic oxide and to keep the surface of the article to be treated clean, and also the boric acid and borate are not poisonous and do not readily vaporize. Therefore, the method of the present invention can be carried out in the open air.
As the V-a group elements contained in the treating mol-ten bath, one or more elements of vanadium (V), niobium (Nb) and tantalum (Ta) can be used, 1% by weight (hereinafter % means iO by weight) of V-a group element dissolved in the treating molten bath being sufficient. In practice, however, the V-a group element may be dissolved into the treating molten bath in a quantity between 1 and 20%. With use of less quantity of V-a group element than 1%, the speed of formation of the carbide layer would be too slow to be accepted for the practical purpose. ~oo much addition of V-a group element in excess of 20% will increase the viscosity of the treatiny molten bath to such a high value that the dipping of the article to be treated upon into the bath may become practically impossible. Even when the immersion is possible with difficulty l 'l~,~
Fig. 11 to 13 are photomicrographs showing vanadium carbide layers on carbon tool steels, which are formed according to Example 3;
10Fig. 14 is a photomicrograph showing a vanadium carbide layer formed on carbon tool steel according to Example 4, Fig. 15 and 16 are graphs obtained in Example 6 and showing the effect of the current density applied to the article treated on the thickness of the layer form~d;
Fig. 17 is a photomicrograph snowing a van~di~n carblde layer formed on carbon tool steel according to Example 6, F_g. 18 is a graph obtained in Example 6 b~ ~-ray micr~, analyzer and showing the contents of the components formlng the vanadium carbide layer, ~oFig. 19 is a phot~mierograph showing a vanadlum oarbide layer formed on carbon tool steel according to Example 7;
Fig. 20 is a photomicrograph showing a niobium carbide layer formed on carbon tool steel according to Example 9, Figs. 21 and 22 are photomicrographs showing vanadium carbide layers fo~med on carbon tool steel according to Example 11 Fig. 23 is an X-ray diffraction chart of the vanadium carbide layer formed on cemented carbide according to ~xample 12;
Fig. 24 is a photomicrograph showing a vanadium carbide layer formed on cemented carbide according to Example 14, 30Fig. 25 is a photomicrographic showing a niobium layer formed or. cemented carbide according to Example~15, Fig. 26 is a photomicrograph showing a rliobium carbide l~Z3~7 layer formed on cemented carbide according to Example 16, Fig. 27 is an X-ray diffraction chart of the niobium carbide layer formed on cemented carbide according to Example 16~
Broadly, the present invention ls directed to an improve-ment of the method for forming a carbide layer of an iron,ferrous alloy or cemented carbide article in a treating molten bath and is characterized in that the treating bath is composed of boric acid or a borate and a V-a group element of the Periodic Table dissolved therein and in that the article immersed in the treat-ing molten bath is treated with an electric current for deposit-ing the V-a group element on the surface of the article. The element deposited reacts with the carbon contained within the article and forms the carbide layer of the V-a group element on thè surface of the article. The method of the present invention comprises preparing a treating molten bath containing a molten boric acid or a borate and a V-a group element, immersing an iron, ferrous alloy or cemented carbide article in the treating molten bath, applying an electric current to the treating molten bath with the article being used as the cathode for forming the carbide layer of the V-a group element on the surface of the article.
The electric current deposits the V-a group element dissolved in the treating molten bath on the surface of the article and accelerates the formation of the carbide layer of the V-a grou~ element on the surface of the articleO ~he voltage of the electric current is relatively low. It is not necessary for said voltage to be enough high -for electrolysing the molten boric acid or borate in the treating molten bath. In order to accelerate the formation of the carbide layer of a V-a group element on the surface of the article, a relatively high voltage (in other words, a relatively large current density of the cathode3 may be employed. In that case, large current density deposits a reduced boron on the surface of the article together b ~ 4 ~Q5Z3~'7 with a V-a group element and the boron reacts with a part of the V-a group element. I'hereforç, the carbide layer of the V-a group element comes to include a small amount oE a boride of a V-a group element such as vanadium boride (VB2), niobium boride (NbB2) and tantalum boride (TaB2), and in some cascs,the boride layer of a V-a group element is formed on the carbide layer of a V~a group element. Said boride of a V-a group element has been known to have a much higher hardness than that of the carbide of a V-a group element. Also said boride has a good wear resistance and corrosion resistance against chemical reagent and molten metal.
Therefore, the boride layer of a V a group element formed and the carbide layer containing the boride work as well as the carbide layer of a V-a group element. However, with a too large current density, the amount of boron brought Qn the surface is too much and prevents a V-a group element from reaching onto the surface of the article. Said boron ~ forms boride such as iron boride and cobalt boride with metals of the mother material of the article. Therefore, a too large current density o~ the anode is not good.
The critical current density of the cathode composed of the article to be treated depends on the substance including a V-a group element in the treating molten bath. For example, in the treating molten bath containing the oxide of a V-a group element, a relatively large current density, 15 A/cm , can be applied for forming the carbide layer of a V-a group element on the surface of the article. In the treating molten bath containing the chlori-de of a V-a group element, the upper limit of the current density for forming the carbide layer of a V-a group element is 3 A/cm2.
The practical lower limit of the current density of the cathode is 0.01 A/cm . ~aowever, when the treating molten bath includes the oxide of V-a group element, more than 0.1 A/cm2 is preferable.
The treating molten bath used in the present invention ¢~*
~S'~3~7 is composed of a molten bo~ic acid or a borate and a substance containing a V-a group element. As said substance, the metals of a V-a group element, alloys containing a V-a g~oup element, the oxide and chloride of a V-a gxoup element such as V203, V205, VOCL2, NaV03, Na2VO~, NH~V02, Nb205, Ta205, VC13, VCl~, NbC14, TaC15, can be used. In order to prepare the treating molten bath, the powder of said substance is introduced in the molten boric acid or borate or the powder of said substance and the powder of said boric acid or borate are mixed together and then the mixture is heated up to its fusing state. By another method, a block of said metals or alloys immersed in the bath as the anode and is anodically dissolved in the molten boric acid or borate for preparing the treating molten bath.
Borate such as sodium borate (borax) (Na2B~07), potassium borate,boric acid and the like and the mixture thereof can be used.
The boric acid and borate have a functlon to dissolve a metallic oxide and to keep the surface of the article to be treated clean, and also the boric acid and borate are not poisonous and do not readily vaporize. Therefore, the method of the present invention can be carried out in the open air.
As the V-a group elements contained in the treating mol-ten bath, one or more elements of vanadium (V), niobium (Nb) and tantalum (Ta) can be used, 1% by weight (hereinafter % means iO by weight) of V-a group element dissolved in the treating molten bath being sufficient. In practice, however, the V-a group element may be dissolved into the treating molten bath in a quantity between 1 and 20%. With use of less quantity of V-a group element than 1%, the speed of formation of the carbide layer would be too slow to be accepted for the practical purpose. ~oo much addition of V-a group element in excess of 20% will increase the viscosity of the treatiny molten bath to such a high value that the dipping of the article to be treated upon into the bath may become practically impossible. Even when the immersion is possible with difficulty l 'l~,~
3~7 only, the resulting carbide layer will become too uneven to be accepted.
The remainder of the treating molten bath is molten boric acid or borate.
When the powders of the metal of a V-a group element or of the alloy containing a V-a group element such as ferrou's al-loys are used as the source, of the treatiny molten bath, the trea-ting molten bath should be ~iven time for dissolving the V-a group element into the molten boric acid or borate before im-mersing the article to be treated into the treating molten bath.In case of preparing the treating molten bath by anodically dis-solving V-a group element, the range of the current density of the anode (the article) for forming the carbide layer on the surface of the article may be from 0.01 to 5 A/cm2. When the formation of the layer is carried out by immersing the article as the cathode in the treating molten bath including the powder of the oxide of a V-a group element, the current density of the cathode may be selected within the range from 0.1 to 15 A/cm2.
When the powder of the chloride of a V-a group element is used in the treating molten bath, the current density of the cathode (article to be treated~ may be selected within the range from O.Ol to 3 A/cm2. When the powder of the oxide or chloride of a V-group element is used in the treating molten bath ageing of the treating molten bath is not necessary because said oxide and chloride can be dissolved quickly into the moIten boric acid or borate.
In case the treating m~lten bath contains the chloride of a V-a group element or a V-a group element which have been dissolved anodically, the sur~ace of the carbide layer formed is very smooth, and the layer does not contain any undissolved particles of the treating molted bath.
To form the carbide layer of a V-a group element on the surface of the article, the ar-ticle is immersed in the treating ~L~5'Z3~7 molten bath as the cathode, and a vessel containing the treatingmolten bath may be used as the anode. If the vessel is made of conductive materials such as steel or carbon and is no-t used as the anode a metal plate or rod dipped in the treating molten bath can be used as the anode. In some cases, a metal block containing a V-a group element can be used as the anode.
Said metal block is anodically dissolved into the treating molten bath during the formation of the carbide layer.
The iron, ferrous alloy or cemented carbide to be treat-ed must contain at least 0.05% of carbon, preferably contain 0.1%
of carbon or higher. The carbon in the article becomes a carbide during the treatment. Namely it is supported that the carbon in the article diffuses to the surface thereof and reacts with the metal from the treating molken bath to form the carbide on the surface of the article. The higher content of the carbon in the article is more preferable for forming the carbide layer.
The iron, ferrous alloy or cemented tungsten carbide article containing less than 0.05% of carbon may not be formed with a uniform and thick carbide layer by the treatment. Also, the article containing at least 0.05% of carbon only in the surface portion thereof can be treated to form a carbide layer on the surface of the article. For example, a pure iron article, which is case-hardened to increase toe carbon content in the surface portion thereof, ~an be used as the article of the present invention.
Instead of iron may be used iron containing carbon and case-hardened iron, ferrous alloy means carbon steel and alloy steel, and instead of ~emented tungsten carbide may be used a s-intered tungsten carbide containing cobalt. Said cemented 3 carbide may include a small amount of titanium carbide, niobium carbide, tantalum carbide and the like.
In some cases, ~he carbon contained in the treating ~ - 8 -~5~3~
molten bath can be used as the source of the carbon for forming the carbide layer on the surface of the article.
However, the formation of the carbide layer is not stable and the use of the carbon ~ ~5'~3~7 in the treating molten bath is not practical.
Before the treatment, it is important to purify the sur-face of the article for forming a good carbide layer by washing out the rust and oil from the surface of the article with acidic aqueous solu-tion.
The treating temperature may be selected within th~
wide rànge from the melting point of boric acid or borate to the melting point of the article to be treated. Preferably, the treat-ing temperature may be selected within the range from 800 to 1100C. With lowering of the treating temperature, the viscosity of the treating molten bath increases gradually and the thickness of the carbide layer formed decreases. However, at a relatively high treating temperature, the treating molten bath deteriorates rapidly. Also the quality of the material forming the article is worsened by increasing the crystal grain sizes of said material.
The *reating time depends upon the thickness of the car-bide layer to be formed treating temperature and the current densi-ty of the anode. Heating shorter than 2 minutes will, however, provide no practically accepted formation of said layer. With the increase of the treating time, the thickness of the carbide layer will be increased correspondingly. In practice, an acceptable thickness of the layer can be realized within 5 hours or shorter time. The preferable range of the treating time will be from 2 minutes to 5 hours.
The vessel for ~eeping the treating molten bath of the present invention can be made of graphite or heat resistant steel.
It is not necessary to carry out the method of the pre-sent invention in the atmosphere of non-oxidation gas, but the method can be carried out into effect either under the air atmos-phere or the inert gas atmosphere.Example 1:
700 grams of borax was introduced into each of two gra-phite crucibles having a 65mm innerdiameter and heated in an elec-_ g _ 1~5;~3~7 tric furnace under the air. One of the crucibles was heated up to930C and the other to 950C. ~hen into each of the crucibles were introduced 117 grams of ferrovanadium (containing 59% of vanadium) powder of less than 100 mesh, mixed together and kept for 1 hour. Thus, two kinds of the treating molten bath were prepared. By using the treating molten bath kept at 930C, each of one group of the specimens having a 7mm diarneter and made of carbon tool steel (JIS SK4) was immersed down to 40mm from the surface of the treating molten bath and treated with an electric current for 3 hours using said specimen as the cathode. The cur-rent density to the cathode applied was within the range from 0 to 2 A/cm2. In the same manner as mentioned above by using the other treating molten bath kept at 950C, each of the other group of the specimens having a 7 mm diameter and made of carbon tool steel was treated for 10 minutes with a current density to the cathod within the range from 3 to 5 A/cm2. After taking the specimens out of each of the treating molten bathes, all the specimens treat-ed were cooled in the air, washed with hot water and examined.
The specimens were cut vertically and the cross sections were polished and microscopically observed. The photomicrographs shown in Figs. 1 to 4 were taken from the specimens treated respectively with a current density of 0.01 A/cm , 0.3 A/cm , 1.0 A/cm and 5.0 A/cm2. From the results by X-ray micro analyzer, the layers formed with a current density of 0.05 A/cm2 or lower than 0.05 A/
cm2 were vanadium carbide composed of vanadium and carbon . FigO 5 shows the distribution of the contents of vanadium, iron, carbon and boron contained in the surface portion of the specimen treated with a current density of 0.01 A/cm . The layers formed with a current density higher than 0.1 A/cm were recognized to be the carbide containing boron. Also a boride layer composed of Fe2B
or FeBC and Fe2B was recognized between said carbide layer and the mother material. Further, it was recognized that the thickness of the boride layer increases with increase of the current density.
.;; . -- 1 0 . ,.
~05'~3~7 Figs. 6 and 7 shows each of the distributions of ~alladium, iron, carbon and boron contained in the layers formed respectively with a current density of 2 A/cm2 and 5 A/cm2. Fig~ 8 shows the effect of the current density on the thickness o1E the layer formed. The thickness of the layers formed increases with increase of the current density. ~Iowever, the layers formed with a current densi-ty of 3 A/cm or higher than 3 A/cm consist mainly of FeB and Fe2B and the thickness of the vanadium carbide layer formed on the layer composed of Fe~ and Fe2B does not increase. Therefore, it is not always good to employ a large current density. However, wi-thin the limits of small current density, the increasing of current density is p~eferable to form a thicker layer of vanadium carbide or of the vanadium carbide containing boron. In -the layers formed with a current density above 0.1 A/cm2, boron was clearly identified.
Although in the layers formed with a current density of Ool A/cm2 or lower than 0.1 A/cm2, boron was not identified, said layers may possibly include boron.
From this example, it was recognized that the appliea-tion of an electric current to the specimen treated increased the thickness of the layers formed on the specimen.
Example 2:
In the same manner as described in Example 1, a treating molten bath composed of 80% of borate and 20% or ferroniobium (con-taining 59% of niobium and 3.9% of tantalum) powder of 100 mesh or finer than 100 mesh was prepared. Each of the specimens made of earbon tool steel (JIS SK~) was treated respectively at 950C
under each of the conditions. Specimen 2 -1 was treated with a current density of 0.03 A/cm for 3 hours, Specimens 2-2 and 2-3 were treated respectively with 0.3 A/cm for 3 hours and with 3 A/cm for 10 minutes. As the eomparison, Specimen 2-A was treated for 3 hours at 950C without applying an elect~ic current.
All the specimens were examined by a microscope, X-ray ~ ~o5Z3~L7 micro analyzer and by X-ray difraction method. The layer formed on Specimen 2-l is shown in Fig 9. The layer had a thickness of 13 microns and a uniform and smooth surface. Fiy. 10 shows the distributions of the contents of niobium, carbon and boron contained in the surface portion of Specimen 2-1, which were obtained by X-ray micron analyzer. From the results of said X-ray micron analyzer and X-ray diffraction method, the layer form-ed was identified to be the niobium carbide containing boron.
Specimen 2-2 was found to have a layer which was similar with the layer formed on Specimen 2-1.
Specimen 2-3 was found to have a niobium carbide layer of about 9 microns thick and a layer composed of iron boride tFe2B) between said niobium carbide and its mother material.
Specimen 2-A was found to have niobiurn carbide layer of 11 microns thick and the layer was recognized to contain a small amount of tantalum.
Example 3:
1000 grams of borax was introduced into a graphite crucible and heated up to 900C for melting the borax in an elec-tric furnace and then a metallic plate, 6 x 40 x 50 mm, made of ferrovanadium (containing 53.7% of vanadium) was dipped in the molten borax. With use of the metallic pla-te and the crucible as an anode and cathode respectively, said metallic plate was anodi-cally dissolved into the molten borax by applying a direct current for 2 hours at a current density of 2 A/cm of the anode. Thus a treating molten bath containing 9.8% of said ferrovanadium.was prcpared.
Next, Specimens 3-1 to 3-6 having a diameter of 7mm and made of carbon tool steel (JIS SI~) were respectively imrnersed into the treating molten bath and were treated at 900C under res-pective conditions. Specimen 3-1 was treated for 2 hours and with a current density of 0.03 A/cm . Specimens 3-2 to 3-6 were treated ~ 523~7 respectively for 2 hours and with 0.1 A/cm , for 2 hours with 0.3 A/cm2, for l hour with 0.7 A/cm2, for 10 minutes with 1.0 A/cm , and for 10 minutes with 3.0 A/cm , All Specimens 3-1 to 3-6 were examined by a microscope, X-ray micro analyzer and by X-ray diffraction method. Specimens 3-l to 3-6 were formed with a layer or layers having a respective thickness of 9 microns, 9 microns, 11 microns, 37 microns, 5 mi-crons and 47 microns. Only one layer was formed on Specimen 3-l and Specimens 3-2 to 3-6 were formed each with two layers. Fig.
ll shows a microphotograph of the layer formed on Specimen 3-1 Figs. 12 and 13 shows respectively microphotographs of the layers formed on Specimens 3-3 and 3-6. From the result of X-ray micro analyzer and X-ray diffraction method, the layer formed on Speci-men 3-1 was identified to be vanadium carbide and the two layers formed on Speclmens 3-2 to 3-6 were identified respectively to be the vanadiurn carbide containing boron (V(C,B) and to be iron boride (FeB or Fe2B) composed of boron and iron which is the main component of the mother material. All the surfaces of the Speci-men 3-l to 3-6 were very smooth.
From this example, it was recognized that the treating molten bath prepared by anodic dissolution gives a very smooth surface of the specimen treated without depositing any small par-ticles to the surface of the article.
Example 4:
In the same manner as described in Example 3, the molten borax was prepared and then a metallic plate, 50 x 45 x 6mm, made of ferrovanadium (containing 53.7% of vanadium~ and a specimen, 40 x 33 x 9mm, made of carbon tool steel (JIS SK5) were dipped in the molten borax while spaced a distance of 15mm from each other.
With use of said metallic plate as the anode and the specimen as the cathode, an electric current was applied to the molten borax for 4 hours at a cathodic current density of 0.3 A/cm2. By the ~C)5Z3~
treatment, the specimen was formed with a layer of about 9 microns.
The layer formed is shown in Fig. 14. Also, the layer was identi-fied to be the vanadium carbide containing boron.
Example 5:
In the same manner as described in Example 4, a metal plate, 50 x 40 x 6mm, made of ferroniobium (containing 58.9% of niobium and 3.6% of tantalum) was anodically dissolved into a mol-ten borax at 900C. Thus, a treating molten bath containing about 8.5% of said ferrovanadium was prepared. Next, a specimen having a diameter of 7 mm and made of carbon tool steel (JIS SK4) was dipped into the treating molten bath as the cathode ! With use of said treating molten bath, said specimen was treated for 3 hours with a current densitv oE 0.03 A/cm . From microscopic observation, a layer of 14 microns was formed on the surface of the specimen. Said layer was identified to be the niobium carbide con~taining a small amount of boron and tantalum by X-ray micro ana-yzer and by X-ray diffraction method.
Example 6:
90 grams of borax was introduced into a graphite cruci-ble having a 35 mm innerdiameter and heated up to 950C for mel-ting the borax in an electric furnace under the air, then 17 grams of vanadium oxide (V205) powder was gradually introduced into the molten borax and mixed with the molten borax for preparing a treat-ing molten bath (which contains 16% of vanadium oxide). In said treating molten bath, several specimens having a 7mm diameter and made of carbon tool steel (JIS SI~4) were respectively treated at 950C for a time ranging from 1 to 90 minutes with a current den-sity ranging from 0 to 15 A/cm2 in the same manner as described in Example 1. All the specimens treated were taken of the treat-ing molten bath, cooled in the air, washed with hot water for dissolviny the treating material adhered to the specimens. The specimens were cut vertically and the cross sections were polished ~OSZ3~
and examined by a microscope and X-ray micro anàlyzer and by X~ray diffraction method. The photomicrograph in Fig. 17 is shown as one of the examples of the layers formed in this example.
From a group of the specimens treated for 10 minutes with a cuxren-t density ranging from 0 to 15 A/cm I line (a), in Fig.
15, was obtained. Line (a) shows the effect of the current density applied to a specimen on the thickness of the v~nadium carbide layer formed on the specimen. In order to show the difference between the vanadium oxide powder used in this Example and the ferrovanadium powder used in Example 1, lines (b) and (c) are shown together with line (a) in Fig. 15. Line (B) was obtained from the specimens treated in the treating molten bath containing 20% of ferrovanadium powder instead of vanadium oxide powder for 30 minutes with a current density rangin~ from 0 to 1 A/cm2. Line (c) was obtained from the specimens treated in said treating molten bath containing 20% of ferrovanadium for 10 minutes with a current density ranging from 3 to S A/cm2.
Although, the treating molten bath containing said ferrovanadium powder can form a vanadium carbide layer on the surface of a specimen without application of an electric current, the treat-ing molten bath containing the vanadium oxide powder can not form a vanadium carbide layer on the surface of a specimem with-out applying an electric current~ Thereforel it is necessary in the case of the treating molten bath composed of molten borax and vanadium oxide powder to apply at least 0.1 A/cm2 of electric current to the specimen to be treated for forming a vanadium carbide layer on the surface of the specimen (with use of a current density of 0.1 A/cm , a layer of 1 micron was formed on the surface of the article treated)O From the difference between the vanadium oxide powder in this Example and ferrovanadium powder in Example 1 the conclusion is that the vanadium oxide must be reduced to metallic vanadium for forming a vanadium carbi-de layer on the surface of the specimen by an electric curren~.
~Lo5Z3~7 The other difference between the vanadium oxide powder and ferrovanadium powder is that the treating molten bath con-taining the vanadium oxide can form a carbide layer with a relatively large current density at which the treating molten bath containing the ferrovanadium can not form a carbide layer on the surface of the specimen treated.
Fig. 18 shows the distributions of the contents of vanadium, carbon, iron and boron forming the surface portion of the specimen treated in the treating molten bath containing vanadium oxide with a current density of 3 A/cm ~ From the distributions and the result of the X-ray diffraction, the surface portion of the specimen was identified to be vanadium carbide containing little boron. Also the layer formed with a current density of 10 A/cm2 was found to contain a little boron.
The layers formed on the surface treated in the treatin~ molten bath containing the ferrovanadium with a relatively large current density were explained in Example l.
From a group of the specimens treated for a time ranging l to 90 minutes with a current density of 5 A/cm , the graph shown in Fig. 16 was obtained. The graph shows the effect of the treating time on the thickness of the carbide layer formed on the surface of the specimen treated.
V205 was used in this Example. However, ~he following oxides and compounds containing vanadium can be used as the oxide of vanadium; VO, V02, V203, Na3V04, NaV03, NH4V03, VOC12, VOCL~ and the like.
Example_7:
In the same manner as described in Example 6, a trea-ting molten bath composed of 87% of borax and 13% of vanadium oxide, V203, was prepared. Next a specimen having a 7mm diameter and made of caxbon tool steel (JIS SK4) was treated in the treating molten bath at 900C ~or lO minutes with a current density of , . .
~,~
` ~OSZ31 7 3 A/cm2. sy the treatment, a la~er of about 4 microns in thickness was formed on the surface of the specimen. The surface condition of the layer was very smooth. The photomicrograph taken from the cross section of the specimen is shown in Fig. 19. And the layer was identified to be vanadium carbide (VC) by X-ray diffraction method.
Example ~3:
In the same manner as described in Example 6, two kinds of treating molten ba~hs were prepared. One was made of 86 % of borax and 14 % of ~aVO3 and the other was made of 70 % of borax and 30 % of NaV04 .H20. Specimen 8-1 having a 7 mm diameter and made of carbon tool steel (JIS SK4) was trea~ed at 900C in the treating molten bath containing NaVO3 for 30 minutes with a current density of 0.1 A/cm2. Specimen 8-2 having the same size and made of the same steel as Specimen 8-1 was treated at 900C in the treating molten bath containing NaVO4 .H2O for 10 minutes with a current density of 1.0 A/cm2. By the treatments, on the surface of Specimen 8-1 was formed a vanadium carbide (VC) layer of about 5 microns in thickness and on the surface of Specimen 8-2 was formed a vanadium carbide lay0r of about 4 microns in thickness.
Example 9:
In the manner as described in Example 6, a treating molten bath made of 93 % of borax and 7 % of Nb2O3 was prepared.
Next, a specimen made of carbon tool steel (JIS SK4) was treated in the treating molten bath at 900C for 60 minutes with a current density of 3 A/cm . By the treatment, a niobium carbide layer shown in Fig. 20 was formed on the surface of the specimen.
Example 1_:
100 grams of borate was introduced into a graphite crucible and heated up to 900C for melting said borate in an electric furnace under the air, and -then 16 ~rarr~s of vanadium chlori-de (VC13) powder was added into the molten borax and mixed together.
~05'~3~7 Thus, a treating molten bath was prepared. Next, Specimens 10-1 to 10-6 having a 7 mm diameter and 40 mm long and made of carbon tool steel (JIS SK4 containing 1.0 /O of carbon) were res-pectively treated in the treating molten bath at 900C for a time ranging from 10 minutes to 60 minutes with a current density ranging from 0.01 to 3.0 A/cm2. After each of the treatments, each of the Specimens was taken out from ~he treating molten bath, cooled in the air and washed out the treating material adhered to the Specimen with hot water. Specimens 10-1 to 10-6 were cut vertically and examined by a mieroscope, X-ray micro analyzer and X-ray diffraction method. On the surface of Specimen 10-1 treated for60 minutes with 0.01 A/cm was formed a vanadium carbide (VC) layer of about 9 microns in thickness. Specimen 10-2, which was treated for 60 minutes with 0.05 A/cm2, was formed with a vanadium carbide layer of about 9 microns in thickness. The photomicrograph taken from Specimen 10-1 is shown in Fig. 21. Specimens 10-3 and 10-4 treated respectively for 30 minutes with a current density of O.1 A/cm2 and 0.S A/cm2 were formed with a layer thereon. The thickness of the layer of Specimen 10-3 was about 4 microns and the thickness of the layer on Specimen 10-~ was about ~ microns.
Said two layers were identified to consist of the upper portion composed of the vanadium carbide containing boron and of the lower portion composed of iron boride (Fe2B). On the surfaces of Specinens 10-5 and 10-6 which were treated for 10 minutes with a current density of 1.0 Ajcm and 3.0 A/cm respectively, a layer of about 10 microns and a layer of about 16 microns were formed respectively. And said two layers were identified to consist of the upper portion composed of the vanadium carbide (VC) containing boron and the lower portion composed of iron boride (Fe2B). The photomicrograph taken from Specimen 10-5 is shown in Fig. 22.
Exam~le 11 :
A treating molten bath made of 700 grams of borax and ~sz~
120 grams of niobium chloridepowder was prepared in a graphite crucible. Next, specimens havin~ a 8 mm diameter and 40 mm long and made of tool alloy steel (JIS SKD61 containing 0.45 % of car-bon)were respectively treated in the treating molten bath at 950C
with use of each of the specimens as the cathode and of the graphite crucible as the anode. On the surface of the specimen treated for 60 minutes with a current density of 0.01 A/cm2, a niobium carbide (NbC) layer of about 4 microns was formed. The specimen treated for 30 minutes with 0.1 A/cm2 was formed with a vanadium carbide layer of about 5 microns. From said two vanadium carbide layers, boron was not detected. On the surface of the specimen treated for 30 minutes with 0~5 A/cm2, a layer of 7 micrnns was formed thereon, and which consisted of the upper portion composed of the niobium carbide containing boron and of the lower portion composed of iron boride (Fe2B). On the surface of the specimen treated for 10 minutes with 1.0 A/cm2, a layer of about 9 microns in thickness was formed thereon. The layer was identified to con-sist of the upper portion composed of the niobium carbide containing boron and of the lower portion composed of iron boride (Fe2B).
Example 12 :
90 grams of borax was introduced in-to a graphite crucible having a 35 mm innerdiameter and heated up to 1000C for melting the borax in an electric furnace under the air, and then 31 grams of vanadium chloride (VC13) powder was gradually introduced and mixed into the molten borax. Thus, a treating molten bath was prepared. ~ext, Specimens 12-1 to 12-5, 40 x 5.5 x 1.0 mm, made of cemented carbide composed of 9 % of cobalt and 91 % of tungsten carbide (WC) were treated respectively in the treating molten bath under each of the conditions shown in Table 1.
~OSZ317 Specimen 12-1 12-2 12-3 12-4 12-5 _ . _ _ _ curxent density (~/cm2) 0.03 0.3 1.0 5~0 10 _ _ _ treating time (hour) 5 hr. 5 hr~ 2 hr. 10 min. 1 min.
On the surface of Specimen 12-1, a layer of about 7 microns was formed. The layer was iden-tified to be vanadium carbide by X-ray diffraction method. Specimens 12-2 and 12-3 were formed respectively with a layer of about 12 microns and of 5 microns. The two layers were recognized to consist of vanadium boride (V3B2) (at the upper portion) and vanadium carbide (at the lower portion). The layer formed on the surface of Specimen 12-5 was identified to be tungsten boride (W2B5). By the result of X-ray micro analyzer of Specimen 12-2, the layer was fou~d to contain about 78 % of vanadium and a large amount of boron. Also, the X-ray diffraction chart of the layer is shown in Fig. 23.
Also the hardness of the layer of Specimen 12-1 was measured to be about Hv 3000. The hardness of the layer of Specimen 12-~ was about Hv 3250. By the way, the hardness of the mother material of Specimens were measured to be about Hv 1525.
Example 13 :
500 grams of borax was introduced into a graphite cruci-ble having a 65 mm innerdiameter and heated up to 1000C, and then 125 grams of ferrovanadium (containing 92 % of vanadium) powder was added and mixed into the borate. Thus, a treating molten bath was prepared. Next two specimens having the same size and made of the same cemented carbide as the specimens used in Example 12 were respectively treated in the treating molten bath with use of each of the specimens as the cathode and of the crucible as the anode.
~he specimen treated for 13 hours with a current density of 0.01 .~ ~
`- 105'~3~7 A/cm2 was formed with a layer of about 15 microns thereon, and the specimen treated for 1 hour with 5 A/cm2 was formed with a layer -20 a ~OS'~3~L7 o about 7 microns thereon. By X-ray micro analyzer and X-ray diffraction method, the layer formed under the condition of 0.01 A/cm2 was identified to be vanadium carbide (VC) and the layer formed under the condition of 5 A/cm2 was identified to consist of vanadium boride (V3B2) (at the upper portion) and vanadium carbide (VC) (at the lower portion). The hardness of the layer formed under the condition of 0.01 A/cm2 was measured to be about Hv 3014.
Example 14 :
ln the same manner as described in Example 6, a treating molten bath was made of 500 grams of borax and 100 grams of V205 powder. Specimens 14-1 to 14-7 having the same size and made of the same cemented carbide were treated respectively in the treatiny molten bath at 1000C under the conditions shown in Table 2.
Specimen 14-1 14-2 14-3 14-4 14-5 14-6 14-7 current densitY
(A/cm ) 0.1 0.5 1.0 5.0 10 20 30 _ _ _ _ _ _ treating time 9 hr. 16 hr. 5 hr. 1 hr. 10 min. 3 min. 1 min.
Each of Specimens 14-2 to 14-7 was formed with a layer thereon. However, Specimen 14-1 was not formed with any layer thereon. The layers formed on Specimens 14-2 to 14-4 were of - about 8 microns, 12 microns and 11 microns respectively and were identified to be vanadium carbide (VC). The layers formed on Specimens 14-S and 14-6 were of about 6 microns and 4 microns respectively and were recognized to be a composite layer composed of vanadium carbide (VC) and vanadium boride (V3B2). However, on the surface of Specimen 14-7, no vanadium was detected. The layers of Specimen 14-4 and 14-5 were measured to contain respectively ~ -21-' l~)SZ3~7 70 % and 94 %.of vanadium. From the layer of Specimen 14-4, no boron was detected. But the layer of Spec.imen 14-5 was found to have a relatively -21 a-~05~33L7 large amount of boron. The photomicrograph taken from Specimen 14-5 is shown in Fig. 24. The hardness of each of the layers formed on Specimen 14-2 and 1~-5 was about Hv 2960 and Hv 3200 respectively.
Fxample 15 :
In the same manner as described in Example 3, the 500 grams of molten borax was prepared, and then a metallic plate, 40 x 35 x 4 mm, made of electroly-tic niobium was anodically dissolved into the molten borax at 1000C for 2 hours with a current density of 1 A/cm2. Thus, a treating molten bath containing about 9.4 % of nio~ium was prepared. Next, Specimens 15-1 to 15-9 having the same size and made of the same cemented carbide as the Specimens used in Example 12 were treated respectively in the treating molten bath at 1000C under the conditions shown in Table 3.
Specimen 15-1 15-2 15-3 15-4 15-5 15-6 15-7 15-8 15-9 current density 0.01 0.05 0.1 0.5 1.0 3.0 5.0 10.020 (A/cm2) .
treating 16hr. 15hr. 15hr. 10hr. 4hr. lhr. lhr. 3min. lmin.
time By each of the trea-tments, on the surface of Specimen 15-2, a vanadium carbide ~VC) layer of about 13 microns was formed. The photomicrograph of the layer is shown in Fig. 25. On each Qf Specimens 15-4 and 15-5, a composite layer of about 15 microns and 6 micrcns respectively was formed. From the layer, niobium carbide (NbC~ and niobium boride (~b3B2) were clearly detected.
The niobium boride was contained in the upper portion of the layer and the niobium carbide was contained in the lower portion 3~7 of the layer. On Specimen 15-7, a composite layer of about 25 microns was formed. The layer was found to consist of Nb3B2 at its upper portion, NbC at its middle and W2B5 at its lower portion.
On Specimens 15-8 and 15-9, composite layers of about 10 microns and 13 microns were formed. The composite layers were found to consist of Nb3B2 at its upper portion, NbC at its middle and Co3B
at its lower portion. The thickness of the layers composed of Nb3s2 and NbC was decreased as the increaseof the current density applied.
By X-ray micro analyser, the layer formed on Specimen 15-8 was found to consist of about 60 % of niobium. ~Iowever the layer formed on Specimen 15-9 does not contain niobium. A
large amount of boron was detected from both of said layers.
However, the layer formed with a higher current density was found to contain a higher content of boron. The hardness of each of the layers formed on Specimens 15-2 and 15-4 was measured to be about Hv 2920 and ~Iv 3190.
Example 16 :
In the same manner as described in Example 6, a treating molten bath composed of 500 grams of borax and 80 gxams of Nb2O5 powder was prepared. Next, Specimens 16-1 to 16-9 having the same size and made of the same cemented carbide as the Specimens used in Example 12 were treated respectively in the treating molten bath at 1000C under the conditions shown in Table 4.
Specimen 16-1 16-2 16-3 16-4 16-5 ~6-6 16-7 16-8 16-9 current density 0.01 0.03 0.05 0.1 0~5 loO 3~0 5~0 10 (A/cm2) treating time 14hr. 15hr. 10hr. 5hr. 13hr. 5hr. 3min. lhr. 10min.
Specimen 16-1 was not Eormed with any layer thereon, however, on the surface of each of Specimens 16-2 to 16-9 a layer having a thickness ranging from 3 to 15 microns was formed.
The layers formed on Specimens 16-2 and 16-3 were identified to be NbC and the layers formed on Specimens 16-4 to 16-~ were recognized to contain NbC and Nb3B2. The layer formed on Specimen 16-9 was identified to be W2B2. As the example an X-ray diffraction chart taken from the layer of Specimen 1~-6 is shown in Fig. 27. By X-ray micro analyser, the layers formed on Specimens 16-4 and 16-7 were measured to contain about 67~ and 57% of niobium respectively. It was difficult to measure the content of boron in each of the layer. However, a relatively large amount Q~ boron was included in each of the layers. The hardness of each layers of Specimens 16-2 and 16-6 was measured to be about Hv 2980 and Hv 3230 respectively.
Exemple 17:
In the same manner as described in example 10, a treating molten bath composed of 115 grams of borax and 25 grams of NbC15 powder was prepared. Next, Specimens 17-1 to 17-7 having the same cemented carbide as the Specimens used in Example 12 were treated respectively in the treating molten bath at 1000 C under the conditions shown in Table 5.
_ Table 5 -Specimen 17-1 17-2 17-3 17-4 17 5 17-6 17-7 Current density 0.05 0.1 0.5 1.0 5.0 15 20 tA/cm2 ) Treating 14 hr. 10 hr. 8 hr. 5 hr. 1 hr. 10 min. 1 min.
._ _ ~5,,~3~7 On the surf~ce of each of Specimens 17-1 to 17-7 was `formed a layer. The thickness of the layer of each of Specimens 17-1 to 17-6 was about 25,27,30,20, 18 and 8 microns respectively.
Each o said layers were recognized to consist o a NbC portion and a W2B5 portion. The thickness of said NbC portion was de-creased as the increase of the current density applied. The layer of Specimen 17-7 was composed of only W2B. The hardness of the layer formed on Specimen 17-2 was about Hv 3000.
Example 18:
In the same manner as described in Example 3, the 500 grams of molten borax was prepared, and then a metallic plate, 50 x 40 x 4mm, made of electrolytic tantalum was anodically dis-solved into the molten borax at 1000C for 1 hour with a current density of 1 A/cm2. Thus, a treating molten bath containing about 11.2% of tantalum was prepared. Next Specimens lg-l to 18-5 having the same size and made of the same cemented carbide as the Specimens used in Example 12 were treated respectively in the treating molten bath at 1000 C under the conditions shown in Table 6.
Table 6 _ Specimen 18-1 18-2 18-3 18-4 18-5 .
(A/cm2) 0.01 0.0S 0.5 1.0 10 Treating time 16 hr. 14 hr. 12 hr. 1 hr. 5 min.
-All the Specimens 18-1 to 18-5 were ormed with a layer thereon. The thickness of the layer of each of Specimens 18-1 to 18-5 was about 20, 23, 25, 13 and 5 microns respectively. By the X-ray difraction method, the layers iLo~'~3~t7 formed on Specimens 18-1 to 18 3 were identified to be tantalum `carbide (TaC). The layer ormed on the surface of Specimen 18-4 was recognized to be composed of TaC and W2B5. The layer formed on Specimen 18-5 was identified to be W2BS. Also by X ray micro analyser, the layers o~ Specimens 18-1 to 1.8-3 were recognized to contain ~oron within the TaC.
The remainder of the treating molten bath is molten boric acid or borate.
When the powders of the metal of a V-a group element or of the alloy containing a V-a group element such as ferrou's al-loys are used as the source, of the treatiny molten bath, the trea-ting molten bath should be ~iven time for dissolving the V-a group element into the molten boric acid or borate before im-mersing the article to be treated into the treating molten bath.In case of preparing the treating molten bath by anodically dis-solving V-a group element, the range of the current density of the anode (the article) for forming the carbide layer on the surface of the article may be from 0.01 to 5 A/cm2. When the formation of the layer is carried out by immersing the article as the cathode in the treating molten bath including the powder of the oxide of a V-a group element, the current density of the cathode may be selected within the range from 0.1 to 15 A/cm2.
When the powder of the chloride of a V-a group element is used in the treating molten bath, the current density of the cathode (article to be treated~ may be selected within the range from O.Ol to 3 A/cm2. When the powder of the oxide or chloride of a V-group element is used in the treating molten bath ageing of the treating molten bath is not necessary because said oxide and chloride can be dissolved quickly into the moIten boric acid or borate.
In case the treating m~lten bath contains the chloride of a V-a group element or a V-a group element which have been dissolved anodically, the sur~ace of the carbide layer formed is very smooth, and the layer does not contain any undissolved particles of the treating molted bath.
To form the carbide layer of a V-a group element on the surface of the article, the ar-ticle is immersed in the treating ~L~5'Z3~7 molten bath as the cathode, and a vessel containing the treatingmolten bath may be used as the anode. If the vessel is made of conductive materials such as steel or carbon and is no-t used as the anode a metal plate or rod dipped in the treating molten bath can be used as the anode. In some cases, a metal block containing a V-a group element can be used as the anode.
Said metal block is anodically dissolved into the treating molten bath during the formation of the carbide layer.
The iron, ferrous alloy or cemented carbide to be treat-ed must contain at least 0.05% of carbon, preferably contain 0.1%
of carbon or higher. The carbon in the article becomes a carbide during the treatment. Namely it is supported that the carbon in the article diffuses to the surface thereof and reacts with the metal from the treating molken bath to form the carbide on the surface of the article. The higher content of the carbon in the article is more preferable for forming the carbide layer.
The iron, ferrous alloy or cemented tungsten carbide article containing less than 0.05% of carbon may not be formed with a uniform and thick carbide layer by the treatment. Also, the article containing at least 0.05% of carbon only in the surface portion thereof can be treated to form a carbide layer on the surface of the article. For example, a pure iron article, which is case-hardened to increase toe carbon content in the surface portion thereof, ~an be used as the article of the present invention.
Instead of iron may be used iron containing carbon and case-hardened iron, ferrous alloy means carbon steel and alloy steel, and instead of ~emented tungsten carbide may be used a s-intered tungsten carbide containing cobalt. Said cemented 3 carbide may include a small amount of titanium carbide, niobium carbide, tantalum carbide and the like.
In some cases, ~he carbon contained in the treating ~ - 8 -~5~3~
molten bath can be used as the source of the carbon for forming the carbide layer on the surface of the article.
However, the formation of the carbide layer is not stable and the use of the carbon ~ ~5'~3~7 in the treating molten bath is not practical.
Before the treatment, it is important to purify the sur-face of the article for forming a good carbide layer by washing out the rust and oil from the surface of the article with acidic aqueous solu-tion.
The treating temperature may be selected within th~
wide rànge from the melting point of boric acid or borate to the melting point of the article to be treated. Preferably, the treat-ing temperature may be selected within the range from 800 to 1100C. With lowering of the treating temperature, the viscosity of the treating molten bath increases gradually and the thickness of the carbide layer formed decreases. However, at a relatively high treating temperature, the treating molten bath deteriorates rapidly. Also the quality of the material forming the article is worsened by increasing the crystal grain sizes of said material.
The *reating time depends upon the thickness of the car-bide layer to be formed treating temperature and the current densi-ty of the anode. Heating shorter than 2 minutes will, however, provide no practically accepted formation of said layer. With the increase of the treating time, the thickness of the carbide layer will be increased correspondingly. In practice, an acceptable thickness of the layer can be realized within 5 hours or shorter time. The preferable range of the treating time will be from 2 minutes to 5 hours.
The vessel for ~eeping the treating molten bath of the present invention can be made of graphite or heat resistant steel.
It is not necessary to carry out the method of the pre-sent invention in the atmosphere of non-oxidation gas, but the method can be carried out into effect either under the air atmos-phere or the inert gas atmosphere.Example 1:
700 grams of borax was introduced into each of two gra-phite crucibles having a 65mm innerdiameter and heated in an elec-_ g _ 1~5;~3~7 tric furnace under the air. One of the crucibles was heated up to930C and the other to 950C. ~hen into each of the crucibles were introduced 117 grams of ferrovanadium (containing 59% of vanadium) powder of less than 100 mesh, mixed together and kept for 1 hour. Thus, two kinds of the treating molten bath were prepared. By using the treating molten bath kept at 930C, each of one group of the specimens having a 7mm diarneter and made of carbon tool steel (JIS SK4) was immersed down to 40mm from the surface of the treating molten bath and treated with an electric current for 3 hours using said specimen as the cathode. The cur-rent density to the cathode applied was within the range from 0 to 2 A/cm2. In the same manner as mentioned above by using the other treating molten bath kept at 950C, each of the other group of the specimens having a 7 mm diameter and made of carbon tool steel was treated for 10 minutes with a current density to the cathod within the range from 3 to 5 A/cm2. After taking the specimens out of each of the treating molten bathes, all the specimens treat-ed were cooled in the air, washed with hot water and examined.
The specimens were cut vertically and the cross sections were polished and microscopically observed. The photomicrographs shown in Figs. 1 to 4 were taken from the specimens treated respectively with a current density of 0.01 A/cm , 0.3 A/cm , 1.0 A/cm and 5.0 A/cm2. From the results by X-ray micro analyzer, the layers formed with a current density of 0.05 A/cm2 or lower than 0.05 A/
cm2 were vanadium carbide composed of vanadium and carbon . FigO 5 shows the distribution of the contents of vanadium, iron, carbon and boron contained in the surface portion of the specimen treated with a current density of 0.01 A/cm . The layers formed with a current density higher than 0.1 A/cm were recognized to be the carbide containing boron. Also a boride layer composed of Fe2B
or FeBC and Fe2B was recognized between said carbide layer and the mother material. Further, it was recognized that the thickness of the boride layer increases with increase of the current density.
.;; . -- 1 0 . ,.
~05'~3~7 Figs. 6 and 7 shows each of the distributions of ~alladium, iron, carbon and boron contained in the layers formed respectively with a current density of 2 A/cm2 and 5 A/cm2. Fig~ 8 shows the effect of the current density on the thickness o1E the layer formed. The thickness of the layers formed increases with increase of the current density. ~Iowever, the layers formed with a current densi-ty of 3 A/cm or higher than 3 A/cm consist mainly of FeB and Fe2B and the thickness of the vanadium carbide layer formed on the layer composed of Fe~ and Fe2B does not increase. Therefore, it is not always good to employ a large current density. However, wi-thin the limits of small current density, the increasing of current density is p~eferable to form a thicker layer of vanadium carbide or of the vanadium carbide containing boron. In -the layers formed with a current density above 0.1 A/cm2, boron was clearly identified.
Although in the layers formed with a current density of Ool A/cm2 or lower than 0.1 A/cm2, boron was not identified, said layers may possibly include boron.
From this example, it was recognized that the appliea-tion of an electric current to the specimen treated increased the thickness of the layers formed on the specimen.
Example 2:
In the same manner as described in Example 1, a treating molten bath composed of 80% of borate and 20% or ferroniobium (con-taining 59% of niobium and 3.9% of tantalum) powder of 100 mesh or finer than 100 mesh was prepared. Each of the specimens made of earbon tool steel (JIS SK~) was treated respectively at 950C
under each of the conditions. Specimen 2 -1 was treated with a current density of 0.03 A/cm for 3 hours, Specimens 2-2 and 2-3 were treated respectively with 0.3 A/cm for 3 hours and with 3 A/cm for 10 minutes. As the eomparison, Specimen 2-A was treated for 3 hours at 950C without applying an elect~ic current.
All the specimens were examined by a microscope, X-ray ~ ~o5Z3~L7 micro analyzer and by X-ray difraction method. The layer formed on Specimen 2-l is shown in Fig 9. The layer had a thickness of 13 microns and a uniform and smooth surface. Fiy. 10 shows the distributions of the contents of niobium, carbon and boron contained in the surface portion of Specimen 2-1, which were obtained by X-ray micron analyzer. From the results of said X-ray micron analyzer and X-ray diffraction method, the layer form-ed was identified to be the niobium carbide containing boron.
Specimen 2-2 was found to have a layer which was similar with the layer formed on Specimen 2-1.
Specimen 2-3 was found to have a niobium carbide layer of about 9 microns thick and a layer composed of iron boride tFe2B) between said niobium carbide and its mother material.
Specimen 2-A was found to have niobiurn carbide layer of 11 microns thick and the layer was recognized to contain a small amount of tantalum.
Example 3:
1000 grams of borax was introduced into a graphite crucible and heated up to 900C for melting the borax in an elec-tric furnace and then a metallic plate, 6 x 40 x 50 mm, made of ferrovanadium (containing 53.7% of vanadium) was dipped in the molten borax. With use of the metallic pla-te and the crucible as an anode and cathode respectively, said metallic plate was anodi-cally dissolved into the molten borax by applying a direct current for 2 hours at a current density of 2 A/cm of the anode. Thus a treating molten bath containing 9.8% of said ferrovanadium.was prcpared.
Next, Specimens 3-1 to 3-6 having a diameter of 7mm and made of carbon tool steel (JIS SI~) were respectively imrnersed into the treating molten bath and were treated at 900C under res-pective conditions. Specimen 3-1 was treated for 2 hours and with a current density of 0.03 A/cm . Specimens 3-2 to 3-6 were treated ~ 523~7 respectively for 2 hours and with 0.1 A/cm , for 2 hours with 0.3 A/cm2, for l hour with 0.7 A/cm2, for 10 minutes with 1.0 A/cm , and for 10 minutes with 3.0 A/cm , All Specimens 3-1 to 3-6 were examined by a microscope, X-ray micro analyzer and by X-ray diffraction method. Specimens 3-l to 3-6 were formed with a layer or layers having a respective thickness of 9 microns, 9 microns, 11 microns, 37 microns, 5 mi-crons and 47 microns. Only one layer was formed on Specimen 3-l and Specimens 3-2 to 3-6 were formed each with two layers. Fig.
ll shows a microphotograph of the layer formed on Specimen 3-1 Figs. 12 and 13 shows respectively microphotographs of the layers formed on Specimens 3-3 and 3-6. From the result of X-ray micro analyzer and X-ray diffraction method, the layer formed on Speci-men 3-1 was identified to be vanadium carbide and the two layers formed on Speclmens 3-2 to 3-6 were identified respectively to be the vanadiurn carbide containing boron (V(C,B) and to be iron boride (FeB or Fe2B) composed of boron and iron which is the main component of the mother material. All the surfaces of the Speci-men 3-l to 3-6 were very smooth.
From this example, it was recognized that the treating molten bath prepared by anodic dissolution gives a very smooth surface of the specimen treated without depositing any small par-ticles to the surface of the article.
Example 4:
In the same manner as described in Example 3, the molten borax was prepared and then a metallic plate, 50 x 45 x 6mm, made of ferrovanadium (containing 53.7% of vanadium~ and a specimen, 40 x 33 x 9mm, made of carbon tool steel (JIS SK5) were dipped in the molten borax while spaced a distance of 15mm from each other.
With use of said metallic plate as the anode and the specimen as the cathode, an electric current was applied to the molten borax for 4 hours at a cathodic current density of 0.3 A/cm2. By the ~C)5Z3~
treatment, the specimen was formed with a layer of about 9 microns.
The layer formed is shown in Fig. 14. Also, the layer was identi-fied to be the vanadium carbide containing boron.
Example 5:
In the same manner as described in Example 4, a metal plate, 50 x 40 x 6mm, made of ferroniobium (containing 58.9% of niobium and 3.6% of tantalum) was anodically dissolved into a mol-ten borax at 900C. Thus, a treating molten bath containing about 8.5% of said ferrovanadium was prepared. Next, a specimen having a diameter of 7 mm and made of carbon tool steel (JIS SK4) was dipped into the treating molten bath as the cathode ! With use of said treating molten bath, said specimen was treated for 3 hours with a current densitv oE 0.03 A/cm . From microscopic observation, a layer of 14 microns was formed on the surface of the specimen. Said layer was identified to be the niobium carbide con~taining a small amount of boron and tantalum by X-ray micro ana-yzer and by X-ray diffraction method.
Example 6:
90 grams of borax was introduced into a graphite cruci-ble having a 35 mm innerdiameter and heated up to 950C for mel-ting the borax in an electric furnace under the air, then 17 grams of vanadium oxide (V205) powder was gradually introduced into the molten borax and mixed with the molten borax for preparing a treat-ing molten bath (which contains 16% of vanadium oxide). In said treating molten bath, several specimens having a 7mm diameter and made of carbon tool steel (JIS SI~4) were respectively treated at 950C for a time ranging from 1 to 90 minutes with a current den-sity ranging from 0 to 15 A/cm2 in the same manner as described in Example 1. All the specimens treated were taken of the treat-ing molten bath, cooled in the air, washed with hot water for dissolviny the treating material adhered to the specimens. The specimens were cut vertically and the cross sections were polished ~OSZ3~
and examined by a microscope and X-ray micro anàlyzer and by X~ray diffraction method. The photomicrograph in Fig. 17 is shown as one of the examples of the layers formed in this example.
From a group of the specimens treated for 10 minutes with a cuxren-t density ranging from 0 to 15 A/cm I line (a), in Fig.
15, was obtained. Line (a) shows the effect of the current density applied to a specimen on the thickness of the v~nadium carbide layer formed on the specimen. In order to show the difference between the vanadium oxide powder used in this Example and the ferrovanadium powder used in Example 1, lines (b) and (c) are shown together with line (a) in Fig. 15. Line (B) was obtained from the specimens treated in the treating molten bath containing 20% of ferrovanadium powder instead of vanadium oxide powder for 30 minutes with a current density rangin~ from 0 to 1 A/cm2. Line (c) was obtained from the specimens treated in said treating molten bath containing 20% of ferrovanadium for 10 minutes with a current density ranging from 3 to S A/cm2.
Although, the treating molten bath containing said ferrovanadium powder can form a vanadium carbide layer on the surface of a specimen without application of an electric current, the treat-ing molten bath containing the vanadium oxide powder can not form a vanadium carbide layer on the surface of a specimem with-out applying an electric current~ Thereforel it is necessary in the case of the treating molten bath composed of molten borax and vanadium oxide powder to apply at least 0.1 A/cm2 of electric current to the specimen to be treated for forming a vanadium carbide layer on the surface of the specimen (with use of a current density of 0.1 A/cm , a layer of 1 micron was formed on the surface of the article treated)O From the difference between the vanadium oxide powder in this Example and ferrovanadium powder in Example 1 the conclusion is that the vanadium oxide must be reduced to metallic vanadium for forming a vanadium carbi-de layer on the surface of the specimen by an electric curren~.
~Lo5Z3~7 The other difference between the vanadium oxide powder and ferrovanadium powder is that the treating molten bath con-taining the vanadium oxide can form a carbide layer with a relatively large current density at which the treating molten bath containing the ferrovanadium can not form a carbide layer on the surface of the specimen treated.
Fig. 18 shows the distributions of the contents of vanadium, carbon, iron and boron forming the surface portion of the specimen treated in the treating molten bath containing vanadium oxide with a current density of 3 A/cm ~ From the distributions and the result of the X-ray diffraction, the surface portion of the specimen was identified to be vanadium carbide containing little boron. Also the layer formed with a current density of 10 A/cm2 was found to contain a little boron.
The layers formed on the surface treated in the treatin~ molten bath containing the ferrovanadium with a relatively large current density were explained in Example l.
From a group of the specimens treated for a time ranging l to 90 minutes with a current density of 5 A/cm , the graph shown in Fig. 16 was obtained. The graph shows the effect of the treating time on the thickness of the carbide layer formed on the surface of the specimen treated.
V205 was used in this Example. However, ~he following oxides and compounds containing vanadium can be used as the oxide of vanadium; VO, V02, V203, Na3V04, NaV03, NH4V03, VOC12, VOCL~ and the like.
Example_7:
In the same manner as described in Example 6, a trea-ting molten bath composed of 87% of borax and 13% of vanadium oxide, V203, was prepared. Next a specimen having a 7mm diameter and made of caxbon tool steel (JIS SK4) was treated in the treating molten bath at 900C ~or lO minutes with a current density of , . .
~,~
` ~OSZ31 7 3 A/cm2. sy the treatment, a la~er of about 4 microns in thickness was formed on the surface of the specimen. The surface condition of the layer was very smooth. The photomicrograph taken from the cross section of the specimen is shown in Fig. 19. And the layer was identified to be vanadium carbide (VC) by X-ray diffraction method.
Example ~3:
In the same manner as described in Example 6, two kinds of treating molten ba~hs were prepared. One was made of 86 % of borax and 14 % of ~aVO3 and the other was made of 70 % of borax and 30 % of NaV04 .H20. Specimen 8-1 having a 7 mm diameter and made of carbon tool steel (JIS SK4) was trea~ed at 900C in the treating molten bath containing NaVO3 for 30 minutes with a current density of 0.1 A/cm2. Specimen 8-2 having the same size and made of the same steel as Specimen 8-1 was treated at 900C in the treating molten bath containing NaVO4 .H2O for 10 minutes with a current density of 1.0 A/cm2. By the treatments, on the surface of Specimen 8-1 was formed a vanadium carbide (VC) layer of about 5 microns in thickness and on the surface of Specimen 8-2 was formed a vanadium carbide lay0r of about 4 microns in thickness.
Example 9:
In the manner as described in Example 6, a treating molten bath made of 93 % of borax and 7 % of Nb2O3 was prepared.
Next, a specimen made of carbon tool steel (JIS SK4) was treated in the treating molten bath at 900C for 60 minutes with a current density of 3 A/cm . By the treatment, a niobium carbide layer shown in Fig. 20 was formed on the surface of the specimen.
Example 1_:
100 grams of borate was introduced into a graphite crucible and heated up to 900C for melting said borate in an electric furnace under the air, and -then 16 ~rarr~s of vanadium chlori-de (VC13) powder was added into the molten borax and mixed together.
~05'~3~7 Thus, a treating molten bath was prepared. Next, Specimens 10-1 to 10-6 having a 7 mm diameter and 40 mm long and made of carbon tool steel (JIS SK4 containing 1.0 /O of carbon) were res-pectively treated in the treating molten bath at 900C for a time ranging from 10 minutes to 60 minutes with a current density ranging from 0.01 to 3.0 A/cm2. After each of the treatments, each of the Specimens was taken out from ~he treating molten bath, cooled in the air and washed out the treating material adhered to the Specimen with hot water. Specimens 10-1 to 10-6 were cut vertically and examined by a mieroscope, X-ray micro analyzer and X-ray diffraction method. On the surface of Specimen 10-1 treated for60 minutes with 0.01 A/cm was formed a vanadium carbide (VC) layer of about 9 microns in thickness. Specimen 10-2, which was treated for 60 minutes with 0.05 A/cm2, was formed with a vanadium carbide layer of about 9 microns in thickness. The photomicrograph taken from Specimen 10-1 is shown in Fig. 21. Specimens 10-3 and 10-4 treated respectively for 30 minutes with a current density of O.1 A/cm2 and 0.S A/cm2 were formed with a layer thereon. The thickness of the layer of Specimen 10-3 was about 4 microns and the thickness of the layer on Specimen 10-~ was about ~ microns.
Said two layers were identified to consist of the upper portion composed of the vanadium carbide containing boron and of the lower portion composed of iron boride (Fe2B). On the surfaces of Specinens 10-5 and 10-6 which were treated for 10 minutes with a current density of 1.0 Ajcm and 3.0 A/cm respectively, a layer of about 10 microns and a layer of about 16 microns were formed respectively. And said two layers were identified to consist of the upper portion composed of the vanadium carbide (VC) containing boron and the lower portion composed of iron boride (Fe2B). The photomicrograph taken from Specimen 10-5 is shown in Fig. 22.
Exam~le 11 :
A treating molten bath made of 700 grams of borax and ~sz~
120 grams of niobium chloridepowder was prepared in a graphite crucible. Next, specimens havin~ a 8 mm diameter and 40 mm long and made of tool alloy steel (JIS SKD61 containing 0.45 % of car-bon)were respectively treated in the treating molten bath at 950C
with use of each of the specimens as the cathode and of the graphite crucible as the anode. On the surface of the specimen treated for 60 minutes with a current density of 0.01 A/cm2, a niobium carbide (NbC) layer of about 4 microns was formed. The specimen treated for 30 minutes with 0.1 A/cm2 was formed with a vanadium carbide layer of about 5 microns. From said two vanadium carbide layers, boron was not detected. On the surface of the specimen treated for 30 minutes with 0~5 A/cm2, a layer of 7 micrnns was formed thereon, and which consisted of the upper portion composed of the niobium carbide containing boron and of the lower portion composed of iron boride (Fe2B). On the surface of the specimen treated for 10 minutes with 1.0 A/cm2, a layer of about 9 microns in thickness was formed thereon. The layer was identified to con-sist of the upper portion composed of the niobium carbide containing boron and of the lower portion composed of iron boride (Fe2B).
Example 12 :
90 grams of borax was introduced in-to a graphite crucible having a 35 mm innerdiameter and heated up to 1000C for melting the borax in an electric furnace under the air, and then 31 grams of vanadium chloride (VC13) powder was gradually introduced and mixed into the molten borax. Thus, a treating molten bath was prepared. ~ext, Specimens 12-1 to 12-5, 40 x 5.5 x 1.0 mm, made of cemented carbide composed of 9 % of cobalt and 91 % of tungsten carbide (WC) were treated respectively in the treating molten bath under each of the conditions shown in Table 1.
~OSZ317 Specimen 12-1 12-2 12-3 12-4 12-5 _ . _ _ _ curxent density (~/cm2) 0.03 0.3 1.0 5~0 10 _ _ _ treating time (hour) 5 hr. 5 hr~ 2 hr. 10 min. 1 min.
On the surface of Specimen 12-1, a layer of about 7 microns was formed. The layer was iden-tified to be vanadium carbide by X-ray diffraction method. Specimens 12-2 and 12-3 were formed respectively with a layer of about 12 microns and of 5 microns. The two layers were recognized to consist of vanadium boride (V3B2) (at the upper portion) and vanadium carbide (at the lower portion). The layer formed on the surface of Specimen 12-5 was identified to be tungsten boride (W2B5). By the result of X-ray micro analyzer of Specimen 12-2, the layer was fou~d to contain about 78 % of vanadium and a large amount of boron. Also, the X-ray diffraction chart of the layer is shown in Fig. 23.
Also the hardness of the layer of Specimen 12-1 was measured to be about Hv 3000. The hardness of the layer of Specimen 12-~ was about Hv 3250. By the way, the hardness of the mother material of Specimens were measured to be about Hv 1525.
Example 13 :
500 grams of borax was introduced into a graphite cruci-ble having a 65 mm innerdiameter and heated up to 1000C, and then 125 grams of ferrovanadium (containing 92 % of vanadium) powder was added and mixed into the borate. Thus, a treating molten bath was prepared. Next two specimens having the same size and made of the same cemented carbide as the specimens used in Example 12 were respectively treated in the treating molten bath with use of each of the specimens as the cathode and of the crucible as the anode.
~he specimen treated for 13 hours with a current density of 0.01 .~ ~
`- 105'~3~7 A/cm2 was formed with a layer of about 15 microns thereon, and the specimen treated for 1 hour with 5 A/cm2 was formed with a layer -20 a ~OS'~3~L7 o about 7 microns thereon. By X-ray micro analyzer and X-ray diffraction method, the layer formed under the condition of 0.01 A/cm2 was identified to be vanadium carbide (VC) and the layer formed under the condition of 5 A/cm2 was identified to consist of vanadium boride (V3B2) (at the upper portion) and vanadium carbide (VC) (at the lower portion). The hardness of the layer formed under the condition of 0.01 A/cm2 was measured to be about Hv 3014.
Example 14 :
ln the same manner as described in Example 6, a treating molten bath was made of 500 grams of borax and 100 grams of V205 powder. Specimens 14-1 to 14-7 having the same size and made of the same cemented carbide were treated respectively in the treatiny molten bath at 1000C under the conditions shown in Table 2.
Specimen 14-1 14-2 14-3 14-4 14-5 14-6 14-7 current densitY
(A/cm ) 0.1 0.5 1.0 5.0 10 20 30 _ _ _ _ _ _ treating time 9 hr. 16 hr. 5 hr. 1 hr. 10 min. 3 min. 1 min.
Each of Specimens 14-2 to 14-7 was formed with a layer thereon. However, Specimen 14-1 was not formed with any layer thereon. The layers formed on Specimens 14-2 to 14-4 were of - about 8 microns, 12 microns and 11 microns respectively and were identified to be vanadium carbide (VC). The layers formed on Specimens 14-S and 14-6 were of about 6 microns and 4 microns respectively and were recognized to be a composite layer composed of vanadium carbide (VC) and vanadium boride (V3B2). However, on the surface of Specimen 14-7, no vanadium was detected. The layers of Specimen 14-4 and 14-5 were measured to contain respectively ~ -21-' l~)SZ3~7 70 % and 94 %.of vanadium. From the layer of Specimen 14-4, no boron was detected. But the layer of Spec.imen 14-5 was found to have a relatively -21 a-~05~33L7 large amount of boron. The photomicrograph taken from Specimen 14-5 is shown in Fig. 24. The hardness of each of the layers formed on Specimen 14-2 and 1~-5 was about Hv 2960 and Hv 3200 respectively.
Fxample 15 :
In the same manner as described in Example 3, the 500 grams of molten borax was prepared, and then a metallic plate, 40 x 35 x 4 mm, made of electroly-tic niobium was anodically dissolved into the molten borax at 1000C for 2 hours with a current density of 1 A/cm2. Thus, a treating molten bath containing about 9.4 % of nio~ium was prepared. Next, Specimens 15-1 to 15-9 having the same size and made of the same cemented carbide as the Specimens used in Example 12 were treated respectively in the treating molten bath at 1000C under the conditions shown in Table 3.
Specimen 15-1 15-2 15-3 15-4 15-5 15-6 15-7 15-8 15-9 current density 0.01 0.05 0.1 0.5 1.0 3.0 5.0 10.020 (A/cm2) .
treating 16hr. 15hr. 15hr. 10hr. 4hr. lhr. lhr. 3min. lmin.
time By each of the trea-tments, on the surface of Specimen 15-2, a vanadium carbide ~VC) layer of about 13 microns was formed. The photomicrograph of the layer is shown in Fig. 25. On each Qf Specimens 15-4 and 15-5, a composite layer of about 15 microns and 6 micrcns respectively was formed. From the layer, niobium carbide (NbC~ and niobium boride (~b3B2) were clearly detected.
The niobium boride was contained in the upper portion of the layer and the niobium carbide was contained in the lower portion 3~7 of the layer. On Specimen 15-7, a composite layer of about 25 microns was formed. The layer was found to consist of Nb3B2 at its upper portion, NbC at its middle and W2B5 at its lower portion.
On Specimens 15-8 and 15-9, composite layers of about 10 microns and 13 microns were formed. The composite layers were found to consist of Nb3B2 at its upper portion, NbC at its middle and Co3B
at its lower portion. The thickness of the layers composed of Nb3s2 and NbC was decreased as the increaseof the current density applied.
By X-ray micro analyser, the layer formed on Specimen 15-8 was found to consist of about 60 % of niobium. ~Iowever the layer formed on Specimen 15-9 does not contain niobium. A
large amount of boron was detected from both of said layers.
However, the layer formed with a higher current density was found to contain a higher content of boron. The hardness of each of the layers formed on Specimens 15-2 and 15-4 was measured to be about Hv 2920 and ~Iv 3190.
Example 16 :
In the same manner as described in Example 6, a treating molten bath composed of 500 grams of borax and 80 gxams of Nb2O5 powder was prepared. Next, Specimens 16-1 to 16-9 having the same size and made of the same cemented carbide as the Specimens used in Example 12 were treated respectively in the treating molten bath at 1000C under the conditions shown in Table 4.
Specimen 16-1 16-2 16-3 16-4 16-5 ~6-6 16-7 16-8 16-9 current density 0.01 0.03 0.05 0.1 0~5 loO 3~0 5~0 10 (A/cm2) treating time 14hr. 15hr. 10hr. 5hr. 13hr. 5hr. 3min. lhr. 10min.
Specimen 16-1 was not Eormed with any layer thereon, however, on the surface of each of Specimens 16-2 to 16-9 a layer having a thickness ranging from 3 to 15 microns was formed.
The layers formed on Specimens 16-2 and 16-3 were identified to be NbC and the layers formed on Specimens 16-4 to 16-~ were recognized to contain NbC and Nb3B2. The layer formed on Specimen 16-9 was identified to be W2B2. As the example an X-ray diffraction chart taken from the layer of Specimen 1~-6 is shown in Fig. 27. By X-ray micro analyser, the layers formed on Specimens 16-4 and 16-7 were measured to contain about 67~ and 57% of niobium respectively. It was difficult to measure the content of boron in each of the layer. However, a relatively large amount Q~ boron was included in each of the layers. The hardness of each layers of Specimens 16-2 and 16-6 was measured to be about Hv 2980 and Hv 3230 respectively.
Exemple 17:
In the same manner as described in example 10, a treating molten bath composed of 115 grams of borax and 25 grams of NbC15 powder was prepared. Next, Specimens 17-1 to 17-7 having the same cemented carbide as the Specimens used in Example 12 were treated respectively in the treating molten bath at 1000 C under the conditions shown in Table 5.
_ Table 5 -Specimen 17-1 17-2 17-3 17-4 17 5 17-6 17-7 Current density 0.05 0.1 0.5 1.0 5.0 15 20 tA/cm2 ) Treating 14 hr. 10 hr. 8 hr. 5 hr. 1 hr. 10 min. 1 min.
._ _ ~5,,~3~7 On the surf~ce of each of Specimens 17-1 to 17-7 was `formed a layer. The thickness of the layer of each of Specimens 17-1 to 17-6 was about 25,27,30,20, 18 and 8 microns respectively.
Each o said layers were recognized to consist o a NbC portion and a W2B5 portion. The thickness of said NbC portion was de-creased as the increase of the current density applied. The layer of Specimen 17-7 was composed of only W2B. The hardness of the layer formed on Specimen 17-2 was about Hv 3000.
Example 18:
In the same manner as described in Example 3, the 500 grams of molten borax was prepared, and then a metallic plate, 50 x 40 x 4mm, made of electrolytic tantalum was anodically dis-solved into the molten borax at 1000C for 1 hour with a current density of 1 A/cm2. Thus, a treating molten bath containing about 11.2% of tantalum was prepared. Next Specimens lg-l to 18-5 having the same size and made of the same cemented carbide as the Specimens used in Example 12 were treated respectively in the treating molten bath at 1000 C under the conditions shown in Table 6.
Table 6 _ Specimen 18-1 18-2 18-3 18-4 18-5 .
(A/cm2) 0.01 0.0S 0.5 1.0 10 Treating time 16 hr. 14 hr. 12 hr. 1 hr. 5 min.
-All the Specimens 18-1 to 18-5 were ormed with a layer thereon. The thickness of the layer of each of Specimens 18-1 to 18-5 was about 20, 23, 25, 13 and 5 microns respectively. By the X-ray difraction method, the layers iLo~'~3~t7 formed on Specimens 18-1 to 18 3 were identified to be tantalum `carbide (TaC). The layer ormed on the surface of Specimen 18-4 was recognized to be composed of TaC and W2B5. The layer formed on Specimen 18-5 was identified to be W2BS. Also by X ray micro analyser, the layers o~ Specimens 18-1 to 1.8-3 were recognized to contain ~oron within the TaC.
Claims (9)
1. A method for forming a carbide layer of a V.a group element of the Periodic Table on the surface of an iron, ferrous alloy or cemented carbide article, comprising the steps of preparing a treating molten bath composed of molten boric acid or a borate and a substance containing a V-a group element of the Periodic Table in a vessel, immersing the article containing at least 0.05% by weight of carbon into the treating molten bath, applying an electric current to the treating molten bath through said article being used as the cathode for depositing the V-a group element on the surface of the article and for forming the carbide layer of said V-a group element with the carbon contained within said article on the surface of said article and taking said article out of the treating molten bath.
2. A method according to claim 1, wherein said borate is selected from the group consisting of sodium borate and potas-sium borate.
3. A method according to claim 1, wherein said subs-tance is a metallic powder containing said V-a group element and the current density of the cathode is selected within the range from 0.01 to 5 A/cm2.
4. A method according to claim 3, wherein said metallic powder consists of the V-a group element.
5. A method according to claim 3, wherein said metallic powder consists of an alloy containing the V-a group element.
6. A method according to claim 5, wherein said alloy is a ferrous alloy.
7. A method according to claim 1, wherein said sub-stance is an oxide of the V-a group element and the current densi-ty of the cathode is selected within the range from 0.1 to 15 A/cm2.
8. A method according to claim 1, wherein said sub-stance is a chloride of the V-a group element and the current density of the cathode is selected within the range from 0.01 to 3 A/cm2.
9. A method according to claim 1, wherein the step of preparing the treating molten bath comprises heating boric acid or a borate in the vessel, dipping a metallic block containing a V-a group element and anodically dissolving said metallic block into the molten boric acid or a borate, the current density of the cathode, in the step of applying an electric current, is selected within a range from 0.01 to 5 A/cm2.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP47043729A JPS5121384B2 (en) | 1972-05-04 | 1972-05-04 | |
| JP4608072A JPS5527146B2 (en) | 1972-05-09 | 1972-05-09 | |
| JP5649372A JPS5216453B2 (en) | 1972-06-08 | 1972-06-08 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1052317A true CA1052317A (en) | 1979-04-10 |
Family
ID=27291652
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA170,290A Expired CA1052317A (en) | 1972-05-04 | 1973-05-03 | Electrolytic formation of group va carbide on an iron, ferrous alloy or cemented carbide article |
Country Status (2)
| Country | Link |
|---|---|
| US (1) | US3887443A (en) |
| CA (1) | CA1052317A (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5429847A (en) * | 1977-08-11 | 1979-03-06 | Toyoda Chuo Kenkyusho Kk | Method of forming composite carbide layer of chromium and one or more of 5a group elements on surface of iron alloy |
| US4430170A (en) | 1983-01-17 | 1984-02-07 | The United States Of America As Represented By The Secretary Of The Navy | Electrodeposition of refractory metal carbides |
| US6458218B1 (en) | 2001-01-16 | 2002-10-01 | Linamar Corporation | Deposition and thermal diffusion of borides and carbides of refractory metals |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2950233A (en) * | 1954-04-29 | 1960-08-23 | Horizons Inc | Production of hard surfaces on base metals |
| US2984605A (en) * | 1959-03-16 | 1961-05-16 | Walter M Weil | Deposition of boron from fused salt baths |
| US3024176A (en) * | 1959-08-04 | 1962-03-06 | Gen Electric | Corrosion resistant coating |
| US3444058A (en) * | 1967-01-16 | 1969-05-13 | Union Carbide Corp | Electrodeposition of refractory metals |
-
1973
- 1973-04-27 US US355283A patent/US3887443A/en not_active Expired - Lifetime
- 1973-05-03 CA CA170,290A patent/CA1052317A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| US3887443A (en) | 1975-06-03 |
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