US3885059A - Method for forming a carbide layer of a IV-b group element of the periodic table on the surface of a cemented carbide article - Google Patents

Method for forming a carbide layer of a IV-b group element of the periodic table on the surface of a cemented carbide article Download PDF

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US3885059A
US3885059A US460148A US46014874A US3885059A US 3885059 A US3885059 A US 3885059A US 460148 A US460148 A US 460148A US 46014874 A US46014874 A US 46014874A US 3885059 A US3885059 A US 3885059A
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borate
molten bath
carbide
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Noboru Komatsu
Tohru Arai
Yoshihiko Sugimoto
Masayoshi Mizutani
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Toyota Central R&D Labs Inc
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C10/00—Solid state diffusion of only metal elements or silicon into metallic material surfaces
    • C23C10/18—Solid state diffusion of only metal elements or silicon into metallic material surfaces using liquids, e.g. salt baths, liquid suspensions
    • C23C10/20—Solid state diffusion of only metal elements or silicon into metallic material surfaces using liquids, e.g. salt baths, liquid suspensions only one element being diffused
    • C23C10/24—Salt bath containing the element to be diffused
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C22/70—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using melts
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C30/00—Coating with metallic material characterised only by the composition of the metallic material, i.e. not characterised by the coating process
    • C23C30/005—Coating with metallic material characterised only by the composition of the metallic material, i.e. not characterised by the coating process on hard metal substrates

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  • ABSTRACT A method for forming a carbide layer of a lV-b group element of the periodic table on the surface of a cemented carbide article in a treating molten bath, comprising preparing a treating molten bath composed of molten boric acid or borate and a IV-b group element dissolved therein and immersing the article in the treating molten bath to deposit the IV-b group element on the surface of the article and to form a carbide layer of the IV-b group element on the surface of the article with the carbon contained in the article.
  • the method of this invention can form easily a smooth and hard carbide layer on the surface of the article. And the formed'layer improves greatly the hardness and wear resistance of the cemented carbide article.
  • This invention relates to a method for forming a carbide layer ofa lV-b group element of the periodic table on the surface of a 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 cemented carbide with the carbide layer formed thereon has a greatly improved hardness, wear resistance and machinability.
  • Cemented carbide tools having a carbide layer such as titanium carbide (TiC) and zirconium carbide (ZrC) have been reported to have a remarkably improved cutting ability and have come to be used practically in these years.
  • a chemical vapor deposition method has been employed. Said coating is to heat an article to be treated in a hydrogen atmosphere containing the vapor of titanium chloride (TiCl and hydrocarbon such as propane, benzene and butane.
  • TiCl and hydrocarbon such as propane, benzene and butane.
  • the atmosphere since titanium and titanium chloride are easily oxidized in an atmosphere containing oxygen or water, the atmosphere must be carefully prepared to exclude oxygen and water from the atmosphere. Also since said atmosphere contains a corrosive titanium chloride and dangerous hydrogen gas, the construction of a treating furnace becomes to be complicated. Therefore, the operability of the method is not good and the treating cost is relatively high.
  • the conventional method for forming a zirconium carbide layer has the same drawbacks as those of the above mentioned method for forming a titanium carbide.
  • HO. 1 is a photomicrograph showing a titanium carbide layer formed on a cemented carbide according to Example 4;
  • FIG. 2 is an X-ray diffraction chart of the layer formed on the surface of a cemented carbide according to Example 4.
  • the present invention is directed to an improvement of the method for forming a carbide layer of a lV-b group element of the periodic table on the surface of a cemented carbide article in a treating mol ten bath composed of molten boric acid or borate and a lV-b group element dissolved therein.
  • the method of the present invention comprises preparing a treating molten bath composed of boric acid or borate and a lV-b group element dissolved therein and immersing a cemented carbide article in the treating molten bath for forming a very hard carbide layer of said lV-b group element on the surface of said article.
  • the dissolved lV-b group element in the treating molten bath reaches to the surface of the article and deposit on the article for forming the carbide layer with the carbon contained within the article.
  • boric acid B 0 and/or borate such as potassium borate borax (K 8 0 and sodium borate (Na B O with a lV-b group element is used.
  • the boric acid and borate can melt at a relatively low temperature and dissolve easily a lV-b group element in the molten boric acid or borate. Moreover they act as a kind of flux capable of keeping the surface of an article to be treated in its clean and fresh state and suppressing the formation of oxide thereon. Therefore, the treating molten bath containing boric oxide or borate gives a smooth and uniform carbide layer on the surface of the article.
  • one or more elements of titanium, zirconium and hafnium can be dissolved in the molten boric acid or borate.
  • any of the following means can be preferably employed.
  • the f rst means utilizes the property of the molten boric acid and borate to dissolve a lV-b group element. This means is easy in operation. However, the velocity of the dissolution of the element into the bath is relatively slow. To accerelate the dissolution, the element should be in a shape having a large contact area. From this point of view, a fine powder (of under 20 mesh) is much preferable than a thin plate. With use of a fine powder, a part of undissolved powder will be float in the treating molten bath and worsen the smoothness of the surface of an article to be treated by sticking to said surface.
  • the other part of undissolved powder will be piled up on the bottom of the vessel holding the treating molten bath and reduce the effective space of the treating molten bath.
  • a pure metal of the element is much preferable than an alloy of the element.
  • Another metallic element contained the metal or alloy of a lV-b group element will react with cemented carbide forming an article to be treated and suppress the formation of a good carbide layer of the IV-b group element on the surface of the article. 5 percent by weight (hereinafter percent means percent by weight) of a IV-b group element in the treating molten bath is sufficient.
  • the lV-b group element may be contained in the treating molten bath in a quantity between about 1 50 percent (the quantity of boric acid or borate being within a range from 50 to 99 percent). With use of less quantity of a IV-b group element than 1 percent, the speed of formation of the carbide layer would be too slow to be accepted for the practical purpose. Too much addition of a lV-b group element than 50 percent will increase the viscosity of the treating molten bath and brings the drawbacks mentioned above due to the increase of undissolved powder of the element.
  • the second means is to use a halide of a lV-b group element such as TiCl TiF,;, Til Na TiF,,-, Na- ZrF HfF HfCl
  • a halide of a lV-b group element such as TiCl TiF,;, Til Na TiF,,-, Na- ZrF HfF HfCl
  • the halides can be dissolved easily and completely without leaving undissolved particles in the molten boric acid or borate so that the operability of the treatment increases and the sticking of undissolved particle to the surface of the article is avoided.
  • the shape of the halide the shape of powder or this plate is preferable as same as the shape of the metal of lV-b group element mentioned in the first means. Since the halide is dissolved quickly, the size of the powder is not necessary to be as fine as the metallic powder in the first means.
  • the halide may be contained in the treating molten bath in a quantity between about 1 and 50 percent.
  • the third means is to dissolve anodically a plate or block of a IV-b group element or of an alloy of the element in the molten bath by use of the plate or block as an anode and use of the vessel holding the bath or an electric conductive material dipped in the bath as a cathode.
  • the speed of the dissolution of the element is very fast compared with that of the powder of the element, and the drawbacks caused from undissolved powder in the first means are avoided completely.
  • the speed of'dissolution of the element is increased according to the increase of the current density applied to the anode.
  • the element is dissolved without applying a current to the anode. Therefore, the current density is not necessary to be large.
  • the practical anodic current density is within from 0.1 to A/cm
  • the treatment of the invention is accomplished by dipping and keeping a cemented carbide article to be treated in the treating molten bath prepared by any of the means mentioned above.
  • preparing the treating bath, by the anodic dissolution of a IV-b group element and the treating of the article can be carried out at the same time.
  • the article to be treated must be immersed in the bath without being contacted with both of the anode and cathode.
  • the treating molten bath prepared by the third means can be solidified by cooling and kept without worsening the quality of the treating material.
  • the treating material can be heated up to the treating temperature to prepare the treating molten bath and the treatment can be carried out with use of the treating molten bath.
  • the IV-b group element dissolved in the treating molten bath reacts with the carbon contained in the cemented carbide forming the article to be treated and forms a carbide layer on the surface of the article.
  • a vessel made of the material which does not react with the treating molten bath and has a high melting point such as graphite, heat resistant steel and nitride can be used. From the practical point, the vessel made of graphite or heat resistant steel is preferable.
  • cemented carbide forming an article to be treated means a sintered tungsten carbide containing cobalt.
  • Said cemented carbide may include a small amount of titanium carbide, niobium carbide. tantalum carbide and the like.
  • the treating temperature may be selected within the range from the liquidified point of the treating molten bath to the melting point of the article to be treated. From the view of practical forming speed of the layer, the treating temperature is preferably 900C or higher than 900C. From the point of deterioration of the quality of the material forming the article during the treatment, the treating temperature is preferably 1200C or lower than l2()OC.
  • a small amount of halide such as NaCl, KC] and NaF. oxide such as P 0 hydroxide such as NaOH and KOH, sulfate, carbonate or nitrate can be added into the treating molten bath to lower the viscosity of the bath.
  • the treating time depends upon the thickness of the carbide layer to be formed, Heating shorter than 1 hour, 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 practise, an acceptable thickness of the layer can be realized within 30 hours or shorter time.
  • EXAMPLE I 500 grams of borax powder was introduced into a graphite crucible and heated up to lOOOC for melting the borax in an electric furnace, and then about 110 grams of metallic titanium flakes of 0.5mm thick was added into the molten borax. Thus a treating molten bath was prepared.
  • EXAMPLE 2 In the same manner as described in Example 1, a treating molten bath was prepared by introducing 10 percent of metallic zirconium powder of under' ZO mesh into percent of molten borax. Next a specimen having the same shape and made of the same material as those of the specimen treated in Example I was dipped in the treating molten bath, kept therein for 16 hours at l000C, taken out therefrom and air cooled. By the treatment, the specimen was formed with a layer of about 10 microns. The layer was tested'by X-ray diffraction method and diffraction lines corresponding to zirconium carbide (ZrC) were clearly detected.
  • ZrC zirconium carbide
  • hardness of the treated specimen was measured to be about Hv 2750.
  • EXAMPLE 3 ln the same manner as described in Example 1, 500 grams of molten borax was prepared in a graphite crucible and then a rod having mm diameter and made of titanium was dipped in the molten borax and anodically dissolved into the molten borax by applying an electric current to the molten borax through the rod used as an anode and the crucible used as a cathode for 2 hours with an anodic current density of 3 A/em By the anodic dissolution, a treating molten bath was prepared. The content of titanium dissolved in the treating molten bath was calculated to be about 8.3 percent.
  • Example l a specimen having the same shape and made of the same material as those of the specimen used in Example l was dipped in the treating molten bath, kept therein for l6 hours at lO0OC, taken out therefrom and air cooled.
  • the specimen was formed with a titanium carbide (TiC) layer of about 12 microns on the surface thereof.
  • EXAMPLE 4 100 grams of borax powder was introduced into a graphite crucible and heated up to lO0OC for melting the borax in an electric furnace, and then about 76 grams of Na TiF powder of under 100 mesh was introduced into the molten borax, thus a treating molten bath containing about 10 percent of titanium was prepared. Next a specimen having the same shape and made of the same cemented carbide as those of the specimen used in Example 1 was clipped in the treating molten bath, kept therein for hours at lO0OC, taken out therefrom and air cooled. By the treatment, a layer having an about 10 microns thick and shown in the photomierograph of FIG. 1 was formed on the surface of the article.
  • a diffraction chart shown in FIG. 2 was given from the formed layer.
  • the chart shows strong diffraction lines of titanium carbide. Also the layer was identified to contain a large quantity of titanium by X-ray micro analyzer.
  • the hardness of the treated specimen was measured to be about Hv 3070.
  • EXAMPLE 5 In the same manner as described in Example 4, a treating molten bath containing 10 percent of zirconium by introducing about 39 grams of ZrCL, powder of under mesh into lOO grams of molten borax. Then, a specimen having the same shape and made of the same cemented carbide as those of the specimen used in Example 1 was dipped in the treating molten bath, kept therein for 15 hours at lO0OC, taken out therefrom and air cooled. By the treatment, a layer of about 5 microns was formed on the surface of the article. From the formed layer, diffraction lines corresponding to the lines of zirconium carbide (ZrC) were detected. The hardness of the treated specimen was measured to be about Hv 2750.
  • a method for the surface treatment of a cemented carbide article comprising the steps of preparing a treating molten bath consisting essentially of boric acid or borate and a substance containing at least one element of the group consisting of titanium, zirconium and hafnium and immersing the article in the treating molten bath, thereby forming a carbide layer of said element on the surface of the article thus treated.
  • borate is selected from the group consisting of sodium borate and potassium borate.
  • a method according to claim 4, wherein said halide is selected from the group consisting of TiCl TiF Til Na- TiF N21 ZrF HfF and HfCl 6.
  • a method according to claim 1, wherein said treat ing molten bath is prepared by the steps of melting boric acid or borate in a vessel, dipping a metallic plate containing said element and dissolving anodically said metallic plate or block into the molten boric acid or borate with an anodic current density within a range from 0.1 to 10 A/cm 7.
  • said cemented carbide article is made of tungsten carbide and

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Abstract

A method for forming a carbide layer of a IV-b group element of the periodic table on the surface of a cemented carbide article in a treating molten bath, comprising preparing a treating molten bath composed of molten boric acid or borate and a IV-b group element dissolved therein and immersing the article in the treating molten bath to deposit the IV-b group element on the surface of the article and to form a carbide layer of the IV-b group element on the surface of the article with the carbon contained in the article. The method of this invention can form easily a smooth and hard carbide layer on the surface of the article. And the formed layer improves greatly the hardness and wear resistance of the cemented carbide article.

Description

United States Patent Komatsu et al.
METHOD FOR FORMING A CARBIDE LAYER OF A IV-B GROUP ELEMENT OF THE PERIODIC TABLE ON THE SURFACE OF A CEMENTED CARBIDE ARTICLE Inventors: Noboru Komatsu, Toyoakeshi;
Tohru Arai, Nagoyashi; Yoshihiko Sugimoto, Nagoyashi; Masayoshi Mizutani, Nagoyashi, all of Japan Kabushiki Kaisha Toyota Chuo Kenkyusho, Nagoyashi, Japan Filed: Apr. 11, 1974 Appl. No.: 460,148
Assignee:
Foreign Application Priority Data Apr. 12, 1973 Japan 48-40821 References Cited UNITED STATES PATENTS 8/1959 Goetzel et al 117/118 3,744,979 7/1973 Kalish 117/127 Primary ExaminerMayer Weinblatt Assistant ExaminerEdith L. Rollins Attorney, Agent, or Firm-Wenderoth, Lind & Ponack [5 7] ABSTRACT A method for forming a carbide layer of a lV-b group element of the periodic table on the surface of a cemented carbide article in a treating molten bath, comprising preparing a treating molten bath composed of molten boric acid or borate and a IV-b group element dissolved therein and immersing the article in the treating molten bath to deposit the IV-b group element on the surface of the article and to form a carbide layer of the IV-b group element on the surface of the article with the carbon contained in the article. The method of this invention can form easily a smooth and hard carbide layer on the surface of the article. And the formed'layer improves greatly the hardness and wear resistance of the cemented carbide article.
7 Claims, 2 Drawing Figures PATENTED 3,885,059
SHEET 10F 2 FIG.1
METHOD FOR FORMING A CARBIDE LAYER OF A IV-B GROUP ELEMENT OF THE PERIODIC TABLE ON THE SURFACE OF A CEMENTED CARBIDE ARTICLE This invention relates to a method for forming a carbide layer ofa lV-b group element of the periodic table on the surface of a 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 cemented carbide with the carbide layer formed thereon has a greatly improved hardness, wear resistance and machinability.
Cemented carbide tools having a carbide layer such as titanium carbide (TiC) and zirconium carbide (ZrC) have been reported to have a remarkably improved cutting ability and have come to be used practically in these years.
As a practical method for forming a titanium carbide on the surface of a cemented carbide article, a chemical vapor deposition method has been employed. Said coating is to heat an article to be treated in a hydrogen atmosphere containing the vapor of titanium chloride (TiCl and hydrocarbon such as propane, benzene and butane. In this coating, since titanium and titanium chloride are easily oxidized in an atmosphere containing oxygen or water, the atmosphere must be carefully prepared to exclude oxygen and water from the atmosphere. Also since said atmosphere contains a corrosive titanium chloride and dangerous hydrogen gas, the construction of a treating furnace becomes to be complicated. Therefore, the operability of the method is not good and the treating cost is relatively high. The conventional method for forming a zirconium carbide layer has the same drawbacks as those of the above mentioned method for forming a titanium carbide.
Therefore, it is the principal object of this invention to provide an improved method for forming a carbide layer of a lV-b group element on the surface of a cemented carbide article in a treating molten bath.
It is another object of this invention to provide a method for forming a carbide layer, which is safe and simple in practice and less expensive.
Other objects of this invention will appear hereinafter.
The novel features that are considered characteristic of the invention are set forth with particularity in the appended claims. The invention, itself, as to its method of operation, together with additional objects and advantages therefore, will best be understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:
HO. 1 is a photomicrograph showing a titanium carbide layer formed on a cemented carbide according to Example 4;
FIG. 2 is an X-ray diffraction chart of the layer formed on the surface of a cemented carbide according to Example 4.
Broadly, the present invention is directed to an improvement of the method for forming a carbide layer of a lV-b group element of the periodic table on the surface of a cemented carbide article in a treating mol ten bath composed of molten boric acid or borate and a lV-b group element dissolved therein. Namely, the method of the present invention comprises preparing a treating molten bath composed of boric acid or borate and a lV-b group element dissolved therein and immersing a cemented carbide article in the treating molten bath for forming a very hard carbide layer of said lV-b group element on the surface of said article. During the treatment, it is believed that the dissolved lV-b group element in the treating molten bath reaches to the surface of the article and deposit on the article for forming the carbide layer with the carbon contained within the article.
As the bath material, a mixture of boric acid (B 0 and/or borate such as potassium borate borax (K 8 0 and sodium borate (Na B O with a lV-b group element is used. The boric acid and borate can melt at a relatively low temperature and dissolve easily a lV-b group element in the molten boric acid or borate. Moreover they act as a kind of flux capable of keeping the surface of an article to be treated in its clean and fresh state and suppressing the formation of oxide thereon. Therefore, the treating molten bath containing boric oxide or borate gives a smooth and uniform carbide layer on the surface of the article.
As the lV-b group elements, one or more elements of titanium, zirconium and hafnium can be dissolved in the molten boric acid or borate.
In order to prepare the treating molten bath, any of the following means can be preferably employed.
1. It is to introduce a metallic powder or thin plate of a lV-b group element or of an alloy containing a lV-bgroup element into a molten boric acid or borate bath. 2. It is to introduce a powder or thin plate of the halide ofa lV-b group element into a molten boric acid or borate bath.
3. It is to dissolve anodically a plate or a block of a IV-b group element or of an alloy containing a lV-b group element in a molten boric acid or borate bath by applying an electric current to the bath with use of the plate as an anode.
The f rst means utilizes the property of the molten boric acid and borate to dissolve a lV-b group element. This means is easy in operation. However, the velocity of the dissolution of the element into the bath is relatively slow. To accerelate the dissolution, the element should be in a shape having a large contact area. From this point of view, a fine powder (of under 20 mesh) is much preferable than a thin plate. With use of a fine powder, a part of undissolved powder will be float in the treating molten bath and worsen the smoothness of the surface of an article to be treated by sticking to said surface. The other part of undissolved powder will be piled up on the bottom of the vessel holding the treating molten bath and reduce the effective space of the treating molten bath. As a source of a lV-b group element, a pure metal of the element is much preferable than an alloy of the element. Another metallic element contained the metal or alloy of a lV-b group element will react with cemented carbide forming an article to be treated and suppress the formation of a good carbide layer of the IV-b group element on the surface of the article. 5 percent by weight (hereinafter percent means percent by weight) of a IV-b group element in the treating molten bath is sufficient. In practice, however, the lV-b group element may be contained in the treating molten bath in a quantity between about 1 50 percent (the quantity of boric acid or borate being within a range from 50 to 99 percent). With use of less quantity of a IV-b group element than 1 percent, the speed of formation of the carbide layer would be too slow to be accepted for the practical purpose. Too much addition of a lV-b group element than 50 percent will increase the viscosity of the treating molten bath and brings the drawbacks mentioned above due to the increase of undissolved powder of the element.
The second means is to use a halide of a lV-b group element such as TiCl TiF,;, Til Na TiF,,-, Na- ZrF HfF HfCl The halides can be dissolved easily and completely without leaving undissolved particles in the molten boric acid or borate so that the operability of the treatment increases and the sticking of undissolved particle to the surface of the article is avoided. As the shape of the halide, the shape of powder or this plate is preferable as same as the shape of the metal of lV-b group element mentioned in the first means. Since the halide is dissolved quickly, the size of the powder is not necessary to be as fine as the metallic powder in the first means.
The halide may be contained in the treating molten bath in a quantity between about 1 and 50 percent.
The third means is to dissolve anodically a plate or block of a IV-b group element or of an alloy of the element in the molten bath by use of the plate or block as an anode and use of the vessel holding the bath or an electric conductive material dipped in the bath as a cathode. In this case, the speed of the dissolution of the element is very fast compared with that of the powder of the element, and the drawbacks caused from undissolved powder in the first means are avoided completely. The speed of'dissolution of the element is increased according to the increase of the current density applied to the anode. However the element is dissolved without applying a current to the anode. Therefore, the current density is not necessary to be large. The practical anodic current density is within from 0.1 to A/cm The treatment of the invention is accomplished by dipping and keeping a cemented carbide article to be treated in the treating molten bath prepared by any of the means mentioned above.
In the third means, preparing the treating bath, by the anodic dissolution of a IV-b group element and the treating of the article can be carried out at the same time. In this case, the article to be treated must be immersed in the bath without being contacted with both of the anode and cathode.
Also the treating molten bath prepared by the third means can be solidified by cooling and kept without worsening the quality of the treating material. When the treatment is necessary, the treating material can be heated up to the treating temperature to prepare the treating molten bath and the treatment can be carried out with use of the treating molten bath.
The IV-b group element dissolved in the treating molten bath reacts with the carbon contained in the cemented carbide forming the article to be treated and forms a carbide layer on the surface of the article.
As the vessel holding the treating molten bath, a vessel made of the material which does not react with the treating molten bath and has a high melting point, such as graphite, heat resistant steel and nitride can be used. From the practical point, the vessel made of graphite or heat resistant steel is preferable.
Here, cemented carbide forming an article to be treated means a sintered tungsten carbide containing cobalt. Said cemented carbide may include a small amount of titanium carbide, niobium carbide. tantalum carbide and the like.
The treating temperature may be selected within the range from the liquidified point of the treating molten bath to the melting point of the article to be treated. From the view of practical forming speed of the layer, the treating temperature is preferably 900C or higher than 900C. From the point of deterioration of the quality of the material forming the article during the treatment, the treating temperature is preferably 1200C or lower than l2()OC.
A small amount of halide such as NaCl, KC] and NaF. oxide such as P 0 hydroxide such as NaOH and KOH, sulfate, carbonate or nitrate can be added into the treating molten bath to lower the viscosity of the bath.
The treating time depends upon the thickness of the carbide layer to be formed, Heating shorter than 1 hour, 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 practise, an acceptable thickness of the layer can be realized within 30 hours or shorter time.
It is not necessary to carry out the method of the present invention in the atmosphere of non-oxidation gas, but the method can be carried out into effect either under the air atmosphere or the inert gas atmosphere.
EXAMPLE I 500 grams of borax powder was introduced into a graphite crucible and heated up to lOOOC for melting the borax in an electric furnace, and then about 110 grams of metallic titanium flakes of 0.5mm thick was added into the molten borax. Thus a treating molten bath was prepared.
Next, a specimen, 1.0 X 5.5 X 30mm, made of cemented carbide composed of 91 percent of tungsten carbide and 9 percent of cobalt was dipped into the treating molten bath kept therein for 15 hours, taken out therefrom and air cooled. The treating material adhered to the surface of the specimen was removed by washing with hot water and then the specimen treated was investigated. After cutting and polishing the specimen, the specimen was micrographically observed, and a layer of about 10 microns thick was found on the surface of the specimen. By X-ray diffraction method, strong diffraction lines'of titanium carbide (TiC) were found from the formed layer and the layer was identitied to be titanium carbide. By a micro vickers hardness tester, the formed layer was measured to be about Hv 3l80. Compared with this the specimen before the treatment was measured to be about H'v I525.
EXAMPLE 2 In the same manner as described in Example 1, a treating molten bath was prepared by introducing 10 percent of metallic zirconium powder of under' ZO mesh into percent of molten borax. Next a specimen having the same shape and made of the same material as those of the specimen treated in Example I was dipped in the treating molten bath, kept therein for 16 hours at l000C, taken out therefrom and air cooled. By the treatment, the specimen was formed with a layer of about 10 microns. The layer was tested'by X-ray diffraction method and diffraction lines corresponding to zirconium carbide (ZrC) were clearly detected. The
hardness of the treated specimen was measured to be about Hv 2750.
EXAMPLE 3 ln the same manner as described in Example 1, 500 grams of molten borax was prepared in a graphite crucible and then a rod having mm diameter and made of titanium was dipped in the molten borax and anodically dissolved into the molten borax by applying an electric current to the molten borax through the rod used as an anode and the crucible used as a cathode for 2 hours with an anodic current density of 3 A/em By the anodic dissolution, a treating molten bath was prepared. The content of titanium dissolved in the treating molten bath was calculated to be about 8.3 percent.
Next, a specimen having the same shape and made of the same material as those of the specimen used in Example l was dipped in the treating molten bath, kept therein for l6 hours at lO0OC, taken out therefrom and air cooled. By this treatment, the specimen was formed with a titanium carbide (TiC) layer of about 12 microns on the surface thereof.
EXAMPLE 4 100 grams of borax powder was introduced into a graphite crucible and heated up to lO0OC for melting the borax in an electric furnace, and then about 76 grams of Na TiF powder of under 100 mesh was introduced into the molten borax, thus a treating molten bath containing about 10 percent of titanium was prepared. Next a specimen having the same shape and made of the same cemented carbide as those of the specimen used in Example 1 was clipped in the treating molten bath, kept therein for hours at lO0OC, taken out therefrom and air cooled. By the treatment, a layer having an about 10 microns thick and shown in the photomierograph of FIG. 1 was formed on the surface of the article. By X-ray diffraction method, a diffraction chart shown in FIG. 2 was given from the formed layer. The chart shows strong diffraction lines of titanium carbide. Also the layer was identified to contain a large quantity of titanium by X-ray micro analyzer.
The hardness of the treated specimen was measured to be about Hv 3070.
EXAMPLE 5 In the same manner as described in Example 4, a treating molten bath containing 10 percent of zirconium by introducing about 39 grams of ZrCL, powder of under mesh into lOO grams of molten borax. Then, a specimen having the same shape and made of the same cemented carbide as those of the specimen used in Example 1 was dipped in the treating molten bath, kept therein for 15 hours at lO0OC, taken out therefrom and air cooled. By the treatment, a layer of about 5 microns was formed on the surface of the article. From the formed layer, diffraction lines corresponding to the lines of zirconium carbide (ZrC) were detected. The hardness of the treated specimen was measured to be about Hv 2750.
What is claimed is:
l. A method for the surface treatment of a cemented carbide article, comprising the steps of preparing a treating molten bath consisting essentially of boric acid or borate and a substance containing at least one element of the group consisting of titanium, zirconium and hafnium and immersing the article in the treating molten bath, thereby forming a carbide layer of said element on the surface of the article thus treated.
2. A method according to claim 1, wherein said borate is selected from the group consisting of sodium borate and potassium borate.
3. A method according to claim 1, wherein said substance is a metallic powder or a thin plate containing said element and said treating molten bath is composed of l to 50 percent by weight of said metallic powder or thin plate and the rest of boric acid or borate.
4. A method according to claim 1, wherein said substance is a halide of said element and the treating molten bath is composed of l to 50 percent by weight of said halide and the rest of boric acid or borate.
5. A method according to claim 4, wherein said halide is selected from the group consisting of TiCl TiF Til Na- TiF N21 ZrF HfF and HfCl 6. A method according to claim 1, wherein said treat ing molten bath is prepared by the steps of melting boric acid or borate in a vessel, dipping a metallic plate containing said element and dissolving anodically said metallic plate or block into the molten boric acid or borate with an anodic current density within a range from 0.1 to 10 A/cm 7. A method according to claim 1, wherein said cemented carbide article is made of tungsten carbide and

Claims (7)

1. A METHOD FOR THE SURFACE TREATMENT OF A CEMENTED CARBIDE ARTICLE, COMPRISING THE STEPS OF PREPARING A TREATING MOLTEN BATH CONSISTING ESSENTIALLY OF BORIC ACID OR BORATE AND A SUBSTANCE CONTAINING AT LEAST ONE ELEMENT OF THE GROUP CONSISTING OF TITANIUM, ZIRCONIUM AND HAFNIUM AND IMMERSING THE ARTICLE IN THE TREATING MOLTEN BATH, THEREBY FORMING A CARBIDE LAYER OF SAID ELEMENT ON THE SURFACE OF THE ARTICLE THUS TREATED.
2. A method according to claim 1, wherein said borate is selected from the group consisting of sodium borate and potassium borate.
3. A method according to claim 1, wherein said substance is a metallic powder or a thin plate containing said element and said treating molten bath is composed of 1 to 50 percent by weight of said metallic powder or thin plate and the rest of boric acid or borate.
4. A method according to claim 1, wherein said substance is a halide of said element and the treating molten bath is composed of 1 to 50 percent by weight of said halide and the rest of boric acid or borate.
5. A method according to claim 4, wherein said halide is selected from the group consisting of TiCl3, TiF6, TiI4, Na2TiF6, Na2ZrF6, HfF4 and HfCl4.
6. A method according to claim 1, wherein said treating molten bath is prepared by the steps of melting boric acid or borate in a vessel, dipping a metallic plate containing said element and dissolving anodically said metallic plate or block into the molten boric acid or borate with an anodic current density within a range from 0.1 to 10 A/cm2.
7. A method according to claiM 1, wherein said cemented carbide article is made of tungsten carbide and cobalt.
US460148A 1973-04-12 1974-04-11 Method for forming a carbide layer of a IV-b group element of the periodic table on the surface of a cemented carbide article Expired - Lifetime US3885059A (en)

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Cited By (8)

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US4158578A (en) * 1977-05-09 1979-06-19 Kabushiki Kaisha Toyota Chuo Kenkyusho Method for forming a carbide layer of a Va-Group element of the periodic table or chromium on the surface of a ferrous alloy article
US4202705A (en) * 1977-06-30 1980-05-13 Kabushiki Kaisha Toyoto Chuo Kenkyusho Treating bath, forming a mixed carbide layer of Va-Group elements on a ferrous alloy surface and resulting product
US4400222A (en) * 1980-06-17 1983-08-23 Hitachi Metals, Ltd. Method for treating surfaces
US4400224A (en) * 1981-04-20 1983-08-23 Kabushiki Kaisha Toyota Chuo Kenkyusho Method for forming a carbide layer on the surface of a ferrous alloy article or a cemented carbide article
US4623517A (en) * 1979-07-07 1986-11-18 Biuro Projektow Przemyslu Metali Niezelaznych Bipromet Method of anti-corrosive protection of silicon carbide products
US5234721A (en) * 1989-05-26 1993-08-10 Rostoker, Inc. Method for forming carbide coating on various metals and their alloys
US5405456A (en) * 1993-10-21 1995-04-11 National Science Council Process of surface hardening for titanium alloy by molten salt carburization
US5534293A (en) * 1992-05-21 1996-07-09 Loral Aerospace Corp. Method for producing hafnium carbide surfaces on carbon based materials

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GB2000814B (en) * 1977-07-07 1982-03-17 Toyoda Chuo Kenkyusho Kk Coating ferrous articles

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US2899338A (en) * 1959-08-11 Thermal element
US3744979A (en) * 1971-04-14 1973-07-10 Adamas Carbide Corp Method of forming a hard surface on cemented carbides and resulting article

Patent Citations (2)

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Publication number Priority date Publication date Assignee Title
US2899338A (en) * 1959-08-11 Thermal element
US3744979A (en) * 1971-04-14 1973-07-10 Adamas Carbide Corp Method of forming a hard surface on cemented carbides and resulting article

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4158578A (en) * 1977-05-09 1979-06-19 Kabushiki Kaisha Toyota Chuo Kenkyusho Method for forming a carbide layer of a Va-Group element of the periodic table or chromium on the surface of a ferrous alloy article
US4202705A (en) * 1977-06-30 1980-05-13 Kabushiki Kaisha Toyoto Chuo Kenkyusho Treating bath, forming a mixed carbide layer of Va-Group elements on a ferrous alloy surface and resulting product
US4623517A (en) * 1979-07-07 1986-11-18 Biuro Projektow Przemyslu Metali Niezelaznych Bipromet Method of anti-corrosive protection of silicon carbide products
US4400222A (en) * 1980-06-17 1983-08-23 Hitachi Metals, Ltd. Method for treating surfaces
US4400224A (en) * 1981-04-20 1983-08-23 Kabushiki Kaisha Toyota Chuo Kenkyusho Method for forming a carbide layer on the surface of a ferrous alloy article or a cemented carbide article
US5234721A (en) * 1989-05-26 1993-08-10 Rostoker, Inc. Method for forming carbide coating on various metals and their alloys
US5534293A (en) * 1992-05-21 1996-07-09 Loral Aerospace Corp. Method for producing hafnium carbide surfaces on carbon based materials
US5405456A (en) * 1993-10-21 1995-04-11 National Science Council Process of surface hardening for titanium alloy by molten salt carburization

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GB1411927A (en) 1975-10-29
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DE2417919A1 (en) 1974-10-24
DE2417919B2 (en) 1976-10-07
FR2225547A1 (en) 1974-11-08
FR2225547B1 (en) 1976-12-17
JPS519688B2 (en) 1976-03-29

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