JP5547864B2 - Discharge surface treatment method and apparatus - Google Patents

Discharge surface treatment method and apparatus Download PDF

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JP5547864B2
JP5547864B2 JP2000600798A JP2000600798A JP5547864B2 JP 5547864 B2 JP5547864 B2 JP 5547864B2 JP 2000600798 A JP2000600798 A JP 2000600798A JP 2000600798 A JP2000600798 A JP 2000600798A JP 5547864 B2 JP5547864 B2 JP 5547864B2
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workpiece
electrode
surface treatment
discharge
electric discharge
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尚武 毛利
学 吉田
昭弘 後藤
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23H—WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL
    • B23H9/00—Machining specially adapted for treating particular metal objects or for obtaining special effects or results on metal objects
    • 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
    • C23C24/00—Coating starting from inorganic powder
    • C23C24/08—Coating starting from inorganic powder by application of heat or pressure and heat
    • 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
    • C23C24/00—Coating starting from inorganic powder
    • C23C24/08—Coating starting from inorganic powder by application of heat or pressure and heat
    • C23C24/10—Coating starting from inorganic powder by application of heat or pressure and heat with intermediate formation of a liquid phase in the layer
    • 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
    • C23C26/00—Coating not provided for in groups C23C2/00 - C23C24/00
    • 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
    • C23C26/00—Coating not provided for in groups C23C2/00 - C23C24/00
    • C23C26/02—Coating not provided for in groups C23C2/00 - C23C24/00 applying molten material to the substrate

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Other Surface Treatments For Metallic Materials (AREA)
  • Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)

Description

この発明は、電極と被加工物の間に放電を発生させ、その放電エネルギにより被加工物表面に硬質被膜を形成する、放電表面処理方法及び装置の改良に関するものである。  The present invention relates to an improvement in a discharge surface treatment method and apparatus in which a discharge is generated between an electrode and a workpiece and a hard film is formed on the workpiece surface by the discharge energy.

従来、被加工物の表面をコーティングして、耐食性、耐摩耗性を付与する技術としては、たとえば特開平５−１４８６１５号公報において開示された放電表面処理方法がある。この技術は、ＷＣ粉末とＣｏ粉末等からなる圧粉体電極を使用して１次加工（堆積加工）を行い、次に銅電極等の比較的電極消耗の少ない電極に交換して２次加工（再溶融加工）を行う、２つの工程からなる金属材料の表面処理方法である。この従来技術は、鋼材に対して数１０μｍ程度の厚みの硬質被膜を形成するには優れた方法であるが、超硬合金のような焼結材料の表面に対しては強固な密着力を持つ硬質被膜形成が困難である等の問題がある。
次に、特開平９−１９２９３７号公報に開示された、超硬合金にも密着力が高い硬質被膜を形成する放電表面処理方法を第７図により説明する。図において、１はＴｉＨ２を圧縮成形してなる圧粉体電極、２は被加工物、３は加工槽、４は加工液、５は圧粉体電極１と被加工物２に印加する電圧及び電流のスイッチングを行うスイッチング素子、６はスイッチング素子５のオン・オフを制御する制御回路、７は電源、８は抵抗器、９は形成された硬質被膜である。このような構成による放電表面処理により、鉄鋼、超硬合金等の表面に数μｍ〜数１０μｍの厚みの硬質被膜を形成することができる。
また、特開平１０−２２５８２４号公報には、Ｔｉ、Ｖ、Ｎｂ、Ｔａ等の高硬度な炭化物を生成する材料を電極として使用して放電を発生させ、被加工物の表面を脱炭させ、わずかに粗い面とした後（前処理）、ＴｉＨ２系の圧粉体電極により放電を発生させ、被加工物の表面処理を行う（本処理）方法が開示されている。この前処理は、本処理においてコーティング材料の付着をよくすることを目的とするものである。また、同様の目的で、ＴｉＨ２系の圧粉体電極が負極性の比較的放電エネルギが小さな条件で前処理を行い、その後、放電エネルギを大きくし、同一の電極であるＴｉＨ２系の圧粉体電極により本処理を行う方法が開示されている。
以上の従来技術においては、いずれの場合も圧粉体電極を用いることが特徴であるが、以下に示す３つの理由により実用化に問題がある。
第１の理由は、実用的な大きさの電極の成形が困難であることである。すなわち、電極を金型等の表面処理に用いる実用的な大きさに成形するには、プレスの能力を飛躍的に大きくしなければならないと共に、粉体状の材料の圧縮成形時に圧力が材料の内部に均一に伝播しないため密度の不均一が大きくなり、ひび割れの発生等の欠陥が生じる。さらに、成形された圧粉体電極は形状が崩れやすく二次加工が困難であると共に、被加工物に形成される硬質被膜にはばらつきが発生し品質が低下する。
第２の理由は、電極用材料の取り扱いが困難なことである。すなわち、Ｔｉ及びＴｉＨ２等の粉末は酸化しやすく、特にＴｉＨ２は空気中でも加水分解を引き起こす等の経時変化が発生し、取り扱いが困難である。さらに、水中に投入すると激しく水素ガスを発生するため、不要になった電極の廃棄処理上の問題もある。
第３の理由は、厚膜の形成が困難なことである。すなわち、従来の方法では数μｍ〜数十μｍの厚さまでが限界であり、工業的に要求されているこれ以上の厚さの硬質被膜の形成ができない。
以下において、前記第３の理由に関連した補足説明を行う。薄膜の形成はドライプロセスである物理蒸着や化学蒸着等により普及しているが、厚膜の形成はこれらの方法では困難であり、現状では溶射法等に依存せざるをえない。溶射法は各種の材料を被加工物上に肉盛りできるがその組織は粗く、金型等の被膜のような精密かつ耐久性が必要な用途への応用は不可能であり、使用材料の制約も多い。Conventionally, as a technique for imparting corrosion resistance and wear resistance by coating the surface of a workpiece, for example, there is a discharge surface treatment method disclosed in Japanese Patent Application Laid-Open No. 5-148615. In this technology, primary processing (deposition processing) is performed using a green compact electrode made of WC powder and Co powder, and then secondary processing is performed by replacing the electrode with a relatively low electrode consumption such as a copper electrode. This is a surface treatment method for a metal material comprising two steps of performing (remelting processing). This prior art is an excellent method for forming a hard film with a thickness of about several tens of μm on steel, but has a strong adhesion to the surface of a sintered material such as cemented carbide. There are problems such as difficulty in forming a hard coating.
Next, a discharge surface treatment method for forming a hard film having a high adhesion force on a cemented carbide disclosed in Japanese Patent Laid-Open No. 9-192937 will be described with reference to FIG. In the figure, 1 is a green compact electrode formed by compression molding TiH 2 , 2 is a workpiece, 3 is a processing tank, 4 is a processing fluid, 5 is a voltage applied to the green compact electrode 1 and the workpiece 2. And a switching element for switching current, 6 is a control circuit for controlling on / off of the switching element 5, 7 is a power source, 8 is a resistor, and 9 is a hard film formed. By the discharge surface treatment with such a configuration, a hard coating having a thickness of several μm to several tens of μm can be formed on the surface of steel, cemented carbide or the like.
Further, in JP-A-10-225824, a material that generates a hard carbide such as Ti, V, Nb, Ta is used as an electrode to generate electric discharge, and the surface of the workpiece is decarburized, A method is disclosed in which after a slightly rough surface (pretreatment), discharge is generated by a TiH 2 green compact electrode to perform surface treatment of the workpiece (main treatment). This pretreatment is intended to improve the adhesion of the coating material in this treatment. Further, for the same purpose, the TiH 2 -based green compact electrode is pretreated under the condition of negative discharge energy and relatively low discharge energy, and then the discharge energy is increased to obtain the same electrode as the TiH 2 -based pressure. A method of performing this treatment with a powder electrode is disclosed.
The above prior art is characterized in that a green compact electrode is used in any case, but there are problems in practical use for the following three reasons.
The first reason is that it is difficult to form a practically sized electrode. In other words, in order to mold the electrode into a practical size used for surface treatment of a mold or the like, the press capability must be dramatically increased, and the pressure is reduced during compression molding of the powdered material. Since it does not propagate uniformly inside, the density non-uniformity becomes large, and defects such as cracks occur. Further, the molded green compact electrode is liable to be deformed and difficult to perform secondary processing, and the hard coating formed on the workpiece is subject to variations and the quality is degraded.
The second reason is that it is difficult to handle the electrode material. That is, powders such as Ti and TiH 2 are easily oxidized, and TiH 2 is difficult to handle due to changes over time such as causing hydrolysis even in the air. Furthermore, since hydrogen gas is violently generated when thrown into water, there is a problem in disposal of electrodes that are no longer necessary.
The third reason is that it is difficult to form a thick film. That is, the conventional method has a limit of a thickness of several μm to several tens of μm, and it is impossible to form a hard coating having a thickness larger than that required industrially.
In the following, a supplementary explanation related to the third reason will be given. Thin film formation is prevalent by dry processes such as physical vapor deposition and chemical vapor deposition, but thick film formation is difficult with these methods, and at present, it must rely on thermal spraying methods and the like. Thermal spraying can deposit various materials on the workpiece, but its structure is rough, and it cannot be applied to applications that require precision and durability such as coatings such as molds. There are many.

この発明は、前記のような従来技術の問題点を解決するためになされたものであり、効率的に被加工物に硬質被膜を形成することができ、電極の成形が容易にできると共に任意の面積範囲で硬質被膜の厚膜を形成することができ、金型、工具、機械要素部品等の様々な機械部品への適用が可能となる放電表面処理方法及び装置を得ることを目的とする。
第１の発明に係る放電表面処理方法は、周期律表第ＩＶａ、Ｖａ、ＶＩａ族に属する金属の炭化物を単体又は複数組み合わせて製造した粉末に、鉄族金属粉もしくは被加工物と同一成分の非鉄系金属粉を単体又は複数組み合わせて混入し、圧縮成形した後に前記鉄族又は非鉄金属粉が溶出し始める温度にて焼成した電極を放電加工用電極とし、前記被加工物の母材に直接放電表面処理する際の電気条件と形成された硬質被膜に放電表面処理する際の電気条件とを被処理材料の特性に合わせて変更するものである。
第２の発明に係る放電表面処理方法は、周期律表第ＩＶａ、Ｖａ、Ｖｌａ族に属する金属の炭化物を単体又は複数組み合わせて製造した粉末に、鉄族金属粉もしくは被加工物と同一成分の非鉄系金属粉を単体又は複数組み合わせて混入し、圧縮成形した後に前記鉄族又は非鉄金属粉が溶出し始める温度にて焼成した電極を放電加工用電極とし、形成された硬質被膜に放電表面処理する際の電気条件を被処理材料の特性に合わせて少なくとも１回変更するものである。
第３の発明に係る放電表面処理方法は、周期律表第ＩＶａ、Ｖａ、ＶＩａ族に属する金属の炭化物を単体又は複数組み合わせて製造した粉末に、鉄族金属粉もしくは被加工物と同一成分の非鉄系金属粉を単体又は複数組み合わせて混入し、圧縮成形した後に前記鉄族又は非鉄金属粉が溶出し始める温度にて焼成した電極を放電加工用電極とし、前記被加工物の母材に直接放電表面処理する際の電気条件と形成された硬質被膜に放電表面処理する際の電気条件とを被処理材料の特性に合わせて変更し、さらに、前記形成された硬質被膜に放電表面処理する際の電気条件を被処理材料の特性に合わせて少なくとも１回変更するものである。
第４の発明に係る放電表面処理方法は、第１の発明に係る放電表面処理方法において、前記放電加工用電極と前記被加工物との間に不活性ガスを介在させるものである。
第５の発明に係る放電表面処理方法は、第２の発明に係る放電表面処理方法において、前記放電加工用電極と前記被加工物との間に不活性ガスを介在させるものである。
第６の発明に係る放電表面処理方法は、第３の発明に係る放電表面処理方法において、前記放電加工用電極と前記被加工物との間に不活性ガスを介在させるものである。
第７の発明に係る放電表面処理方法は、第１の発明に係る放電表面処理方法において、前記放電加工用電極を前記被加工物に対して走査させて、前記被加工物表面に前記硬質被膜を形成するものである。
第８の発明に係る放電表面処理方法は、第２の発明に係る放電表面処理方法において、前記放電加工用電極を前記被加工物に対して走査させて、前記被加工物表面に前記硬質被膜を形成するものである。
第９の発明に係る放電表面処理方法は、第３の発明に係る放電表面処理方法において、前記放電加工用電極を前記被加工物に対して走査させて、前記被加工物表面に前記硬質被膜を形成するものである。
第１０の発明に係る放電表面処理装置は、周期律表第ＩＶａ、Ｖａ、ＶＩａ族に属する金属の炭化物を単体又は複数組み合わせて製造した粉末に、鉄族金属粉もしくは被加工物と同一成分の非鉄系金属粉を単体又は複数組み合わせて混入し、圧縮成形した後に前記鉄族又は非鉄金属粉が溶出し始める温度にて焼成した電極を放電加工用電極とし、前記被加工物の母材に直接放電表面処理する際の電気条件と形成された硬質被膜に放電表面処理する際の電気条件とを被処理材料の特性に合わせて変更する切り替え手段を備えるものである。
第１１の発明に係る放電表面処理装置は、周期律表第ＩＶａ、Ｖａ、ＶＩａ族に属する金属の炭化物を単体又は複数組み合わせて製造した粉末に、鉄族金属粉もしくは被加工物と同一成分の非鉄系金属粉を単体又は複数組み合わせて混入し、圧縮成形した後に前記鉄族又は非鉄金属粉が溶出し始める温度にて焼成した電極を放電加工用電極とし、形成された硬質被膜に放電表面処理する際の電気条件を被処理材料の特性に合わせて少なくとも１回変更する切り替え手段を備えるものである。
第１２の発明に係る放電表面処理装置は、周期律表第ＩＶａ、Ｖａ、ＶＩａ族に属する金属の炭化物を単体又は複数組み合わせて製造した粉末に、鉄族金属粉もしくは被加工物と同一成分の非鉄系金属粉を単体又は複数組み合わせて混入し、圧縮成形した後に前記鉄族又は非鉄金属粉が溶出し始める温度にて焼成した電極を放電加工用電極とし、前記被加工物の母材に直接放電表面処理する際の電気条件と形成された硬質被膜に放電表面処理する際の電気条件とを被処理材料の特性に合わせて変更する第１の切り替え手段と、前記形成された硬質被膜に放電表面処理する際の電気条件を被処理材料の特性に合わせて少なくとも１回変更する第２の切り替え手段を備えるものである。
第１３の発明に係る放電表面処理装置は、第１０の発明に係る放電表面処理装置において、前記放電加工用電極と前記被加工物との間に不活性ガスを介在させる不活性ガス供給手段を備えるものである。
第１４の発明に係る放電表面処理装置は、第１１の発明に係る放電表面処理装置において、前記放電加工用電極と前記被加工物との間に不活性ガスを介在させる不活性ガス供給手段を備えるものである。
第１５の発明に係る放電表面処理装置は、第１２の発明に係る放電表面処理装置において、前記放電加工用電極と前記被加工物との間に不活性ガスを介在させる不活性ガス供給手段を備えるものである。
第１６の発明に係る放電表面処理装置は、第１０の発明に係る放電表面処理装置において、前記放電加工用電極と前記被加工物とをＸ方向、Ｙ方向、及びＺ方向に相対移動させるＸ軸駆動装置、Ｙ軸駆動装置、及びＺ軸駆動装置とを備え、前記Ｘ軸駆動装置、前記Ｙ軸駆動装置、及び前記Ｚ軸駆動装置により、前記放電加工用電極を前記被加工物に対して走査させて、前記被加工物表面に前記硬質被膜を形成するものである。
第１７の発明に係る放電表面処理装置は、第１１の発明に係る放電表面処理装置において、前記放電加工用電極と前記被加工物とをＸ方向、Ｙ方向、及びＺ方向に相対移動させるＸ軸駆動装置、Ｙ軸駆動装置、及びＺ軸駆動装置とを備え、前記Ｘ軸駆動装置、前記Ｙ軸駆動装置、及び前記Ｚ軸駆動装置により、前記放電加工用電極を前記被加工物に対して走査させて、前記被加工物表面に前記硬質被膜を形成するものである。
第１８の発明に係る放電表面処理装置は、第１２の発明に係る放電表面処理装置において、前記放電加工用電極と前記被加工物とをＸ方向、Ｙ方向、及びＺ方向に相対移動させるＸ軸駆動装置、Ｙ軸駆動装置、及びＺ軸駆動装置とを備え、前記Ｘ軸駆動装置、前記Ｙ軸駆動装置、及び前記Ｚ軸駆動装置により、前記放電加工用電極を前記被加工物に対して走査させて、前記被加工物表面に前記硬質被膜を形成するものである。
この発明は、前記のように構成されているので、以下に示すような効果を奏する。
第１〜第３の発明に係るに係る放電表面処理方法は、電極の成形が容易にできると共に効率的に被加工物に密着性の高い硬質被膜を形成することができ、金型、工具、機械要素部品等の様々な機械部品への適用が可能となる放電表面処理方法が得られる効果がある。また、電極の面積とほぼ等しい面積に硬質被膜を被加工物上に堆積できるため、マスキング処理が不要となる効果もある。
第４の発明の放電表面処理方法は、第１の発明の効果に加えて、構成が簡単になる効果がある。
第５の発明の放電表面処理方法は、第２の発明の効果に加えて、構成が簡単になる効果がある。
第６の発明の放電表面処理方法は、第３の発明の効果に加えて、構成が簡単になる効果がある。
第７の発明の放電表面処理方法は、第１の発明の効果に加えて、小形の放電加工用電極を用いて走査させながら加工することができ、大形の特定形状の放電加工用電極を用いる必要がなく、金型等の３次元自由曲面を持つ被加工物の全曲面にわたって前記小形の放電加工用電極を走査させ、全面積において等しく、あるいは必要に応じて膜厚を変化させながら硬質被膜を形成することができる効果がある。
第８の発明の放電表面処理方法は、第２の発明の効果に加えて、小形の放電加工用電極を用いて走査させながら加工することができ、大形の特定形状の放電加工用電極を用いる必要がなく、金型等の３次元自由曲面を持つ被加工物の全曲面にわたって前記小形の放電加工用電極を走査させ、全面積において等しく、あるいは必要に応じて膜厚を変化させながら硬質被膜を形成することができる効果がある。
第９の発明の放電表面処理方法は、第３の発明の効果に加えて、小形の放電加工用電極を用いて走査させながら加工することができ、大形の特定形状の放電加工用電極を用いる必要がなく、金型等の３次元自由曲面を持つ被加工物の全曲面にわたって前記小形の放電加工用電極を走査させ、全面積において等しく、あるいは必要に応じて膜厚を変化させながら硬質被膜を形成することができる効果がある。
第１０〜第１２の発明に係るに係る放電表面処理装置は、電極の成形が容易にできると共に効率的に被加工物に密着性の高い硬質被膜を形成することができ、金型、工具、機械要素部品等の様々な機械部品への適用が可能となる放電表面処理装置が得られる効果がある。また、電極の面積とほぼ等しい面積に硬質被膜を被加工物上に堆積できるため、マスキング処理が不要となる効果もある。
第１３の発明の放電表面処理装置は、第１０の発明の効果に加えて、構成が簡単になる効果がある。
第１４の発明の放電表面処理装置は、第１１の発明の効果に加えて、構成が簡単になる効果がある。
第１５の発明の放電表面処理装置は、第１２の発明の効果に加えて、構成が簡単になる効果がある。
第１６の発明の放電表面処理装置は、第１０の発明の効果に加えて、小形の放電加工用電極を用いて走査させながら加工することができ、大形の特定形状の放電加工用電極を用いる必要がなく、金型等の３次元自由曲面を持つ被加工物の全曲面にわたって前記小形の放電加工用電極を走査させ、全面積において等しく、あるいは必要に応じて膜厚を変化させながら硬質被膜を形成することができる効果がある。
第１７の発明の放電表面処理装置は、第１１の発明の効果に加えて、小形の放電加工用電極を用いて走査させながら加工することができ、大形の特定形状の放電加工用電極を用いる必要がなく、金型等の３次元自由曲面を持つ被加工物の全曲面にわたって前記小形の放電加工用電極を走査させ、全面積において等しく、あるいは必要に応じて膜厚を変化させながら硬質被膜を形成することができる効果がある。
第１８の発明の放電表面処理装置は、第１２の発明の効果に加えて、小形の放電加工用電極を用いて走査させながら加工することができ、大形の特定形状の放電加工用電極を用いる必要がなく、金型等の３次元自由曲面を持つ被加工物の全曲面にわたって前記小形の放電加工用電極を走査させ、全面積において等しく、あるいは必要に応じて膜厚を変化させながら硬質被膜を形成することができる効果がある。The present invention has been made to solve the above-described problems of the prior art, and can efficiently form a hard coating on a workpiece, facilitate the formation of an electrode, and can be arbitrarily formed. It is an object of the present invention to provide a discharge surface treatment method and apparatus which can form a thick hard film in an area range and can be applied to various machine parts such as molds, tools and machine element parts.
In the discharge surface treatment method according to the first aspect of the present invention, a powder produced by combining a single or a plurality of metal carbides belonging to groups IVa, Va, and VIa of the periodic table, with the same component as the iron group metal powder or workpiece. A non-ferrous metal powder is mixed alone or in combination, and after compression molding, the electrode fired at a temperature at which the iron group or non-ferrous metal powder begins to elute is used as an electrode for electric discharge machining, and directly on the base material of the workpiece The electrical conditions for performing the discharge surface treatment and the electrical conditions for performing the discharge surface treatment on the formed hard coating are changed in accordance with the characteristics of the material to be treated.
In the discharge surface treatment method according to the second aspect of the invention, a powder produced by combining a single or a plurality of metal carbides belonging to Groups IVa, Va, and Vla of the periodic table, with the same component as the iron group metal powder or workpiece. A non-ferrous metal powder is mixed alone or in combination, and after compression molding, the electrode fired at a temperature at which the iron group or non-ferrous metal powder begins to elute is used as an electrode for electric discharge machining, and the formed hard coating is subjected to discharge surface treatment. In this case, the electrical conditions are changed at least once according to the characteristics of the material to be processed.
In the discharge surface treatment method according to the third aspect of the invention, a powder produced by combining a single or a plurality of metal carbides belonging to Groups IVa, Va, and VIa of the periodic table into an iron group metal powder or the same component as the workpiece is used. A non-ferrous metal powder is mixed alone or in combination, and after compression molding, the electrode fired at a temperature at which the iron group or non-ferrous metal powder begins to elute is used as an electrode for electric discharge machining, and directly on the base material of the workpiece When the electrical conditions for the discharge surface treatment and the electrical conditions for the discharge surface treatment of the formed hard coating are changed in accordance with the characteristics of the material to be treated, and the discharge coating is further performed on the formed hard coating The electrical conditions are changed at least once according to the characteristics of the material to be processed.
A discharge surface treatment method according to a fourth invention is the discharge surface treatment method according to the first invention, wherein an inert gas is interposed between the electrode for electric discharge machining and the workpiece.
A discharge surface treatment method according to a fifth invention is the discharge surface treatment method according to the second invention, wherein an inert gas is interposed between the electrode for electric discharge machining and the workpiece.
A discharge surface treatment method according to a sixth invention is the discharge surface treatment method according to the third invention, wherein an inert gas is interposed between the electrode for electric discharge machining and the workpiece.
An electric discharge surface treatment method according to a seventh invention is the electric discharge surface treatment method according to the first invention, wherein the electric discharge machining electrode is scanned with respect to the workpiece, and the hard coating is applied to the workpiece surface. Is formed.
An electric discharge surface treatment method according to an eighth aspect of the present invention is the electric discharge surface treatment method according to the second aspect of the present invention, wherein the electric discharge machining electrode is scanned with respect to the workpiece, and the hard coating is applied to the workpiece surface. Is formed.
An electric discharge surface treatment method according to a ninth invention is the electric discharge surface treatment method according to the third invention, wherein the electric discharge machining electrode is scanned with respect to the workpiece, and the hard coating is applied to the workpiece surface. Is formed.
The discharge surface treatment apparatus according to the tenth aspect of the present invention is the same as the iron group metal powder or the workpiece with the powder produced by combining single or plural metal carbides belonging to groups IVa, Va and VIa of the periodic table. A non-ferrous metal powder is mixed alone or in combination, and after compression molding, the electrode fired at a temperature at which the iron group or non-ferrous metal powder begins to elute is used as an electrode for electric discharge machining, and directly on the base material of the workpiece Switching means is provided for changing the electrical conditions for performing the discharge surface treatment and the electrical conditions for performing the discharge surface treatment on the formed hard coating in accordance with the characteristics of the material to be treated.
The discharge surface treatment apparatus according to the eleventh aspect of the present invention is the same as the iron group metal powder or the work piece in the powder produced by combining single or plural metal carbides belonging to groups IVa, Va and VIa of the periodic table. A non-ferrous metal powder is mixed alone or in combination, and after compression molding, the electrode fired at a temperature at which the iron group or non-ferrous metal powder begins to elute is used as an electrode for electric discharge machining, and the formed hard coating is subjected to discharge surface treatment. Switching means for changing electrical conditions at the time of changing at least once according to the characteristics of the material to be processed is provided.
The discharge surface treatment apparatus according to the twelfth aspect of the present invention is the same as the iron group metal powder or the work piece in the powder produced by combining single or plural metal carbides belonging to groups IVa, Va and VIa of the periodic table. A non-ferrous metal powder is mixed alone or in combination, and after compression molding, the electrode fired at a temperature at which the iron group or non-ferrous metal powder begins to elute is used as an electrode for electric discharge machining, and directly on the base material of the workpiece First switching means for changing the electrical conditions for performing the discharge surface treatment and the electrical conditions for performing the discharge surface treatment on the formed hard coating in accordance with the characteristics of the material to be treated, and discharging to the formed hard coating A second switching means is provided that changes the electrical conditions for the surface treatment at least once in accordance with the characteristics of the material to be treated.
An electric discharge surface treatment apparatus according to a thirteenth aspect of the present invention is the electric discharge surface treatment apparatus according to the tenth aspect of the present invention, comprising an inert gas supply means for interposing an inert gas between the electric discharge machining electrode and the workpiece. It is to be prepared.
An electric discharge surface treatment apparatus according to a fourteenth aspect of the present invention is the electric discharge surface treatment apparatus according to the eleventh aspect of the present invention, comprising an inert gas supply means for interposing an inert gas between the electric discharge machining electrode and the workpiece. It is to be prepared.
An electric discharge surface treatment apparatus according to a fifteenth aspect of the present invention is the electric discharge surface treatment apparatus according to the twelfth aspect of the present invention, comprising an inert gas supply means for interposing an inert gas between the electric discharge machining electrode and the workpiece. It is to be prepared.
An electric discharge surface treatment apparatus according to a sixteenth invention is the electric discharge surface treatment apparatus according to the tenth invention, wherein the electric discharge machining electrode and the workpiece are moved relative to each other in the X, Y, and Z directions. An X-axis drive device, a Y-axis drive device, and a Z-axis drive device. The X-axis drive device, the Y-axis drive device, and the Z-axis drive device provide the EDM electrode to the workpiece. Scanning to form the hard coating on the surface of the workpiece.
An electric discharge surface treatment apparatus according to a seventeenth aspect is the electric discharge surface treatment apparatus according to the eleventh aspect, wherein the electric discharge machining electrode and the workpiece are moved relative to each other in the X, Y, and Z directions. An X-axis drive device, a Y-axis drive device, and a Z-axis drive device. The X-axis drive device, the Y-axis drive device, and the Z-axis drive device provide the EDM electrode to the workpiece. Scanning to form the hard coating on the surface of the workpiece.
An electric discharge surface treatment apparatus according to an eighteenth aspect of the present invention is the electric discharge surface treatment apparatus according to the twelfth aspect of the present invention, wherein the electric discharge machining electrode and the workpiece are moved relative to each other in the X, Y, and Z directions. An X-axis drive device, a Y-axis drive device, and a Z-axis drive device. The X-axis drive device, the Y-axis drive device, and the Z-axis drive device provide the EDM electrode to the workpiece. Scanning to form the hard coating on the surface of the workpiece.
Since the present invention is configured as described above, the following effects can be obtained.
The discharge surface treatment method according to the first to third aspects of the invention can easily form an electrode and efficiently form a hard film with high adhesion on a workpiece. There is an effect of obtaining a discharge surface treatment method that can be applied to various machine parts such as machine element parts. In addition, since the hard coating can be deposited on the workpiece in an area substantially equal to the area of the electrode, there is an effect that masking processing is not required.
The discharge surface treatment method of the fourth invention has the effect of simplifying the configuration in addition to the effect of the first invention.
The discharge surface treatment method of the fifth invention has the effect of simplifying the configuration in addition to the effect of the second invention.
The discharge surface treatment method of the sixth invention has the effect of simplifying the configuration in addition to the effect of the third invention.
In addition to the effect of the first invention, the electric discharge surface treatment method of the seventh invention can be processed while scanning using a small electric discharge machining electrode. It is not necessary to use, and the small electric discharge machining electrode is scanned over the entire curved surface of a workpiece having a three-dimensional free-form surface such as a mold, and the entire area is equal or hard while changing the film thickness as necessary. There exists an effect which can form a film.
In addition to the effects of the second invention, the electric discharge surface treatment method of the eighth invention can be processed while scanning using a small electric discharge machining electrode. It is not necessary to use, and the small electric discharge machining electrode is scanned over the entire curved surface of a workpiece having a three-dimensional free-form surface such as a mold, and the entire area is equal or hard while changing the film thickness as necessary. There exists an effect which can form a film.
In addition to the effect of the third invention, the electric discharge surface treatment method of the ninth invention can be processed while scanning using a small electric discharge machining electrode. It is not necessary to use, and the small electric discharge machining electrode is scanned over the entire curved surface of a workpiece having a three-dimensional free-form surface such as a mold, and the entire area is equal or hard while changing the film thickness as necessary. There exists an effect which can form a film.
The discharge surface treatment apparatus according to the tenth to twelfth aspects of the present invention can easily form an electrode and can efficiently form a hard film with high adhesion on a work piece. There is an effect of obtaining a discharge surface treatment apparatus that can be applied to various machine parts such as machine element parts. In addition, since the hard coating can be deposited on the workpiece in an area substantially equal to the area of the electrode, there is an effect that masking processing is not required.
The discharge surface treatment apparatus according to the thirteenth invention has the effect of simplifying the structure in addition to the effect of the tenth invention.
In addition to the effect of the eleventh invention, the discharge surface treatment apparatus of the fourteenth invention has an effect of simplifying the configuration.
The discharge surface treatment apparatus according to the fifteenth aspect of the invention has the effect of simplifying the configuration in addition to the effect of the twelfth aspect of the invention.
In addition to the effects of the tenth invention, the electric discharge surface treatment apparatus of the sixteenth invention can be processed while scanning using a small electric discharge machining electrode. It is not necessary to use, and the small electric discharge machining electrode is scanned over the entire curved surface of a workpiece having a three-dimensional free-form surface such as a mold, and the entire area is equal or hard while changing the film thickness as necessary. There exists an effect which can form a film.
In addition to the effect of the eleventh invention, the electric discharge surface treatment apparatus of the seventeenth invention can be processed while scanning using a small electric discharge machining electrode, and a large specific shape electric discharge machining electrode can be formed. It is not necessary to use, and the small electric discharge machining electrode is scanned over the entire curved surface of a workpiece having a three-dimensional free-form surface such as a mold, and the entire area is equal or hard while changing the film thickness as necessary. There exists an effect which can form a film.
In addition to the effects of the twelfth invention, the electric discharge surface treatment apparatus of the eighteenth invention can be processed while scanning using a small electric discharge machining electrode. It is not necessary to use, and the small electric discharge machining electrode is scanned over the entire curved surface of a workpiece having a three-dimensional free-form surface such as a mold, and the entire area is equal or hard while changing the film thickness as necessary. There exists an effect which can form a film.

第１図は、この発明の実施の形態１の放電表面処理方法及び装置を示す構成図である。
第２図は、この発明の実施の形態１の放電表面処理方法及び装置における連続放電による硬質被膜の堆積状況を示す図である。
第３図は、この発明の実施の形態１の放電表面処理方法及び装置における厚膜の形成の様子とそのときの放電電流を示す図である。
第４図は、この発明の実施の形態１の放電表面処理方法及び装置における電気条件の変更手段を示す図である。
第５図は、この発明の実施の形態２の放電表面処理方法及び装置を示す構成図である。
第６図は、この発明の実施の形態３の放電表面処理方法及び装置を示す構成図である。
第７図は、従来の放電表面処理方法を示す構成図である。FIG. 1 is a block diagram showing a discharge surface treatment method and apparatus according to Embodiment 1 of the present invention.
FIG. 2 is a diagram showing a hard coating deposition state by continuous discharge in the discharge surface treatment method and apparatus according to Embodiment 1 of the present invention.
FIG. 3 is a diagram showing the state of thick film formation and the discharge current at that time in the discharge surface treatment method and apparatus according to Embodiment 1 of the present invention.
FIG. 4 is a diagram showing means for changing electrical conditions in the discharge surface treatment method and apparatus according to Embodiment 1 of the present invention.
FIG. 5 is a block diagram showing a discharge surface treatment method and apparatus according to Embodiment 2 of the present invention.
FIG. 6 is a block diagram showing a discharge surface treatment method and apparatus according to Embodiment 3 of the present invention.
FIG. 7 is a block diagram showing a conventional discharge surface treatment method.

実施の形態１．
第１図は、この発明の実施の形態１の放電表面処理方法及び装置を示す構成図であり、図において、２は被加工物、３は加工槽、４は絶縁性の油あるいは水を主体とした加工液、１０は送り用モータ、１１は送りネジ、１２は放電加工用電極、１３は被加工物２の上に形成された硬質被膜、１４は電源を備えさらに電流、電圧を制御する制御装置である。ここで、送り用モータ１０は、図示しない制御系により、送りネジ１１を介して放電加工用電極１２を被加工物２に向かってサーボ送り、定速送り等の必要な制御モードで送ることができる構成を持っている。
前記の加工液４は、絶縁性の油あるいは水を主体とするものであるが、加工液４に絶縁性の油を使用する場合は、広く普及した放電加工装置の技術をそのまま応用できること、比較的簡単に構成できること等の利点がある。また、加工液に水を使用すると、反応と同時に水酸化物を生成することもあり、高品質の被膜を必要とする場合には問題が発生する可能性がある。しかし、現在では広く普及しているワイヤ放電加工装置の無電解電源を用いると、前記欠点を最小限に抑えることができ、加工液に水を使用する場合でも、実用的には加工液に絶縁性の油を使用する場合と同一性状の硬質被膜を形成できる。
次に、放電加工用電極１２の製作方法について説明する。周期律表第ＩＶａ、Ｖａ、ＶＩａ族に属する金属の炭化物（たとえばＷＣ、ＴｉＣ、ＴａＣ等）を単体もしくは複数組み合わせた粉末に、Ｆｅ、Ｃｏ、Ｎｉ等の鉄族金属粉もしくは被加工物と同一成分の非鉄系金属粉（たとえば、Ａｌ合金粉等）を単体もしくは組み合わせて混入させ、圧縮成形により一定形状の圧粉体電極を製作する。その後、真空炉等を用いて炉内温度を徐々に上げていき、機械加工に耐えうる強度を圧粉体電極に与え、かつ硬化しすぎないように、たとえば白墨程度にまで硬化させる（この工程を予備焼結工程と言う）。この状態ではＣｏ等の鉄族金属が溶出し始め炭化物の隙間を埋めるようになり、いわゆる炭化物の固溶体を作る。また、一方では炭化物間の接触部においては相互に結合が進むが比較的焼成温度が低く本焼結に至らない温度のため弱い結合となっている。このような予備焼結工程を経た電極を取り出し、必要な形状に機械加工及び寸法出しを行った上で放電加工用電極１２として用いる。
前記のような予備焼結工程の条件は電極材料によって異なるが、予め実験によって決定することができる。たとえば、焼成温度はおよそ４００℃〜１１００℃の範囲となる。
この場合において、重要な点は予備焼結工程における焼成温度をおよそ１１００℃以上に上げないことである。この温度を超えると電極が硬化しすぎ、次に行う放電加工において、電極材料がアーク放電による熱衝撃によって不均一に脱落し極間に正常に供給されない不具合が生じ、被加工物に形成される被膜の品質に大きく影響する。
次に、硬質被膜１３の形成方法について説明する。放電加工用電極１２と被加工物２の間に断続あるいは連続のアーク放電を発生させると、極間はアーク熱により局部的に高温状態となる。まず一発のアーク放電が発生するとその熱衝撃エネルギによって予備焼結した放電加工用電極１２の被加工物２に対向する部分において、一部の電極材料が極間に脱落すると同時に粉状になって放出される。極間は瞬間的には数千℃以上の高温プラズマ状態となり電極材料の大半は完全な溶融状態となる。電極に対向する被加工物の表面もアーク放電の発生位置においては瞬間に加熱され、電極材料と同様に溶融状態となる。この高温状態において溶融した電極材料及び被加工物が相互に混ざり合い、電極材料と被加工物の母材との合金相が被加工物に形成される。次に、極間及びその周囲に加工液が存在するため急激に冷却され、高温状態から冷却の過程において、鉄族金属の液相及び炭化物である固相間の界面反応又は炭化物同士の固相間の固溶体化反応が一瞬にして起こり、極めて短時間のうちに本焼結が行われる。このようにして、硬質被膜１３が被加工物２上に形成される。この工程を繰り返していくと、時間の経過と共に被膜の堆積が進行して厚膜を形成することができる。
第２図は、連続放電による硬質被膜の堆積状況を示しており、それぞれの単発放電による硬質被膜が折り重なるようにして堆積していく様子が明確に観察できる。
第３図は、厚膜の形成の様子とそのときの放電電流を示したものであり、放電加工用電極１２としてＷＣ−Ｃｏを用い、被加工物２として鋼材を用いる場合を示している。また、第３図の（ａ）は被加工物２の母材に直接放電させる場合、第３図の（ｂ）は硬質被膜１３が形成されてからさらに放電させる場合を示している。被加工物２の母材に直接放電させる場合と硬質被膜１３が形成されてから放電させる場合で被処理材料の特性に合わせて、電気条件である放電電流値Ｉｐ、放電電流パルス幅τｐ及び休止時間τｒを変更している。また、場合によっては電極極性も変更する。これは、母材と形成された硬質被膜では材質、硬度が異なるためであり、母材に直接放電させる場合と硬質被膜が形成されてからさらに放電させる場合とで被処理材料の特性に合わせて電気条件を変え、被処理材料に適切な電気条件を採用することにより、より短時間での処理と密着性の高い硬質被膜を形成することが可能になる。このような、被処理材料の特性に合わせた適切な電気条件は、予め実験等により決定しておき、制御装置１４により被処理材料の特性に合わせて変更することができる。たとえば、放電電流値Ｉｐ、放電電流パルス幅τｐ及び休止時間τｒの変更は、第４図に示すような制御回路によるスイッチ１５、１６の切り替え及びスイッチングの制御により行うことができる。
また、前記においては母材に直接放電させる場合と硬質被膜が形成されてからさらに放電させる場合とで電気条件を変更する場合を示したが、硬質被膜の厚膜が形成されていく途中においても、被処理材料の特性に合わせて電気条件を変更してもよい。
また、第４図においては、２個のスイッチを切り替える場合を示したが、３個以上のスイッチがあってもよい。また、可変抵抗により電流を変化させる等、電流を変えることができる手段であればよい。
さらに、第３図では、被加工物の母材が鋼材の場合を示したが、被加工物の母材が超硬合金の場合は、電極にはＴｉ系材料を用いればよい。このような被処理材と電極の様々な組み合わせに対応して、電流波形を変更する。
実施の形態２．
第５図は、この発明の実施の形態２の放電表面処理方法及び装置を示す構成図であり、図において、２は被加工物、１２は放電加工用電極、１３は被加工物２の上に形成された硬質被膜、１４は電源を備えさらに電流、電圧を制御する制御装置である。図示しないＸ軸駆動装置、Ｙ軸駆動装置、及びＺ軸駆動装置により、放電加工用電極１２と被加工物２をＸ方向、Ｙ方向、及びＺ方向に相対移動させながら、被加工物２の表面に硬質被膜１３を形成する。たとえば、被加工物２が金型の場合を考えると、その表面は平面ではなく三次元形状の複雑な自由曲面を持つが、前記のＸ軸駆動装置、Ｙ軸駆動装置、及びＺ軸駆動装置により、放電加工用電極１２を金型の自由曲面に沿って間隙を一定にあるいはサーボ電圧を一定に維持しながら走査すればよい。この場合、電極の消耗が非常に速いため、電極消耗に対する補正送りが必要になり、電極を支持する主軸のＺ方向の運動制御を正確にかつ速く行う必要がある。以上のような動作を繰り返し、金型を構成する全曲面にわたって電極を走査させ、全面積において等しく、あるいは必要に応じて膜厚を変化させながら硬質被膜を堆積させることができる。
また、被加工物の母材に直接放電させる場合と硬質被膜が形成されてからさらに放電させる場合、あるいは、硬質被膜の厚膜が形成されていく途中において、被処理材料の特性に合わせて電気条件を変え、被処理材料に適切な電気条件を採用することにより、より短時間での処理と密着性の高い硬質被膜を形成することが可能になる。
実施の形態３．
第６図は、この発明の実施の形態３の放電表面処理方法及び装置を示す構成図であり、気中放電を示している。図において、２は被加工物、１０は送り用モータ、１１は送りネジ、１２は放電加工用電極、１３は被加工物２の上に形成された硬質被膜、１４は電源を備えさらに電流、電圧を制御する制御装置、１７はガス源、１８通路、１９は供給パイプである。ガス源１７は配管を経由して放電加工用電極１２の内部に設けられた通路１８に接続される。制御装置１４の電源による通電中、ガス源１７より空気もしくは窒素ガス等の不活性ガスを必要な量だけ供給する。供給パイプ１９は電極内部に通路を設けられない場合に、電極外部よりガスを供給する例を示すものであり、極間に向けてガスが噴出される。ガス供給の目的は、極間の冷却と余剰な電極材料の系外への搬出であり、前記の加工液の役目と同様である。このガスの供給がないと、被加工物上の硬質被膜形成を安定して行うことは困難である。使用するガスの種類としては、環境面を考慮して、空気もしくは窒素ガスが適当である。
このような気中放電においても、被加工物の母材に直接放電させる場合と硬質被膜が形成されてからさらに放電させる場合、あるいは、硬質被膜の厚膜が形成されていく途中において、被処理材料の特性に合わせて電気条件を変え、被処理材料に適切な電気条件を採用することにより、より短時間での処理と密着性の高い硬質被膜を形成することが可能になる。Embodiment 1 FIG.
FIG. 1 is a block diagram showing a discharge surface treatment method and apparatus according to Embodiment 1 of the present invention. In the figure, 2 is a workpiece, 3 is a processing tank, and 4 is mainly composed of insulating oil or water. 10 is a feed motor, 11 is a feed screw, 12 is an electrode for electric discharge machining, 13 is a hard film formed on the workpiece 2, 14 is equipped with a power supply, and further controls current and voltage. It is a control device. Here, the feed motor 10 can feed the electric discharge machining electrode 12 toward the workpiece 2 via the feed screw 11 in a necessary control mode such as servo feed or constant speed feed by a control system (not shown). Have a configuration that can.
The machining fluid 4 is mainly composed of insulating oil or water. However, when insulating oil is used as the machining fluid 4, it is possible to apply the technology of the widely used electrical discharge machining apparatus as it is, comparison There are advantages such as easy configuration. In addition, when water is used as the working fluid, hydroxide may be generated simultaneously with the reaction, which may cause problems when a high-quality coating is required. However, if the electroless power source of the wire electrical discharge machining apparatus that is widely used nowadays is used, the above-mentioned drawback can be minimized, and even when water is used as the machining fluid, it is practically insulated from the machining fluid. Can form a hard film having the same properties as when a natural oil is used.
Next, a method for manufacturing the electric discharge machining electrode 12 will be described. Same as iron group metal powders such as Fe, Co, Ni, or work piece, with powder of metal carbides belonging to group IVa, Va, VIa of periodic table (for example, WC, TiC, TaC, etc.) alone or in combination. A non-ferrous metal powder (for example, Al alloy powder or the like) as a component is mixed alone or in combination, and a green compact electrode having a fixed shape is manufactured by compression molding. Thereafter, the furnace temperature is gradually raised using a vacuum furnace or the like, giving the green compact electrode strength sufficient to withstand machining, and curing it to a level of, for example, black ink (this process) Is referred to as a pre-sintering process). In this state, iron group metals such as Co begin to elute and fill the gaps between the carbides, creating a so-called carbide solid solution. On the other hand, in the contact portion between the carbides, the bonding proceeds to each other, but the bonding temperature is weak because of the relatively low firing temperature that does not lead to the main sintering. The electrode that has undergone such a pre-sintering step is taken out, machined and dimensioned into a required shape, and used as an electric discharge machining electrode 12.
The conditions of the pre-sintering process as described above vary depending on the electrode material, but can be determined in advance by experiments. For example, the firing temperature is in the range of approximately 400 ° C to 1100 ° C.
In this case, the important point is that the firing temperature in the pre-sintering process is not raised to about 1100 ° C. or higher. If this temperature is exceeded, the electrode will be hardened too much, and in the subsequent electric discharge machining, the electrode material will drop off unevenly due to the thermal shock caused by arc discharge, causing a problem that the electrode material will not be supplied normally between the electrodes, and will be formed on the workpiece It greatly affects the quality of the coating.
Next, a method for forming the hard coating 13 will be described. When intermittent or continuous arc discharge is generated between the electric discharge machining electrode 12 and the workpiece 2, the gap between the electrodes is locally heated by arc heat. First, when a single arc discharge occurs, a portion of the electrode material drops off between the electrodes at the portion facing the workpiece 2 of the electrode 12 for electrical discharge machining that has been pre-sintered by the thermal shock energy and becomes powdery at the same time. Released. The gap between the electrodes instantaneously becomes a high-temperature plasma state of several thousand degrees Celsius or more, and most of the electrode material is completely melted. The surface of the work piece facing the electrode is also instantaneously heated at the position where the arc discharge is generated, and is in a molten state like the electrode material. The electrode material and workpiece to be melted in this high temperature state are mixed with each other, and an alloy phase of the electrode material and the base material of the workpiece is formed on the workpiece. Next, since there is a working fluid between and around the electrodes, it is rapidly cooled, and in the process of cooling from a high temperature state, an interfacial reaction between a liquid phase of iron group metal and a solid phase that is carbide or a solid phase between carbides The solid solution reaction takes place in an instant, and the main sintering is performed in an extremely short time. In this way, the hard coating 13 is formed on the workpiece 2. If this process is repeated, the deposition of the film proceeds with the passage of time, and a thick film can be formed.
FIG. 2 shows the state of deposition of the hard coating by continuous discharge, and it can be clearly observed that the hard coating by each single discharge is deposited so as to be folded.
FIG. 3 shows the state of thick film formation and the discharge current at that time, and shows the case where WC-Co is used as the electrode 12 for electric discharge machining and the steel material is used as the workpiece 2. 3 (a) shows a case where the discharge is performed directly on the base material of the workpiece 2, and FIG. 3 (b) shows a case where the discharge is further performed after the hard coating 13 is formed. The discharge current value Ip, the discharge current pulse width τp, and the rest, which are electrical conditions, are selected in accordance with the characteristics of the material to be processed in the case of discharging directly to the base material of the workpiece 2 and the case of discharging after the hard coating 13 is formed. The time τr is changed. In some cases, the electrode polarity is also changed. This is because the material and hardness are different between the base material and the hard coating formed. According to the characteristics of the material to be treated, the case where the base material is directly discharged and the case where the base material is further discharged after the hard coating is formed. By changing the electrical conditions and adopting the appropriate electrical conditions for the material to be processed, it is possible to form a hard film with a shorter processing time and higher adhesion. Such an appropriate electrical condition according to the characteristics of the material to be processed can be determined in advance by experiments or the like, and can be changed by the control device 14 according to the characteristics of the material to be processed. For example, the change of the discharge current value Ip, the discharge current pulse width τp and the rest time τr can be performed by switching the switches 15 and 16 and controlling the switching by the control circuit as shown in FIG.
Moreover, in the above, the case where the electrical condition is changed between the case where the base material is directly discharged and the case where the hard film is further discharged after the hard film is formed is shown. The electrical conditions may be changed according to the characteristics of the material to be processed.
4 shows a case where two switches are switched, there may be three or more switches. Further, any means capable of changing the current, such as changing the current with a variable resistor, may be used.
Further, FIG. 3 shows the case where the base material of the workpiece is a steel material. However, when the base material of the workpiece is a cemented carbide, a Ti-based material may be used for the electrode. The current waveform is changed in accordance with various combinations of the material to be processed and the electrodes.
Embodiment 2. FIG.
FIG. 5 is a block diagram showing an electric discharge surface treatment method and apparatus according to Embodiment 2 of the present invention. In FIG. 5, 2 is a workpiece, 12 is an electrode for electric discharge machining, and 13 is an upper surface of the workpiece 2. A hard coating 14 is provided with a power source and further controls a current and voltage. The X-axis driving device, the Y-axis driving device, and the Z-axis driving device (not shown) move the EDM electrode 12 and the workpiece 2 relative to each other in the X, Y, and Z directions while moving the workpiece 2 A hard coating 13 is formed on the surface. For example, considering the case where the workpiece 2 is a mold, the surface thereof is not a flat surface but has a complicated free-form surface having a three-dimensional shape. However, the X-axis driving device, the Y-axis driving device, and the Z-axis driving device described above are used. Thus, the electric discharge machining electrode 12 may be scanned along the free curved surface of the mold while maintaining a constant gap or constant servo voltage. In this case, since the consumption of the electrode is very fast, correction feed for the electrode consumption is necessary, and it is necessary to accurately and quickly control the movement of the main shaft supporting the electrode in the Z direction. By repeating the above operation, the electrodes can be scanned over the entire curved surface constituting the mold, and the hard film can be deposited while being equal over the entire area or changing the film thickness as required.
In addition, when the discharge is performed directly on the base material of the workpiece, when the discharge is further performed after the hard coating is formed, or when the thick film of the hard coating is being formed, the electric power is adjusted according to the characteristics of the material to be processed. By changing the conditions and adopting appropriate electrical conditions for the material to be processed, it is possible to form a hard film with a shorter processing time and higher adhesion.
Embodiment 3 FIG.
FIG. 6 is a block diagram showing a discharge surface treatment method and apparatus according to Embodiment 3 of the present invention, and shows air discharge. In the figure, 2 is a workpiece, 10 is a feed motor, 11 is a feed screw, 12 is an electrode for electric discharge machining, 13 is a hard coating formed on the workpiece 2, 14 is a power supply and further has an electric current, A control device for controlling the voltage, 17 is a gas source, 18 passages, and 19 is a supply pipe. The gas source 17 is connected to a passage 18 provided inside the electric discharge machining electrode 12 via a pipe. During energization by the power source of the control device 14, a necessary amount of an inert gas such as air or nitrogen gas is supplied from the gas source 17. The supply pipe 19 shows an example in which a gas is supplied from the outside of the electrode when a passage is not provided inside the electrode, and the gas is jetted toward the gap. The purpose of the gas supply is cooling between the electrodes and carrying out excess electrode material out of the system, which is the same as the role of the processing liquid. Without this gas supply, it is difficult to stably form a hard film on the workpiece. As the type of gas to be used, air or nitrogen gas is appropriate in consideration of the environment.
Even in such aerial discharge, when the discharge is performed directly on the base material of the workpiece and when further discharging is performed after the hard coating is formed, or in the middle of the thick coating of the hard coating being formed, By changing the electrical conditions in accordance with the characteristics of the material and adopting the appropriate electrical conditions for the material to be processed, it is possible to form a hard coating with high processing and shorter adhesion.

以上のように、この発明に係る放電表面処理方法及び装置は、被加工物表面の硬質被膜形成に用いられるのに適している。  As described above, the discharge surface treatment method and apparatus according to the present invention are suitable for use in forming a hard film on the surface of a workpiece.

Claims (1)

放電加工用電極と被加工物との間に放電を発生させ、前記放電エネルギにより前記被加工物表面に硬質被膜を形成する工程を繰り返すことにより、前記被加工物としての母材の表面に対して時間の経過と共に前記硬質被膜の堆積が進行して厚膜を形成する放電表面処理方法において、
周期律表第ＩＶａ、Ｖａ、ＶＩａ族に属する金属の炭化物を単体又は複数組み合わせて製造した粉末に、鉄族金属粉もしくは前記被加工物と同一成分の非鉄系金属粉を単体又は複数組み合わせて混入し、圧縮成形した後に予備焼結した焼結電極を前記放電加工用電極とし、
前記母材に直接放電表面処理する際の電気条件である放電電流、放電電流パルス幅および休止時間により前記母材に堆積加工し、
その後、前記母材に堆積加工した際の電気条件を、前記母材に形成された前記硬質被膜に放電表面処理する際の電気条件である放電電流、放電電流パルス幅および休止時間に変更して前記母材に形成された硬質皮膜上にさらに堆積加工する
ことを特徴とする放電表面処理方法。 By generating a discharge between the electrode for electric discharge machining and the workpiece and forming a hard film on the workpiece surface by the discharge energy , the surface of the base material as the workpiece is repeated. In the discharge surface treatment method in which the deposition of the hard coating proceeds to form a thick film over time ,
Periodic table IVa, Va, VIa mixed with powders of single or multiple metal carbides belonging to Group IV, mixed with single or multiple non-ferrous metal powders of the same component as the workpiece. And a sintered electrode pre-sintered after compression molding as the electrode for electric discharge machining,
Electrical conditions der Ru discharge current when processing directly discharge surface before Kihaha material, deposited processed into the base material by the discharge current pulse width and pause time,
Thereafter, the electrical conditions under which deposited processed into the base material, the electrical conditions der Ru discharge current when a discharge surface treatment in the hard coating formed on the base material, to change the discharge current pulse width and pause time An electric discharge surface treatment method , further comprising depositing on the hard film formed on the base material .
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