Chemistry: electrical and wave energy – Processes and products – Electrostatic field or electrical discharge
Patent
1991-05-17
1992-11-17
Valentine, Donald R.
Chemistry: electrical and wave energy
Processes and products
Electrostatic field or electrical discharge
20412946, 20412975, 20419215, 20419238, 204DIG9, 427249, 427450, 427560, B23H 900, C25F 322
Patent
active
051640511
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a method for the deposition of a diamond film on a hard metal substrate by the vapor phase diamond synthesis process for the manufacture of a cutting tool or the like and more particularly to a method for the deposition of dense and highly adhesive diamond on the substrate.
BACKGROUND ART
As methods of treatment to be employed in the deposition of a diamond film by the vapor phase process on a hard metal substrate for the purpose of enhancing adhesive force between the deposited diamond film and the substrate, etching with a chemical substance such as an acid or an alkali (48th Scientific Lecture Meeting, 18a-T-4, Japan Applied Physics Society), scratching treatment with diamond powder (48th Scientific Lecture Meeting, 18a-T-5, Japan Applied Physics Society), and etching in a specific gas containing an alcohol (Japanese Patent Public Disclosure HEI 1-145396), etc. have been known to the art.
However, when, for example, a tool manufactured by forming a diamond film on hard metal lathe tip treated by one of these methods is actually used in cutting, the diamond film quickly exfoliates from the tip. Thus adhesive strength of a practical level cannot be obtained.
When a diamond film is formed on a hard metal substrate by the conventional method of surface treatment, the adhesive strength between the substrate and the diamond film is not sufficient. When the hard metal substrate coated with the diamond film is used as in cutting with a lathe, for example, this cutting work has the problem of ready exfoliation of the diamond film.
An object of this invention is to provide a method for the deposition of a diamond film with high adhesive strength on a hard metal substrate by the vapor phase process for the synthesis of diamond.
DISCLOSURE OF INVENTION
As a result of their study in search of a way of enhancing adhesive strength between a deposited diamond film and a hard metal substrate, the present inventors found that it is advantageous to provide protuberances serving as anchors on the surface of the substrate, specifically that protuberances are readily produced when the substrate surface is subjected to electrochemical treatment, namely to electrolytic polishing with a pulse voltage, and that the adhesive strength of the diamond film to the substrate becomes high with increasing thickness, length, and density of these protuberances, and based on this knowledge, they accomplished the present invention.
Specifically, in the present invention, when the hard metal substrate is subjected to electrolytic polishing with a pulse voltage, the protuberances formed on the surface of the hard metal substrate can be varied in size and density proportionately to changes of frequency and pulse width of the pulse voltage applied to the substrate.
This invention further comprises scratching with an abrasive powder the hard metal substrate having protuberances produced by the aforementioned electrolytic polishing. The electrolytic polishing in this case may be performed with a constant voltage. When a diamond film is deposited by the vapor phase process on the surface of a hard metal substrate treated by the method just mentioned, there is obtained a composite having the diamond film deposited with high adhesiveness on the substrate.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 represents a device used in the synthesis of diamond by the combustion flame method in Example 1.
FIG. 2 represents a device used in the synthesis of diamond by the hot filament method in Examples 2 and 3.
BEST MODE FOR CARRYING OUT THE INVENTION
Now, the present invention will be described in detail below.
Hard metal refers to what is obtained by sintering a carbide, nitride, boride, or silicide of a metal of Groups IV, V, or VI in the Periodic Table of Elements by the use of a binder of such a metal as Co, Ni, or Fe or an alloy thereof. The WC-Co type hard metal may be cited as a typical example.
When a substrate of such hard metal is subjected to electrolytic polishing with a pulse voltage, the surfac
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Komaki Kunio
Yanagisawa Masaaki
Showa Denko K. K.
Valentine Donald R.
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