Removing method of hard coating film

The present invention relates to a removing method of hard coating film made of, for example, TiAlN or TiCN, and; more particularly, to the removing method of hard coating film with almost no damaging a main body.

A hard coating film coated member is known in which a surface of a main body is coated or covered with a hard coating film. The hard coating film is composed of a metal carbide, a metal nitride, or a metal carbonitride in Group IIIb, IVa, Va, or VIa of the periodic table of the elements, or composed of a solid solution of these compounds. The hard coating film coated working tool, such as an end mill, a tap, a drill, or a bit produced by coating the surface of a tool base material (main body) made of a super-hard alloy with the above-mentioned hard coating film has been proposed in, for example, Patent Literature 1. At least a working part of the working tool surface at which a cutting blade or the like is provided, is coated. A PVD (physical vapor deposition) method, such as an ion plating method, is employed for coating the hard coating film.

In the thus structured hard coating film coated member, the hard coating film may be worn out or damaged, or defective articles may be produced or created by, for example, bad coating in a production process. It is conceivable to remove the hard coating film to thereby reuse the main body such as the tool base material. That is, the hard coating film is chemically resolved with a wet process by a hydrogen peroxide solution or the like, to be removed from the main body.

[Patent Literature 1] Japanese Patent Publication No. 2005-7555A

However, when the hard coating film is removed using the chemical reaction as mentioned above, the main body may be precedingly i.e. in advance exposed partially because of non-uniformity in thickness of the hard coating film or because of a difference in a coating film removing speed, thus following problems being caused. In this case, since the exposed surface of the main body is also damaged by a treatment liquid, upon complete removal of the hard coating film, the surface of the main body is partially roughened or weakened. For example, when the main body is made of a super-hard alloy, WC particles in a surface layer are chemically eroded, so that the surface may be weakened, and a change in shape of the main body, such as roundness or diameter decrease of the edge of a cutting blade, may occur. When the thus shape changed main body is re-coated with the hard coating film, adhesive properties may be impaired resulting from the surface weakness, so that the original coating performance (durability or abrasion resistance) cannot be obtained, or the edge of the blade may be rounded to thereby lower the cutting performance.

The present invention has been made in view of these circumstances, and has an object to remove a hard coating film with almost no damaging a main body of a hard coating film coated member.

For achieving the above object, a first aspect of the present invention is related to a removing method of hard coating film from a main body of a hard coating film coated member, a surface of the main body being coated with the hard coating film composing of a metal carbide, a metal nitride, or a metal carbonitride in Group IIIb, IVa, Va, or VIa of the periodic table of the elements, or composing of a solid solution of these compounds.

The removing method of hard coating film is characterized by that the hard coating film is removed from the main body by irradiating an ion beam onto the hard coating film and etching the hard coating film.

In second aspect of the present invention, the etching is performed by irradiating the ion beam created using an inert gas as a working gas onto the hard coating film.

In the third aspect of the present invention, the coating film removing method is comprised of a first etching step of etching the hard coating film by irradiating the ion beam created using a first inert gas as a working gas onto the hard coating film; and a second etching step of etching the hard coating film by irradiating the ion beam created after switching of working gas from the first inert gas to a second inert gas of which atomic weight is smaller than the first inert gas onto the hard coating film.

In the fourth aspect of the present invention, the first etching step uses any one of radon, xenon, and krypton as the working gas in, and the second etching step uses an argon gas as the working gas.

In the fifth aspect of the present invention, the main body is made of a super-hard alloy.

In the sixth aspect of the present invention, the hard coating film coated member is a hard coating film coated working tool in which at least a working part is coated with the hard coating film.

According to the removing method of hard coating film of the first aspect of the present invention, the hard coating film i.e. hard coating layer is removed from the main body mainly by the sputtering i.e. sputtering phenomenon by irradiation of the ion beam. Therefore, even if the surface of the main body is precedingly exposed partially because of the thickness non-uniformity in the hard coating film or because of the coating film removing speed difference, following effects can be rendered. The surface weakness of the main body by the chemical erosion can be suppressed. Thanks to the small influence of the coating film removal on the main body, changes in the shape and the dimension of the main body become smaller, compared with a case in which the hard coating film is removed mainly using the chemical reaction.

As a result, the main body can be re-used with no modification or with only a slight modification thereof Thus, not only the hard coating film-coated member can be reproduced at low cost by being re-coated with the hard coating film, but the adhesion strength of the hard coating film to the main body is increased. Therefore, the original coating performance (durability, abrasion resistance, etc.) which is the same as a new article can be rendered.

According to the second aspect of the invention, the hard coating film is etched by irradiation of the ion beam created using the inert gas as the working gas, so that the hard coating film is mechanically removed mainly by the sputtering using the ion irradiation. Therefore, although the removing speed becomes slow, the main body surface can be completely prevented from being weakened by the chemical erosion even upon the surface being exposed. As a result, the adhesion strength of the hard coating film to the main body upon re-coating is further increased.

According to the third aspect of the present invention, in the first etching step, the etching is performed using the first inert gas having comparatively large atomic weight, so that the hard coating film can be efficiently removed using the sputtering of ions having the large mass. In the second etching step, etching is performed using the second inert gas having comparatively small atomic weight, so that the hard coating film is gradually removed using the sputtering of ions having the small mass. Appropriately setting the processing time period of the first and second steps can shorten the time period required for the coating film removing operation with suppressing the influence thereof on the main body (changes in shape and dimension) to the minimum. Basically, the working gas is sufficiently switched between the first and second etching steps so that the both steps can be continuously performed, with holding the hard coating film coated member in a predetermined etching-treatment container.