JPS5836671B2 - Surface treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a surface treatment method for forming a hard colored coating of high decorative value on the surface of a metal or alloy.

It is well known to form a hard yellow coating such as a titanium nitride coating on the surface of a metal or alloy, and this has generally been done by methods such as sputtering and ion plating.

In the sputtering method, the metal or alloy is held in a vacuum chamber and once evacuated to a vacuum of 10-5 to 10-6 Torr, nitrogen-containing gas is introduced to increase the pressure to 10-2 to 10-3 Torr.
A titanium nitride film is formed on the metal or alloy by performing high-frequency discharge within an electrode structure in which one electrode is made of titanium (referred to as a target).

A titanium nitride film is formed on a substrate by the reaction of titanium spattered from a target with nitrogen gas in the atmosphere, but the hardness, crystal structure, and color tone of the film vary widely depending on the composition ratio of titanium and nitrogen. .

Furthermore, the characteristics of these films vary widely depending on sputtering conditions such as input power, target area, and distance between the target and the substrate.

On the other hand, it is very difficult to control the reaction between titanium and nitrogen gas in the plasma and to keep the sputtering conditions constant, so the resulting films vary widely in film properties such as color tone and crystal structure. Ru.

Particularly in film formation, the first requirement is good adhesion between the substrate and the film, but the conventional film has high internal stress and easily deteriorates with a film thickness of several thousand λ. It often peeled off.

Another known method is to form a titanium nitride film by ion plating, but this method involves first evacuating the vacuum chamber to a vacuum of 10-5 to 10-6 Torr and then introducing nitrogen gas. Pressure 10-2 to 10-' Torr
titanium is evaporated from an electron beam evaporation source, plasma is generated by direct current high pressure or high frequency power, nitrogen gas and titanium are ionized, activated and reacted, and a titanium nitride film is formed on the substrate. It is.

In this case as well, it is difficult to keep the nitrogen gas partial pressure constant and to control the reaction between titanium and nitrogen gas in the discharge plasma to a constant level, so it is necessary to form a film with a stable color tone and constant characteristics. That was impossible.

In addition, the resulting film, like that obtained by sputtering, was severely peeled off due to internal stress and could not be put to practical use.

The object of the present invention is to eliminate these drawbacks in coating properties and provide a hard coating with high decorative value and excellent adhesion.

The gist of the present invention to achieve the above object is to form a hard, colored titanium nitride film on the surface of a metal or alloy, and then heat treat it in an oxygen-containing atmosphere to remove the surface layer of the titanium nitride. The objective is to harden the film, remove the internal stress of the film, eliminate the non-uniformity of the film due to slight deviations in manufacturing conditions during film formation, and give the film a certain color tone and certain characteristics.

A detailed explanation will be given below based on examples.

Apply a titanium nitride coating of approximately 3 to 5 μm on a stainless steel watch case by sputtering or ion plating.
Shaped to a thickness of

Next, it is placed in an electric furnace and heat treated at 300°C for 1 hour in air.

After the titanium nitride film is formed, each part of the watch case or the case itself has a different color tone due to slight differences in the film formation conditions, and it has unstable characteristics that easily peels off in a hygroscopic atmosphere. The coating after heat treatment has a golden color similar to gold, and it is difficult to discern any difference in tone even when comparing each part or case individually.

Further, the adhesion of the film was significantly improved, and no peeling was observed not only in a hygroscopic atmosphere but also in 10 consecutive thermal cycle tests from -40°C to room temperature to +80°C.

The optimal heat treatment conditions vary depending on the thickness of the titanium nitride film.
For thicknesses below 3μ, low temperature and short time (250℃, 30 minutes)
Heat treatment is possible at
A long heat treatment (450°C, 2 hours) is required.

Although the case of a stainless steel substrate has been described as an example above, the present invention can be applied to any metal or alloy such as brass, aluminum alloy, iron alloy coated with a nickel film.

Moreover, it can be applied not only to watch cases, but also to products that have strict color tone restrictions and include decorative elements.

This method is also effective in forming titanium nitride coatings on tools that have few decorative elements but require a high degree of adhesion of the coating.

Claims (1)

[Claims] 1. In a surface-treated member in which a titanium nitride film is formed on the surface of a metal or an alloy, after forming the titanium nitride film, heat treatment is performed in an atmosphere containing oxygen to oxidize the surface layer of titanium nitride. A surface treatment method characterized by: 2. The surface treatment method according to claim 1, wherein the metal or alloy is stainless steel, brass, nickel-coated brass, aluminum alloy, or iron alloy. 3. The surface treatment method according to claim 1, wherein the titanium nitride film is formed by reactive sputtering or ion plating.