Diamondlike carbon hard multilayer film formed body and method for producing the same

Abstract

A diamondlike carbon hard multilayer formed film body comprises a substrate, a diamondlike carbon film mainly composed of diamondlike carbon, and an intermediate layer between the substrate and the diamondlike carbon film. The diamondlike carbon film is composed of, in order from the substrate side, a first diamondlike carbon film and a second diamondlike carbon film. The surface hardness of the first diamondlike carbon film is within the range from not less than 10 GPa to not more than 40 GPa based on nanoindentation test, and the surface hardness of the second diamondlike carbon film is within the range from more than 40 GPa to not more than 90 GPa based on nanoindentation test. According to such a structure, even if a DLC multilayer containing high-hardness DLC film on the outermost surface side is formed in a thickness of not less than about 3 μm on a substrate of a wide range extending from a material with high hardness such as cemented carbide to an iron-based material with low hardness, excellent adhesion to both the substrate and the DLC film can be ensured in addition to excellent wear resistance.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a hard multilayer film formed body which has a diamondlike carbon film on the outermost layer side, and a method for producing the same. The diamondlike carbon hard multilayer film formed body according to the present invention is suitably used for a surface protective film for a member which especially requires wear resistance in automobile parts, machine parts, precision tools, cutting tools, because it exhibits excellent adhesiveness to a substrate. [0003] 2. Description of the Related Art [0004] Diamondlike carbon (hereinafter referred to as “DLC”) is amorphous carbon having intermediate properties between diamond and graphite, and called hard carbon, hard amorphous carbon, amorphous carbon, delmorphous carbon, i-carbon, diamond-shape carbon or the like. The DLC is used, for example, as a protective film for a member which requires wear resistance because of high hardness as well...

AI Technical Summary

Benefits of technology

The present invention provides a diamondlike carbon hard multilayer film formed body that exhibits excellent adhesiveness and wear resistance. This is achieved by forming an intermediate layer on a substrate and then sequentially depositing a first and second diamondlike carbon film on the intermediate layer. The surface hardness of the second diamondlike carbon film increases stepwise or continuously from the interface side between the first and second films towards the outermost layer. The substrate can be composed of cemented carbide or iron-based material, and the intermediate layer can be composed of a first metal layer and an amorphous layer containing at least one metal selected from the group consisting of W, Ta, Mo, and Nb, or a composite metal layer comprising a metal of Cr and / or Al and at least one metal selected from the group consisting of W, Ta, Mo, and Nb. The thickness of the intermediate layer is preferably between 10% and 50% of the total thickness of the diamondlike carbon hard multilayer film formed body. The method for producing the film formed body involves preparing a substrate, forming an intermediate layer on the substrate, and sequentially depositing a first and second diamondlike carbon film on the intermediate layer. The film formed body exhibits excellent adhesiveness and wear resistance even when a DLC multilayer film containing a high-hardness DLC film is formed on a substrate of a wide range of materials.

Problems solved by technology

However, a DLC film with high hardness has an extremely large internal stress, and its deformability is extremely small.

Therefore, it has a disadvantage of easily separating with low adhesiveness to the substrate.

However, in this method, since the mixing effect of C is used for forming the mixed layer as described above, the thickness of the mixed layer is limited to a narrow range from about 10 to 500 Å. Therefore, a hardness difference is caused between the substrate and the DLC film (in a case having no intermediate layer) or between the intermediate layer and the DLC film (in a case having the intermediate layer), which are arranged through such a thin mixed layer.

However, when the substrate is composed of a material with relatively low hardness such as an iron-based substrate, which is generally used for mechanical parts, easy separation of DLC film becomes problematic.

When the thickness of a multilayer film containing DLC film on the outermost surface side (a multilayer film including the intermediate layer and the DLC film, which may be hereinafter called DLC multilayer film) is as thick as not less than about 3 μm, this problem becomes noticeable because the whole stress of the DLC multilayer film is increased.

However, it is principally difficult for the sputtering including UBM sputtering to form a DLC film with extremely high hardness as in the AIP which uses carbon ion as a raw material.

Therefore, the DLC film formed using the sputtering is inferior in wear resistance to the DLC film formed using AIP.

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