JP2012041589A - Surface structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a hard layer in a simpler and easier way, the hard layer being constituted of a DLC (Diamond-Like Carbon) film in a state in which propagation of peeling is suppressed.SOLUTION: A surface structure includes a surface 102 which is a rough surface of a base material 101, and the hard layer 103 comprising a diamond-like carbon formed on the surface 102. The arithmetic surface roughness of the surface 102 is in a range between 0.2 and 0.4, and the thickness of the hard layer 103 is in a range of 1-3 μm. The rough surface can be formed, for example, by the blasting such as sand blasting, and rough grinding such as buffing. The hard layer 103 is obtained by depositing a DLC film by the well-known PVD method on the surface 102 of the base material 101. For example, the DLC film can be formed by the ion-plating method and the sputtering method using graphite as a target.

Description

  The present invention relates to a surface structure with improved friction resistance.

  A control valve, a gas governor, or the like is a device having a sliding surface having a contact friction portion. In the sliding portion of such an apparatus, the contact friction portion is made of a hard material in order to improve the friction resistance, and is hard-treated by heat treatment or the like. There is also a technique for improving the friction resistance by forming a hard layer in the contact friction portion. Further, a lubricant is used in order to improve the slidability in the contact friction portion.

  However, the range of usable lubricants is limited, for example, it is difficult to use in an environment where the pressure is exhausted under reduced pressure, and there is a problem that maintenance and maintenance are always necessary because it involves a change with time. On the other hand, diamond-like carbon (DLC) is available as a hard layer material that provides excellent slidability without using a lubricant (see Patent Documents 1, 2, 3, and 4).

  However, when a crack occurs in the DLC film, there is a problem in that the film peels at once over a wide area starting from the generated crack. With respect to this problem, in Patent Documents 1, 2, 3, and 4, the DLC film is divided into segments. By dividing into segments, first, the progress of peeling of the DLC film can be suppressed, and even if the film peels in one segment, the adjacent segment is not affected. Thereby, progress of peeling can be suppressed and the lifetime of the film can be extended. Moreover, by dividing into segments, a large strain applied to the DLC film accompanying the deformation of the matrix can be avoided, and the progress of peeling can be suppressed.

WO2006 / 095907 JP 2010-007117 A JP 2003-147525 A JP 2007-083726 A

  However, there is a problem that it is not easy to divide the DLC film into segments. For example, in Patent Documents 3 and 4, a DLC film is formed on a segment by masking in a lattice shape using a wire mesh of tungsten wire. Further, in Patent Document 2, a DLC film is formed on a segment by a so-called lift-off method in which a convex pattern having a pattern shape corresponding to the segment form is formed, a DLC film is deposited thereon, and then the convex pattern is removed. Is forming. As described above, in any case, a mask is used, and there are problems of positional accuracy and an increase in manufacturing processes.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to make it possible to more easily form a hard layer composed of a DLC film in a state in which the progress of peeling is suppressed. And

  The surface structure according to the present invention includes a roughened surface of a base material and a hard layer made of diamond-like carbon formed on the surface, and has an arithmetic surface roughness of 0.1 to 0.4. The hard layer has a thickness of 1 to 3 μm. In addition, the hard layer should just be comprised from the diamond-like carbon film | membrane which coat | covers the surface.

  As described above, according to the present invention, since the hard layer made of diamond-like carbon is formed on the surface of the roughened base material, it is composed of the DLC film in a state in which the progress of peeling is suppressed. The excellent effect that the hard layer to be formed can be formed more easily is obtained.

FIG. 1 is a cross-sectional view showing the structure of the surface structure in the embodiment of the present invention. FIG. 2 is a characteristic diagram showing the results of a frictional wear test performed on a hard layer made of a DLC film. FIG. 3 is a metallographic micrograph of the surface of the hard layer made of the DLC film after performing the frictional wear test. FIG. 4 is a metallographic micrograph of the surface of the hard layer made of the DLC film after performing the frictional wear test. FIG. 5 is a metallographic micrograph of the surface of the hard layer made of the DLC film after performing the frictional wear test. FIG. 6 is an electron micrograph of a hard layer made of a DLC film. FIG. 7 is an electron micrograph of a hard layer made of a DLC film. FIG. 8 is an electron micrograph of a hard layer made of a DLC film. FIG. 9 is an electron micrograph of a hard layer made of a DLC film.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing the structure of the surface structure in the embodiment of the present invention. This surface structure includes a rough surface 102 of the substrate 101 and a hard layer 103 made of diamond-like carbon (DLC) formed on the surface 102. The arithmetic surface roughness of the surface 102 is in the range of 0.1 to 0.4, and the hard layer 103 is in the range of the layer thickness of 1 to 3 μm. Such a rough surface can be formed by, for example, processing by blasting such as sand blasting or rough polishing such as buffing.

  The hard layer 103 may be formed by depositing DLC on the surface 102 of the substrate 101 by a well-known PVD method. For example, DLC can be deposited by ion plating or sputtering using graphite as a target. Moreover, the hard layer 103 should just be formed so that the surface 102 may be coat | covered. Since the hard layer 103 is formed on the roughened surface 102, the hard layer 103 has a plurality of cracks 104. In other words, the hard layer 103 is composed of a plurality of DLC films divided into segments. As described above, according to the present embodiment, simply forming the DLC film results in a state of being divided into segments, so that a hard layer that is difficult to peel can be formed more easily.

  As described above, according to the above-described embodiment, since it is not necessary to use a so-called stencil mask such as a wire mesh or a mask pattern made of a resist or the like, a hard layer composed of a DLC film in which the progress of peeling is suppressed. However, it can be formed more easily.

  Hereinafter, evaluation of the actually produced sample will be described.

[sample]
As a sample, a substrate obtained by processing SUS316 into a disk shape was used. Sample 1 has a surface roughness of Ra0.2, sample 2 has a surface roughness of Ra0.002, and sample 3 has a surface roughness of Ra0.8. The sample 1 corresponds to the substrate 101 of the above-described embodiment. Sample 1 has a surface roughness Ra of 0.2 by well-known buffing. Sample 2 was set to Ra0.002 by well-known mirror polishing. The surface of the sample 2 is in a so-called mirror-finished state. In Sample 3, the surface of the SUS316 disk was processed with a lathe to obtain Ra 0.8. The formed hard layer had a layer thickness of 1 μm.

[Evaluation Method 1]
Evaluation is performed by a ball-on-disk friction and wear test using a load increasing method using 9.6 mm diameter alumina spheres. The maximum load is 15 kg. The sliding speed is 0.15 m / sec, and the critical load when the formed hard layer breaks is determined from the change in the friction coefficient.

[Evaluation Method 2]
In each sample, the state of the hard layer surface after the frictional wear test is observed with a metal microscope.

[result]
First, as shown in FIG. 2A, sample 1 has no significant change in the coefficient of friction in the range of the maximum load load in the frictional wear test, and the destruction of the hard layer is not confirmed. On the other hand, as shown in FIG. 2 (b), the friction coefficient of the sample 2 increases beyond the measurement limit before the load of 5 kg, and at this point, the hard layer is confirmed to be broken. Further, as shown in FIG. 2 (c), the friction coefficient of the sample 3 increases beyond the measurement limit at a load of 2 kg, and at this point in time, the hard layer is confirmed to be broken. In addition, the friction coefficient of Sample 3 gradually increases until the load is 2 kg.

  Next, it shows about the observation result by a metal microscope. In the sample 1, as shown in the photograph of FIG. 3, streak-like cutting marks are confirmed at the frictional wear test location, but the hard layer remains. On the other hand, as shown in the photograph of FIG. Similarly, as shown in the photograph of FIG. 5, it can be seen that the hard layer at the frictional wear test location is peeled off from Sample 3.

  Next, the case where the surface of the substrate was mirror-finished to form a DLC film (hard layer) and the case where the DLC film was formed on the roughened surface according to the present embodiment were compared with an electron microscope. The results will be described.

  First, when a DLC film is formed on the mirror-finished surface, it can be seen that a flat film is formed as shown in the photograph (2000 times) in FIG. On the other hand, when the DLC film is formed on the rough surface according to the present embodiment, as shown in the photograph (2000 times) in FIG. It can be seen that cracks are formed.

  Moreover, as shown in the photograph (1000 times) of FIG. 8, it can be seen that film peeling occurred over a wide range at the place where the above-described frictional wear test was performed on the DLC film formed on the mirror-finished surface. In contrast, the frictional wear test described above for the DLC film formed on the roughened surface according to the present embodiment has a frictional portion as shown in the photograph of FIG. 9 (1500 times). It is observed that the surface of the base material is exposed white, but it is partial, and it can be seen that the DLC film remains in other portions. Further, it can be seen that the portion where the base material is exposed corresponds to a rough convex portion.

  As is clear from the results of the above experiments, according to the surface structure with Ra0.2, a high wear resistance state is obtained. Moreover, the same result (state with high abrasion resistance) is obtained in Ra0.1-0.4. This is presumably because, according to the present embodiment, the hard layer is in a state equivalent to being divided into segments.

  It should be noted that the present invention is not limited to the embodiment described above, and that many modifications can be implemented by those having ordinary knowledge in the art within the technical idea of the present invention. It is obvious. For example, the DLC film may be formed not only by the PVD method but also by the CVD method. A DLC film can be formed by a plasma assisted CVD method using a hydrocarbon gas such as acetylene as a source gas. Further, the base material is not limited to stainless steel such as SUS, and the same applies even if it is made of a metal material such as aluminum or magnesium.

  101 ... substrate, 102 ... surface, 103 ... hard layer, 104 ... crack.

Claims (2)

A roughened surface of the substrate;
A hard layer made of diamond-like carbon formed on the surface,
The arithmetic surface roughness of the surface is in the range of 0.1 to 0.4,
The hard layer has a surface thickness in the range of 1 to 3 μm. The surface structure of claim 1, wherein
The hard structure is composed of a diamond-like carbon film that covers the surface.