JPH06331536A - Evaluation test method of contact property of ceramic thin film - Google Patents

Abstract

PURPOSE:To simply evaluate the contact property of a ceramic thin film formed on the surface of a metal matrix by a method wherein the center of a test piece is impacted and bent at a prescribed angle to produce cracks in the ceramic thin film and its production range is measured. CONSTITUTION:A test piece 1 on which a ceramic thin film 2 is formed is impacted within a range in which a test-piece preform is not broken down, and the contact property of the thin film 2 can be evaluated. The less the thin film 2 is exfoliated or a crack 3 is produced the better the contact property of the thin film 2 is. The bend angle of the test piece 1 is desirably 2 to 8 deg. when the test piece 1 on which the thin film 2 is formed on the blow side is used. The damaged situation of the thin film 2 in the crack production region 3 produced around the blow center 4 of the test piece 1 after a test is observed by the naked eye of by using an optical microscope, and the production range L of the crack and the interval of cracks as required are measured. The dispersion of measurements which have been repeated 10 times under individual conditions is small at 10% or lower with reference to the individual mean values.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adhesion evaluation test method for a ceramic thin film formed on the surface of a metal base material.

[0002]

2. Description of the Related Art As a static adhesion evaluation test method for a thin film, a method for measuring the adhesion state of the thin film is described in Ohm Co., Ltd., Thin Film Handbook 1983. When the strength of the thin film is large, the direct method is adopted. Among them, there are a scratch method, an ultrasonic method, an electromagnetic pulling method, a laser crushing method, a friction method, a thermal method, an indentation method, a shearing method, and a bending method, which will be described later.

[0003] On page 329 of the above handbook, there is a description about the scratch test, which describes a method of pressing a stylus vertically against the thin film to apply a load, and then peeling the thin film from the substrate by scratching. There is.

In this method, the needle is pressed vertically against the substrate having the thin film formed on its surface to move in the lateral direction, so that the indentation of the substrate by the needle (indenta).
A large shear stress is applied to the edge part of the section, and the peeling progresses there.

The needle used in this method is made of steel, diamond, or the like whose tip has a known radius of curvature.

In order to show the size of the adhesion, the load value (g) that can make a scratch is usually displayed as it is, but when it is necessary to obtain a physically meaningful value. The shear stress value f _s (kg / mm ² ) at the edge of the depression is calculated by the following equations (1) and (2).

[0007]

## EQU1 ## f _s = aP / (r ² −a ² ) ^1/2 (1)

[0008]

[Formula 2] a = (W / πP) ^1/2 (2)

R: radius of curvature of tip of needle (mm) P: static pressure at tip of needle to Brinell hardness of substrate (kg / mm)
² ) W: Load applied to the needle (kg) π: Circularity

[0010]

The prior art evaluates the adhesion of the thin film by the above method, but when determining the peeling start position, the scratch mark is observed in detail by an optical microscope or the like to determine the peeling start position. It is necessary to judge and measure the indentation width at that position.

At this time, since the peeling pattern is not uniform,
Identification of the peeling start position is subjectivity and tends to cause variations in measurement data.

In order to avoid the complexity, even if the peeling start position is read from the differential value of the load change during the scratch test, or the load change pattern is not always clear even when read from the continuously recorded chart, there is a variation in the measured data. It was great.

An object of the present invention is to provide a test method for easily evaluating the adhesion of a ceramic thin film formed on the surface of a metal base material.

[0014]

In order to solve the above problems, the present invention provides a knife-edge-shaped test piece in which the ceramic thin film is formed on the surface of a metal base material in the central portion in the longitudinal direction in parallel with the short side. Adhesion of ceramic thin film characterized by evaluating the adhesion of the ceramic thin film by applying an impact, bending the test piece at a predetermined angle to generate a crack in the ceramic thin film, and measuring the range of occurrence of the crack. It is a sex evaluation test method.

The crack width is preferably wide in order to improve the measurement accuracy, but
If the base material is bent greatly, the base material will break during the test, and the error will increase due to peeling of the thin film in the test part, breakage of the test piece, and secondary damage to the ceramic thin film due to the impact during scattering. The range of the generated cracks may be appropriately selected.

[0016]

The present invention will be described in detail below.

When the base material of the test piece is deformed by the impact test, the ceramic thin film formed on the surface of the test piece is also deformed according to the deformation of the base material, and if the material strength is exceeded, the ceramic thin film is broken.

Here, a case where a hammer, which is an impact portion, collides from the ceramic thin film side formed on the surface of the base material toward the base material will be described.

When the base material is deformed in the traveling direction of the hammer due to the impact of the hammer, the ceramic thin film exerts a tensile stress on the base material side in the ceramic thin film and a compressive stress on the outer surface side in accordance with the deformation of the base material. Occurs.

When each stress exceeds the material strength of the ceramic thin film, it breaks. When an external force that is permanently deformed by a hammer collision is applied to the test piece, the test piece reaches the maximum deformation amount, and then the elastic deformation is released to allow the permanent deformation.

The reason why the ceramic thin film on the surface of the test piece after the impact test is cracked is that the generated stress causes partial cracking or peeling of the film, which widens the crack due to the release of the elastic deformation. It is supposed to do.

When the base material is bent and there is a difference in elastic modulus between the base material and the ceramic thin film, shear stress is generated at the interface between the base material and the ceramic thin film, and when the value exceeds the shear strength, the ceramic thin film is formed. Peel off.

By this peeling, of the stress generated in the surroundings, the portion corresponding to the energy accompanying the peeling is released.

As described above, the peeling of the base material and the ceramic thin film is caused not only by the bending of the base material but also by the difference in elastic deformability of the base material and the ceramic thin film, but the peeling or cracking of the ceramic thin film does not occur. It can be said that the better the adhesion of the ceramic thin film is.

In the test method of the present invention, a Charpy impact tester is used as an impact tester, a Charpy test piece or a JIS standard bending test piece is used as a test shape, and a shock is applied to a test piece on which a ceramic thin film is formed by a hammer. It is preferable.

As described above, according to the method of the present invention, the adhesion of the ceramic thin film can be evaluated by applying an impact to the test film on which the ceramic thin film is formed within the range where the base material of the test piece is not broken.

The bending angle of the test piece according to the present invention is preferably 2 to 8 degrees when the test piece having the ceramic thin film formed on the striking side is used. If it is less than 2 degrees, the crack width generated in the ceramic thin film in the test portion is small and the measurement variation is large.

If it exceeds 8 degrees, the ceramic thin film of the test part, especially the ceramic thin film of the part directly hit by the striking part, is severely damaged, and it is not possible to judge the state of crack occurrence, or the impact value of the metal base material. In some cases, the test piece breaks, and the ceramic thin film near the striking portion peels off. Therefore, it may not be possible to observe the damage state of the ceramic thin film.

In order to set the bending angle of the test piece used in the present invention to 2 to 8 degrees, an impact applying test is performed in advance using a test piece made of only the base material, and the characteristics of the base material are appropriately determined. An appropriate impact load should be applied.

[0030]

[Example] In advance, an impact test in which a JIS standard bending test piece size of 3 × 4 × 40 mm is used and an impact load is applied to a surface of 4 × 40 mm using a test piece made only of a metal base material made of SKD11, and a hammer is swung up. The test conditions were selected so that the bending angle was 5 degrees by changing the angle.

In this test, the hammer length is 23c.
The center of gravity of the m ヽ hammer was 17 cm, the total weight of the hammer was 1.26 kg, and the hammer swing-up angle was 120 degrees.

The test pieces used in the method of the present invention are 3 × 4 ×
JIS standard bending test piece size of 40mm, SKD11
A ceramic thin film having a thickness of 5 μm was formed by PVD method on one surface of a base material of 4 × 40 mm, and the impact load condition was performed in advance using a test piece composed of only the base material. An impact test was conducted under the same conditions as the test.

FIG. 1 is a perspective view showing a typical example of the test piece after the impact test used in the present invention. In FIG. 1, 1 is SK
A test piece made of D11 and having a size of 3 × 4 × 40 mm, 2 is a ceramic thin film deposition surface on which a ceramic thin film is deposited to a thickness of 5 μm on a 4 × 40 mm surface of a base material, and 3 shown by hatching occurs in the center of the test piece It is a cracked part.

The test piece was subjected to an impact test and its center was 5
The impact load was selected so that it bends every time.

FIG. 2 is a view in which the condition of the crack generation region 3 generated in the central portion of the test piece shown in FIG. 1 is magnified 20 times.

Reference numeral 3 denotes a crack generation area in the center of the test piece, 4 is a center of impact applied to the center of the test piece, and L is a crack generation range.

After the test, the damage condition of the ceramic thin film in the crack generation region 3 centered around the striking center 4 of the test piece,
Observation with a naked eye or an optical microscope was performed to measure the crack occurrence range (L: distance mm) and, if necessary, the crack interval.

The crack generation range (L) in FIG. 2 was measured for the test pieces with different ceramic thin film compositions.
Shown in. The horizontal axis of FIG. 3 represents the film composition of the ceramic thin film, and the vertical axis represents the crack generation range (L).

According to the method of the present invention, it can be clearly identified that the crack generation range (L) changes depending on the composition of the ceramic thin film.

That is, the larger the value of X, the larger the value of the crack generation range, and in this case, it can be determined that the TiN ceramic thin film has excellent adhesion.

Further, the variation in the measured values repeated 10 times under each condition was 10% or less with respect to each average value. This is small compared to the dispersion of the measured values by the scratch test method of FIG. 4 described later.

For comparison, the adhesion of ceramic thin films was compared by the scratch test method.

The metal base material used in the comparative example and the film forming conditions of the ceramic thin film were the same as those in this example.

The size of the metal base material was 25 × 25 × 5 mm, and a ceramic thin film was formed on the surface of 25 × 25 mm.
For comparison, FIG. 4 shows the measurement results of the adhesion force obtained by the scratch test method.

The horizontal axis of FIG. 4 represents the composition of the ceramic thin film, and the vertical axis represents the adhesion of the ceramic thin film.

The variation of the measured value after repeating the test 10 times for each composition is about 10 to 30%, it varies depending on the composition, and the tendency between the composition and the adhesion is unclear, and the relationship with the composition is judged. Have difficulty.

In the present invention, the test piece size of 3 × 4 × 40 mm and the material SKD11 of the metal base material are not limited to the above examples, and may be appropriately selected according to the properties of the ceramic thin film to be evaluated. Good.

As for the crack generation range, as shown in the above-mentioned embodiment, in the entire crack generation area 3, one of the boundaries with the center of impact as the boundary, one of the longer ones and the shorter one, and the average value thereof are selected. It may be used as evaluation data.

[0049]

According to the present invention, it is possible to evaluate the adhesion of a ceramic thin film by an impact load, which has not been available in the prior art, which is simpler and more accurate than the conventional scratch test method. Since the measured value can be obtained, it is an excellent method for evaluating the quality judgment of the ceramic thin film.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a test piece after an impact test used in the present invention.

FIG. 2 is an example showing an enlarged view of a crack generation region of a test piece according to the present invention.

FIG. 3 is a diagram showing a relationship between a composition of a ceramic thin film of a test piece according to the present invention and a crack generation range (L) generated in the ceramic thin film.

FIG. 4 is a diagram showing a relationship between a ceramic thin film composition obtained by a conventional scratch test method and its adhesion.

[Explanation of symbols]

 1 Test piece after impact test 2 Deposition surface of ceramic thin film 3 Crack generation area at center of test piece 4 Impact center L Crack generation area on one side

Claims (2)

[Claims] 1. A test piece having a ceramic thin film formed on a surface of a metal base material is subjected to a knife-edge-like impact parallel to a short side at a central portion in a longitudinal direction of the test piece, and the test piece is bent at a predetermined angle. A test method for evaluating the adhesion of a ceramic thin film, characterized in that the adhesion of the ceramic thin film is evaluated by generating a crack in the thin film and measuring the range of occurrence of the crack. 2. A test method for evaluating adhesion of a ceramic thin film, wherein the bending angle of the test piece is 2 to 8 degrees.