JPH07120378A - Testing method for adhesion property of film - Google Patents

Abstract

PURPOSE:To determine the adhesion property of a film simply and nondestructively by a method wherein a spherical body or a cylindrical body having a prescribed diameter is rolled, under a prescribed load, onto the surface of a film for an object to be tested. CONSTITUTION:A testing device 3 is placed on an object 1, to be measured, which is composed of a preform 10 and a film 11, and a steel ball 2 is pressed onto the surface of the film 11 under a prescribed pressure P by a hydraulic cylinder apparatus 32. Then, while a plate 31 is being moved along a guide track 30, whether an interface has been exfoliated or not is detected by an ultrasonic flaw detector 33. A maximum shearing stress taumax at a time when the interface is exfoliated can be used an index to determine the adhesion property. A shearing stress tau can be decided unequivocally on the basis of tauproportional (P/r<2>), where (r) represents the radius of the steel ball 2 and P represents a pressure applied to the steel ball 2. In addition, regarding the film whose shearing strength is clear, conditions for P and (r) which cause an exfoliation are found in advance, and a working curve is formed. Then, the adhesion strength of the film 11 can be evaluated quantitatively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating adhesion test method for quantitatively evaluating the adhesion of a test object having a coating such as a plating layer and a thermal spray layer to the base material of the coating.

[0002]

2. Description of the Related Art As a test method for evaluating the adhesion of a coating such as a plating layer or a sprayed layer to a base material, for example, a bending test method of pushing a plate-shaped test piece with a jig or a plate-shaped test piece Impact test method (JIS H8661-196)
1), Peel test method (JIS H8305-1982) in which a grid is cut on the test piece and adhesive tape is affixed and peeled off, and heat peel test method (JIS H8664-19) that repeats heating and cooling.
77) are known. However, with these test methods, it is difficult to quantitatively evaluate the adhesion of the coating.

Also, an adhesion test method for adhering the film surfaces of a pair of plate-shaped test pieces to each other and peeling them off to the left and right (JIS H8664-
1997, Japanese Unexamined Patent Publication No. 2-47537), a method of blasting with spherical shot particles (Japanese Unexamined Patent Publication No. 5-107179, Japanese Unexamined Patent Publication No.
Test methods such as JP-A 3-108636) are also known. According to these methods, the film adhesion can be quantitatively evaluated.

[0004]

However, the conventional test method described above is a destructive inspection in which the shape of the test piece is defined. Therefore, it is difficult to test an actual component, and a test piece has to be manufactured, resulting in a large number of man-hours. In addition, the test apparatus is often large and expensive, and there is a cost problem.

The present invention has been made in view of such circumstances, and it is an object of the present invention to be simple, to test actual parts, and to enable quantitative evaluation.

[0006]

[Means for Solving the Problems] The film adhesion test method of the present invention for solving the above-mentioned problems is an adhesion property of a film of an object to be tested, which is composed of a base material and a film formed on the surface of the base material, to the base material. Is a method of testing a spherical body or a cylindrical body having a predetermined diameter on a surface of a film of a test object under a predetermined load.

[0007]

In the coating adhesion test method of the present invention, as shown in FIG. 1, an indenter having a radius r such as a sphere is formed on the surface of the DUT 1 including the base material 10 and the coating 11 formed on the surface of the base material 10. Two
Is to be rolled with a predetermined load P. Thereby, when r and P are in a predetermined condition, the film 11 is separated from the base material 10 and the interface separation 12 occurs.

FIG. 2 schematically shows a case where a sphere having a radius r is brought into contact with a plane with a load P. Assuming that the radius of the contact surface is a, there is a relationship among a, r, and P as shown in [Equation 1].

[0009]

[Equation 1]

[0010] When the maximum pressure occurring in the contact surface center and P _0, P _0, r, relationship shown in expression (2) expression between P.

[0011]

[Equation 2]

E ₁ and E ₂ are Young's moduli, ν ₁ and ν ₂ are Poisson's ratios, and subscripts 1 and 2 indicate the material characteristics of the object under test and the sphere, respectively. The distribution of shear stress occurs in the depth direction below the contact surface, and the depth z is calculated from Hertz's equation.
The principal shear stress τ _{1 at} the position of is represented by the formula [3].

[0013]

[Equation 3]

[0014] Thus from Formula 3 wherein for example, a maximum shear stress tau _max is, [nu = 0.3, when z = 0.47a τ _max =
Calculated as 0.31P. And from the above equation, it became clear that the shear stress τ is proportional to (P / r ² ) ^1/3 as in the equation [4].

[0015]

[Equation 4]

Therefore, in the present invention, this theory is applied to a member having a film, and a sphere having a predetermined radius r is applied on the surface of the film with a predetermined load P.
To generate shear stress in the film thickness t direction. The shear stress generated here is uniquely determined from the equation (4). Therefore, for example, the conditions of P and r at which peeling occurs in a film having a clear shear strength are obtained in advance, and a calibration curve as shown in FIG. 3 is created based on the conditions. Then, by using the test method of the present invention, it is possible to quantitatively evaluate the adhesion strength of the coating by examining the presence or absence of peeling of the coating of the test object tested under the predetermined conditions of P and r obtained above. it can.

When a cylinder having a radius r is used in place of the sphere, the radius of the contact surface is given by the formula [5] between a and r, P, l, where the length of the cylinder is l. I have a relationship.

[0018]

[Equation 5]

There is a relationship between the maximum pressure P ₀ generated at the center of the contact surface and r, P, l as shown in [Equation 6].

[0020]

[Equation 6]

Therefore, for example, if ν = 0.3, z =
When 0.786 a, τ _max = 0.301 P is calculated, and even in the case of a cylinder, the shear stress is uniquely determined for r, P and l like the sphere, and the adhesion strength can be quantitatively evaluated.

[0022]

EXAMPLES The present invention will be specifically described below with reference to examples. Figure 5
The test apparatus used in this example is shown in FIG. This test equipment 3
Is a guide rack 30 and a plate 31 movably held on the guide rack 30 along the guide rack 30.
And an ultrasonic flaw detector 33 and a hydraulic cylinder device 32 fixed to the plate 31.

A steel ball 2 made of SVJ2 is held on the tip of the piston of the hydraulic cylinder device 32, and the film 11 of the DUT 1 is held.
Can be pressurized. The applied pressure is the pressure regulator 3
Adjustable with 4. Further, the signal of the ultrasonic flaw detector 33 is amplified and output by the amplifier 35, and it is possible to determine whether or not the interface between the base material 10 and the film 11 is separated. Although the steel ball 2 is used in this embodiment, the material thereof can be appropriately selected according to the material of the test object.

In this test apparatus 3, the DUT 1 is placed parallel to the guide rack 30, and the hydraulic cylinder device 32 presses the steel ball 2 against the surface of the film 11 with a predetermined pressure. When the plate 31 moves to the right in FIG. 2, the steel ball 2 rolls while pressing the coating 11, and the pressing surface has the ultrasonic flaw detector 3
In 3, the presence or absence of peeling is detected. In this test device,
Since the distance between the steel ball 2 and the ultrasonic flaw detector 33 is extremely small, any material having a flat surface portion equal to or larger than the distance can be used without being limited to a plate-shaped test object. Also guide rack 3
The shape of the DUT is not limited as long as the shape of 0 corresponds to the surface shape of the DUT. <Preliminary Experiment> The surface of the S45C steel material was blasted to a surface roughness of 40 μmRz, and then HVOF (High
A Ni coating having a thickness of 0.3 mm was formed by thermal spraying of Velocity Oxygen Fuel. Here, the temperature conditions of the material at the time of thermal spraying were changed, and the thermal sprayed test piece was prepared under three levels of conditions: water cooled material, heated material, and no heating / cooling of the material.

For each test piece, the film shear strength was measured using the shearing jig shown in FIG. The results are shown in Table 1.

[0026]

[Table 1] The shearing jig 6 shown in FIG. 5 has a base 62 having a mounting portion 60 and a cylinder hole 61, a piston portion 63 movably held in the cylinder hole 61 and having a pressing protrusion 63a, and a piston portion 63 Extruding section 64 and punch 6
5 and a guide hole 66 for guiding the punch 65.

Using this shearing jig 6, the shear strength of the film was measured as follows. First, the test piece 1 was installed on the mounting portion 60, the position of the coating film 11 was adjusted by the extrusion portion 64, and the tip end portion 65a of the punch 65 was pressed against the coating film 11 to separate the coating film 11 from the base material 10. Then, when the pushing force of the punch 65 when the film 11 was peeled off was P and the cross-sectional area of the film 11 was S, P / S was calculated to be the film shear strength. <Selection of test conditions> Next, using the test apparatus shown in FIG.
While changing the values of the radius r of the steel ball 2 and the pressing force P,
The conditions under which interfacial peeling occurred in the film 11 were measured using a test piece having a film shear strength of 50 MPa. As a result, the radius r
It was revealed that interfacial peeling occurs when a steel ball 2 of 25.4 mm is used and pressure is applied with a load of 8 kg or more.

Further, using steel balls 2 having a radius r = 25.4 mm, the test pieces having a coating shear strength of 30 MPa and 80 MPa were tested under the same conditions of pressing with a load of 8 kg or more. Interfacial peeling occurred in the coating of the test piece, but interfacial peeling did not occur in the coating of the test piece having a coating shear strength of 80 MPa. That is,
To determine whether the film shear strength of the film is less than 50 MPa or 50 MPa or more by rolling the steel ball 2 having a radius r = 25.4 mm while applying a load of less than 8 kg, with or without interfacial peeling. You can

[0029]

That is, according to the film adhesion test method of the present invention, since a sphere or a cylinder is simply rolled on the surface of the object to be tested, it is not necessary to prepare a special test piece, and the number of steps can be greatly increased. It can be reduced. Moreover, since it is a non-destructive inspection, the actual parts can be directly subjected to the test.

Since the adhesion can be quantitatively evaluated by the test method of the present invention, the accuracy of the evaluation is remarkably improved and the data can be finely analyzed.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a test method of the present invention.

FIG. 2 is a schematic explanatory view of the action of the test method of the present invention.

FIG. 3 is a graph showing an example of a calibration curve used for evaluation from test data of the present invention.

FIG. 4 is a front view showing a partial cross section of a test apparatus used in one example of the present invention.

FIG. 5 is a cross-sectional view of a shearing jig used in an example of the present invention.

[Explanation of symbols]

1: DUT 2: Steel ball
3: Testing device 10: Base material 11: Film 1
2: Interface peeling 32: Hydraulic cylinder device 33: Ultrasonic flaw detector

Claims (1)

[Claims] 1. A method for testing the adhesion of a coating of an object to be tested, which comprises a base material and a coating formed on the surface of the base material, to the base material, wherein the coating surface of the object to be tested. A coating adhesion test method characterized by rolling a sphere or a cylinder having a predetermined diameter under a predetermined load.