Hardness detection method for enhancing visibility of indentation under microscope

Abstract

The invention provides a hardness detection method for enhancing indentation visibility, and relates to the technical field of physical detection methods. The method comprises the following steps: carrying out metal spraying treatment on a test sample of which the hardness needs to be measured, carrying out a Vickers indentation experiment, measuring the length of a Vickers indentation diagonal line by using a microscope, and calculating through a correction formula to obtain the hardness value of the material. According to the scheme, the problem that indentations of some special materials cannot be shot by a microscope is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of physical detection methods, and in particular to a hardness detection method for enhancing indentation visibility under a microscope. Background Art

[0002] In the field of micro-Vickers hardness testing, the Vickers hardness test is a widely used method for measuring material hardness. It involves applying an indenter with a specific geometric shape (usually a square or diamond-shaped indenter) to the surface of the material and applying a certain load, which then forms an indentation on the material surface. By measuring the diagonal length of the indentation, the hardness value of the material can be calculated. This method is widely used for hardness testing of various materials due to its ease of operation and high measurement accuracy. However, the traditional Vickers hardness test has limitations when testing certain special materials. For example, some highly light-absorbing black materials such as CBN and graphite, as well as some transparent or translucent materials such as single crystal sapphire and SiO2, are difficult to distinguish the boundaries of the indentation under a microscope, which poses certain difficulties in measuring the indentation size and is relatively difficult to detect. Summary of the Invention

[0003] The present invention discloses a hardness testing method for enhancing indentation visibility, aiming to solve the above-mentioned problems.

[0004] The present invention adopts the following scheme:

[0005] A hardness testing method for enhancing indentation visibility, comprising the following steps:

[0006] S1. Start the experiment. Use a quadrangular pyramid indenter to apply a load to the sample to form a Vickers indentation. Observe whether the Vickers indentation is obvious under a microscope. If obvious, directly measure the diagonal length and calculate its Vickers hardness value. If not obvious, proceed to the next step.

[0007] S2. Spray gold on the surface of the material to be tested and calculate the thickness h of the gold layer;

[0008] S3. Perform the experiment again and measure the diagonal length D.

[0009] S4. Determine the ratio of the diagonal length to the gold layer thickness. If the ratio is less than a preset threshold, correct the diagonal length and directly calculate the Vickers hardness value of the measured sample using the diagonal length D obtained in step S3. If the ratio is greater than or equal to the preset threshold, correct the diagonal length obtained in step S3 and calculate the Vickers hardness.

[0010] Furthermore, in step S1, the calculation formula of the Vickers hardness value HV is:

[0011]

[0012] Where F is the applied load in N; D is the average diagonal length of the indentation in millimeters; ɑ is the top angle of the pyramid indenter; and 0.102 is a constant used to convert units into hardness values.

[0013] Furthermore, in step S2, the calculation formula for the thickness of the gold layer is:

[0014] h=K·I·V·T; where K is a constant; I is the current of the metal spraying device, in mA; V is the cathode voltage, in KV; and T is the operating time of the metal spraying device, in seconds.

[0015] Further, in step S4, the ratio of the diagonal length to the gold layer thickness is determined. When , it means that the diagonal error caused by the gold layer thickness does not exceed the national standard range, and the Vickers hardness is calculated directly based on the measured diagonal length;

[0016] when When , it means that the diagonal error caused by the thickness of the gold layer exceeds the national standard range, and the measured diagonal length should be corrected.

[0017] Further, in step S4, when When , the correction formula for the diagonal length is:

[0018]

[0019] At this time, the calculation formula of Vickers hardness value HV is:

[0020]

[0021] Furthermore, when considering the change in thickness of the metal after being pressed, the thickness of the gold layer after being pressed, h′, is deduced based on the principle of constant metal volume:

[0022]

[0023] Then the diagonal length considering the change in gold layer thickness is:

[0024]

[0025] At this time, the calculation formula of Vickers hardness HV′ after gold spraying is:

[0026]

[0027] Beneficial effects:

[0028] This solution improves the resolution of indentation microscopy by sputtering the material surface with gold. This is because the sputtered material has excellent conductivity, which increases the signal-to-noise ratio, resulting in better imaging quality. This solves the problem of microscopy failing to capture indentations on some special materials. Furthermore, by correcting the diagonal length value, more accurate measurements can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 1 is a flow chart of a hardness testing method for enhancing indentation visibility in Example 1 of the present invention;

[0030] Figure 2 1 is a schematic top view of a Vickers indentation formed on a sample to be tested according to an embodiment of the present invention;

[0031] Figure 3 is a schematic cross-sectional view of a Vickers indentation formed on a sample to be tested according to an embodiment of the present invention;

[0032] Figure 4 Schematic diagram of the Vickers indentation observed when the sample to be tested is not coated with a gold spraying layer according to an embodiment of the present invention;

[0033] Figure 5 Schematic diagram of the Vickers indentation observed after the gold spraying layer is applied to the sample to be tested according to an embodiment of the present invention;

[0034] Figure 6 1 is a flow chart of a hardness testing method for enhancing indentation visibility in Example 2 of the present invention;

[0035] Reference numerals: Vickers indentation 1 , sample to be tested 2 , gold layer 3 . DETAILED DESCRIPTION

[0036] Example 1

[0037] Combine Figures 1 to 3 As shown, this embodiment provides a hardness testing method for enhancing indentation visibility, and the specific steps are as follows:

[0038] S1. Start the experiment by applying a load to the sample 2 to be tested using a quadrangular pyramid indenter to form a Vickers indentation 1. Observe under a microscope whether the Vickers indentation 1 is obvious. If obvious, directly measure the diagonal length and calculate its Vickers hardness value. If not obvious, proceed to the next step.

[0039] S2. Perform gold spraying on the surface of the material to be tested and calculate the thickness h of the gold layer 3;

[0040] S3. Perform the experiment again and measure the diagonal length D.

[0041] S4. Determine the ratio of the diagonal length to the thickness of the gold layer 3. If the ratio is less than a preset threshold, correct the diagonal length and directly calculate the Vickers hardness value of the measured sample using the diagonal length D obtained in step S3. If the ratio is greater than or equal to the preset threshold, correct the diagonal length obtained in step S3 and calculate the Vickers hardness.

[0042] In this embodiment, in step S1, a load F is applied to the sample 2 to be tested using a quadrangular pyramid indenter to form a Vickers indentation 1 on the surface of the sample 2 to be tested. The Vickers indentation 1 is a quadrangular pyramid-shaped groove. Figure 1 Then observe whether the Vickers indentation 1 is obvious under a microscope. To observe whether the Vickers indentation 1 is obvious, mainly observe whether the boundary of the Vickers indentation 1 is clear under a high-power microscope. You can judge based on experience. Figure 4 This is the picture before processing. The boundaries are not clear and the size cannot be accurately measured. Figure 5 This is a Vickers indentation 1 made at another location after gold spraying. It can be clearly seen that the boundary is clear and can be used to measure the diagonal length.

[0043] In this embodiment, in step S1, the calculation formula of the Vickers hardness value HV is:

[0044]

[0045] Where F is the applied load in N; D is the average diagonal length of the indentation in millimeters; ɑ is the angle of the pyramidal indenter; and 0.102 is a constant used to convert units to hardness values. This formula allows the Vickers hardness value to be directly calculated after measuring the diagonal length of the Vickers indentation 1.

[0046] In this embodiment, in step S2, the thickness of the gold layer 3 can be calculated based on the current, voltage and duration of the spraying. Specifically, the calculation formula is:

[0047] h = K·I·V·T;

[0048] Where K is a constant; I is the current of the electrospray gun, in mA; V is the cathode voltage, in kV; and T is the electrospray gun operating time, in seconds. K is related to the type of target material and working gas. For example, in this embodiment, using a gold target and air as an example, the K value is 0.07.

[0049] In this embodiment, in step S4, according to the Chinese national standard "GB / T 4340.1-2009" for Vickers hardness test, the relative error rate of the indentation diagonal length measurement should be controlled within ±0.5%. The angle ɑ of the quadrangular pyramid indenter is 136°. According to the geometric relationship, the actual error when measuring the diagonal length is Therefore, the error rate is When this value is greater than 0.5% specified in the national standard, it needs to be corrected using the correction formula. Therefore, it can be concluded that the condition for the measured indentation diagonal length to be corrected is That is, the ratio of the diagonal length to the thickness of the gold layer 3. When the diagonal error caused by the thickness of the gold layer 3 does not exceed the national standard range, directly use the measured diagonal length and substitute the diagonal length into the formula Calculated.

[0050] when When , it means that the diagonal error caused by the thickness of the gold layer 3 exceeds the national standard range, and the measured diagonal length is corrected. The correction formula for the diagonal length is: Where D′ is the corrected diagonal length.

[0051] At this time, the calculation formula of Vickers hardness value HV is:

[0052] Thus, the Vickers hardness value after the diagonal length is corrected is obtained, thereby improving the accuracy of the detection.

[0053] By spraying a gold layer 3 on the surface to be tested and then making a Vickers indentation 1, the resolution of the indentation under a microscope is improved. Finally, the Vickers hardness of the material is calculated according to the correction formula. This can solve the problem that the Vickers indentation 1 of some highly light-absorbing black materials, such as CBN and graphite, or some transparent or translucent materials, such as single crystal sapphire and SiO2, is not obvious under the microscope, resulting in the inability to measure their Vickers hardness, thereby improving the accuracy of detection.

[0054] Example 2

[0055] Combine Figure 6 As shown in the figure, since the thickness of the metal layer will change after being pressed, it is necessary to further consider the change in the thickness of the metal after being pressed. According to the principle of constant metal volume, the corrected calculation formula for the thickness h′ of the gold layer 3 after the indentation is derived as follows:

[0056]

[0057] The correction formula for the diagonal length considering the thickness change of the gold layer 3 is:

[0058]

[0059] At this time, the calculation formula of Vickers hardness HV′ after gold spraying is:

[0060]

[0061] By correcting the thickness of the gold layer 3 and the length of the diagonal line, a more accurate detection value can be obtained.

[0062] In the above embodiment, the resolution of the indentation microscope is improved by sputtering the material surface with gold. This is because the sputtered material has excellent high conductivity, which can increase the signal-to-noise ratio, thereby achieving better imaging quality. This solves the problem of some special materials not being able to capture the indentation of the microscope. Through single or multiple corrections, more accurate detection values ​​can be obtained.

[0063] It should be understood that the above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention.

[0064] The above description of the drawings used in the implementation manner only shows certain embodiments of the present invention and should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without making any creative efforts.

Claims

1. A hardness testing method for enhancing indentation visibility, characterized in that: The specific steps are as follows: S1. Start the experiment. Use a quadrangular pyramid indenter to apply a load to the sample to form a Vickers indentation. Observe whether the Vickers indentation is obvious under a microscope. If obvious, directly measure the diagonal length and calculate its Vickers hardness value. If not obvious, proceed to the next step. S2. Spray gold on the surface of the material to be tested and calculate the thickness h of the gold layer; S3. Perform the experiment again and measure the diagonal length D. S4. Determine the ratio of the diagonal length to the gold layer thickness. If the ratio is less than a preset threshold, correct the diagonal length and directly calculate the Vickers hardness value of the measured sample using the diagonal length D obtained in step S3. If the ratio is greater than or equal to the preset threshold, correct the diagonal length obtained in step S3 and calculate the Vickers hardness.

2. The hardness testing method for enhancing indentation visibility according to claim 1, characterized in that: In step S1, the calculation formula of the Vickers hardness value HV is: Where F is the applied load in N; D is the average diagonal length of the indentation in millimeters; ɑ is the top angle of the pyramid indenter; and 0.102 is a constant used to convert units into hardness values.

3. The hardness testing method for enhancing indentation visibility according to claim 2, characterized in that: In step S2, the calculation formula for the gold layer thickness is: h=K·I·V·T; where K is a constant; I is the current of the metal spraying device, in mA; V is the cathode voltage, in KV; and T is the operating time of the metal spraying device, in seconds.

4. The hardness testing method for enhancing indentation visibility according to claim 3, characterized in that: In step S4, the ratio of the diagonal length to the thickness of the gold layer is determined. When , it means that the diagonal error caused by the gold layer thickness does not exceed the national standard range, and the Vickers hardness is calculated directly based on the measured diagonal length; when When , it means that the diagonal error caused by the gold layer thickness exceeds the national standard range, and the measured diagonal length is corrected to obtain the corrected diagonal length D′.

5. The hardness testing method for enhancing indentation visibility according to claim 4, characterized in that: In step S4, when When , the correction formula for the diagonal length is: At this time, the calculation formula of Vickers hardness value HV is:

6. The hardness testing method for enhancing indentation visibility according to claim 4, characterized in that: When considering the change in thickness of the metal after being pressed, the thickness of the gold layer after being pressed, h′, is deduced based on the principle of constant metal volume: Then the diagonal length considering the change in gold layer thickness is: At this time, the calculation formula of Vickers hardness HV′ after gold spraying is:

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