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National Standard of the People's Republic of China
Metallic and related coatings -Vickers and Knoop microhardness tests
Metallic and related coatings -Vickers and Knoop microhardness tests UDC669.058
GB9T90-88
This standard adopts 1S04516-1980 (E) "Metallic and related coatings -Vickers and Knoop microhardness tests". 1 Scope of application
This standard is applicable to the Vickers and Knoop microhardness test of electroplated coatings, autocatalytic coatings, and sprayed coatings of ten metallic coatings. It is also applicable to the Vickers and Knoop microhardness test of anodized films on aluminum. The test force is lower than 10V during the test. To obtain satisfactory results, the coating must be of sufficient thickness, and it is generally advisable to test on the cross section. 2 Reference standards
GB4342 Metal microhardness test method CB64162 Metal and other inorganic covers cross-section original microscope measurement method GB817) Numerical rounding rules
3 Test principle
This test is to use a specified test force, a rigid indenter with a certain shape to press into the measured covering layer at an appropriate pressing speed, maintain the test force for a specified time and then remove the test force, then measure the diagonal length of the indentation, and substitute the diagonal length into the hardness calculation formula (see Chapter 4) or look up the table according to the diagonal length (see Appendix A for Knoop microhardness values, and Appendix A and Appendix B of GH4342 for Vickers hardness values), and finally obtain the Vickers and Knoop microhardness values. 4 Symbols and explanations
4.1 Symbols and explanations are shown in Table 1 a
Approved by the State Administration of Technical Supervision on September 5, 1988 and implemented on September 1, 1989
Disk unit
CB9790-88
Test force
Arithmetic
Average length of the two diagonals of the indentation d and d
Vickers hardness value:
0.102 ×F
1.854×10m
×_0.102 ×F
Length of the long diagonal of the indentation
Knoop hardness value:
14.229 × 10f
: 1. is the area of the inclined surface of the indentation, A, is the area of the projection of the indentation, and its unit is Xmm, and its value corresponds to the diagonal value of the ten indentations. 5 Equipment
5.1 Test instrument
The test instrument is a microhardness tester.
The hardness tester is used to slowly and vertically press the indenter into the surface to be measured, and make the indenter stay there for a specified time according to the specified test force.
5.2 Indenter
6.2.1 Shape and size
5.2.1.1 Vickers indenter
The indenter is a diamond regular tetrahedron (see Figure 1), and the vertex angle between its two opposite faces should be 136\±0.25\. This angle should be verified using a tool microscope with a magnification of 50 times or more. The approximate relationship between the diagonal lines d\ and d, and the indentation depth 1 is; d'+d\
The four axes facing the indenter should have the same inclination (within the error of 0.3\) and intersect at one point. Under normal conditions, the aperture figure at the intersection is as shown in Figure 2, and its top transverse edge should not be greater than 0.5um. 5.2.1.2 Knoop indenter
Vickers indenter
GB 9790-88
Figure 2 Vickers indenter top edgebZxz.net
The indenter is a diamond pyramid with a drop-shaped base (Figure 3). The vertex angle between the two opposite edges in the length direction should be 172.5+0.08°, and the vertex angle between the two opposite edges in the width direction should be 130\±0.08°. This angle should be verified using a microscope with an aperture magnification of 50 times or more.
The four axes facing the pressure head should have the same inclination (within the error of 20.2\) and intersect at one point. The enlarged figure of the intersection under normal conditions is shown in Figure 4. The cross edge of the top end should not be greater than 1 twist. Figure 3 Knoop pressure head
5.2.2 Surface condition
GB9790-86
Natural can USA
Dance Union
Figure 4 Knoop compaction top cross edge
The pressure head surface should be within 0.15t1m from the top end. When magnified by a microscope 400 times or more, there should be no cracks, sand gums, corners and scratches. The surface roughness R should not exceed 10.025m. Check the pressure head regularly. When removing foreign dirt, the method is to press the pressure head into copper or steel with lower hardness to remove it, or it can be immersed in a solvent that is harmless to the equipment for cleaning. If cracks, breakage or loosening occurs during the test, it should be replaced immediately. The cracks and other defects of the indenter can often be detected by checking the shape and symmetry of the indentation. 5.3 Standard hardness block
Standard hardness blocks should be used to calibrate the microhardness tester and measurement operation. The hardness value range of the standard hardness block used should be consistent with the hardness value range of the cover to be tested. The standard hardness block is a fine-grained metal and has a known average hardness value measured under the specific test force specified by the manufacturer of the microhardness tester or microhardness tester. The test force for verification should be consistent with the specific test force used by the standard hardness block used.
6 Factors affecting hardness accuracy
Test force
Compared with the macro hardness value obtained by the tester at 10N, the microhardness determination is more affected by the test force. Comparable hardness values can only be obtained when the test force and holding time are the same. The anisotropy of the material also affects the hardness value, so it is necessary to specify the test position of the specimen. To obtain the most accurate hardness value of the coating, the maximum test force appropriate to the coating thickness should be used (see Figure 5 and 7.2.1, 7.2.2, 7.3). Only by using the same test force can comparable results be obtained. The following test forces should be used for the coating: Materials with low hardness (30 HV), precious metals and their alloys, and thin coatings - hard oxide film on lead - 0.490 V (0.050 kgf) Non-precious metal materials with high hardness (3 HV):
01.981 N (0.100 kgf):
0.245 N (0.025 kgf):
6.2 Speed of the indenter
GB 9790—88
Figure 5 Relationship between the maximum available test force of the Vickers indenter and the thickness of the coating
If the speed at which the indenter contacts the surface to be tested is too large, the hardness value obtained will be too low! The speed at which the test piece is in contact with the test piece should be reduced to a reasonable level that does not result in a high hardness value. The appropriate speed is 15 to 70 μm/s. To determine whether the speed used is correct, the test should be repeated by gradually reducing the speed. The speed at which the hardness value does not change significantly when the speed is lower than a certain value is the speed that should be obtained under the selected test force. The above test should be carried out using the same material and test force as the actual hardness determination. The holding time of the test force is normally 10 to 155. If the holding time is different, the actual holding time should be stated in the test report in accordance with 8.2. If the holding time of the test force is less than 1 μs, the size of the indentation may be related to the holding time, and the hardness may be too high. For some materials that creep at room temperature, the holding time of the test force has a greater impact. 6.4 Vibration Vibration is a serious source of error regardless of the test force used, and this effect is more obvious when the test force is small. If vibration exists, the hardness value obtained will be too low. This source of error can be detected by comparative measurement using a standard specimen with a hardness close to that of the test surface (see 5.3). To reduce the impact of movement, the specimen can be mounted on a rigid support table. 6.5 Surface condition of the specimen
6. 5.1 Roughness
GB9T90—88
If the surface of the specimen is rough, it is impossible to accurately measure the length of the diagonal of the indentation, so the microhardness is generally measured on the cross section of the specimen. The specimen must be chemically, electrolytically or mechanically polished. During mechanical polishing, local heating or work hardening should be minimized as much as possible, otherwise the original hardness value will change. Because the surface of the sprayed metal layer is rough, such a coating should generally be tested for microhardness on the cross section. If the surface has been ground and polished, it can also be determined on the surface. 6.5.2 Surface ratio
Surface ratio will bring certain errors to hardness determination, and this error increases with the decrease of curvature radius. The hardness indication on the convex surface is higher than the actual value, and the hardness indication on the convex surface is lower than the actual value. If the Vickers hardness must be measured on the surface of the test specimen with a large curvature, the influence of the curvature can be eliminated by using the correction factor (see Appendix of GB4342). The hardness value is corrected by the correction factor obtained by measuring the test specimen with a curvature of the same diameter as the test object, with a hardness roughly equal to that of the test object and with known hardness. If the part is cylindrical, the long diagonal line of the indenter is adjusted to the axis direction of the cylinder. 6.6 Test specimen orientation
6.6.1 Adjustment of the test surface
In the case where the test surface is not perpendicular to the axis of the indenter, the measurement is invalid. If the material to be tested is isotropic, and the two sides of the same diagonal line are obviously unequal, it indicates that the test surface is not perpendicular to the axis of the indenter. 6.6.2 Surface inclination
If the test surface tilts during the test, the indentation will be deformed. Therefore, the test sample should be fixed on the stage or the test tool so that the surface to be measured is perpendicular to the direction of the test force. This state should be maintained throughout the test. 6.7 Brittle materials
If cracks appear in the test sample during the test, the true hardness value cannot be obtained. The problem of indentation is usually solved by reducing the test force.
8.8 Microscope resolution
When the magnification is 100 times or more, the non-abrasive objective lens used can achieve the measurement accuracy specified in Article 7.5. When using the lighting system, the direction of the sample to be measured should be at an angle to the optical axis, and the size of the illumination beam should be adjusted through the field of view light bar so that the reflected beam illuminates more than two-half of the field of view, but is always limited to not passing through the entire field of view. Using a green filter, the measurement can be carried out within the maximum discrimination ability of the human eye. 6.9 Position of long marks
The size and shape of the indentation are affected by other materials near the coating. For example, if the indentation is close to the substrate and the substrate is softer than the coating, the hardness value obtained may be lower. If the indentation has an abnormal shape, it indicates an error due to this reason (see 7.2.1, 7.2.3 and 7.3).
Determination process
.1 Selection of test force
Unless otherwise specified or selected by the technical principle, the appropriate test force of 61 specifications shall be used. If, for some reason, other test forces are used, the hardness values obtained may be significantly different from the hardness values obtained using the specified test forces, but the results can be used for comparison and reference. 7.2 Determination of the cross-section of the covering layer
7.2.1 Micro-covering layer thickness
When using a test indenter, the covering layer should be thick enough so that when the test surface is correctly positioned and one diagonal of the indentation is perpendicular to the edge of the covering room, the indentation can meet the following requirements! 9, The distance between the corner of the pressure gauge and the red edge of the coating layer should be at least one-half of the diagonal line. The lengths of the two diagonals should be roughly equal, and the difference should be within 5%. C: The four sides of the pressure gauge should be basically equal, and the difference should be within 5%. When using the Knoop pressure gauge, the thickness of the soft coating (gold, silver, etc.) should be at least 40um, and the thickness of the hard coating (nickel, cobalt, iron) and hard precious metals and their alloys should be at least 25μm. T.2.2 Sample preparation
GB 9790---88
Cut the sample and cover it with a metal layer with a thickness of not less than 12 μm. The hardness of the metal and the sample should be approximately the same and have good contrast.
In accordance with the relevant provisions of IEC 6462, the sample shall be clamped, ground, polished and etched. During this process, the hardening must be reduced to a minimum (see 6.5.1).
7.2.3 Indentation
The diagonal of the indentation shall be in the middle of the overburden and halfway along the edge of the overburden. The diagonal of the Vickers positive mark shall be approximately 90° to the interface between the overburden and the substrate. The distance between the centers of the two indentations shall be at least 2.5 times the length of the measured diagonal. When measuring cloud-like materials, the interface shall be regarded as the edge of the indentation. .3 Measurement on the surface of the covering layer
Before carrying out hardness measurement on the surface of the covering layer, the thickness of the covering layer should be measured using relevant standards such as B6462. The test force used should be such that the depth of the indentation is less than one tenth of the hardness of the covering layer (see Figure 5, i.e., for Vickers hardness determinations, the thickness of the covering layer should be at least 1.4 times the diagonal length of the indentation, and for Knoop hardness determinations, the thickness of the covering layer should be at least 0.35 times the diagonal length of the indentation. Satisfactory test results can only be obtained with thinner coverings when the silica content of the base and covering layers is similar. 7.4 Temperature The test shall be carried out at 23 ± 5°C. If the test is not carried out at this temperature, the actual temperature during the test shall be stated in the test report (see Chapter 9). 7.5 Optical hardness measurement The hardness mark shall be measured in the center of the field of view. The indentation area shall not exceed one tenth of the total field of view. The indentation shall be measured with a micrometer auto-mirror or, preferably, with a screw micrometer H-mirror. The measuring cursor that determines the indication should always be moved to the measuring part from the same direction, and the reading should always be taken with one edge of its scale line as the reference. Use a standard ruler with an accuracy of not less than 10%. 1um and 100% equal divisions to calibrate the spiral micrometer and the mirror. To achieve a measurement error of 6% or less, the length of the indentation diagonal should be not less than 16um. 7.6 Calculation
When calculating the Vickers hardness, d should be the arithmetic mean of the lengths of the two indentation diagonals measured separately. If the measured material is an amorphous or fine-grained material, the hardness measurement result is considered valid only when the difference in the length of its two diagonals is less than 10% of the longer diagonal.
At least five indentations should be taken for each sample, and the average hardness value should be calculated. When the hardness value is equal to or greater than 100, adjust Round to an integer, round to one decimal place when between 10 and 100, and round to two decimal places when less than 10. The rounding method shall be in accordance with GB8170. 7.7 Test sample
If the thickness of the product coating does not meet the requirements and the hardness cannot be measured, a test sample can be made under conditions close to production conditions for hardness measurement. The hardness value obtained in this way may not reflect the true hardness of the product, but if such a hardness value corresponds to other properties of the coating, such as wear resistance, these numbers may be useful. These numbers can be effectively used to control the electroplating bath solution, especially for layers whose virtual hardness is very sensitive to the bath solution and other parameters, such as the bath solution for gold plating. When making test samples, all conditions, such as current density, temperature, stirring and bath composition, should be as close as possible to the actual hardness of the product. It can be close to the conditions of international products. B. Result representation
8.1. The test results shall record the fluctuation range of hardness values obtained by at least five indentations (highest value and lowest value), and also record the average hardness value.
8.2. When expressing the test results, the symbols for Vickers hardness and IK are HV and IK respectively. The hardness range measured is listed before this symbol, and the number attached after it indicates the test force (in Newton). If the test force is not maintained for 10 to 15 seconds, add a slash and the holding time after the test force value.
For example: 310 to 320HV0.981 means that the Vickers microhardness value measured by using a test force of 0.981N (.1G0kgf) and maintaining it for 1 to 15 seconds is 310320
GB4T$O table.
67~70HK0.245/20 means that the Knoop microhardness value measured by holding the test force of 0.245N (0.025kgf) for 20s is 6770.
9 Test report
The test report of microhardness measurement shall include the following contents: a. The number of this national standard,
, use appropriate symbols and explain the microhardness value obtained (see Section 4) c. Whether the hardness measurement is carried out on the cross section of the covering layer or on the covering pressure surface! d. Explain the special conditions in the test, such as non-normal temperature (see 7.4), non-standard holding time of the test force (see 6,3), etc.!
e: Other operating conditions that are arbitrarily selected outside the provisions of this standard and have an impact on the measurement results. Mark for
GB9790-88
Appendix A
Table of Knoop microhardness values with a test force of 1gf (supplement)
For products with a line measurement accuracy of .1 micrometers, the microhardness value is 0.2
Indentation for
GB 9790te
Diagonal measurement accuracy of 0.1um, the microhardness value is 0.3
Indentation for
GH9790--88
Diagonal measurement accuracy of 0.1um, the microhardness value is 0.3
Indentation for
GB 9790—88
Diagonal measurement accuracy of 0.1μm Nutian hardness value 0.3
11,449
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