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GB/T 33819-2017 English PDF (GBT33819-2017)

GB/T 33819-2017 English PDF (GBT33819-2017)

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GB/T 33819-2017: Hard metal -- Palmqvist toughness test

GB/T 33819-2017
Hardmetals.Palmqvist toughness test
ICS 77.160
H16
National Standards of People's Republic of China
Cemented carbide Pap test
(ISO 28079.2009, IDT)
Released on.2017-05-31
2017-12-01 implementation
General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China China National Standardization Administration issued
Foreword
This standard was drafted in accordance with the rules given in GB/T 1.1-2009. This standard uses the translation method equivalent to ISO 28079.2009 "hard alloy Pap value toughness test". For ease of use, this standard makes the following editorial changes to ISO 28079.2009. --- For ease of use, HV(P) in Chapter 3 adds N/mm2 as a unit;
--- Will be 6.2 W, corrected to WG;
--- Added the note in Appendix A.
This standard was proposed by the China Nonferrous Metals Industry Association. This standard is under the jurisdiction of the National Nonferrous Metals Standardization Technical Committee (SAC/TC243). This standard was drafted. Xiamen Tungsten Industry Co., Ltd. (Technology Center), Xiamen Golden Heron Special Alloy Co., Ltd., Nanchang Cemented Carbide limited liability company.
The main drafters of this standard. Chen Dongyu, Zhu Guirong, Nie Hongbo, Zhang Shouquan, Sun Xiaotong, Zhang Yuqi. Cemented carbide Pap test
1 Scope
This standard specifies the method for testing the Barcolage toughness of cemented carbide and cermet by indentation at room temperature. This standard applies to the testing of metal-bonded carbides and carbonitrides (often referred to as cemented carbide or cermet). The toughness is calculated by testing the total length of the cracks emitted from the apex angles of the Vickers hardness indentations. The test procedure proposed in this standard is usually It is carried out at room temperature and can be extended to test at high or low temperatures if agreed. The test procedure proposed in this standard is used in the routine laboratory air ring. Conducted in the environment; not in corrosive environments such as strong acid or seawater environments. 2 Normative references
The following documents are indispensable for the application of this document. For dated references, only dated versions apply to this article. Pieces. For undated references, the latest edition (including all amendments) applies to this document. ISO 3878 Hardmetal Vickers Hardness Test Method (Hardmetals-Vickershardnesstest) 3 symbols and units
The following symbols and units apply to this document.
A. Constant 0.0028.
d. average of the indentation diagonal, mm.
D1, d2. single indentation diagonal value, mm.
E. Young's modulus, N/mm2.
F. indentation load (toughness calculation), N.
G. strain energy release rate, J/m2.
H. hardness, kgf/mm2.
HV(P). Vickers hardness at load P (kgf), kgf/mm2 or N/mm2.
Kic. Plane strain fracture toughness, MN/m3/2.
Ln. crack length at the top corner of the indentation, mm.
P. indentation load (Vickers hardness method), kgf.
T. total crack length, mm.
Tn. the crack length from vertex to vertex, mm.
WG. Barcolt toughness, N/mm or J/m2, 1 N/mm = 1000 J/m2.
WK. Pap fracture toughness, MN/m3/2.
ν. Poisson's ratio.
4 sample and sample preparation
4.1 Sample size and sampling
This standard has no special requirements on the shape of the sample, as long as a flat and parallel set of tests can be prepared on the sample to meet the indentation test. Sample (test surface and back). Pressurized hot inlays can produce parallel planes, while cold inlays cannot produce parallel planes. Parallel sample faces are easily obtained with a diamond cutter or an electric spark cutting device. The surface of the sample after cutting should be polished. Suggest A 0.2 mm thick material should be removed prior to final polishing to ensure a representative test surface. For example, cemented carbide Vickers hardness test mark The standard (see ISO 3878) specifies the removal of 0.2 mm.
Note. The thickness of the test piece recommended in M. Heinonen (UNMIST) [19] is at least 10 times the crack length. Because the stress state of the sample depends on For materials that support indentations and their cracks, too thin samples may not give representative results. Using a thermosetting resin inlaid sample, it can be square A flat and parallel test surface is produced directly. However, the disadvantage is that it is subsequently subjected to an annealing treatment (usually heat treatment at 800 ° C in a vacuum) 1h) To eliminate surface residual stress, the sample should be taken out of the resin before entering the annealing furnace. 4.2 Sample surface preparation
The flatness of the surface of the specimen is a basic requirement for the shape of the indentation. When testing, it can be confirmed by measuring the diagonal length of the Vickers indentation. The flatness of the surface of the sample. If the difference in the length of the two diagonals of the indentation exceeds 1%, the surface of the sample is not flat, and the test result invalid.
In view of the fact that the silicon carbide grinding wheel introduces greater residual stress, the method requires a metal bonded 40 μm particle size diamond wheel. The surface of the sample is ground in the presence of a grinding fluid. Then the grinding plane is polished, it is recommended to use at least three abrasive grains Polishing, first with a minimum particle size of 30μm diamond abrasive, followed by 6μm and 1μm polishing, the final stage needs to use no flannel.
Note. If the final polishing stage is long enough to remove all damage from the flat grinding, this process can produce an unstressed surface. however, It is difficult to prove the above situation because there is not a large amount of test data comparing only the polished and post-polished samples. 4.3 Surface condition of the sample
Stable test results require no residual stress on the sample surface (see Reference [8]). Polishing the method of stress removal requires a cumbersome system Sexual measurements to ensure that the surface of the specimen is unaffected by stress is almost impossible in practice. Usually, the surface of the sample is polished to meet the micro The metallographic structure of the structure was observed, and then the residual stress was removed by vacuum annealing at 800 ° C for 1 h according to Exner's research results [8]. If not Testing with an annealed polished surface should be noted in the test report. Note. New materials developed in recent years with finer WC particle size (measured by linear intercept method with a particle size of less than 0.8 μm) There can be higher residual stresses. Eliminating the residual stress of these materials may require longer annealing times or higher annealing temperatures. Adopt higher The annealing temperature may be a better choice, but further research is needed. The annealing step increases the complexity of the sample surface preparation process, but it Ensure that there are no residual stresses on the surface.
5 instruments
5.1 Overview
The test equipment used for the indentation test of the specimen shall be calibrated in accordance with national standards. The shape of the indentation should be checked regularly to determine Whether the indenter is damaged. The diagonal and crack length can be measured in the microscope attached to the hardness tester, or a separate microscope can be used. These dimensions are measured, but the measuring device should be calibrated using the appropriate standards. 5.2 Indentation
The test method and test equipment for indentation shall be in accordance with the requirements of ISO 3878. Diamond indenters should be standard. 5.3 Indentation and crack measurement
The indentation diagonal and crack length were measured using a metered microscope. It is also possible to project an image onto the screen and follow the relevant standards. The stage micrometer is used for calibration.
6 Test steps and test conditions
6.1 Indentation preparation
The indentation is made using a static load hardness tester, and the hardness tester used should be calibrated at least once a year. This standard recommends the use of Vickers diamond indenter Indentations are made at a single load (rather than a series load). The load for the indentation shall be 30 kgf, and when there is no visible crack under this load, Increase the load to 100kgf. Sometimes, there is no visible crack under 100kgf load, unless there is more in-depth research verification, this standard recommends Measurement results with more than 100kgf are invalid. When measuring, first two indentations should be made, and the toughness values calculated by the two should be compared. Order, in accordance with the uncertainty of measurement (see Chapter 8), consider the two test results acceptable. If the difference between the two exceeds uncertainty For the degree, the third indentation should be added and the test results are expressed as the average with standard deviation. If two test values are uncertain in measurement Within the sex, the results are expressed as the mean without standard deviation. In addition, a series of loads can be used to obtain the indentation, and the toughness of the material can be calculated by plotting the relationship between the load and the total length of the indentation. If you use this method to obtain WG and WK values, you should indicate this in the test report. 6.2 Indentation and crack length measurement
This standard recommends the use of optical measurement of the diagonal and crack length of the indentation (as shown in Figure 1), the magnification should be at least 500 times, and measured Each magnification used in the measurement is corrected.
If you have a suitable microscope, you can take pictures of indentations and cracks or project their images onto the measurement screen. Measure and record two Indentation diagonal length. At 500 times magnification, if the difference between the lengths of the two diagonals exceeds 2 mm, it means that the sample is not flat enough and needs to be re-applied. experimenting.
This method recommends two methods for measuring crack length. The test results are independent of the crack length measurement method (see Reference [28]), The next two methods can be used.
a) Method A.
The distance from the end of one crack to the end of the other crack in the two diagonal directions is measured, and the total crack length is two The sum of the values minus the sum of the diagonal lengths of the indentations (see Figure 1). Note. This method is not feasible if the magnification is 500 times, because the distance from one crack end to the other end of the crack is usually too long. A field of view cannot be fully presented.
b) Method B.
At 500 times, the distance from each vertex of the indentation to the end of the crack was measured to obtain the length of each crack. Crack length The total crack length can be obtained by adding. If the starting point of the crack does not coincide with the apex of the indentation, then the crack must be along the edge of the indentation. The crack length is measured at the starting place.
The indentation loading P is usually 30 kgf.
The following is an alternative method for calculating the crack length ln and toughness WG (as shown in Figure 1). 1) Optional Method 1.
i) Measure the distance between the ends of the crack.
6.3 Test validity
If there is more than one crack from the apex of the indentation, the indentation should be discarded and the test is invalid. If the total length of the crack is less than 40 μm, it is considered that there is a large uncertainty in the test result, which should be specifically noted in the test report. Note. For a load of 30 kgf, the material with a hardness of 1000 HV30 corresponds to a toughness value WG of 7360 N/m (or WK of about 25 MN/m3/2). These hard Materials with a degree of 1000 HV30 may have a coarse-grained microstructure, that is, the length of the individual cracks at each vertex of the indentation does not exceed 1 or 2 grain sizes. The crack is too short to ensure that the crack value sampling result is representative of the entire volume of the cemented carbide sample. Under the load of 30kgf, if the difference between the diagonal lengths of the two indentations exceeds 4μm (4μm is 2mm at 500x magnification), It indicates that the surface of the sample is not flat enough and the test is invalid. 7 analysis
7.1 Vickers hardness
The average of the two diagonal readings is divided by the calibration value at that magnification and converted to d. Hard alloy Vickers hardness HV meter The formula is as follows.
The Vickers hardness values of the 30 kgf and 100 kgf loads are represented as HV30 and HV100, respectively. Note. Various hardness standards are being converted to N/mm2 instead of kgf/mm2. Currently, the international standard method for Vickers hardness testing (ISO 6507-1) is expressed in kgf. So this practice is retained in this standard.
The hardness value is only reserved to an integer number, for example. greater than 1000 HV is 4 significant digits; less than 1000 HV is 3 significant digits. 7.2 Resilience
Two different toughness values can be calculated, namely the Barcolt toughness WG and the Barcolt fracture toughness WK. The following is the formula for calculating the Barcolt toughness, Method A (single indentation load). For Method B (multiple load values), the ratio F/T is the reciprocal of the slope of the line fitted to the total length of the crack and the loaded value. HV unit is N/mm2 and the A value is 0.0028.
If two indentations or specimens are prepared, calculate two values and report the average; if three or more indentations or specimens are obtained, take Its mean and standard deviation. The result should retain three significant figures. 8 Measurement uncertainty
The ability of the Pap test method to distinguish the toughness of various materials depends on the hardness of the material. For a hardness of.2000 HV, the uncertainty is ±10N/mm; for hardness 1500HV, the uncertainty is ±110N/mm; for the hardness of 1250HV, the uncertainty is ±550N/mm.
9 test report
The test report should include the following.
a) the standard number;
b) the type and condition of the material;
c) identification of the sample;
d) the sampling position and direction of the sample;
e) surface preparation method;
f) indentation load;
g) analytical methods;
h) the form of the form or the result of generating a computer file;
i) effectiveness assessment;
j) various operations not within the limits of this standard;
k) Various details that affect the experimental results.

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