Metallic and oxide coatings; Measurement of coating thickness; Microscopical method
Some standard content:
National Standard of the People's Republic of China
Metallic and oxide coatings
Metallic and oxide coatings -- Measurement of coating thickness - Microscopical method UDC 689.058: 531
.717.1
GB 6462—86
This standard specifies the method for cross-sectional microscopic measurement of the local thickness of metal coatings and oxide coatings using a metallographic microscope. This standard can also measure the local thickness of glaze or porcelain coatings and the thickness of thin films. The absolute accuracy of the measurement using a metallographic microscope can reach 0.8μm.
This method can be used as an arbitration method for the measurement of the thickness of metal coatings and oxide layers. This standard is equivalent to the international standard IS01463-1982 "Method for microscopic measurement of cross-sectional thickness of metal and oxide coatings" Note: Local thickness: The specified number of measurements is made in the specified part of the sample, and the thickness is taken as the average value. 1 Method Overview
Cut a sample from the specified position on the test piece, mount it, and then grind, polish and diffusely etch the cross section appropriately. Use a calibrated ruler to measure the thickness of the cross section of the coating. 2 Factors affecting measurement accuracy
2.1 Surface roughness
If the surface of the coating or the substrate of the coating is rough, one or two interface lines in contact with the cross section of the coating are also irregular, so that accurate measurement cannot be made [see A.4 in Appendix A (Supplement)]. 2.2 Slope of the cross section
The cross section must be perpendicular to the coating to be measured. If there is a deviation, the measured thickness will be greater than the true thickness. If the verticality deviation is 10°, the measured value will be 1.5% greater than the true thickness.
2.3 Deformation of the blue coating
During the process of mounting the specimen and preparing the cross section, excessive temperature and pressure will cause deformation of the soft or low melting point coating. When preparing the cross section of brittle materials, excessive grinding will also cause deformation. 2.4 Chamfering of the coating edgewww.bzxz.net
When preparing the specimen, improper mounting, grinding, polishing and etching will cause the edge of the cross section of the coating to be chamfered or uneven. The true thickness cannot be obtained by microscopic measurement. Therefore, before mounting, the specimen is often plated to minimize the edge chamfer (see A.1).
2.5 Additional coating
In order to protect the edge of the coating when preparing the cross section and avoid measurement errors, additional coating should often be applied to the specimen. Before additional coating, care should be taken not to damage the coating to be measured and to avoid thinning the coating due to degreasing, pickling or alloying. 2.6 Etching
Proper etching can produce a dark and clear interface line on the interface line of two metals; excessive etching will make the interface line unclear or the line wider, causing measurement errors.
2.7 Covering
National Bureau of Standards 1986-06-11 Issued
1987-05-01 Implementation
GB6462-86
Improper polishing can cause one metal to cover another metal, causing the real interface line of the two metals to be blurred or irregular, and fail to meet the requirements of straightness and clarity. In order to confirm whether there is covering, polishing, etching and thickness measurement can be repeated. If the measurement results have obvious changes, it means that there is covering in the measurement. 2.8 Magnification
For any coating thickness to be measured, the measurement error generally increases with the decrease of magnification. Generally, when selecting the magnification, the field of view diameter should be 1.5 to 3 times the thickness of the coating. 2.9 Calibration of the teaching stage micrometer
If the teaching stage micrometer is not calibrated more strictly, it will produce an error of one percent, and the error of the micrometer calibration will be reflected in the measurement of the sample. The commonly used calibration method is: take the full scale length as the correct, then use the screw micrometer to measure the length of each grid, and calculate the scale value of each grid according to the ratio. 2.10 Calibration of the eyepiece micrometer
The screw micrometer can provide accurate measurement results. The calibration of the eyepiece should be higher than the measurement accuracy, and the calibration of the eyepiece should be completed by the operator who measures the thickness.
The repeated calibration error of the eyepiece micrometer should be less than 1%. The two lines used to calibrate the stage micrometer should be within 0.2 μm or 0.1% of each other (some stage micrometers have manufacturer-verified accuracy; some have errors of 1 or 2 μm at 2 mm and 0.4 μm or more at 0.1 mm and 0.01 mm. If the stage micrometer has not been verified for accuracy, it should be calibrated).
The nonlinear characteristics of the eyepiece micrometer can also cause errors of up to 1% at short distances. 2.11 Alignment
The return clearance of the eyepiece micrometer can also cause measurement errors. This error is eliminated if the alignment process is performed in the same direction.
2.12 Consistency of Magnification
The magnification may not be consistent across the field of view, so errors will occur if the interface is not centered on the optical axis and the same section of the field of view is calibrated and measured.
2.13 Lens quality
Unclear images are also a factor that can lead to incorrect measurements. Poor quality lenses make it difficult to make accurate measurements. Monochromatic light beams can be used to improve image clarity.
2.14 Eyepiece orientation
The eyepiece alignment line must be perpendicular to the interface line of the cross section of the cover layer during alignment. If it deviates by 10', the error is 1.5%. 2.15 Mirror cartridge length
Changes in the mirror cartridge length will cause changes in magnification. If this change occurs during calibration and measurement, the measurement will be inaccurate. The mirror cartridge length may change when the eyepiece is repositioned in the cartridge, when the eyepiece cartridge focal length is changed, and when the microscope is fine-tuned.
3 Preparation of cross sections
In the process of mounting, grinding, polishing and etching the sample, the requirements are as follows: 3.1 The cross section is perpendicular to the covering layer;
3.2 The surface of the covering layer is flat, and the entire width of its image should be focused at the same time under the magnification taken during measurement; 3.3 The deformed material caused by cutting and preparing the cross section should be removed. 3.4 The interface on the cross section of the covering layer can be clearly determined only by the contrast of appearance or by a thin line that is easy to distinguish. In addition to the above content, the method of preparing the cross section is described in detail in Appendix A. -Some typical etching agents are listed in Appendix B (Supplement)
GB6462-86
4.1 Attention should be paid to the influence of various factors listed in Chapter 2 and Appendix A on the measurement. 4.2 Calibrate the microscope and its measuring device with a verified or calibrated stage micrometer. 4.3 Measure the width of the cross section image of the covering layer, and measure at least five points along the length on the microscopic section. 5 Accuracy requirements
The use and calibration of the microscope and its accessories, as well as the preparation method of the cross section, should be selected so that the error of the coating thickness to be measured is within the larger value of 1μm or 10% of the true thickness. Under good conditions, using a metallographic microscope, this method can obtain an absolute measurement accuracy of 0.8μm. When the thickness is greater than 25μm, the reasonable error is 5% or less. Test report
The test report should include the following:
a. The location of the cross section on the plated part; b.
The thickness measured at each point (see 4.3) in microns, if greater than 1mm in millimeters: local thickness, the arithmetic mean calculated from the measured values; the length of the distribution of the measuring points on the cross section.
GB6462-86
Appendix A
Guidelines for cross-section preparation and thickness measurement (supplement)
The preparation of the specimen and the measurement of the coating thickness are greatly affected by the various processes. There are many applicable process methods, and it is unreasonable to stipulate that only one process method should be adopted. However, it is impossible to include all the applicable process methods. The techniques described in this appendix are only a guide. They are for use by metallographers when measuring the coating thickness. A.1 Mounting
In order to prevent the cross-section edge of the coating from being chamfered, the outer surface of the coating should be supported, and no gap should be left between the coating and the support. For this purpose, a metal with a hardness close to that of the coating is often plated on the specimen as an additional coating with a thickness of at least 10um. For hard, brittle coatings (such as oxides or chromium coatings), the specimen can be tightly wrapped with a layer of soft aluminum foil before mounting. If the coating is soft, a softer metal coating cannot be added, because the softer the metal, the easier it is to be polished away. Cadmium should not be added to zinc and cadmium coatings because copper will be dissolved and deposited on zinc and cadmium coatings during etching. Cadmium should be added to zinc coatings and vice versa.
A.2 Grinding and polishing
It is critical to keep the cross section of the inlay perpendicular to the covering layer. When inlaying plastics, several thin sheets of similar metal must be clamped at the edge of the outer surface.
Before grinding, a reference mark is engraved on the edge of the inlay, so that the inclination from the horizontal can be easily determined. The grinding operation direction is at a 45-degree angle to the surface of the covering layer. Each time the sandpaper is changed, the grinding direction should be 90° to the previous direction. The grinding time should not be too long and the pressure should be kept to a minimum.
Suitable sandpaper and lubricant should be used for grinding the inlaid specimen. Generally, 100 or 180 sandpaper, water and colorless alcohol are used. When all deformed parts are ground off and the true wheel of the specimen is revealed, 240, 320, 500, and 600 sandpaper can be used for grinding in turn. Each grinding time should not exceed 30 to 40 seconds, and finally polish on the polishing disc for 2 to 3 minutes. The polishing disc is adhered with a grinding paste with diamond grains of 4-8uⅢ, and colorless alcohol is used as a lubricant to eliminate scratches for easy observation. If the surface polishing level is particularly high, a grinding paste with diamond grains of about 1μm can be used for polishing. When preparing very soft metal samples, sand grains are easily embedded in the metal surface during the grinding process. At this time, the sandpaper should be completely immersed in the lubricant, or a circulating lubricant should be used to minimize the embedding amount. If the sand grains are already embedded, the method of removal is: after grinding and before diamond polishing, use a light short-time fine polishing, or perform a few etching and polishing alternating cycles. A. Diffuse etching
In order to increase the contrast between metal layers, remove the traces of metal covering and show a thin line at the interface of the cover layer, the method of diffuse etching is usually appropriate. Some typical etchants are listed in Appendix B. A.4 Measurement
The measuring instrument generally uses a screw micrometer or an eyepiece micrometer, the latter of which has poor accuracy. The measurement method of projecting the image onto a frosted glass plate is usually unsatisfactory because the image clarity and calibration readings are relatively poor. The measuring instrument should be calibrated at least once before and after the measurement. The calibration and coating measurement should be completed by the same operator. The stage micrometer and coating should be placed in the center of the field of view. Each measurement point should be measured at least twice. The measurement values are averaged. For strict arbitration measurements, the best technology and high-precision instruments must be used, and the specimens with smooth coating and substrate surfaces must be prepared. All steps in preparing cross-sections and coating thickness measurements, from coarse sandpaper grinding to measurement, should be performed at least twice. The reproducibility is within 2% or 0.5μm.
GB6462—86
Some microscopes are prone to spontaneous movement of the stage relative to the objective lens, generally caused by uneven thermal effects of the light source. This movement will cause measurement errors when medium and high magnifications are selected in thickness measurements. The method to eliminate the error is to measure twice for each interval, once from left to right and once from right to left, so as to minimize the error and complete the whole measurement quickly. 324
Etching agent
GB 6462--86
Appendix B
Some typical etching agents used at room temperature
(Supplement)
Etching agent
B.1 Nitric acid solution (specific gravity 1.42g/mL): 5mL95% ethanol (V/V) solution: 95mL
Ferric trifluoride hexahydrate (FeCl.6H0): 10gHydrochloric acid solution (specific gravity 1.16g/mL): 2mL95% ethanol (V/V) solution: 98mL
Nitric acid solution (specific gravity 1.42g/mL): 50mLB.3
Glacial acetic acid: 50mL
Ammonium persulfate: 10g
Ammonium hydroxide solution (specific gravity 0.8g/mL): 2mLDistilled water: 90mL
Nitric acid solution (specific gravity 1.42g/mL): 5mLB.5
Hydrofluoric acid solution (specific gravity 1.14g/mL): 2mLDistilled water: 93mL
Chromic anhydride (Cr0,): 20g
Sodium sulfate: 1.5g
Distilled radium water: 100g
Hydrofluoric acid solution (specific gravity 1.14g/mL): 2mLB.7
Distilled radium water: 98mL
Note: Be careful in the preparation, use, storage, transportation and removal of these etchants. Scope and description
For nickel or chromium coatings on steel. Etch steel. This etchant should be newly formulated.
For gold, lead, silver, nickel and copper inlays on steel, copper and copper alloy substrates.
Etch steel, copper and steel alloys.
For multi-layer nickel plating on steel and copper alloys, showing structure and distinguishing each layer of nickel. Etch nickel, over-corrosion of steel and pot alloys. For tin and pick alloy coatings on steel and copper alloys. Etch copper and steel alloys.
This etchant should be newly formulated. ||t t||For nickel and pot plating of aluminum and aluminum alloys
Etching aluminum and its alloys
For zinc and cadmium plating on steel, and copper plating on zinc alloys
Etching zinc, zinc alloys and cadmium
For anodizing of aluminum alloys
Etching aluminum and its alloys
Additional remarks:
GB646286
This standard was proposed by the Ministry of Machinery Industry of the People's Republic of China and is under the jurisdiction of the Wuhan Institute of Materials Protection of the Ministry of Machinery Industry. The Wuhan Institute of Materials Protection of the Ministry of Machinery Industry is responsible for drafting this standard. The main drafter of this standard is Li Hanlian.3
Glacial acetic acid: 50mL
Ammonium persulfate: 10g
Ammonium hydroxide solution (specific gravity 0.8g/mL): 2mLDistilled water: 90mL
Nitric acid solution (specific gravity 1.42g/mL): 5mLB.5
Hydrofluoric acid solution (specific gravity 1.14g/mL): 2mLDistilled water: 93mL
Chromic anhydride (Cr0,): 20g
Sodium sulfate: 1.5g
Distilled radium water: 100g
Hydrofluoric acid solution (specific gravity 1.14g/mL): 2mLB.7
Distilled radium water: 98mL
Note: Be careful in the preparation, use, storage, transportation and removal of these etchants. Scope and description
For nickel or chromium coatings on steel. Etch steel. This etchant should be newly formulated.
For gold, lead, silver, nickel and copper inlays on steel, copper and copper alloy substrates.
Etch steel, copper and steel alloys.
For multi-layer nickel plating on steel and copper alloys, showing structure and distinguishing each layer of nickel. Etch nickel, over-corrosion of steel and pot alloys. For tin and pick alloy coatings on steel and copper alloys. Etch copper and steel alloys.
This etchant should be newly formulated. ||t t||For nickel and pot plating of aluminum and aluminum alloys
Etching aluminum and its alloys
For zinc and cadmium plating on steel, and copper plating on zinc alloys
Etching zinc, zinc alloys and cadmium
For anodizing of aluminum alloys
Etching aluminum and its alloys
Additional remarks:
GB646286
This standard was proposed by the Ministry of Machinery Industry of the People's Republic of China and is under the jurisdiction of the Wuhan Institute of Materials Protection of the Ministry of Machinery Industry. The Wuhan Institute of Materials Protection of the Ministry of Machinery Industry is responsible for drafting this standard. The main drafter of this standard is Li Hanlian.3
Glacial acetic acid: 50mL
Ammonium persulfate: 10g
Ammonium hydroxide solution (specific gravity 0.8g/mL): 2mLDistilled water: 90mL
Nitric acid solution (specific gravity 1.42g/mL): 5mLB.5
Hydrofluoric acid solution (specific gravity 1.14g/mL): 2mLDistilled water: 93mL
Chromic anhydride (Cr0,): 20g
Sodium sulfate: 1.5g
Distilled radium water: 100g
Hydrofluoric acid solution (specific gravity 1.14g/mL): 2mLB.7
Distilled radium water: 98mL
Note: Be careful in the preparation, use, storage, transportation and removal of these etchants. Scope and description
For nickel or chromium coatings on steel. Etch steel. This etchant should be newly formulated.
For gold, lead, silver, nickel and copper inlays on steel, copper and copper alloy substrates.
Etch steel, copper and steel alloys.
For multi-layer nickel plating on steel and copper alloys, showing structure and distinguishing each layer of nickel. Etch nickel, over-corrosion of steel and pot alloys. For tin and pick alloy coatings on steel and copper alloys. Etch copper and steel alloys.
This etchant should be newly formulated. ||t t||For nickel and pot plating of aluminum and aluminum alloys
Etching aluminum and its alloys
For zinc and cadmium plating on steel, and copper plating on zinc alloys
Etching zinc, zinc alloys and cadmium
For anodizing of aluminum alloys
Etching aluminum and its alloys
Additional remarks:
GB646286
This standard was proposed by the Ministry of Machinery Industry of the People's Republic of China and is under the jurisdiction of the Wuhan Institute of Materials Protection of the Ministry of Machinery Industry. The Wuhan Institute of Materials Protection of the Ministry of Machinery Industry is responsible for drafting this standard. The main drafter of this standard is Li Hanlian.
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