An indicator suitable for on-site metallographic examination, its preparation method and application process

Abstract

This invention relates to an indicator suitable for on-site metallographic inspection, its preparation method, and application process. The indicator formulation, by weight, comprises the following components: 95-105 parts etchant and 50-70 parts bentonite. The indicator prepared by this invention is suitable for metallographic testing because commonly used acids (indicators) are fluid, while the indicator prepared by this invention is non-flowing, conductive, and electrolytic, maintaining its original corrosive effect. It is easy to clean, thus preventing corrosive damage to the inspected equipment (workpiece) and avoiding injury to personnel from dripping indicator due to the testing location (e.g., supine position). Therefore, it is particularly suitable for on-site metallographic testing. The formulation of this invention is simple, odorless, and reusable.

Description

Technical Field

[0001] This invention relates to metallographic inspection technology, specifically to a non-flowing indicator suitable for on-site metallographic examination, and its preparation method and application process. Background Technology

[0002] On-site metallographic testing technology is relative to laboratory metallographic testing. It is a testing method that involves grinding and polishing the surface of the equipment (workpiece) under test on-site, then displaying its microstructure with a metallographic display agent, and then observing the microstructure with an on-site metallographic microscope, or through on-site image acquisition equipment or metallographic replicas.

[0003] On-site metallographic inspection is a crucial method for extending metallographic inspection to the field and for failure analysis, ensuring the quality and safety of equipment from manufacturing to operation. However, the display process directly impacts the safety standards and accuracy of on-site metallographic inspection. On-site metallographic display typically employs two methods: electrolysis and wiping.

[0004] Currently, halogen-free chromic acid solutions are commonly used for nuclear-grade stainless steel and nickel-based materials. All relevant industry standards, such as GB / T6394 and GB / T13298, recommend highly fluid acid solutions (indicators) for use with low-carbon and low-alloy steels, exhibiting strong oxidizing and corrosive properties. In on-site metallographic testing, the locations being tested are highly random, and testing may be required at any location. The flowing or dripping indicator not only poses a significant threat to laboratory personnel but also causes corrosion and contamination damage to the tested equipment (workpiece). To avoid harm to laboratory personnel and the tested equipment (workpiece) during on-site use, a safer and more effective indicator is needed. Summary of the Invention

[0005] To address the aforementioned deficiencies of existing technologies, this invention provides an indicator suitable for on-site metallographic inspection. This indicator is non-flowing, conductive, and electrolytic, maintaining its original corrosive effect. It is easy to clean, meaning it will not cause corrosive damage to the inspected equipment (workpiece) or cause injury to the inspecting personnel due to dripping of the indicator caused by the inspection position (such as an upward orientation).

[0006] The technical objective of this invention is achieved through the following technical solution:

[0007] This invention provides a display agent suitable for on-site metallographic examination, comprising the following components by weight: 95-105 parts of etchant display agent and 50-70 parts of bentonite.

[0008] Furthermore, the etching agent of the present invention is an acidic solution; preferably, the etching agent is a chromic acid solution or a nitric acid solution.

[0009] Furthermore, the chromic acid solution of the present invention is prepared by the following method: 100 ml of water is mixed with 25-30 g of chromium trioxide.

[0010] Furthermore, the nitric acid solution of the present invention is prepared by mixing 100 ml of water with 10 ± 1 ml of nitric acid (mass fraction 65% to 68%).

[0011] Another technical objective of this invention is to provide a method for preparing an indicator suitable for on-site metallographic examination, comprising the following steps:

[0012] 1) Preparation of etching and display agents;

[0013] 2) Weigh 95-105 parts of etching agent and 50-70 parts of bentonite, and mix them evenly to obtain the final product.

[0014] Furthermore, the etching agent of the present invention is an acidic etching agent; preferably, the etching agent is a chromic acid solution or a nitric acid solution.

[0015] Another technical objective of this invention is to provide an application process for an indicator suitable for on-site metallographic testing, comprising the following steps:

[0016] 1) Pre-treatment: Grind, mechanically polish, and clean the surface to be inspected;

[0017] 2) Electrolysis: The indicator agent described in claim 1 is loaded into an on-site electrolyzer, the power is turned on, and electrolysis is carried out.

[0018] Furthermore, the electrolysis described in this invention uses a voltage of 5–8V, a current of 3.0–5.0A, and an electrolysis time of 60–180s.

[0019] Another technical objective of this invention is to provide an application process for an indicator suitable for on-site metallographic testing, comprising the following steps:

[0020] 1) Pre-treatment: Grind, mechanically polish, and clean the surface to be inspected;

[0021] 2) Application: Apply the display agent as described in claim 1 to the detection surface, allow it to stand, electrolyze the display, and then wipe away any remaining display agent with alcohol.

[0022] The present invention has the following advantages over the prior art:

[0023] Compared with existing technologies, the indicator used in this invention for conventional metallographic testing is non-flowing, yet maintains its original corrosive effect. It is easy to clean, will not cause corrosive damage to the tested equipment (workpiece), and will not cause harm to the testing personnel due to indicator dripping. Therefore, it is particularly suitable for on-site metallographic testing. The indicator formula of this invention is simple, has no irritating odor, and can be reused. Attached Figure Description

[0024] Figure 1a This is a scene diagram of the electrolysis of chromic acid paste 1 in Example 1; Figure 1b This is a scene diagram showing the inspected equipment (workpiece) after electrolysis of chromic acid paste 1 in Example 1, where no contamination or corrosion was observed.

[0025] Figure 2 The microstructure (100X) of SA-240MTP 316LN austenitic stainless steel obtained by electrolysis of chromic acid paste in Example 1-1 is shown.

[0026] Figure 3a These are scene diagrams from the electrolysis of chromic acid paste in Examples 1-2; Figure 3b The images show the scene after electrolysis of chromic acid paste in Examples 1-2, where the inspected equipment (workpiece) was not contaminated or corroded.

[0027] Figure 4 Examples 1-2 show the microstructure (100X) of SA-240MTP 316LN austenitic stainless steel obtained by electrolysis of chromic acid paste.

[0028] Figure 5a These are scene diagrams from the electrolysis of chromic acid paste in Examples 1-3; Figure 5b The images show the scene after electrolysis of chromic acid paste in Examples 1-3, where the inspected equipment (workpiece) was not contaminated or corroded.

[0029] Figure 6 Examples 1-3 show the microstructure (100X) of SA-240MTP 316LN austenitic stainless steel obtained by electrolysis of chromic acid paste.

[0030] Figure 7a This is a scene illustration from Example 2-1, showing the nitric acid paste. Figure 7b This is a scene diagram showing the inspected equipment (workpiece) after the nitric acid paste was applied, indicating that it was not contaminated or corroded. (Example 2-1)

[0031] Figure 8 The image shows the morphology of SA-508MGr.3CL.3 tissue obtained after exposure to nitric acid paste in Example 2-1 (100X).

[0032] Figure 9a This is a scene illustration from Example 2-2, showing the nitric acid paste. Figure 9b This is a scene diagram showing the inspected equipment (workpiece) after the nitric acid paste was applied, indicating that it was not contaminated or corroded. (Example 2-2)

[0033] Figure 10 The image shows the morphology of SA-508MGr.3CL.3 tissue obtained after exposure to nitric acid paste in Example 2-2 (100X).

[0034] Figure 11a These are scene illustrations from Examples 2-3, showing the effects of nitric acid paste. Figure 11b The images shown are from Examples 2-3, illustrating a scenario where the inspected equipment (workpiece) was not contaminated or corroded after the nitric acid paste was applied.

[0035] Figure 12 The image shows the morphology of SA-508MGr.3CL.3 tissue obtained after exposure to nitric acid paste in Examples 2-3 (100X).

[0036] Figure 13a This is a scene diagram of the electrolysis of chromic acid aqueous solution in Comparative Example 1; Figure 13b This is a scene of contamination and corrosion of the tested equipment (workpiece) after electrolysis of chromic acid aqueous solution, as shown in Comparative Example 1.

[0037] Figure 14 The microstructure of SA-240MTP 316LN austenitic stainless steel obtained by electrolysis of chromic acid aqueous solution in Comparative Example 2 is shown in 100X (microstructure after chromic acid electrolysis).

[0038] Figure 15a This is a scene diagram of nitric acid alcohol in Comparative Example 2; Figure 15b This is a comparative example 2, showing the contaminated and corroded scene of the inspected equipment (workpiece) after being exposed to nitric acid and alcohol.

[0039] Figure 16 Comparative Example 2: morphology of SA-508MGr.3CL.3 tissue obtained with nitric acid and alcohol (100X). Detailed Implementation

[0040] The technical features of the technical solution provided by the present invention will be further clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] Example 1-1

[0042] 1. Preparation method of display agent suitable for on-site metallographic examination

[0043] 1) Preparation of etching agent chromic acid: Measure 100ml of distilled water, weigh 25g of chromium trioxide, pour the distilled water and chromium trioxide into a glass container in sequence, stir evenly with a glass rod to obtain chromic acid solution;

[0044] 2) Preparation of the display agent (chromic acid paste)

[0045] Take 100ml of the chromic acid aqueous solution prepared in step 1), weigh 50g of bentonite, and pour the chromic acid aqueous solution and bentonite into a glass container in sequence. Stir evenly with a glass rod to obtain chromic acid paste.

[0046] 2. Implementation process of indicator for on-site metallographic testing

[0047] 2.1 The inclined surface of the workpiece made of material SA-240MTP 316LN is used as the inspection object.

[0048] 1) Pretreatment: Taking the inclined surface of a workpiece made of SA-240MTP 316LN material as an example, the inspection surface is first coarsely ground with sandpaper and then finely ground, then mechanically polished with diamond spray, and finally cleaned with anhydrous ethanol cotton balls.

[0049] 2) Electrolysis: Electrolysis is performed using an on-site electrolysis apparatus. First, the prepared indicator (chromic acid paste) is filled into the on-site electrolysis container; the electrodes are connected to the battery; the anode is connected to the equipment under inspection (workpiece); the electrolysis container is connected to the cathode, and electrolysis is performed. The electrolysis parameters used are: voltage of 6V, current of 3.06A, and electrolysis time of 60s; electrolysis is carried out inside the electrolysis container.

[0050] Electrolysis process such as Figure 1a As shown, after electrolysis is completed, as Figure 1b The workpiece shown was not contaminated; on-site metallographic observation and image acquisition: after cleaning and drying with anhydrous ethanol cotton balls, a clear austenitic microstructure was observed under an on-site metallographic microscope as shown in the image. Figure 2 As shown, the electrolysis display effect is good.

[0051] Examples 1-2

[0052] 1. Preparation method of display agent suitable for on-site metallographic examination

[0053] 1) Preparation of etching agent chromic acid: Measure 100ml of distilled water, weigh 25g of chromium trioxide, pour the distilled water and chromium trioxide into a glass container in sequence, stir evenly with a glass rod to obtain chromic acid solution;

[0054] 2) Preparation of the display agent (chromic acid paste)

[0055] Take 100ml of the chromic acid aqueous solution prepared in step 1), weigh 60g of bentonite, and pour the chromic acid aqueous solution and bentonite into a glass container in sequence. Stir evenly with a glass rod to obtain chromic acid paste.

[0056] 2. Implementation process of indicator for on-site metallographic testing

[0057] 2.1 The inclined surface of the workpiece made of material SA-240MTP 316LN is used as the inspection object.

[0058] 1) Pretreatment: Taking the inclined surface of a workpiece made of SA-240MTP 316LN material as an example, the inspection surface is first coarsely ground with sandpaper and then finely ground, then mechanically polished with diamond spray, and finally cleaned with anhydrous ethanol cotton balls.

[0059] 2) Electrolysis: Electrolysis is performed using an on-site electrolysis apparatus. First, the prepared indicator (chromic acid paste) is filled into the on-site electrolysis container; the electrodes are connected to the battery; the anode is connected to the equipment under inspection (workpiece); the electrolysis container is connected to the cathode, and electrolysis is performed. The electrolysis parameters used are: voltage of 6V, current of 3.06A, and electrolysis time of 60s; electrolysis is carried out inside the electrolysis container.

[0060] Electrolysis process such as Figure 3a As shown, after electrolysis is completed, as Figure 3b As shown, the workpiece was not damaged by contamination; on-site metallographic observation and image acquisition: after cleaning and drying with anhydrous ethanol cotton balls, a clear austenitic microstructure was observed under an on-site metallographic microscope as shown in the image. Figure 4 As shown, the electrolysis display effect is good.

[0061] Examples 1-3

[0062] 1. Preparation method of display agent suitable for on-site metallographic examination

[0063] 1) Preparation of etching agent chromic acid: Measure 100ml of distilled water, weigh 25g of chromium trioxide, pour the distilled water and chromium trioxide into a glass container in sequence, stir evenly with a glass rod to obtain chromic acid solution;

[0064] 2) Preparation of the display agent (chromic acid paste)

[0065] Take 100ml of the chromic acid aqueous solution prepared in step 1), weigh 70g of bentonite, and pour the chromic acid aqueous solution and bentonite into a glass container in sequence. Stir evenly with a glass rod to obtain chromic acid paste.

[0066] 2. Implementation process of indicator for on-site metallographic testing

[0067] 2.1 The inclined surface of the workpiece made of material SA-240MTP 316LN is used as the inspection object.

[0068] 1) Pretreatment: Taking the inclined surface of a workpiece made of SA-240MTP 316LN material as an example, the inspection surface is first coarsely ground with sandpaper and then finely ground, then mechanically polished with diamond spray, and finally cleaned with anhydrous ethanol cotton balls.

[0069] 2) Electrolysis: Electrolysis is performed using an on-site electrolysis apparatus. First, the prepared indicator (chromic acid paste) is filled into the on-site electrolysis container; the electrodes are connected to the battery; the anode is connected to the equipment under inspection (workpiece); the electrolysis container is connected to the cathode, and electrolysis is performed. The electrolysis parameters used are: voltage of 6V, current of 3.06A, and electrolysis time of 60s; electrolysis is carried out inside the electrolysis container.

[0070] Electrolysis process such as Figure 5a As shown, after electrolysis, the workpiece was not contaminated or damaged. Figure 5b As shown; On-site metallographic observation and image acquisition: After cleaning and drying with anhydrous ethanol cotton balls, clear austenitic morphology was observed under an on-site metallographic microscope as shown. Figure 6 As shown, the electrolysis display effect is good.

[0071] Example 2-1

[0072] 1. Preparation method of display agent suitable for on-site metallographic examination

[0073] 1) Preparation of nitric acid aqueous solution for etching agent: Measure 100ml of distilled water and 10ml of nitric acid, pour the distilled water and nitric acid into a glass container in sequence, stir well with a glass rod to obtain nitric acid aqueous solution;

[0074] 2) Preparation of the display agent (nitric acid paste):

[0075] Take 100ml of the nitric acid solution prepared in step 1), weigh 50g of bentonite, and pour the nitric acid solution and bentonite into a glass container in sequence. Stir well with a glass rod to obtain nitric acid paste.

[0076] 2. Implementation process of indicator for on-site metallographic testing

[0077] 1) Pretreatment: Taking the inclined surface of the workpiece made of material SA-508MGr.3CL.3 as an example, the inspection surface is coarsely ground and finely ground with sandpaper in sequence, then mechanically polished with diamond spray, and then cleaned with anhydrous ethanol cotton balls.

[0078] 2) Application: Gently apply the nitric acid paste evenly to the polished test surface, let it stand for about 30 seconds, and then gently wipe off the paste with a cotton ball soaked in anhydrous ethanol; the application process of the nitric acid paste is shown below. Figure 7a As shown, after the display is complete... Figure 7b As shown, the workpiece was not damaged by contamination. On-site metallographic observation and image acquisition: After cleaning with anhydrous ethanol cotton balls, a clear tempered sorbite and bainite microstructure was observed under a metallographic microscope, as shown in the image. Figure 8 As shown, the application effect is good.

[0079] Example 2-2

[0080] 1. Preparation method of display agent suitable for on-site metallographic examination

[0081] 1) Preparation of nitric acid aqueous solution for etching agent: Measure 100ml of distilled water and 10ml of nitric acid, pour the distilled water and nitric acid into a glass container in sequence, stir well with a glass rod to obtain nitric acid aqueous solution;

[0082] 2) Preparation of the display agent (nitric acid paste):

[0083] Take 100ml of the nitric acid solution prepared in step 1), weigh 60g of bentonite, and pour the nitric acid solution and bentonite into a glass container in sequence. Stir well with a glass rod to obtain nitric acid paste.

[0084] 2. Implementation process of indicator for on-site metallographic testing

[0085] 1) Pretreatment: Taking the inclined surface of the workpiece made of material SA-508MGr.3CL.3 as an example, the inspection surface is coarsely ground and finely ground with sandpaper in sequence, then mechanically polished with diamond spray, and then cleaned with anhydrous ethanol cotton balls.

[0086] 2) Application: Gently apply the nitric acid paste evenly to the polished test surface, let it stand for about 30 seconds, and then gently wipe off the paste with a cotton ball soaked in anhydrous ethanol; the application process is as follows. Figure 9a As shown, after the coating is applied, the workpiece is not contaminated or damaged. Figure 9b As shown; on-site metallographic observation and image acquisition: After cleaning with anhydrous ethanol cotton balls, a clear tempered sorbite and bainite microstructure was observed under a metallographic microscope, as shown in the image. Figure 10 As shown, the application effect is good.

[0087] Example 2-3

[0088] 1. Preparation method of display agent suitable for on-site metallographic examination

[0089] 1) Preparation of nitric acid aqueous solution for etching agent: Measure 100ml of distilled water and 10ml of nitric acid, pour the distilled water and nitric acid into a glass container in sequence, stir well with a glass rod to obtain nitric acid aqueous solution;

[0090] 2) Preparation of the display agent (nitric acid paste)

[0091] Take 100ml of the nitric acid solution prepared in step 1), weigh 70g of bentonite, and pour the nitric acid solution and bentonite into a glass container in sequence. Stir well with a glass rod to obtain nitric acid paste.

[0092] 2. Implementation process of indicator for on-site metallographic testing

[0093] 1) Pretreatment: Taking the inclined surface of the workpiece made of material SA-508MGr.3CL.3 as an example, the inspection surface is coarsely ground and finely ground with sandpaper in sequence, then mechanically polished with diamond spray, and then cleaned with anhydrous ethanol cotton balls.

[0094] 2) Application: Gently apply the nitric acid paste evenly to the polished test surface, let it stand for about 30 seconds, and then gently wipe off the paste with a cotton ball soaked in anhydrous ethanol; the application process is as follows. Figure 11a As shown, after the coating is applied, the workpiece is not contaminated or damaged. Figure 11b As shown; on-site metallographic observation and image acquisition: After cleaning with anhydrous ethanol cotton balls, a clear tempered sorbite and bainite microstructure was observed under a metallographic microscope, as shown in the image. Figure 12 As shown, the application effect is good.

[0095] Figure 2 , Figure 4 , Figure 6 , Figure 8 , Figure 10 and Figure 12 To utilize the display agents prepared in Examples 1-1 to 2-3 of this invention and the resulting display effects, the original cleanliness of the workpiece surface is maintained, and the microstructure is clearly displayed. Compared with the prior art, the workpiece is no longer contaminated by the display agent, protecting the safety and health of the experimental personnel. The display time is shorter, the original properties of the display agent are maintained, and the display effect is better.

[0096] Comparative Example 1

[0097] 1. Prepare chromic acid aqueous solution for electrolytic display agent

[0098] Measure 75ml of distilled water and weigh 25g of chromium trioxide. Pour the distilled water and chromium trioxide into a glass container and stir with a glass rod until well mixed to obtain a chromic acid solution.

[0099] 2. Electrolysis

[0100] Taking the inclined surface of a workpiece made of SA-240MTP 316LN material as an example, electrolysis was performed using an on-site electrolysis apparatus. First, the prepared chromic acid aqueous solution was introduced into the electrolyte supply bottle; the electrodes were connected to the battery; the anode and cathode were connected to the metallographic sample respectively; the electrolyte supply bottle was squeezed to ensure full contact between the electrolyte and the sample; electrolysis was then performed using the following parameters: voltage 10V, current 3.5A, and electrolysis time 120s; the electrolysis process was carried out on the inspected surface, and the chromic acid aqueous solution was constantly flowing during the process. Figure 13a After electrolysis, the workpiece is contaminated and damaged by the flowing chromic acid aqueous solution, see... Figure 13b .

[0101] 3. On-site metallographic observation and image acquisition

[0102] The morphology of the austenitic structure was observed under a metallographic microscope, such as... Figure 14 As shown.

[0103] Comparative Example 2

[0104] 1. Prepare nitric acid aqueous solution indicator

[0105] Measure 100ml of distilled water and 10ml of nitric acid, pour the distilled water and nitric acid into a glass container in sequence, and stir well with a glass rod to obtain a nitric acid solution.

[0106] 2. Wipe

[0107] Taking the inclined surface of a workpiece made of material SA-508MGr.3CL.3 as an example, the inspection surface is first coarsely ground with sandpaper, then finely ground, and finally mechanically polished with diamond spray. Then it is cleaned with anhydrous ethanol. Using tweezers, a cotton ball soaked in a prepared nitric acid solution is used to wipe the polished inspection surface using standard methods. It is then rinsed with water, cleaned with anhydrous ethanol, and dried with a hair dryer. The wiping process is as follows: Figure 15a As shown, the scene after wiping is as follows. Figure 15b As shown, the workpiece was contaminated and damaged by the flowing nitric acid aqueous solution.

[0108] 3. On-site metallographic observation and image acquisition

[0109] Clear tempered sorbite and bainite microstructure was observed under a metallographic microscope, such as... Figure 16 As shown.

[0110] The above observations show that the workpieces in Comparative Examples 1 and 2 were damaged by contamination from the flowing nitric acid aqueous solution, while the workpieces in Examples 1-1 to 2-3 were not damaged by contamination.

[0111] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A construction process for an indicator suitable for on-site metallographic testing, characterized in that, Includes the following steps: 1) Pre-treatment: Grind, mechanically polish, and clean the surface to be inspected; 2) Electrolysis: Load the display agent into the on-site electrolyzer, connect the power supply, and carry out electrolysis; The indicator comprises the following components by weight: 95-105 parts of etchant and 50-70 parts of bentonite; The etching agent is a chromic acid solution or a nitric acid solution; The preparation method of the display agent includes the following steps: preparing an etchant; weighing 95-105 parts of etchant and 50-70 parts of bentonite, and stirring evenly to obtain the final product.

2. The construction process according to claim 1, characterized in that, The chromic acid solution is prepared by mixing 100 ml of water with 25-30 g of chromium trioxide.

3. The construction process according to claim 1, characterized in that, The nitric acid solution is prepared by mixing 100 ml of water with 10 ± 1 ml of nitric acid.

4. The construction process according to claim 1, characterized in that, The electrolysis is performed at a voltage of 5~8V, a current of 3.0~5.0A, and an electrolysis time of 60~180s.

5. The construction process according to claim 1, characterized in that, After electrolysis, wipe off any residual electrolysis reagent with alcohol and blow dry the detection surface.

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