Etching agent and method for displaying microstructure of high-temperature alloy GH6159

Abstract

The invention relates to an aggressive agent and method for displaying a microstructure of a high-temperature alloy GH6159. The aggressive agent is prepared from 0.5-1 g of zinc nitrate, 60-80 ml of hydrochloric acid, 7-10 ml of sulfuric acid, 80-100 ml of absolute ethyl alcohol and 15-20 ml of glycerinum. The display method of the microstructure of the high-temperature alloy GH6159 comprises the following steps: (1) preparing an aggressive agent; (2) preparing a sample; (3) sample erosion; (4) cleaning the sample; and (5) observing with a metallographic microscope. The aggressive agent provided by the invention is simple to prepare and convenient to use, the obtained crystal boundary is clear and complete, and the aggressive agent is very easy to popularize and use in laboratories.

Description

Technical Field

[0001] The present invention belongs to the technical field of metallographic inspection, and particularly relates to an etchant and method for revealing the microstructure of superalloy GH6159 at high temperature. Background Art

[0002] With the rapid development of modern industrial technology, especially in high-tech fields such as aerospace and petrochemical industries, the requirements for material properties are increasing day by day. As a new type of cobalt-based precipitation hardening wrought superalloy with high strength, high temperature resistance and corrosion resistance, superalloy GH6159 shows broad application prospects in the above fields by virtue of its excellent properties.

[0003] (I) The main application fields of superalloy GH6159 include but are not limited to the following aspects: 1. Aerospace: As the preferred material for aircraft engine fasteners and high-strength bolts in high-temperature and high-pressure environments, superalloy GH6159 is widely used in manufacturing key components of advanced aircraft engines, such as sealing discs, turbine discs, high-load bolts connecting the high-pressure compressor shaft and the high-pressure turbine shaft, etc.; its excellent high-temperature strength, oxidation resistance and corrosion resistance ensure the stable operation of the engine in high-temperature, high-pressure and corrosive media.

[0004] 2. Petrochemical industry: In the petrochemical industry, superalloy GH6159 also performs excellently; its good corrosion resistance enables it to resist the erosion of chemical media such as acids, alkalis and salts, so it is widely used in manufacturing key components such as anti-corrosion equipment and pipelines. At the same time, its high strength and excellent plasticity and toughness also meet the harsh requirements for material properties in the petrochemical industry.

[0005] 3. Other industrial fields: In addition to the aerospace and petrochemical industries, superalloy GH6159 can also be used in other industrial fields that require high-strength, high-temperature and corrosion-resistant materials; for example, in the fields of energy, automotive, shipbuilding, etc., superalloy GH6159 can also be used as the manufacturing material for key components.

[0006] (II) The reason why superalloy GH6159 can be widely used in the above fields mainly benefits from the following performance characteristics: 1. High strength: Superalloy GH6159 realizes the characteristic of ultra-high strength through various strengthening mechanisms such as solid solution strengthening, precipitation strengthening and cold deformation strengthening. Even in high-temperature environments, its strength can still remain stable.

[0007] 2. High temperature resistance: Superalloy GH6159 can maintain stable mechanical properties and chemical properties at high temperatures, meeting the use requirements in high-temperature environments.

[0008] 3. Corrosion resistance: The superalloy GH6159 has excellent corrosion resistance, capable of withstanding the erosion of various chemical media and extending the service life of the material.

[0009] 4. Good plasticity and toughness: While maintaining high strength, the superalloy GH6159 also has good plasticity and toughness, ensuring reliable use under complex working conditions.

[0010] 5. Excellent machining performance: The superalloy GH6159 has good machinability and weldability, and can be formed by hot working, cold working, etc. to meet the processing requirements of different products.

[0011] In view of the excellent performance and broad application prospects of the superalloy GH6159 in the fields of aerospace, petrochemical, etc., it is of great significance to conduct in-depth research and development on this alloy.

[0012] The microstructure of the superalloy GH6159 at room temperature is austenite. The austenite grain size level has a great influence on the properties of the material, which can provide an important reference basis for production personnel to formulate the material heat treatment process. However, due to its good oxidation resistance and corrosion resistance, when using a variety of etching reagents to etch it, the ideal effect cannot be achieved. The austenite grain boundaries are not fully displayed, and there is a lot of corrosion product covering the entire observation surface, seriously affecting the accuracy of the grain size level number results. Summary of the Invention

[0013] The technical problem to be solved by the present invention is to provide an etching agent and method for displaying the microstructure of the superalloy GH6159, which can make the austenite metallographic structure of the superalloy GH6159 clear and the grain boundaries complete.

[0014] To solve the above technical problems, the technical solutions adopted by the present invention are as follows: An etching agent for displaying the microstructure of the superalloy GH6159 is prepared by mixing 0.5 - 1 g of zinc nitrate, 60 - 80 ml of hydrochloric acid, 7 - 10 ml of sulfuric acid, 80 - 100 ml of absolute ethanol, and 15 - 20 ml of glycerol.

[0015] Further, the preparation process of the etching agent for displaying the microstructure of the superalloy GH6159 of the present invention is as follows: Slowly pour the hydrochloric acid into the absolute ethanol, then sequentially add zinc nitrate and glycerol. After standing for 2 - 5 minutes, slowly add sulfuric acid and stir evenly.

[0016] Further, the hydrochloric acid, sulfuric acid, and absolute ethanol of the present invention are all of analytical purity.

[0017] Further, the mass fraction of the hydrochloric acid of the present invention is 36.5%, and the mass fraction of the sulfuric acid is 98%.

[0018] A method for displaying the microstructure of superalloy GH6159, comprising the following steps: (1) Prepare the etchant described in the present invention; (2) Specimen preparation: Cut a specimen of superalloy GH6159, and grind and polish the surface to be inspected of the specimen until it is mirror-like and free of scratches; (3) Specimen etching: Heat the etchant prepared in step (1) to 50 - 60 °C and keep it warm; Place the polished surface of the specimen prepared in step (2) facing upwards into the etchant for etching, and the etching time is 2 - 5 min; (4) Specimen cleaning: Take out the specimen after etching in step (3), rinse it with running water, and at the same time wipe it repeatedly with absorbent cotton to remove the black substances attached to the corroded surface of the specimen during the corrosion process. Finally, rinse it with water and alcohol in sequence and dry it; (5) Observe the microstructure of superalloy GH6159 under a microscope.

[0019] Further, in the method for displaying the microstructure of superalloy GH6159 of the present invention, the area of the surface to be inspected of the specimen in step (3) is 200 ± 50 mm 2 , and the height of the specimen is 10 - 15 mm.

[0020] Further, in the method for displaying the microstructure of superalloy GH6159 of the present invention, the specific operation of the grinding and polishing in step (2) is as follows: Grind the surface to be inspected of the specimen successively on 180#, 400#, 600#, 800#, 1000#, and 1500# water sandpapers from coarse to fine, and then polish it on a silk polishing cloth with adhesive backing by spraying diamond polishing agent with a particle size of 2.5 μm.

[0021] Further, in the method for displaying the microstructure of superalloy GH6159 of the present invention, step (3) is carried out in a laboratory with a fume hood.

[0022] Further, in the method for displaying the microstructure of superalloy GH6159 of the present invention, the liquid level of the etchant in step (3) exceeds the specimen.

[0023] Further, in the method for displaying the microstructure of superalloy GH6159 of the present invention, the heating in step (3) adopts a water bath heating method.

[0024] Further, the superalloy GH6159 of the present invention is sampled under a solution treatment process.

[0025] The inventive principle of the technical solution of the present invention lies in:

[0026] The microstructure of GH6159 described in the present invention is twinned austenite. According to the grain boundary engineering theory, the grain boundary energies of the twin grain boundaries and the grain boundaries in the austenite are different, and the twin grain boundaries in the austenite belong to low-energy grain boundaries. In order to ensure sufficient corrosiveness of the etchant, a hydrochloric acid solution with a relatively high concentration is selected. The addition of a small amount of zinc nitrate (Zn(NO 3 ) 2 ) mainly plays the role of an acidifying catalyst, which can accelerate the grain boundary corrosion rate and shorten the corrosion time. The addition of a small amount of sulfuric acid is used to dissolve cobalt compounds and carbides during the etching process, which can avoid the adhesion and aggregation of the dissolution products on the corrosion surface. Both anhydrous ethanol and glycerol are organic substances and belong to alcohols. The two are mutually soluble. When added to the hydrochloric acid solution, they can protect the low-energy twin grain boundaries, thereby realizing the synchronous display of twin grain boundaries and grain boundaries and achieving an ideal microstructure display effect.

[0027] The beneficial effects produced by adopting the above technical solutions are as follows:

[0028] 1. The etchant described in the present invention can make the austenite grains of the superalloy GH6159 complete and the grain boundaries clear; during the measurement of the grain size, an accurate grain size grade number can be obtained.

[0029] 2. The etchant provided by the present invention is simple to prepare, easy to use, and easy to be popularized and used in the laboratory, and can play a greater role in the industry. Brief Description of the Drawings

[0030] Figure 1 The microstructure of the superalloy GH6159 shown by the method of Example 1; Figure 2 The microstructure of the superalloy GH6159 shown by the method of Example 2; Figure 3 The microstructure of the superalloy GH6159 shown by the method of Example 3; Figure 4 The microstructure of the superalloy GH6159 shown by the method of Example 4. Detailed Description of the Invention

[0031] The present invention will be further described in detail below with reference to the drawings and specific embodiments. Example 1

[0032] A method for showing the microstructure of the superalloy GH6159 includes the following steps: (1) Preparation of the etchant: Slowly pour 60 ml of hydrochloric acid into 80 ml of anhydrous ethanol, then sequentially add 0.5 g of zinc nitrate and 15 ml of glycerol. After standing for 2 minutes, slowly add 7 ml of sulfuric acid and stir evenly.

[0033] (2) Specimen preparation: Cut a solution-treated superalloy GH6159 specimen. Grind the surface to be inspected of the specimen successively on 180#, 400#, 600#, 800#, 1000#, and 1500# water sandpapers from coarse to fine. After grinding it flat, spray diamond polishing agent with a particle size of 2.5 μm on a silk polishing cloth for polishing until the surface is mirror-like and free of scratches. Rinse it thoroughly with water, then rinse it with alcohol, and then dry it with a hair dryer.

[0034] (3) Specimen etching: In a laboratory with a fume hood, turn on the fume hood. Using the water bath heating method, heat the etching agent prepared in step (1) to 50 °C and keep it warm. Place the polished surface of the specimen prepared in step (2) facing up into the etching agent, with the liquid level of the etching agent exceeding the specimen, and the etching time is 2 minutes.

[0035] (4) Specimen cleaning: Take out the etched specimen, rinse the specimen with flowing water, and at the same time repeatedly wipe the corrosion products on the corroded surface with absorbent cotton while observing until all the corrosion products disappear. Finally, rinse it with water and alcohol and then dry it.

[0036] (5) Observe the microstructure of superalloy GH6159 under a microscope, as Figure 1 shown, the visible structure is austenite, and the grain boundaries are clear and complete. Example 2

[0037] A method for showing the microstructure of superalloy GH6159, comprising the following steps: (1) Etching agent preparation: Slowly pour 65 ml of hydrochloric acid into 85 ml of absolute ethanol, then successively add 0.7 g of zinc nitrate and 16 ml of glycerol. After standing for 3 minutes, slowly add 8 ml of sulfuric acid and stir evenly.

[0038] (2) Specimen preparation: Cut a solution-treated superalloy GH6159 specimen. Grind the surface to be inspected of the specimen successively on 180#, 400#, 600#, 800#, 1000#, and 1500# water sandpapers from coarse to fine. After grinding it flat, spray diamond polishing agent with a particle size of 2.5 μm on a silk polishing cloth for polishing until the surface is mirror-like and free of scratches. Rinse it thoroughly with water, then rinse it with alcohol, and then dry it with a hair dryer.

[0039] (3) Specimen etching: In a laboratory with a fume hood, turn on the fume hood. Using the water bath heating method, heat the etching agent prepared in step (1) to 53 °C and keep it warm. Place the polished surface of the specimen prepared in step (2) facing up into the etching agent, with the liquid level of the etching agent exceeding the specimen, and the etching time is 3 minutes.

[0040] (4)Specimen cleaning: Take out the eroded specimen, rinse the specimen with running water, and at the same time repeatedly wipe the corrosion products on the corroded surface with absorbent cotton, and observe while wiping until all the corrosion products disappear. Finally, wash with water and alcohol and then dry with a blower.

[0041] (5)Observe the microstructure of superalloy GH6159 under a microscope, as Figure 2 shown. It can be seen that the microstructure is austenite, and the grain boundaries are clear and complete. Example 3

[0042] A method for displaying the microstructure of superalloy GH6159 includes the following steps: (1)Etchant preparation: Slowly pour 70 ml of hydrochloric acid into 90 ml of absolute ethanol, then sequentially add 0.9 g of zinc nitrate and 18 ml of glycerol. After standing for 4 minutes, slowly add 9 ml of sulfuric acid and stir evenly.

[0043] (2)Specimen preparation: Cut a specimen of solution-treated superalloy GH6159. Grind the surface to be inspected of the specimen successively on 180#, 400#, 600#, 800#, 1000#, and 1500# water sandpapers from coarse to fine. After grinding smoothly, spray diamond polishing paste with a particle size of 2.5 μm on a silk polishing cloth for polishing until the surface is mirror-like and free of scratches. Rinse with water, then rinse with alcohol, and then dry with a blower.

[0044] (3)Specimen etching: In a laboratory with a fume hood, turn on the fume hood; use a water bath heating method to heat the etchant prepared in step (1) to 57 °C and keep it warm; place the polished surface of the specimen prepared in step (2) facing up into the etchant, with the liquid level of the etchant exceeding the specimen, and the etching time is 4 min.

[0045] (4)Specimen cleaning: Take out the eroded specimen, rinse the specimen with running water, and at the same time repeatedly wipe the corrosion products on the corroded surface with absorbent cotton, and observe while wiping until all the corrosion products disappear. Finally, wash with water and alcohol and then dry with a blower.

[0046] (5)Observe the microstructure of superalloy GH6159 under a microscope, as Figure 3 shown. It can be seen that the microstructure is austenite, and the grain boundaries are clear and complete. Example 4

[0047] A method for displaying the microstructure of superalloy GH6159 includes the following steps: (1)Etchant preparation: Slowly pour 80 ml of hydrochloric acid into 100 ml of absolute ethanol, then sequentially add 1 g of zinc nitrate and 20 ml of glycerol. After standing for 5 minutes, slowly add 10 ml of sulfuric acid and stir evenly.

[0048] (2)Specimen preparation: Cut a solution-treated superalloy GH6159 specimen. Grind the surface to be inspected of the specimen successively on 180#, 400#, 600#, 800#, 1000#, and 1500# water abrasive papers from coarse to fine. After grinding it flat, spray diamond polishing agent with a particle size of 2.5 μm on a silk polishing cloth for polishing until the surface is mirror-like and scratch-free. Rinse it thoroughly with water, then rinse it with alcohol, and then dry it with a hair dryer.

[0049] (3)Specimen etching: In a laboratory with a fume hood, turn on the fume hood. Heat the etchant prepared in step (1) to 60 °C by water bath heating and keep it warm. Place the polished surface of the specimen prepared in step (2) facing up into the etchant, with the liquid level of the etchant exceeding the specimen, and the etching time is 5 min.

[0050] (4)Specimen cleaning: Take out the etched specimen, rinse the specimen with running water, and at the same time repeatedly wipe the dirt generated on the corroded surface with absorbent cotton, observing while wiping until the black substance disappears. Finally, rinse it with water and alcohol and then dry it.

[0051] (5)Observe the microstructure of superalloy GH6159 under a microscope. As Figure 4 shown, the visible microstructure is austenite, and the grain boundaries are clear and complete.

Claims

1. An etchant for displaying the microstructure of high temperature alloy GH6159, characterized in that: The etchant is prepared from 0.5-1g zinc nitrate, 60-80ml hydrochloric acid, 7-10ml sulfuric acid, 80-100ml anhydrous ethanol and 15-20ml glycerol.

2. The etchant for displaying the microstructure of the high temperature alloy GH6159 according to claim 1, characterized in that: The preparation process of the etchant is as follows: slowly pour hydrochloric acid into anhydrous ethanol, then add zinc nitrate and glycerol in sequence, let it stand for 2-5 minutes, slowly add sulfuric acid, and stir evenly.

3. A method for displaying the microstructure of a high temperature alloy GH6159, comprising the following steps: Prepare the etching agent according to claim 1; Sample preparation: Cut the high-temperature alloy GH6159 sample, grind and polish the surface to be tested until it is mirror-like and has no scratches; Sample etching: heat the etching agent prepared in step (1) to 50-60°C and keep it warm; place the sample prepared in step (2) with the polished surface facing upward into the etching agent for etching for 2-5 minutes; Sample cleaning: Take out the sample after corrosion in step (3), rinse it with running water, and wipe it repeatedly with absorbent cotton to remove the black matter attached to the corrosion surface of the sample during the corrosion process. Finally, rinse it with water and alcohol in turn, and blow it dry; Observe under a microscope.

4. A method for displaying the microstructure of high temperature alloy GH6159 according to claim 3, characterized in that: The specific operation of the grinding and polishing in step (2) is as follows: the surface of the sample to be tested is grinded from coarse to fine on 180#, 400#, 600#, 800#, 1000#, and 1500# water-abrasive sandpaper in sequence, and then polished by spraying a diamond polishing agent with a particle size of 2.5 μm on a silk polishing cloth with a backing adhesive.

5. The method for displaying the microstructure of the high temperature alloy GH6159 according to claim 3, characterized in that: In step (3), the etchant liquid level exceeds the sample.

6. The method for displaying the microstructure of the high temperature alloy GH6159 according to claim 3, characterized in that: The heating in step (3) is water bath heating.

7. The method for displaying the microstructure of the high temperature alloy GH6159 according to claim 3, characterized in that: The high temperature alloy GH6159 is sampled under the solid solution process.

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