Metallographic corrosion method of N06625 alloy

Abstract

The invention discloses a metallographic corrosion method of an N06625 alloy, which belongs to the technical field of metal processing, and comprises the following steps: (1) adopting a bar with the specification of phi 204 mm, comprising the following chemical components in percentage by mass: 20-22% of Cr, 8-10% of Mo, 3-4% of Nb, 0.05-0.06% of C, less than or equal to 0.5% of Mn, 2.5-3.0% of Fe, 0.5-0.8% of Al + Ti and the balance of Ni, sampling at a position which is 1 / 2 of the radius of a disc with the thickness of 20 mm at the head of the finished bar, the detection position of the metallographic phase corresponds to the radial-axial direction of the bar; (2) carrying out chemical corrosion on the sample after hot inlaying, grinding and polishing; according to the metallographic corrosion method adopting the newly-proportioned chemical corrosion solution, the metallographic microstructure of the alloy is clear in morphology, intergranular carbides are displayed, and the novel corrosion method is suitable for inspection of the grain size and the carbides of the N06625 alloy.

Description

Technical Field

[0001] The invention relates to the technical field of metallographic corrosion of alloys, in particular to a metallographic corrosion method of a N06625 alloy. Background Art

[0002] With the progress of industrialization and the improvement of people's living standards, the demand for petroleum energy and chemical industry is increasing, which further promotes the vigorous development of the petrochemical industry. Increasing the transportation distance of petrochemical pipelines is an important measure for my country to cope with the global energy crisis and achieve a sustained industrialization process. Nickel-based alloy N06625 is a solid solution-strengthened high-temperature alloy. The chemical composition of the alloy contains a large number of alloy elements, which makes the alloy have excellent mechanical properties. Therefore, it is widely used in industrial fields such as petrochemicals. However, long-term service in such harsh working environments will cause changes in the microstructure of the alloy, which may lead to a decrease in the mechanical properties of the alloy. Therefore, the characterization of the microstructure of N06625, especially the observation of intergranular carbides, will have an important impact on the later service of the alloy.

[0003] There are many grain boundary carbides in the forged structure of the high-temperature alloy used in the present invention. It is difficult to show the secondary carbides between grains by traditional corrosion methods, and the grain boundary corrosion is not obvious. In addition, there are factors such as precipitation phases in the N06625 grains. The grain boundaries, secondary carbides at the grain boundaries, primary carbides and precipitation phases can all be shown by the new corrosion method, so that the characterization of the N06625 microstructure is more accurate and the accuracy of the alloy detection results is improved. Summary of the invention

[0004] The object of the present invention is to provide a metallographic corrosion method for N06625 alloy to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A metallographic corrosion method for N06625 alloy, using a rod with a specification of Φ204mm, the chemical composition mass percentage is: Cr: 22%, Mo: 10%, Nb: 4%, C: 0.06%, Mn: 0.5%: Fe: 3.0%, Al+Ti: 0.8%, the balance is Ni, a sample is taken at 1 / 2 of the radius of a 20mm thick disc at the head of the finished rod, the sample is hot-mounted, ground, polished, and then chemically corroded, a new ratio of chemical corrosion liquid (water: hydrochloric acid: alcohol: hydrogen peroxide = 3: 10: 10: 1) is used to chemically corrode the N06625 alloy at a constant temperature (30°C), and intergranular carbides are displayed through a specific electrochemical corrosion reaction. The new corrosion method makes the metallographic microstructure of the alloy clear and displays intergranular carbides. The new corrosion method is suitable for the inspection of the grain size and carbides of the N06625 alloy, and includes the following steps:

[0007] S1. Cut a 20mm thick disc from the head of the Φ204mm finished bar, and use wire cutting to sample at 1 / 2 of the disc radius. The sample size is 10×10×10mm. The sample is polished with 400 mesh, 800 mesh, and 1200 mesh sandpaper in turn, and then machine polished. The sample is cleaned to ensure that there is no debris or dust on the sample surface;

[0008] S2. Prepare a new chemical corrosion solution with a ratio of water: hydrochloric acid: alcohol: hydrogen peroxide = 3:10:10:1. After preparation, let the new corrosion solution stand for 300 minutes before use;

[0009] S3. Before chemical corrosion, the new corrosion solution is kept at 30℃ for 15 minutes, and the temperature of the corrosion solution is measured to be 30℃±1℃ before the sample is immersed in corrosion. The corrosion time is 420s, and 1ml of hydrogen peroxide is dripped every 120s. After the corrosion is completed, the sample is cleaned with alcohol and water;

[0010] Preferably, in step S1, the sampling position and size are sampled on the finished bar, and the sample is polished with 400 mesh, 800 mesh, and 1200 mesh sandpaper in sequence, and then machine polished.

[0011] Preferably, in step S2, the ratio of the cold new chemical etching solution is water: hydrochloric acid: alcohol: hydrogen peroxide = 3:10:10:1. After the preparation, the new etching solution is left to stand for 300 minutes before use.

[0012] Preferably, in step S3, before chemical etching, the new type of etching solution is kept at 30°C for 15 minutes, and then the temperature of the etching solution is measured to be 30°C±1°C before the sample is immersed in the etching, and the etching time is 420 seconds, and 1 ml of hydrogen peroxide is dripped every 120 seconds.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: the present application uses a new type of corrosion solution and corrosion method to chemically corrode the N06625 alloy, so that the metallographic microstructure morphology of the alloy is clear, intergranular carbides are displayed, the difficulty of observing intergranular carbides under an optical microscope is reduced, and the alloy grain size assessment is more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 High magnification of Φ36mm bar: (a) core 100×; (b) R / 2100×; (c) edge 100×; DETAILED DESCRIPTION

[0015] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0016] See also Figure 1

[0017] In the embodiment of the present invention, the carbide rating adopts the GB / T 14999.6-2010 standard, and the sample is taken from the center, R / 2, and edge of the rod billet and then polished and the structure is observed with a metallographic microscope;

[0018] In the embodiment of the invention, the grain size rating adopts the ASTM E 112 standard, and samples are taken from the center, R / 2, and edge of the rod billet and then the structure is observed with a metallographic microscope;

[0019] The present invention provides a technical solution:

[0020] A metallographic corrosion method for N06625 alloy, using a rod with a specification of Φ204mm, the chemical composition mass percentage is: Cr: 22%, Mo: 10%, Nb: 4%, C: 0.06%, Mn: 0.5%: Fe: 3.0%, Al+Ti: 0.8%, the balance is Ni, a sample is taken at the 1 / 2 radius of a 20mm thick disc cut from the head of the finished rod, the sample is hot mounted, ground, polished and then chemically corroded, a new ratio of chemical corrosion liquid (water: hydrochloric acid: alcohol: hydrogen peroxide = 3: 10: 10: 1) is used to chemically corrode the N06625 alloy at a constant temperature (30°C), and intergranular carbides are displayed through a specific electrochemical corrosion reaction. The new corrosion method makes the metallographic microstructure of the alloy clear and displays intergranular carbides. The new corrosion method is suitable for the inspection of the grain size and carbides of the N06625 alloy, and includes the following steps:

[0021] S1. Cut a 20mm thick disc from the head of the Φ204mm finished bar, and use wire cutting to sample at 1 / 2 of the disc radius. The sample size is 10×10×10mm. The sample is polished with 400 mesh, 800 mesh, and 1200 mesh sandpaper in turn, and then machine polished. The sample is cleaned to ensure that there is no debris or dust on the sample surface;

[0022] S2. Prepare a new chemical corrosion solution with a ratio of water: hydrochloric acid: alcohol: hydrogen peroxide = 3:10:10:1. After preparation, let the new corrosion solution stand for 300 minutes before use;

[0023] S3. Before chemical corrosion, the new corrosion solution is kept at 30℃ for 15 minutes, and the temperature of the corrosion solution is measured to be 30℃±1℃ before the sample is immersed in corrosion. The corrosion time is 420s, and 1ml of hydrogen peroxide is dripped every 120s. After the corrosion is completed, the sample is cleaned with alcohol and water;

[0024] Furthermore, in step S1, a disc with a thickness of 20 mm is cut from the head of the Φ204 mm finished rod, and a sample is taken at 1 / 2 of the radius of the disc by wire cutting. The sample size is 10×10×10 mm. The sample is polished with 400 mesh, 800 mesh, and 1200 mesh sandpaper in sequence, and then machine polished. The sample is cleaned to ensure that there is no debris or dust on the surface of the sample.

[0025] Furthermore, in step S2, a new chemical corrosion solution is prepared in a ratio of water: hydrochloric acid: alcohol: hydrogen peroxide = 3:10:10:1. After preparation, the new corrosion solution is left to stand for 300 minutes before use.

[0026] Furthermore, in step S3, before chemical corrosion, the new corrosion solution is kept at 30°C for 15 minutes, and then the temperature of the corrosion solution is measured to be 30°C±1°C before the sample is immersed in corrosion. The corrosion time is 420 seconds, and 1 ml of hydrogen peroxide is dripped every 120 seconds. After the corrosion is completed, the sample is cleaned with alcohol and water.

[0027] Example 1

[0028] A metallographic corrosion method for N06625 alloy, using a rod with a specification of Φ204mm, the chemical composition mass percentage is: Cr: 22%, Mo: 10%, Nb: 4%, C: 0.06%, Mn: 0.5%: Fe: 3.0%, Al+Ti: 0.8%, the balance is Ni, a sample is taken at 1 / 2 of the radius of a 20mm thick disc at the head of the finished rod, the sample is hot-mounted, ground, polished, and then chemically corroded, a new ratio of chemical corrosion liquid (water: hydrochloric acid: alcohol: hydrogen peroxide = 3: 10: 10: 1) is used to chemically corrode the N06625 alloy at a constant temperature (30°C), and intergranular carbides are displayed through a specific electrochemical corrosion reaction. The new corrosion method makes the metallographic microstructure of the alloy clear and displays intergranular carbides. The new corrosion method is suitable for the inspection of the grain size and carbides of the N06625 alloy, and includes the following steps:

[0029] S1. Cut a 20mm thick disc from the head of the Φ204mm finished bar, and use wire cutting to sample at 1 / 2 of the disc radius. The sample size is 10×10×10mm. The sample is polished with 400 mesh, 800 mesh, and 1200 mesh sandpaper in turn, and then machine polished. The sample is cleaned to ensure that there is no debris or dust on the sample surface;

[0030] S2. Prepare a new chemical corrosion solution with a ratio of water: hydrochloric acid: alcohol: hydrogen peroxide = 3:10:10:1. After preparation, the new corrosion solution is left to stand for 185 minutes before use;

[0031] S3. Before chemical corrosion, the new corrosion solution is kept at 30℃ for 12 minutes. After the temperature of the corrosion solution is measured to be 30℃, the sample is immersed in corrosion for 380 seconds. 1ml of hydrogen peroxide is dripped every 120 seconds. After the corrosion is completed, the sample is cleaned with alcohol and water.

[0032] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A metallographic corrosion method for N06625 alloy, using a rod of Φ204mm specification, the chemical composition mass percentage is: Cr: 20%-22%, Mo: 8%-10%, Nb: 3%-4%, C: 0.05%-0.06%, Mn≤0.5%: Fe: 2.5%-3.0%, Al+Ti: 0.5%-0.8%, the balance is Ni, sampling is taken at 1 / 2 of the radius of a 20mm thick disc at the head of the finished rod, the sample is hot-mounted, ground, polished and then chemically corroded, the N06625 alloy is chemically corroded at a constant temperature (30°C) using a proportioned chemical corrosive liquid, and intergranular carbides are displayed through a specific electrochemical corrosion reaction; the metallographic microstructure morphology of the alloy is made clear by the corrosion method, and the intergranular carbides are displayed. The corrosion method is suitable for the inspection of the grain size and carbides of the N06625 alloy, and comprises the following steps: S1. Cut a 20mm thick disc from the head of the Φ204mm finished bar, and use wire cutting to sample at 1 / 2 of the disc radius. The sample size is 10×10×10mm. The sample is polished with 400 mesh, 800 mesh, and 1200 mesh sandpaper in turn, and then machine polished. The sample is cleaned to ensure that there is no debris or dust on the sample surface; S2. Prepare a chemical corrosion solution with a ratio of water: hydrochloric acid: alcohol: hydrogen peroxide = 3:10:10:

1. After preparation, let the new corrosion solution stand for 150 to 300 minutes before use; S3. Before chemical corrosion, the new corrosion solution is kept at 30℃ for 10-15min, and the temperature of the corrosion solution is measured to be 30℃±1℃ before the sample is immersed in corrosion. The corrosion time is 360-420s, and 1ml of hydrogen peroxide is dripped every 120s. After the corrosion is completed, the sample is cleaned with alcohol and water; 2. The metallographic corrosion method of N06625 alloy according to claim 1, characterized in that: The ratio of the chemical etching solution is water: hydrochloric acid: alcohol: hydrogen peroxide = 3:10:10:1 3. The metallographic corrosion method of N06625 alloy according to claim 1, characterized in that: Step S1: Sample the sampling position and size on the finished bar, grind it with 400 mesh, 800 mesh and 1200 mesh sandpaper in sequence, and then perform machine polishing.

4. The metallographic corrosion method of N06625 alloy according to claim 2, characterized in that: The chemical etching ratio in step S2 is water: hydrochloric acid: alcohol: hydrogen peroxide = 3:10:10:

1. After the preparation, the new etching solution is left to stand for 150 to 300 minutes before use.

5. The metallographic corrosion method of N06625 alloy according to claim 3, characterized in that: Before the chemical corrosion in step S3, the chemical corrosion is kept at 30°C for 10-15 minutes, and then the temperature of the corrosion solution is measured to be 30°C±1°C, and then the sample is immersed and corroded. The corrosion time is 360-420s, and 1ml of hydrogen peroxide is dripped every 120s.

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