Corrosive agent and method for displaying metallographic phase of Ni-Co-based alloy

Abstract

The invention belongs to the technical field of metallographic detection, and particularly discloses a corrosive agent and method for displaying a metallographic phase of a Ni-Co-based alloy, and the corrosive agent is prepared from 3-10 g of ammonium persulfate, 5-15 g of copper sulfate, 30-50 mL of hydrochloric acid and 50-100 mL of absolute ethyl alcohol. The method comprises the steps of sample preparation, sample corrosion and metallographic structure observation. According to the corrosive agent and the method provided by the invention, a complete and clear austenite metallographic structure can be obtained, and the detection accuracy of the Ni-Co-based alloy is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of metallographic detection, and in particular relates to an etchant and a method for displaying the metallographic phase of a Ni-Co based alloy. Background Art

[0002] High-temperature alloys are key components used in aero-engines. They need to withstand greater thermal shocks, which determines the reliability, safety and stability of the entire engine. With the improvement of aero-engine performance, high-temperature alloy components in aero-engines are constantly developing towards precision, complexity, high quality and high standardization. At present, iron-based alloys, nickel-based alloys, titanium-based alloys and chromium-based alloys have been widely used in the manufacture of high-temperature parts of aero-engines. Among them, NiCo alloys have low cost, high strength, high thermal corrosion resistance, excellent mechanical, high temperature resistance and hot processing properties, and Ni-Co-based high-temperature alloys have been selected as high-generation aero-engine turbine disk materials working at temperatures of 750°C and above. In the microscopic field, the metallographic structure of NiCo alloy is austenite. The boundaries of the austenite grains of NiCo alloys displayed by traditional corrosive agents are unclear, which seriously affects the test and research on the microstructure of aero-engine parts. This time, the improved corrosive agent and organization display method were used to make NiCo alloy display a relatively complete and clear austenite structure at room temperature. Summary of the invention

[0003] To solve the above problems, the present invention provides an etchant and method for displaying the metallographic structure of Ni-Co based alloys, which can obtain a complete and clear austenite metallographic structure and improve the accuracy of Ni-Co based alloy detection.

[0004] The present invention is achieved through the following technical solutions: The invention discloses an etchant for displaying the metallographic phase of a Ni-Co based alloy. The etchant is prepared from 3-10g of ammonium persulfate, 5-15g of copper sulfate, 30-50ml of hydrochloric acid and 50-100ml of anhydrous ethanol.

[0005] A method for displaying the metallographic structure of a Ni-Co based alloy comprises sample preparation, sample corrosion and metallographic structure observation.

[0006] Furthermore, the sample preparation of the present invention is as follows: the surface of the sample to be tested is ground and polished in sequence until the surface to be tested is mirror-like and has no obvious scratches, and then rinsed with water and anhydrous ethanol and blown dry.

[0007] Furthermore, the grinding described in the present invention includes coarse grinding and fine grinding.

[0008] Furthermore, the sample corrosion of the present invention comprises placing the sample in a corrosive agent for corrosion, wherein the corrosive agent is prepared from 3 to 10 g of ammonium persulfate, 5 to 15 g of copper sulfate, 30 to 50 mL of hydrochloric acid, and 50 to 100 mL of anhydrous ethanol.

[0009] Furthermore, the sample corrosion of the present invention has a corrosion time of 5 to 10 seconds.

[0010] Furthermore, the Ni-Co based alloy of the present invention is sampled after a solid solution process.

[0011] The method of the present invention can obtain an austenite structure with distinct grain boundaries.

[0012] The inventive principle of the technical solution of the present invention is: The hydrochloric acid in the etching solution can destroy the passivation film and oxide film on the surface of the sample, playing a major role in corrosion; ammonium persulfate is an accelerator that promotes the dissolution and corrosion of metal ions; copper sulfate can accelerate the chemical reaction on the metal surface, making the metallographic structure contrast more obvious; anhydrous ethanol helps dissolve other components, so that the components in the etching agent are evenly mixed, which is also conducive to the rapid drying of the sample after corrosion and reduces the impact of residual liquid on subsequent observations.

[0013] Ammonium persulfate is added to the etchant of the present invention, and the high solubility of persulfate and its corrosive effect on metals are utilized to clearly display the boundaries, thereby being able to more accurately reveal the metallographic structure.

[0014] The technical solution of the present invention has the following beneficial effects: The reagents selected for the etchant of the present invention are all commonly used chemicals in laboratories, which ensures the easy availability of experimental materials and can be prepared at room temperature.

[0015] The method of the invention is simple, reliable, can clearly display the microstructure characteristics of the Ni-Co based alloy, and is suitable for metallographic analysis of the Ni-Co based alloy.

[0016] The method of the present invention can effectively solve the problems existing in the microstructure observation of Ni-Co based alloys, and in particular can clearly display the microstructure of the alloy. It overcomes the common difficulties in traditional technologies, such as the unclear boundaries of austenite grains and the coverage of the alloy surface by oxides. The method of the present invention can more accurately identify and analyze austenite grains and their boundaries, effectively remove or reduce the influence of surface oxides, and thus provide strong technical support for in-depth research on the performance of Ni-Co based alloys. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The metallographic structure of Ni-Co based alloy steel of Example 1 of the present invention (200x); Figure 2The metallographic structure of Ni-Co based alloy steel of Example 2 of the present invention (200x); Figure 3 This is the metallographic structure of the Ni-Co based alloy steel of Example 3 of the present invention (200x). DETAILED DESCRIPTION

[0018] The present invention will be described in detail below through embodiments and corresponding drawings. Example 1

[0019] A method for displaying the metallographic phase of a Ni-Co based alloy comprises the following steps: (1) Sample preparation: Cut the Ni-Co alloy GH93 after the solution process into square specimens of 30mm×30mm×15mm, and perform rough grinding and fine grinding on the test surface of the specimen in turn. Specifically, use 180 mesh, 400 mesh, 600 mesh, 1000 mesh, and 1500 mesh water-based sandpaper for grinding, and each new grinding mark can completely cover the previous grinding mark; then rinse the surface of the specimen with tap water and anhydrous ethanol, and blow dry. Spray the polishing spray on the polishing cloth, and then polish the ground test surface of the specimen until the Ni-Co alloy GH93 test surface is a mirror surface with no obvious scratches; clean the test surface of the specimen with tap water and anhydrous ethanol, and blow dry to complete the sample preparation before corrosion.

[0020] (2) Sample corrosion: Immerse the sample surface for corrosion for 5 seconds. The corrosion agent is prepared by 3g of ammonium persulfate, 10g of copper sulfate, 40mL of hydrochloric acid, and 50mL of anhydrous ethanol. After corrosion, rinse off the excess corrosion agent with tap water and anhydrous ethanol, and blow dry.

[0021] (3) Microstructure observation: The surface of the Ni-Co based alloy GH93 after corrosion was observed using a metallographic microscope. The results are as follows: Figure 1 As shown. Figure 1 It can be seen that the austenite structure in the metallographic structure of the Ni-Co based alloy GH93 obtained in this embodiment is complete and has clear grain boundaries. Example 2

[0022] A method for displaying the metallographic phase of a Ni-Co based alloy comprises the following steps: (1) Sample preparation: Cut the Ni-Co alloy GH4251 after the solution process into square specimens of 30mm×30mm×15mm, and perform rough grinding and fine grinding on the test surface of the specimen in turn. Specifically, use 180 mesh, 400 mesh, 800 mesh, 1200 mesh, and 1500 mesh water-based sandpaper for grinding, and each new grinding mark can completely cover the previous grinding mark; then rinse the sample surface with tap water and anhydrous ethanol, and blow dry. Spray the polishing spray on the polishing cloth, and then polish the ground test surface of the sample until the Ni-Co alloy GH4251 test surface is a mirror surface with no obvious scratches; clean the test surface of the sample with tap water and anhydrous ethanol, and blow dry to complete the sample preparation before corrosion.

[0023] (2) Sample corrosion: Immerse the sample surface for corrosion for 8 seconds. The corrosion agent is prepared by 10g of ammonium persulfate, 5g of copper sulfate, 30mL of hydrochloric acid, and 100mL of anhydrous ethanol. After corrosion, rinse off the excess corrosion agent with tap water and anhydrous ethanol, and blow dry.

[0024] (3) Organization observation: The surface of the Ni-Co based alloy GH4251 after corrosion was observed using a metallographic microscope. The results are as follows: Figure 2 As shown. Figure 2 It can be seen that the austenite structure in the metallographic structure of the Ni-Co based alloy GH4251 obtained in this embodiment is complete and has clear grain boundaries. Example 3

[0025] A method for displaying the metallographic phase of a Ni-Co based alloy comprises the following steps: (1) Sample preparation: The Ni-Co alloy MP35N after the solution treatment was cut into square specimens of 30 mm × 30 mm × 15 mm. The test surface of the specimen was coarsely ground and finely ground in sequence. Specifically, 180 mesh, 400 mesh, 600 mesh, 1000 mesh, and 1500 mesh water-based sandpaper were used for grinding, and each new grinding mark could completely cover the previous grinding mark. The surface of the specimen was then rinsed with tap water and anhydrous ethanol and blown dry. The polishing spray was sprayed on the polishing cloth, and then the ground test surface of the specimen was polished until the test surface of the Ni-Co alloy MP35N was a mirror surface with no obvious scratches. The test surface of the specimen was cleaned with tap water and anhydrous ethanol and blown dry to complete the sample preparation before corrosion.

[0026] (2) Sample corrosion: Immerse the sample surface for corrosion for 10 seconds in an etchant prepared from 5 g of ammonium persulfate, 15 g of copper sulfate, 50 mL of hydrochloric acid, and 75 mL of anhydrous ethanol. After corrosion is completed, rinse off excess etchant with tap water and anhydrous ethanol, and blow dry.

[0027] (3) Microstructure observation: The surface of the Ni-Co alloy MP35N after corrosion was observed using a metallographic microscope. The results are as follows: Figure 3 As shown. Figure 3 It can be seen that the austenite structure in the metallographic structure of the Ni-Co based alloy MP35N obtained in this embodiment is complete and the grain boundaries are clear.

Claims

1. An etchant for showing the metallographic structure of a Ni-Co based alloy, characterized in that: The corrosive agent is prepared from 3-10 g of ammonium persulfate, 5-15 g of copper sulfate, 30-50 mL of hydrochloric acid and 50-100 mL of anhydrous ethanol.

2. A method for displaying the metallographic structure of a Ni-Co based alloy, characterized in that: The method comprises sample preparation, sample corrosion and metallographic structure observation; the corrosive agent used for sample corrosion is prepared from 3-10g of ammonium persulfate, 5-15g of copper sulfate, 30-50mL of hydrochloric acid and 50-100mL of anhydrous ethanol.

3. A method for displaying the metallographic phase of a Ni-Co based alloy according to claim 2, characterized in that: The corrosion time of the sample corrosion is 5 to 10 seconds.

4. A method for displaying the metallographic phase of a Ni-Co based alloy according to claim 2, characterized in that: The specific operation of the sample preparation is: grinding and polishing the surface of the sample to be tested in sequence until the surface to be tested is mirror-like and has no obvious scratches, and then washing with water and anhydrous ethanol and blowing dry.

5. A method for displaying the metallographic phase of a Ni-Co based alloy according to claim 4, characterized in that: The grinding includes coarse grinding and fine grinding.

6. A method for displaying the metallographic phase of a Ni-Co based alloy according to claim 2, characterized in that: The Ni-Co based alloy is sampled after a solid solution process.

7. A method for displaying the metallographic phase of a Ni-Co based alloy according to claim 2, characterized in that: The method can obtain an austenite structure with distinct grain boundaries.

Images