A corrosion method for high alloy steel material with simultaneous visualization of grains and structure

Abstract

The present invention relates to a corrosion method for simultaneously revealing the grains and structure of a high-alloy steel material, and belongs to the technical field of high-alloy steel metallographic corrosion. The present invention mechanically grinds high-alloy steel samples in different heat treatment process states; mechanically polishes the mechanically grinded high-alloy steel samples, then sequentially cleans them with deionized water and ethanol, and blows them dry to obtain high-alloy steel metallographic samples; according to the different heat treatment process states of the high-alloy steel samples, the high-alloy steel metallographic samples are immersed in a corrosive solution and corroded until dark gray corrosion rust stains appear on the surface of the high-alloy steel metallographic samples; the corrosive solution comprises concentrated hydrochloric acid, concentrated nitric acid, FeCl3, and anhydrous ethanol; the high-alloy steel metallographic samples corroded by the corrosive solution are placed in deionized water, the sample surface is wiped with cotton until the dark gray corrosion rust stains turn dark silver, the sample is then cleaned with anhydrous ethanol and blown dry, and the microstructure and grain morphology of the high-alloy steel sample are observed using a metallographic microscope.

Description

Technical Field

[0001] The invention relates to a corrosion method for jointly revealing crystal grains and structures of a high-alloy steel material, belonging to the technical field of metallographic corrosion of high-alloy steel. Background Art

[0002] High-alloy steels are primarily used in mining machinery, transmission gears, bearings, high-speed cutting tools, and other applications requiring complex service performance. With the increasing demand for technological advancements and industrial production, service environments are becoming increasingly demanding, placing even higher demands on high-alloy steels. In these challenging environments, high-alloy steels are not only subjected to prolonged periods of high temperature, high impact, and high fatigue stress, but are also frequently subjected to brief, transient heating events. Therefore, high-alloy steels must exhibit excellent high-temperature oxidation resistance, high dimensional stability, high high-temperature hardness, and good toughness and contact fatigue resistance. To meet these performance requirements, these materials typically have high carbon contents and complex alloying element ratios, with high concentrations of these elements. Therefore, studying the microstructure of high-alloy steels is crucial for understanding the relationship between composition, structure, and performance. However, due to their complex composition and specialized processing conditions, the preparation of metallographic specimens for these materials under different processing conditions is complex. Furthermore, the corrosion process requires different corrosive media for grain and microstructure analysis. The commonly used methods for corrosion of high alloy steel grains and microstructures are as follows: (1) Use 1g KMnO4 + 90mL H2O + 10mL concentrated sulfuric acid solution in a 60℃ water bath for 2h to perform grain boundary corrosion; (2) Use 2g CuCl2 + 50ml HCl + 50ml H2O solution to corrode for 5s to observe carbides and matrix microstructure.

[0003] The above metallographic etching agents are relatively complicated to operate during the application process. They need to be heated or corroded for a long time to reveal the grains or microstructure of the experimental materials. Especially in terms of grain visualization, the operation is complicated and time-consuming, and the effect of corroding grains and microstructure cannot be achieved at the same time. Summary of the Invention

[0004] In view of the technical problems such as the harsh corrosion conditions for the visualization of high-alloy steel grains and microstructures, and the inability to simultaneously present grains and microstructures, the present invention proposes a corrosion method for the simultaneous visualization of grains and microstructures of high-alloy steel materials. By immersing and corroding the surface of a polished high-alloy steel sample with a specific corrosive agent, good microstructure and grain corrosion effects can be simultaneously obtained in a short period of time. After corroding high-alloy steel, the alloy grain boundaries and microstructures under different heat treatment states can be clearly observed by the method of the present invention, which is suitable for studying the grain morphology, grain size and microstructure of high-alloy steel under different heat treatment process states.

[0005] A corrosion method for high alloy steel material with simultaneous manifestation of grain and structure, comprising the following steps:

[0006] (1) High alloy steel samples in different heat treatment process states were mechanically polished with 360 mesh, 600 mesh, 800 mesh, 1000 mesh, and 2000 mesh sandpaper in sequence; the heat treatment process state was quenched, tempered, or cold treated;

[0007] (2) mechanically polishing the mechanically ground high-alloy steel sample, then washing it with deionized water and ethanol in sequence, and drying it to obtain a high-alloy steel metallographic sample;

[0008] (3) According to the different heat treatment process conditions of the high-alloy steel samples, the high-alloy steel metallographic samples are immersed in a corrosive solution and corroded until dark gray corrosion rust stains appear on the surface of the high-alloy steel metallographic samples; the corrosive solution is composed of commercially available concentrated hydrochloric acid, concentrated nitric acid, FeCl3 and anhydrous ethanol;

[0009] (4) The metallographic specimens of high-alloy steel corroded by the corrosive solution were placed under deionized water, and the surface of the specimens was wiped with cotton until the dark gray corrosion stains turned into dark silver. The specimens were then cleaned with anhydrous ethanol and blown dry, and the microstructure and grain morphology of the high-alloy steel specimens were observed using a metallographic microscope.

[0010] The alloy composition of the high alloy steel is as follows: in terms of mass percentage, the C content in the high alloy steel is 0.1-0.15%, the total content of alloy elements is 29-36%, the total content of impurity elements P and S is not more than 0.02%, and the rest is Fe.

[0011] Preferably, the specific method of mechanical polishing in step (2) is: using a woolen polishing cloth and a diamond polishing paste with a particle size of 0.5 μm to perform mechanical polishing until the surface is mirror-like and there are no polishing marks in different directions under optical microscope observation.

[0012] The liquid-to-solid ratio of concentrated hydrochloric acid, concentrated nitric acid, FeCl3 and anhydrous ethanol in the etching solution of step (3) is 5-25:0.5-1:1-5:5-25.

[0013] The heat treatment process state of the high alloy steel sample is the quenching state, and the calculation formula of the corrosion time t of the high alloy steel metallographic sample after being immersed in the corrosive liquid is:

[0014] t = -1.25x + 11.42;

[0015] Where, t is the corrosion immersion time, min; x is the mass fraction of FeCl3 in the corrosive medium;

[0016] The heat treatment process state of the high alloy steel sample is the tempered state. The calculation formula for the corrosion time t of the high alloy steel metallographic sample after immersion in the corrosive solution is:

[0017] t = -1.25x + 21.42;

[0018] Where, t is the corrosion immersion time, min; x is the mass fraction of FeCl3 in the corrosive medium;

[0019] The heat treatment process state of the high alloy steel sample is the cold treatment state. The calculation formula of the corrosion time t of the high alloy steel metallographic sample immersed in the corrosive solution is:

[0020] t = -1.25x + 16.42;

[0021] Where, t is the corrosion immersion time, min; x is the mass fraction of FeCl3 in the corrosive medium.

[0022] Preferably, the heat treatment process state of the high alloy steel sample in step (3) is a quenched state, and the high alloy steel metallographic sample is immersed in the corrosive solution and corroded for 5 to 10 minutes;

[0023] The heat treatment process state of the high alloy steel sample is the tempered state, and the high alloy steel metallographic sample is immersed in the corrosive solution for 15 to 20 minutes;

[0024] The heat treatment process state of the high alloy steel sample is the cold treatment state, and the high alloy steel metallographic sample is immersed in the corrosive solution and corroded for 10 to 15 minutes.

[0025] The corrosion principle of high alloy steel grains and microstructures: After quenching, almost all alloy elements of high alloy steel are dissolved in the matrix martensite phase. During the corrosion process, the quenched martensite phase is relatively coarse, the atomic arrangement at the grain boundary is irregular and the free energy is high. - The grain boundaries and structures are easily corroded in acidic environments, so that the grain boundaries and structures can be revealed in a shorter corrosion time; after deep cryogenic treatment, the martensite phase of high alloy steel materials is refined and a small amount of fine precipitates are generated. During the corrosion process, the corrosion time is prolonged due to the dense structure; after tempering treatment, the structure of high alloy steel materials is further refined into tempered structure, which is different from quenched martensite and is accompanied by a large amount of precipitates. The denser tempered structure and the mutual influence between different phases lead to further extension of the corrosion time.

[0026] The beneficial effects of the present invention are:

[0027] (1) The present invention uses a specific corrosive agent to immerse and corrode the surface of a polished high-alloy steel sample for a specific time, thereby simultaneously obtaining good microstructure and grain corrosion effects in a short period of time;

[0028] (2) After the high alloy steel is corroded, the alloy grain boundaries and microstructures under different heat treatment conditions can be clearly observed by the method of the present invention, which is suitable for studying the grain morphology, grain size and microstructure of high alloy steel under different heat treatment process conditions;

[0029] (3) The method of the present invention has low requirements for the corrosive environment and simple operation steps, which effectively saves time and economic costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a 200x metallographic image of the quenched high alloy steel prepared in Example 1;

[0031] Figure 2 This is a 200x metallographic image of the quenched high alloy steel prepared in Example 2;

[0032] Figure 3 This is a 200x metallographic image of the quenched high alloy steel prepared in Example 3;

[0033] Figure 4 This is a 200x metallographic image of the tempered high alloy steel prepared in Example 4;

[0034] Figure 5 This is a 200x metallographic image of the tempered high alloy steel prepared in Example 5;

[0035] Figure 6 This is a 200x metallographic image of the tempered high-alloy steel prepared in Example 6;

[0036] Figure 7 This is a 100x metallographic image of the cold-treated high-alloy steel prepared in Example 7;

[0037] Figure 8 This is a 100x metallographic image of the cold-treated high-alloy steel prepared in Example 8;

[0038] Figure 9 This is a 100x metallographic image of the cold-treated high-alloy steel prepared in Example 9;

[0039] Figure 10 This is a 100x metallographic image of the high-alloy steel prepared using the method of 1g KMnO4+90mL H2O+10mL concentrated sulfuric acid solution in Comparative Example 1;

[0040] Figure 11 This is a 500x metallographic image of high-alloy steel prepared using the 2g CuCl2+50ml HCl+50ml H2O solution method in Comparative Example 2. DETAILED DESCRIPTION

[0041] The present invention will be further described in detail below in conjunction with specific embodiments, but the protection scope of the present invention is not limited to the contents described above.

[0042] The alloy composition of the high alloy steel in the embodiment of the present invention is as follows: in terms of mass percentage, the C content in the high alloy steel is 0.1-0.15%, the total content of alloying elements is 29-36%, the total content of impurity elements P and S is no more than 0.02%, and the rest is Fe.

[0043] Example 1: A corrosion method for simultaneously revealing grains and microstructures of high-alloy steel materials, comprising the following steps:

[0044] (1) The quenched high alloy steel sample was mechanically polished with 360 mesh, 600 mesh, 800 mesh, 1000 mesh, and 2000 mesh sandpaper in sequence;

[0045] (2) The mechanically polished high-alloy steel sample was mechanically polished using a woolen polishing cloth and a diamond polishing paste with a particle size of 0.5 μm until the surface was mirror-like and there were no polishing marks in different directions under optical microscope observation. The sample was then washed with deionized water and ethanol in sequence and dried to obtain a high-alloy steel metallographic sample.

[0046] (3) Calculate the corrosion time of the high-alloy steel metallographic sample after immersion in a corrosive solution based on the heat treatment process state (quenched state) of the high-alloy steel sample. The corrosive solution consists of 5 mL of commercially available concentrated hydrochloric acid, 0.5 mL of concentrated nitric acid (mass concentration of 65%), 1 g of FeCl3, and 5 mL of anhydrous ethanol.

[0047] t = -1.25x + 11.42;

[0048] Where, t is the corrosion immersion time, min; x is the mass fraction of FeCl3 in the corrosive medium;

[0049] In this embodiment, t is 10.17 min. Therefore, when the high-alloy steel metallographic specimen is immersed in the corrosive solution and corroded for 10.17 min, dark gray corrosion rust stains appear on the surface of the high-alloy steel metallographic specimen.

[0050] (4) The high-alloy steel metallographic specimen corroded by the corrosive solution was placed in deionized water, and the surface of the specimen was wiped with cotton until the dark gray rust stains turned into dark silver. The specimen was then cleaned with anhydrous ethanol and blown dry. The microstructure and grain morphology of the high-alloy steel specimen were observed using a metallographic microscope;

[0051] The 200x metallographic picture of the quenched high alloy steel prepared in this embodiment is shown in Figure 1 ,from Figure 1 The clear microstructure and grain morphology of high alloy steel materials can be seen at the same time.

[0052] Example 2: A corrosion method for simultaneously revealing grains and microstructures of high-alloy steel materials, comprising the following steps:

[0053] (1) The quenched high alloy steel sample was mechanically polished with 360 mesh, 600 mesh, 800 mesh, 1000 mesh, and 2000 mesh sandpaper in sequence;

[0054] (2) The mechanically polished high-alloy steel sample was mechanically polished using a woolen polishing cloth and a diamond polishing paste with a particle size of 0.5 μm until the surface was mirror-like and there were no polishing marks in different directions under optical microscope observation. The sample was then washed with deionized water and ethanol in sequence and dried to obtain a high-alloy steel metallographic sample.

[0055] (3) Calculate the corrosion time of the high-alloy steel metallographic sample after immersion in a corrosive solution based on the heat treatment process state (quenched state) of the high-alloy steel sample. The corrosive solution consists of 15 mL of commercially available concentrated hydrochloric acid, 0.75 mL of concentrated nitric acid (mass concentration of 65%), 3 g of FeCl3, and 15 mL of anhydrous ethanol.

[0056] t = -1.25x + 11.42;

[0057] Where, t is the corrosion immersion time, min; x is the mass fraction of FeCl3 in the corrosive medium;

[0058] In this embodiment, t is 7.67 min. Therefore, the high alloy steel metallographic sample is immersed in the corrosive solution and corroded for 7.67 min. Dark gray corrosion rust stains appear on the surface of the high alloy steel metallographic sample.

[0059] (4) The high-alloy steel metallographic specimen corroded by the corrosive solution was placed in deionized water, and the surface of the specimen was wiped with cotton until the dark gray rust stains turned into dark silver. The specimen was then cleaned with anhydrous ethanol and blown dry. The microstructure and grain morphology of the high-alloy steel specimen were observed using a metallographic microscope;

[0060] The 200x metallographic picture of the quenched high alloy steel prepared in this embodiment is shown in Figure 2 ,from Figure 2 The clear microstructure and grain morphology of high alloy steel materials can be seen at the same time.

[0061] Example 3: A corrosion method for simultaneously revealing grains and microstructures of high-alloy steel materials, comprising the following steps:

[0062] (1) The quenched high alloy steel sample was mechanically polished with 360 mesh, 600 mesh, 800 mesh, 1000 mesh, and 2000 mesh sandpaper in sequence;

[0063] (2) The mechanically polished high-alloy steel sample was mechanically polished using a woolen polishing cloth and a diamond polishing paste with a particle size of 0.5 μm until the surface was mirror-like and there were no polishing marks in different directions under optical microscope observation. The sample was then washed with deionized water and ethanol in sequence and dried to obtain a high-alloy steel metallographic sample.

[0064] (3) Calculate the corrosion time of the high-alloy steel metallographic sample after immersion in a corrosive solution based on the heat treatment process state (quenched state) of the high-alloy steel sample. The corrosive solution consists of 25 mL of commercially available concentrated hydrochloric acid, 1 mL of concentrated nitric acid (mass concentration of 65%), 5 g of FeCl3, and 25 mL of anhydrous ethanol.

[0065] t = -1.25x + 11.42;

[0066] Where, t is the corrosion immersion time, min; x is the mass fraction of FeCl3 in the corrosive medium;

[0067] In this embodiment, t is 5.17 min. Therefore, when the high-alloy steel metallographic sample is immersed in the corrosive solution and corroded for 5.17 min, dark gray corrosion rust stains appear on the surface of the high-alloy steel metallographic sample.

[0068] (4) The high-alloy steel metallographic specimen corroded by the corrosive solution was placed in deionized water, and the surface of the specimen was wiped with cotton until the dark gray rust stains turned into dark silver. The specimen was then cleaned with anhydrous ethanol and blown dry. The microstructure and grain morphology of the high-alloy steel specimen were observed using a metallographic microscope;

[0069] The 200x metallographic picture of the quenched high alloy steel prepared in this embodiment is shown in Figure 3 ,from Figure 3 The clear microstructure and grain morphology of high alloy steel materials can be seen at the same time.

[0070] Example 4: A corrosion method for simultaneously revealing grains and microstructures of high-alloy steel materials, comprising the following steps:

[0071] (1) The tempered high alloy steel sample was mechanically polished with 360 mesh, 600 mesh, 800 mesh, 1000 mesh, and 2000 mesh sandpaper in sequence;

[0072] (2) The mechanically polished high-alloy steel sample was mechanically polished using a woolen polishing cloth and a diamond polishing paste with a particle size of 0.5 μm until the surface was mirror-like and there were no polishing marks in different directions under optical microscope observation. The sample was then washed with deionized water and ethanol in sequence and dried to obtain a high-alloy steel metallographic sample.

[0073] (3) Calculate the corrosion time of the high-alloy steel metallographic sample after immersion in a corrosive solution based on the heat treatment process state (tempered state) of the high-alloy steel sample. The corrosive solution consists of 5 mL of commercially available concentrated hydrochloric acid, 0.5 mL of concentrated nitric acid (mass concentration of 65%), 1 g of FeCl3, and 5 mL of anhydrous ethanol.

[0074] t = -1.25x + 21.42;

[0075] Where, t is the corrosion immersion time, min; x is the mass fraction of FeCl3 in the corrosive medium;

[0076] In this embodiment, t is 20.17 min. Therefore, the high-alloy steel metallographic sample is immersed in the corrosive solution and corroded for 20.17 min. Dark gray corrosion rust stains appear on the surface of the high-alloy steel metallographic sample.

[0077] (4) The high-alloy steel metallographic specimen corroded by the corrosive solution was placed in deionized water, and the surface of the specimen was wiped with cotton until the dark gray rust stains turned into dark silver. The specimen was then cleaned with anhydrous ethanol and blown dry. The microstructure and grain morphology of the high-alloy steel specimen were observed using a metallographic microscope;

[0078] The 200x metallographic picture of the tempered high alloy steel prepared in this embodiment is shown in Figure 4 ,from Figure 4 The clear microstructure and grain morphology of high alloy steel materials can be seen at the same time.

[0079] Example 5: A corrosion method for simultaneously revealing grains and microstructures of high-alloy steel materials, comprising the following steps:

[0080] (1) The tempered high alloy steel sample was mechanically polished with 360 mesh, 600 mesh, 800 mesh, 1000 mesh, and 2000 mesh sandpaper in sequence;

[0081] (2) The mechanically polished high-alloy steel sample was mechanically polished using a woolen polishing cloth and a diamond polishing paste with a particle size of 0.5 μm until the surface was mirror-like and there were no polishing marks in different directions under optical microscope observation. The sample was then washed with deionized water and ethanol in sequence and dried to obtain a high-alloy steel metallographic sample.

[0082] (3) Calculate the corrosion time of the high-alloy steel metallographic sample after immersion in a corrosive solution based on the heat treatment process state (tempered state) of the high-alloy steel sample. The corrosive solution consists of 15 mL of commercially available concentrated hydrochloric acid, 0.75 mL of concentrated nitric acid (mass concentration of 65%), 3 g of FeCl3, and 15 mL of anhydrous ethanol.

[0083] t = -1.25x + 21.42;

[0084] Where, t is the corrosion immersion time, min; x is the mass fraction of FeCl3 in the corrosive medium;

[0085] In this embodiment, t is 17.67 min. Therefore, the high-alloy steel metallographic sample is immersed in the corrosive solution and corroded for 17.67 min. Dark gray corrosion rust stains appear on the surface of the high-alloy steel metallographic sample.

[0086] (4) The high-alloy steel metallographic specimen corroded by the corrosive solution was placed in deionized water, and the surface of the specimen was wiped with cotton until the dark gray rust stains turned into dark silver. The specimen was then cleaned with anhydrous ethanol and blown dry. The microstructure and grain morphology of the high-alloy steel specimen were observed using a metallographic microscope;

[0087] The 200x metallographic picture of the tempered high alloy steel prepared in this embodiment is shown in Figure 5 ,from Figure 5 The clear microstructure and grain morphology of high alloy steel materials can be seen at the same time.

[0088] Example 6: A corrosion method for simultaneously revealing grains and microstructures of high-alloy steel materials, comprising the following steps:

[0089] (1) The tempered high alloy steel sample was mechanically polished with 360 mesh, 600 mesh, 800 mesh, 1000 mesh, and 2000 mesh sandpaper in sequence;

[0090] (2) The mechanically polished high-alloy steel sample was mechanically polished using a woolen polishing cloth and a diamond polishing paste with a particle size of 0.5 μm until the surface was mirror-like and there were no polishing marks in different directions under optical microscope observation. The sample was then washed with deionized water and ethanol in sequence and dried to obtain a high-alloy steel metallographic sample.

[0091] (3) Calculate the corrosion time of the high-alloy steel metallographic sample after immersion in a corrosive solution based on the heat treatment process state (tempered state) of the high-alloy steel sample. The corrosive solution consists of 25 mL of commercially available concentrated hydrochloric acid, 1 mL of concentrated nitric acid (mass concentration of 65%), 5 g of FeCl3, and 25 mL of anhydrous ethanol.

[0092] t = -1.25x + 21.42;

[0093] Where, t is the corrosion immersion time, min; x is the mass fraction of FeCl3 in the corrosive medium;

[0094] In this embodiment, t is 15.17 min. Therefore, when the high-alloy steel metallographic specimen is immersed in the corrosive solution and corroded for 15.17 min, dark gray corrosion rust stains appear on the surface of the high-alloy steel metallographic specimen.

[0095] (4) The high-alloy steel metallographic specimen corroded by the corrosive solution was placed in deionized water, and the surface of the specimen was wiped with cotton until the dark gray rust stains turned into dark silver. The specimen was then cleaned with anhydrous ethanol and blown dry. The microstructure and grain morphology of the high-alloy steel specimen were observed using a metallographic microscope;

[0096] The 200x metallographic picture of the tempered high alloy steel prepared in this embodiment is shown in Figure 6 ,from Figure 6 The clear microstructure and grain morphology of high alloy steel materials can be seen at the same time.

[0097] Example 7: A corrosion method for high alloy steel material with both grain and structure (see Figure 1 ), the specific steps are as follows:

[0098] (1) The cryogenically treated high alloy steel sample was mechanically polished with 360 mesh, 600 mesh, 800 mesh, 1000 mesh, and 2000 mesh sandpaper in sequence;

[0099] (2) The mechanically polished high-alloy steel sample was mechanically polished using a woolen polishing cloth and a diamond polishing paste with a particle size of 0.5 μm until the surface was mirror-like and there were no polishing marks in different directions under optical microscope observation. The sample was then washed with deionized water and ethanol in sequence and dried to obtain a high-alloy steel metallographic sample.

[0100] (3) Calculate the corrosion time of the high-alloy steel metallographic sample after immersion in a corrosive solution based on the heat treatment process status (cryogenic treatment status) of the high-alloy steel sample. The corrosive solution consists of 5 mL of commercially available concentrated hydrochloric acid, 0.5 mL of concentrated nitric acid (mass concentration of 65%), 1 g of FeCl3, and 5 mL of anhydrous ethanol.

[0101] t = -1.25x + 16.42;

[0102] Where, t is the corrosion immersion time, min; x is the mass fraction of FeCl3 in the corrosive medium;

[0103] In this embodiment, t is 15.17 min. Therefore, when the high-alloy steel metallographic specimen is immersed in the corrosive solution and corroded for 15.17 min, dark gray corrosion rust stains appear on the surface of the high-alloy steel metallographic specimen.

[0104] (4) The high-alloy steel metallographic specimen corroded by the corrosive solution was placed in deionized water, and the surface of the specimen was wiped with cotton until the dark gray rust stains turned into dark silver. The specimen was then cleaned with anhydrous ethanol and blown dry. The microstructure and grain morphology of the high-alloy steel specimen were observed using a metallographic microscope;

[0105] The 100x metallographic picture of the cryogenically treated high alloy steel prepared in this embodiment is shown in Figure 7 ,from Figure 7 The clear microstructure and grain morphology of high alloy steel materials can be seen at the same time.

[0106] Example 8: A corrosion method for simultaneously revealing grains and microstructures of a high-alloy steel material, comprising the following steps:

[0107] (1) The cryogenically treated high alloy steel sample was mechanically polished with 360 mesh, 600 mesh, 800 mesh, 1000 mesh, and 2000 mesh sandpaper in sequence;

[0108] (2) The mechanically polished high-alloy steel sample was mechanically polished using a woolen polishing cloth and a diamond polishing paste with a particle size of 0.5 μm until the surface was mirror-like and there were no polishing marks in different directions under optical microscope observation. The sample was then washed with deionized water and ethanol in sequence and dried to obtain a high-alloy steel metallographic sample.

[0109] (3) Calculate the corrosion time of the high-alloy steel metallographic sample after immersion in a corrosive solution based on the heat treatment process status (cryogenic treatment status) of the high-alloy steel sample. The corrosive solution consists of 15 mL of commercially available concentrated hydrochloric acid, 0.75 mL of concentrated nitric acid (mass concentration of 65%), 3 g of FeCl3, and 15 mL of anhydrous ethanol.

[0110] t = -1.25x + 16.42;

[0111] Where, t is the corrosion immersion time, min; x is the mass fraction of FeCl3 in the corrosive medium;

[0112] In this embodiment, t is 12.67 min. Therefore, the high-alloy steel metallographic sample is immersed in the corrosive solution and corroded for 12.67 min. Dark gray corrosion rust stains appear on the surface of the high-alloy steel metallographic sample.

[0113] (4) The high-alloy steel metallographic specimen corroded by the corrosive solution was placed in deionized water, and the surface of the specimen was wiped with cotton until the dark gray rust stains turned into dark silver. The specimen was then cleaned with anhydrous ethanol and blown dry. The microstructure and grain morphology of the high-alloy steel specimen were observed using a metallographic microscope;

[0114] The 100x metallographic picture of the cryogenically treated high alloy steel prepared in this embodiment is shown in Figure 8 ,from Figure 8 The clear microstructure and grain morphology of high alloy steel materials can be seen at the same time.

[0115] Example 9: A corrosion method for high alloy steel material with both grain and structure (see Figure 1 ), the specific steps are as follows:

[0116] (1) The cryogenically treated high alloy steel sample was mechanically polished with 360 mesh, 600 mesh, 800 mesh, 1000 mesh, and 2000 mesh sandpaper in sequence;

[0117] (2) The mechanically polished high-alloy steel sample was mechanically polished using a woolen polishing cloth and a diamond polishing paste with a particle size of 0.5 μm until the surface was mirror-like and there were no polishing marks in different directions under optical microscope observation. The sample was then washed with deionized water and ethanol in sequence and dried to obtain a high-alloy steel metallographic sample.

[0118] (3) Calculate the corrosion time of the high-alloy steel metallographic sample after immersion in a corrosive solution based on the heat treatment process status (cryogenic treatment status) of the high-alloy steel sample. The corrosive solution consists of 25 mL of commercially available concentrated hydrochloric acid, 1 mL of concentrated nitric acid (mass concentration of 65%), 5 g of FeCl3, and 25 mL of anhydrous ethanol.

[0119] t = -1.25x + 16.42;

[0120] Where, t is the corrosion immersion time, min; x is the mass fraction of FeCl3 in the corrosive medium;

[0121] In this embodiment, t is 10.17 min. Therefore, when the high-alloy steel metallographic specimen is immersed in the corrosive solution and corroded for 10.17 min, dark gray corrosion rust stains appear on the surface of the high-alloy steel metallographic specimen.

[0122] (4) The high-alloy steel metallographic specimen corroded by the corrosive solution was placed in deionized water, and the surface of the specimen was wiped with cotton until the dark gray rust stains turned into dark silver. The specimen was then cleaned with anhydrous ethanol and blown dry. The microstructure and grain morphology of the high-alloy steel specimen were observed using a metallographic microscope;

[0123] The 100x metallographic picture of the cryogenically treated high alloy steel prepared in this embodiment is shown in Figure 9 ,from Figure 9 The clear microstructure and grain morphology of high alloy steel materials can be seen at the same time.

[0124] Comparative Example 1: High alloy steel metallographic corrosion method, the specific steps are as follows:

[0125] (1) The quenched high alloy steel sample was mechanically polished with 360 mesh, 600 mesh, 800 mesh, 1000 mesh, and 2000 mesh sandpaper in sequence;

[0126] (2) The mechanically polished high-alloy steel sample was mechanically polished using a woolen polishing cloth and a diamond polishing paste with a particle size of 0.5 μm until the surface was mirror-like and there were no polishing marks in different directions under optical microscope observation. The sample was then washed with deionized water and ethanol in sequence and dried to obtain a high-alloy steel metallographic sample.

[0127] (3) The high alloy steel metallographic specimen was immersed in a corrosive solution for 2 hours; the corrosive solution consisted of 1 g KMnO4, 90 mL H2O, and 10 mL commercially available concentrated sulfuric acid;

[0128] (4) The metallographic specimens of high alloy steel corroded by the corrosive solution were cleaned with deionized water and anhydrous ethanol in turn and dried, and the microstructure and grain morphology of the high alloy steel specimens were observed using a metallographic microscope;

[0129] The 100x metallographic picture of the high alloy steel prepared in this comparative example is shown in Figure 10 ,from Figure 10 It can be seen that this corrosion method can only obtain the grain morphology but cannot reveal the microstructure. Moreover, the operation is complicated and time-consuming.

[0130] Comparative Example 2: High alloy steel metallographic corrosion method, the specific steps are as follows:

[0131] (1) The tempered high alloy steel sample was mechanically polished with 360 mesh, 600 mesh, 800 mesh, 1000 mesh, and 2000 mesh sandpaper in sequence;

[0132] (2) The mechanically polished high-alloy steel sample was mechanically polished using a woolen polishing cloth and a diamond polishing paste with a particle size of 0.5 μm until the surface was mirror-like and there were no polishing marks in different directions under optical microscope observation. The sample was then washed with deionized water and ethanol in sequence and dried to obtain a high-alloy steel metallographic sample.

[0133] (3) The high alloy steel metallographic specimen was immersed in a corrosive solution for 5 seconds; the corrosive solution consisted of 2 g CuCl2, 50 ml HCl (commercially available concentrated hydrochloric acid), and 50 ml H2O;

[0134] (4) The metallographic specimens of high alloy steel corroded by the corrosive solution were cleaned with deionized water and anhydrous ethanol in turn and dried, and the microstructure and grain morphology of the high alloy steel specimens were observed using a metallographic microscope;

[0135] The 500x metallographic picture of the high alloy steel prepared in this comparative example is shown in Figure 11 ,from Figure 11 It can be seen that this corrosion method can only obtain the microstructure but cannot reveal the grain morphology.

[0136] The above describes the specific embodiments of the present invention in detail, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in this field without departing from the scope of the present invention.

Claims

1. A corrosion method for high alloy steel material with simultaneous manifestation of grain and structure, characterized in that: The specific steps are as follows: (1) High alloy steel samples in different heat treatment process states were mechanically polished with 360 mesh, 600 mesh, 800 mesh, 1000 mesh, and 2000 mesh sandpaper in sequence; the heat treatment process state was quenched, tempered, or cold treated; (2) The mechanically ground high alloy steel sample was mechanically polished, then washed with deionized water and ethanol in sequence, and dried to obtain a high alloy steel metallographic sample; (3) According to different heat treatment process states of the high alloy steel samples, the high alloy steel metallographic samples are immersed in a corrosive solution and corroded until dark gray corrosion rust stains appear on the surface of the high alloy steel metallographic samples; the corrosive solution is composed of concentrated hydrochloric acid, concentrated nitric acid, FeCl3 and anhydrous ethanol; the liquid-to-solid ratio of concentrated hydrochloric acid, concentrated nitric acid, FeCl3 and anhydrous ethanol in the corrosive solution is 5~25:0.5~1:1~5:5~25; The heat treatment process state of the high alloy steel sample is the quenching state, and the calculation formula of the corrosion time t of the high alloy steel metallographic sample after being immersed in the corrosive liquid is: t=-1.25x+11.42; Where, t is the corrosion immersion time, min; x is the mass fraction of FeCl3 in the corrosive medium; The heat treatment process state of the high alloy steel sample is the tempered state. The calculation formula for the corrosion time t of the high alloy steel metallographic sample after immersion in the corrosive solution is: t=-1.25x+21.42; Where, t is the corrosion immersion time, min; x is the mass fraction of FeCl3 in the corrosive medium; The heat treatment process state of the high alloy steel sample is the cold treatment state. The calculation formula of the corrosion time t of the high alloy steel metallographic sample immersed in the corrosive solution is: t=-1.25x+16.42; Where, t is the corrosion immersion time, min; x is the mass fraction of FeCl3 in the corrosive medium; (4) The metallographic specimens of high-alloy steel corroded by the corrosive solution were placed under deionized water. The surface of the specimens was wiped with cotton until the dark gray rust stains turned into dark silver. The specimens were then cleaned with anhydrous ethanol and blown dry. The microstructure and grain morphology of the high-alloy steel specimens were observed using a metallographic microscope.

2. The corrosion method for co-displaying grains and microstructure of high alloy steel material according to claim 1, characterized in that: The specific method of mechanical polishing in step (2) is: using a woolen polishing cloth and a diamond polishing paste with a particle size of 0.5 μm to perform mechanical polishing until the surface is mirror-like and there are no polishing marks in different directions under optical microscope observation.

3. The corrosion method for co-displaying grains and microstructure of high alloy steel material according to claim 1, characterized in that: In step (3), the heat treatment process state of the high alloy steel sample is the quenching state, and the high alloy steel metallographic sample is immersed in the corrosive solution for 5 to 10 minutes; The heat treatment process state of the high alloy steel sample is the tempered state, and the high alloy steel metallographic sample is immersed in the corrosive solution for 15 to 20 minutes; The heat treatment process state of the high alloy steel sample is the cold treatment state, and the high alloy steel metallographic sample is immersed in the corrosive solution for 10 to 15 minutes.

Images