Corrosive liquid for nickel-based superalloy and corrosion method thereof

Abstract

A kind of corrosion liquid for nickel-based superalloy and its corrosion method, corrosion liquid includes hydrochloric acid, nitric acid and organic corrosion inhibitor, the volume ratio of hydrochloric acid, nitric acid and organic corrosion inhibitor is 12-20:4-7:1, wherein the mass concentration of hydrochloric acid is 36%-38%, the mass concentration of nitric acid is 36%-38%, and the organic corrosion inhibitor is the mixture of methanol and glycerol, wherein the volume ratio of methanol and glycerol is 1.5-3:1.The corrosion method for the above-mentioned corrosion liquid for nickel-based superalloy corrosion is as follows: the corrosion liquid is dropped to the corrosion surface of nickel-based superalloy after cleaning and polishing, the corrosion time is 8-13s, then the corrosion liquid on the surface of the corroded nickel-based superalloy is removed by water cleaning and anhydrous ethanol ultrasonic cleaning.The corrosion liquid and corrosion method can reduce the dissolution of nickel-based superalloy, prevent hydrogen embrittlement of base metal, significantly reduce corrosion pits, and obtain efficient corrosion morphology.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of corrosion liquid for nickel-based superalloy and its corrosion method, belong to 3D printing technical field. BACKGROUND

[0002] The hot end components of aero-engine have strict requirements on high temperature performance, and high temperature alloy can meet the needs of such components, and is praised as the crown of modern industry. Generally, the performance level of engine is determined by the performance of high temperature alloy. According to the investigation, the use amount of high temperature alloy in an advanced aero-engine can account for 55%-65% of the total weight of aero-engine, among which, nickel-based superalloy is widely used due to its excellent performance. Nickel-based superalloy generally works under the condition of a certain stress above 600℃, and it not only has good high temperature oxidation resistance and corrosion resistance, but also has high high temperature strength, creep strength and endurance strength, and good fatigue resistance. It is mainly used for structural components working under high temperature conditions in aerospace field, such as working blades, turbine discs, combustion chambers and the like of aero-engine.

[0003] After the forming of nickel-based superalloy is completed, it needs to be characterized and analyzed to determine the forming quality and defects. In the characterization and analysis, the material is ground to the corresponding mesh number and then polished, etched and the like. Etching includes chemical etching and electrochemical etching, both of which can change the structure of the metal surface, thereby causing the corrosion of the metal. Electrochemical etching is realized by electrochemical reaction between metal and electrolyte in solution, and it is difficult to achieve ideal effect for observing topological dense phase such as μ phase and σ phase; while chemical etching is realized by reaction between metal and oxidizing agent in solution, and the morphology, size and volume fraction of topological dense phase such as γ phase, γ', γ'' and μ phase can be observed, in addition, the chemical etching method is simple, convenient to operate, and does not need too many instruments to hold, and can be widely applied to most traditional cast nickel-based superalloy, laser selective melting or laser melting deposition formed nickel-based superalloy, and nickel-based superalloy obtained after heat treatment of various forming methods.

[0004] In the chemical etching process, the composition and proportion of the etching solution and the etching method will significantly affect the etching effect. In the invention with the publication number CN110670115A, Feikang Rapid Manufacturing Technology Co., Ltd. proposes an etchant suitable for as-deposited GH3536 alloy and an etching method thereof. The etching solution is prepared according to water 50-150 ml: hydrochloric acid 100-200 ml: chromium oxide 10-30 g, the mass concentration of hydrochloric acid is 36%-38%, the etching voltage is 20-30 V, and the etching time is 3-10 seconds. Although this method can efficiently etch the as-deposited GH3536 alloy, this etching method is complex, the etching voltage is too high (excessive voltage can easily cause over-etching, and insufficient voltage can easily cause under-etching), the etching time is not easy to control, which can cause incomplete etching, and the carbonides precipitated in the subsequent heat treatment can contain chromium oxide and other brittle phases, affecting the performance of the material. SUMMARY

[0005] The purpose of the present application is to provide an etching solution for nickel-based superalloys and an etching method thereof. The etching solution and the etching method can reduce the dissolution of nickel-based superalloys, prevent hydrogen embrittlement of the base metal, significantly reduce etching pits, and obtain an efficient etching morphology.

[0006] The technical solution adopted by the present application to achieve its purpose is: an etching solution for nickel-based superalloys, comprising hydrochloric acid, nitric acid, and an organic corrosion inhibitor, the volume ratio of the hydrochloric acid, nitric acid, and organic corrosion inhibitor being 12-20:4-7:1, wherein the mass concentration of the hydrochloric acid is 36%-38%, the mass concentration of the nitric acid is 36%-38%, and the organic corrosion inhibitor is a mixture of methanol and glycerol, wherein the volume ratio of methanol to glycerol is 1.5-3:1.

[0007] Further, the hydrochloric acid, nitric acid, methanol, and glycerol in the etching solution of the present application are all of analytical purity.

[0008] Further, the volume ratio of the hydrochloric acid, nitric acid, and organic corrosion inhibitor in the etching solution of the present application is 15:5:1.

[0009] Further, the volume ratio of methanol to glycerol in the organic corrosion inhibitor in the etching solution of the present application is 2:1.

[0010] Further, the mass concentration of methanol in the organic corrosion inhibitor in the etching solution of the present application is above 99.5%, and the mass concentration of glycerol is above 99.5%.

[0011] Further, the nickel-based superalloy of the present application includes GH3536, GH3230, and GH4169 nickel-based superalloys.

[0012] The corrosion method of the corrosion solution for the nickel-based superalloy comprises the following steps: dropping the corrosion solution on the surface of the nickel-based superalloy to be corroded after cleaning and polishing, and removing the corrosion solution on the surface of the nickel-based superalloy after corrosion by cleaning with water and ultrasonic cleaning with anhydrous ethanol, wherein the corrosion time is 8-13s.

[0013] Further, the corrosion time in the corrosion method is 10s.

[0014] Compared with the prior art, the corrosion solution has the following beneficial effects:

[0015] The corrosion solution has the following composition: hydrochloric acid, nitric acid and organic corrosion inhibitor, wherein the volume ratio of the hydrochloric acid, the nitric acid and the organic corrosion inhibitor is 15-20:5-7:1, and the organic corrosion inhibitor is composed of methanol and glycerol, and the volume ratio of the methanol and the glycerol is 1.5-3:1. The organic corrosion inhibitor with the above-mentioned composition is used for the nickel-based superalloy with a gamma phase as a matrix phase, so that a film is formed on the surface of the metal to protect the metal, the strong oxidizing property of the mixed solution of pure hydrochloric acid and pure nitric acid on the surface of the metal is weakened, the dissolution of the matrix metal is reduced, hydrogen embrittlement of the matrix metal is prevented, the corrosion pits are obviously reduced, and efficient corrosion morphology is obtained.

[0016] Through a large number of tests, it is verified that the corrosion solution with the above-mentioned composition is used for corrosion of the nickel-based superalloy, and the corrosion degree is moderate within the corrosion time of 8-13s, so that under-corrosion caused by too short corrosion time and over-corrosion caused by too long corrosion time are prevented, and the observation of the metallographic morphology is facilitated. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 Figure 4 is a metallographic morphology diagram of the GH3536 nickel-based superalloy after corrosion in Example 1 of the present application.

[0018] Figure 2 Figure 4 is a metallographic morphology diagram of the GH3536 nickel-based superalloy after corrosion in Example 1 of the present application.

[0019] Figure 3 Figure 4 is a metallographic morphology diagram of the GH3536 nickel-based superalloy after corrosion in Example 1 of the present application.

[0020] Figure 4 Figure 4 is a metallographic morphology diagram of the GH3536 nickel-based superalloy after corrosion in Example 1 of the present application.

[0021] Figure 5 Figure 4 is a metallographic morphology diagram of the GH3536 nickel-based superalloy after corrosion in Example 1 of the present application.

[0022] Figure 6 Figure 4 is a metallographic morphology diagram of the GH3536 nickel-based superalloy after corrosion in Example 1 of the present application.

[0023] Figure 7The metallographic morphology of GH3536 high-temperature nickel-based alloy after corrosion in Comparative Example 6. DETAILED DESCRIPTION

[0024] Example 1

[0025] A corrosion solution for a nickel-based high-temperature alloy, comprising hydrochloric acid, nitric acid and an organic corrosion inhibitor, wherein the volume ratio of the hydrochloric acid, the nitric acid and the organic corrosion inhibitor is 15:5:1, wherein the mass concentration of the hydrochloric acid is 36%-38%, the mass concentration of the nitric acid is 36%-38%, the organic corrosion inhibitor is a mixture of methanol and glycerol with a volume ratio of 2:1, wherein the mass concentration of the methanol is more than 99.5% and the mass concentration of the glycerol is more than 99.5%. The corrosion solution in this example is prepared by mixing 30 ml of hydrochloric acid, 10 ml of nitric acid and 2 ml of the organic corrosion inhibitor.

[0026] In this example, the hydrochloric acid, the nitric acid, the methanol and the glycerol are all of analytical purity.

[0027] A GH3536 nickel-based high-temperature alloy sample is prepared using an SLM process, the sample is ground to 2000# or 2500# with sandpaper and then mechanically polished with a diamond polishing paste of type W2.5 until the surface is free of obvious scratches, and then the sample is chemically etched, the specific steps being: in a fume hood, the polished sample is cleaned with alcohol, the corrosion solution is sucked into a glass glue dropper and then evenly dropped onto the surface to be etched, the etching time is 10 s, then the etched sample is first washed with clean water and then ultrasonically cleaned in a beaker containing anhydrous ethanol in an ultrasonic cleaner to thoroughly clean the corrosion solution on the surface of the sample.

[0028] Figure 1 The metallographic morphology of GH3536 high-temperature nickel-based alloy after corrosion in this example, where a) is the metallographic microscopic morphology at 100 times under the printing state perpendicular to the build direction; b) is the metallographic microscopic morphology at 100 times under the printing state parallel to the build direction; c) is the metallographic microscopic morphology at 100 times under the heat treatment state; d) is the metallographic microscopic morphology at 200 times under the printing state perpendicular to the build direction; e) is the metallographic microscopic morphology at 200 times under the printing state parallel to the build direction; f) is the metallographic microscopic morphology at 200 times under the heat treatment state. As shown in the figure, this corrosion solution and corrosion method can clearly see the molten pool morphology under the metallographic microscope, there are fewer etching pits on the metallographic surface, and the dendritic structure in the molten pool can be observed, proving that the corrosion solution can efficiently etch. In addition, the recrystallized grains and grain morphology on the surface of the material after etching and heat treatment can be clearly observed, and the carbide precipitates around the grain boundaries can also be observed, showing good corrosion effect.

[0029] Example 2

[0030] A kind of corrosion liquid for nickel-based superalloy, including hydrochloric acid, nitric acid and organic corrosion inhibitor, wherein the volume ratio of hydrochloric acid, nitric acid and organic corrosion inhibitor is 12:4:1, wherein the mass concentration of hydrochloric acid is 36%-38%, the mass concentration of nitric acid is 36%-38%, the organic corrosion inhibitor is the mixture of methanol and glycerol, and the volume ratio is 2:1, wherein the mass concentration of methanol is more than 99.5%, and the mass concentration of glycerol is more than 99.5%.The corrosion liquid in the example is prepared by 24ml of hydrochloric acid, 8ml of nitric acid and 2ml of organic corrosion inhibitor.

[0031] In the example, hydrochloric acid, nitric acid, methanol and glycerol are all analytical pure purity levels.

[0032] GH3536 nickel-based superalloy samples are prepared using SLM process, the samples are ground to 2000# or 2500# with sandpaper and then mechanically polished to the surface without obvious scratches with diamond polishing paste of W2.5 type, and then chemically etched, the specific steps are as follows: in the fume hood, clean the polished sample with alcohol, then use a glass glue head dropper to absorb the etching liquid and drop it evenly on the surface to be etched, the etching time is 10s, then wash the etched sample with clean water, and then ultrasonic cleaning in a beaker containing absolute ethanol to thoroughly clean the etching liquid on the surface of the sample.

[0033] The etching liquid and etching method can clearly see the molten pool morphology under the metallographic microscope, the etching pits on the metallographic surface are less, and the dendritic structure in the molten pool can be observed, which proves that the etching liquid can efficiently etch. In addition, the recrystallized grains and grain morphology on the surface of the material after heat treatment can be clearly observed, and the carbide and other precipitated phases around the grain boundary can be observed, which shows good etching effect.

[0034] Example 3

[0035] A kind of corrosion liquid for nickel-based superalloy, including hydrochloric acid, nitric acid and organic corrosion inhibitor, wherein the volume ratio of hydrochloric acid, nitric acid and organic corrosion inhibitor is 20:7:1, wherein the mass concentration of hydrochloric acid is 36%-38%, the mass concentration of nitric acid is 36%-38%, the organic corrosion inhibitor is the mixture of methanol and glycerol, and the volume ratio is 2:1, wherein the mass concentration of methanol is more than 99.5%, and the mass concentration of glycerol is more than 99.5%.The corrosion liquid in the example is prepared by 40ml of hydrochloric acid, 14ml of nitric acid and 2ml of organic corrosion inhibitor.

[0036] In the example, hydrochloric acid, nitric acid, methanol and glycerol are all analytical pure purity levels.

[0037] The GH3536 nickel-based superalloy sample prepared by the SLM process is ground to 2000# or 2500# with sandpaper and then mechanically polished to the surface without obvious scratches by using a diamond polishing paste with a model of W2.5, and then the sample is chemically etched, and the specific steps are as follows: in a fume hood, the polished sample is cleaned with alcohol, the etching solution is sucked into a glass glue head dropper and then uniformly dropped onto the surface to be etched, the etching time is 10s, then the etched sample is first washed with clean water and then ultrasonically cleaned in a beaker containing anhydrous ethanol by using an ultrasonic cleaning machine to thoroughly clean the etching solution on the surface of the sample.

[0038] The etching solution and the etching method can clearly observe the molten pool morphology under a metallographic microscope, the etching pits on the metallographic surface are less, and the dendritic structure in the molten pool can be observed, which proves that the etching solution can efficiently etch. In addition, the recrystallized grains and grain morphology on the surface of the material after heat treatment can be clearly observed, and the carbide precipitates around the grain boundaries can be observed, which shows good etching effect.

[0039] Example 4

[0040] An etching solution for a nickel-based superalloy, comprising hydrochloric acid, nitric acid and an organic corrosion inhibitor, wherein the volume ratio of hydrochloric acid, nitric acid and organic corrosion inhibitor is 15:5:1, wherein the mass concentration of hydrochloric acid is 36%-38%, the mass concentration of nitric acid is 36%-38%, the organic corrosion inhibitor is a mixture of methanol and glycerol with a volume ratio of 2:1, wherein the mass concentration of methanol is more than 99.5%, and the mass concentration of glycerol is more than 99.5%. The etching solution in this example is prepared by mixing 30ml of hydrochloric acid, 10ml of nitric acid and 2ml of organic corrosion inhibitor.

[0041] In this example, the hydrochloric acid, nitric acid, methanol and glycerol are all of analytical purity.

[0042] The GH3536 nickel-based superalloy sample prepared by the SLM process is ground to 2000# or 2500# with sandpaper and then mechanically polished to the surface without obvious scratches by using a diamond polishing paste with a model of W2.5, and then the sample is chemically etched, and the specific steps are as follows: in a fume hood, the polished sample is cleaned with alcohol, the etching solution is sucked into a glass glue head dropper and then uniformly dropped onto the surface to be etched, the etching time is 13s, then the etched sample is first washed with clean water and then ultrasonically cleaned in a beaker containing anhydrous ethanol by using an ultrasonic cleaning machine to thoroughly clean the etching solution on the surface of the sample.

[0043] Figure 2For the metallographic morphology of GH3536 high-temperature nickel-based alloy after corrosion in this example, a) is the metallographic microstructure perpendicular to the build direction at 100 times under the printing state, and c) is the metallographic microstructure perpendicular to the build direction at 200 times under the printing state. As can be seen from the figure, this etching solution and etching method can clearly see the molten pool morphology under the metallographic microscope, the etching pits on the metallographic surface are less, and the dendritic structure in the molten pool can be observed, proving that the etching solution can be efficiently etched. In addition, the grains and grain morphology on the surface of the material after heat treatment can be clearly observed, and the carbides and other precipitated phases around the grain boundaries can be observed, showing good etching effect.

[0044] Example 5

[0045] An etching solution for nickel-based high-temperature alloy, comprising hydrochloric acid, nitric acid and organic corrosion inhibitor, wherein the volume ratio of hydrochloric acid, nitric acid and organic corrosion inhibitor is 15:5:1, wherein the mass concentration of hydrochloric acid is 36%-38%, the mass concentration of nitric acid is 36%-38%, the organic corrosion inhibitor is a mixture of methanol and glycerol with a volume ratio of 2:1, wherein the mass concentration of methanol is more than 99.5%, and the mass concentration of glycerol is more than 99.5%. The etching solution in this example is prepared from 30ml of hydrochloric acid, 10ml of nitric acid and 2ml of organic corrosion inhibitor.

[0046] In this example, the hydrochloric acid, nitric acid, methanol and glycerol are all analytical pure purity levels.

[0047] GH3536 nickel-based high-temperature alloy samples were prepared using SLM process, the samples were ground to 2000# or 2500# with sandpaper and then mechanically polished with diamond polishing paste of W2.5 type until there were no obvious scratches on the surface, and then the samples were chemically etched, the specific steps were as follows: in a fume hood, the polished sample was cleaned with alcohol, the etching solution was sucked into a glass glue dropper and dropped evenly on the surface to be etched, the etching time was 8s, then the etched sample was first washed with water, and then ultrasonic cleaned in a beaker containing absolute ethanol to thoroughly clean the etching solution on the surface of the sample.

[0048] Figure 3 For the metallographic morphology of GH3536 high-temperature nickel-based alloy after corrosion in this example, a) is the metallographic microstructure perpendicular to the build direction at 100 times under the printing state, and c) is the metallographic microstructure perpendicular to the build direction at 200 times under the printing state. As can be seen from the figure, this etching solution and etching method can clearly see the molten pool morphology under the metallographic microscope, the etching pits on the metallographic surface are less, and the dendritic structure in the molten pool can be observed, proving that the etching solution can be efficiently etched. In addition, the grains and grain morphology on the surface of the material after heat treatment can be clearly observed, and the carbides and other precipitated phases around the grain boundaries can be observed, showing good etching effect.

[0049] Example 6

[0050] A corrosion liquid for nickel-based superalloy, comprising hydrochloric acid, nitric acid and organic corrosion inhibitor, wherein the volume ratio of hydrochloric acid, nitric acid and organic corrosion inhibitor is 12:4:1, wherein the mass concentration of hydrochloric acid is 36%-38%, the mass concentration of nitric acid is 36%-38%, the organic corrosion inhibitor is a mixture of methanol and glycerol with a volume ratio of 2:1, wherein the mass concentration of methanol is more than 99.5%, and the mass concentration of glycerol is more than 99.5%. The corrosion liquid in this example is prepared from 24ml of hydrochloric acid, 8ml of nitric acid and 2ml of organic corrosion inhibitor.

[0051] In this example, the hydrochloric acid, nitric acid, methanol and glycerol are all of analytical purity.

[0052] GH3230 nickel-based superalloy samples were prepared using the SLM process, the samples were ground to 2000# or 2500# with sandpaper and then mechanically polished with diamond polishing paste of type W2.5 until the surface was free of obvious scratches, and then the samples were chemically etched, the specific steps were as follows: in a fume hood, the polished samples were cleaned with alcohol, the corrosion liquid was sucked into a glass glue head dropper and dropped evenly onto the surface to be etched, the etching time was 10s, then the etched sample was first washed with clean water, and then ultrasonic cleaned in a beaker containing absolute ethanol to thoroughly wash the corrosion liquid on the surface of the sample.

[0053] This corrosion liquid and corrosion method can clearly see the molten pool morphology under a metallographic microscope, there are fewer etching pits on the metallographic surface, and the dendritic structure in the molten pool can be observed, proving that this corrosion liquid can efficiently etch. In addition, the recrystallized grains and grain morphology on the surface of the material after heat treatment can be clearly observed, and the carbide precipitates around the grain boundaries can also be observed, showing good corrosion effect.

[0054] Example 7

[0055] A corrosion liquid for nickel-based superalloy, comprising hydrochloric acid, nitric acid and organic corrosion inhibitor, wherein the volume ratio of hydrochloric acid, nitric acid and organic corrosion inhibitor is 12:4:1, wherein the mass concentration of hydrochloric acid is 36%-38%, the mass concentration of nitric acid is 36%-38%, the organic corrosion inhibitor is a mixture of methanol and glycerol with a volume ratio of 2:1, wherein the mass concentration of methanol is more than 99.5%, and the mass concentration of glycerol is more than 99.5%. The corrosion liquid in this example is prepared from 24ml of hydrochloric acid, 8ml of nitric acid and 2ml of organic corrosion inhibitor.

[0056] In this example, the hydrochloric acid, nitric acid, methanol and glycerol are all of analytical purity.

[0057] The GH4169 nickel-based superalloy sample prepared by the SLM process is ground to 2000# or 2500# with sandpaper and then mechanically polished with a diamond polishing paste of type W2.5 until the surface is free of obvious scratches, and then the sample is chemically etched. The specific steps are as follows: in a fume hood, clean the polished sample with alcohol, then use a glass glue head dropper to absorb the etching solution and evenly drop it onto the surface to be etched, the etching time is 10s, then the etched sample is first washed with clean water, and then ultrasonic cleaned in a beaker containing absolute ethanol by an ultrasonic cleaner to thoroughly clean the etching solution on the surface of the sample.

[0058] The etching solution and etching method can clearly see the molten pool morphology under the metallographic microscope, the metallographic surface etching pit is less, and the dendritic structure in the molten pool can be observed, which proves that the etching solution can be efficiently etched. In addition, the recrystallized grains and grain morphology on the surface of the material after heat treatment can be clearly observed, and the carbide and other precipitated phases around the grain boundary can be observed, which shows good etching effect.

[0059] An etching solution for nickel-based superalloy, comprising hydrochloric acid and nitric acid, wherein the volume ratio of hydrochloric acid to nitric acid is 3:1, and the mass concentration of hydrochloric acid is 36%-38% and the mass concentration of nitric acid is 36%-38%. The etching solution in this example is prepared by 30ml of hydrochloric acid and 10ml of nitric acid.

[0060] In this example, the hydrochloric acid and nitric acid are both analytical pure grade.

[0061] The GH3536 nickel-based superalloy sample prepared by the SLM process is ground to 2000# or 2500# with sandpaper and then mechanically polished with a diamond polishing paste of type W2.5 until the surface is free of obvious scratches, and then the sample is chemically etched. The specific steps are as follows: in a fume hood, clean the polished sample with alcohol, then use a glass glue head dropper to absorb the etching solution and evenly drop it onto the surface to be etched, the etching time is 10s, then the etched sample is first washed with clean water, and then ultrasonic cleaned in a beaker containing absolute ethanol by an ultrasonic cleaner to thoroughly clean the etching solution on the surface of the sample.

[0062] Figure 4 The GH3536 high-temperature nickel-based alloy sample after etching in this comparative example is observed under a metallographic microscope, and a 50x microscopic morphology of the sample perpendicular to the build direction is printed. As shown in the figure, although the etching solution and etching method can see the molten pool morphology under the metallographic microscope, the overall molten pool shows over-etching by the metallographic microscope, and some etching pits are observed on the metallographic surface, which is not conducive to subsequent research.

[0063] Comparative Example 2

[0064] A corrosion liquid for nickel-based superalloy, comprising hydrochloric acid, nitric acid and organic corrosion inhibitor, wherein the volume ratio of hydrochloric acid, nitric acid and organic corrosion inhibitor is 6:2:1, wherein the mass concentration of hydrochloric acid is 36%-38%, the mass concentration of nitric acid is 36%-38%, the organic corrosion inhibitor is a mixture of methanol and glycerol with a volume ratio of 2:1, wherein the mass concentration of methanol is more than 99.5%, and the mass concentration of glycerol is more than 99.5%. The corrosion liquid in this example is prepared by mixing 30ml of hydrochloric acid, 10ml of nitric acid and 5ml of organic corrosion inhibitor.

[0065] In this example, the hydrochloric acid, nitric acid, methanol and glycerol are all analytical pure.

[0066] A GH3536 nickel-based superalloy sample is prepared using the SLM process, and then the sample is ground to 2000# or 2500# with sandpaper and mechanically polished with a diamond polishing paste of type W2.5 until the surface is free of obvious scratches. Then the polished sample is chemically etched, and the specific steps are as follows: in a fume hood, the polished sample is cleaned with alcohol, the corrosion liquid is sucked into a glass glue dropper and dropped evenly onto the surface to be etched, the etching time is 10s, then the etched sample is first washed with clean water, and then ultrasonic cleaned in a beaker containing absolute ethanol to thoroughly clean the corrosion liquid on the surface of the sample.

[0067] This corrosion liquid and corrosion method will cause under-etching due to the increase of the amount of organic corrosion inhibitor, the molten pool line cannot be observed, and the dendritic structure cannot be observed.

[0068] Comparative Example 3

[0069] A corrosion liquid for nickel-based superalloy, comprising hydrochloric acid, nitric acid and organic corrosion inhibitor, wherein the volume ratio of hydrochloric acid, nitric acid and organic corrosion inhibitor is 45:10:2, wherein the mass concentration of hydrochloric acid is 36%-38%, the mass concentration of nitric acid is 36%-38%, the organic corrosion inhibitor is a mixture of methanol and glycerol with a volume ratio of 2:1, wherein the mass concentration of methanol is more than 99.5%, and the mass concentration of glycerol is more than 99.5%. The corrosion liquid in this example is prepared by mixing 45ml of hydrochloric acid, 10ml of nitric acid and 2ml of organic corrosion inhibitor.

[0070] In this example, the hydrochloric acid, nitric acid, methanol and glycerol are all analytical pure.

[0071] The GH3536 nickel-based superalloy sample prepared by the SLM process is ground to 2000# or 2500# with sandpaper and then mechanically polished to the surface without obvious scratches by using a diamond polishing paste with a model of W2.5, and then the sample is chemically etched, and the specific steps are as follows: in a fume hood, the polished sample is cleaned with alcohol, the etching solution is sucked into a glass glue head dropper and then dripped onto the surface to be etched, the etching time is 10s, and then the etched sample is cleaned with water and then ultrasonically cleaned in a beaker containing anhydrous ethanol by using an ultrasonic cleaner to thoroughly clean the etching solution on the surface of the sample.

[0072] The etching solution and the etching method can observe the molten pool morphology under a metallographic microscope, but due to the increase of the proportion of hydrochloric acid, the molten pool as a whole presents an over-etched appearance, which is black as a whole and the molten pool line is not obvious, which is not conducive to the subsequent research on texture or mechanism.

[0073] Comparative Example 4

[0074] An etching solution for a nickel-based superalloy includes hydrochloric acid, nitric acid and an organic corrosion inhibitor, wherein the volume ratio of the hydrochloric acid, the nitric acid and the organic corrosion inhibitor is 30:15:2, the mass concentration of the hydrochloric acid is 36%-38%, the mass concentration of the nitric acid is 36%-38%, the organic corrosion inhibitor is a mixture of methanol and glycerol with a volume ratio of 2:1, the mass concentration of the methanol is more than 99.5%, and the mass concentration of the glycerol is more than 99.5%. The etching solution in this example is prepared by mixing 30ml of hydrochloric acid, 15ml of nitric acid and 2ml of the organic corrosion inhibitor.

[0075] In this example, the hydrochloric acid, the nitric acid, the methanol and the glycerol are all of analytical purity.

[0076] The GH3536 nickel-based superalloy sample prepared by the SLM process is ground to 2000# or 2500# with sandpaper and then mechanically polished to the surface without obvious scratches by using a diamond polishing paste with a model of W2.5, and then the sample is chemically etched, and the specific steps are as follows: in a fume hood, the polished sample is cleaned with alcohol, the etching solution is sucked into a glass glue head dropper and then dripped onto the surface to be etched, the etching time is 10s, and then the etched sample is cleaned with water and then ultrasonically cleaned in a beaker containing anhydrous ethanol by using an ultrasonic cleaner to thoroughly clean the etching solution on the surface of the sample.

[0077] Figure 5A 50 times microscopic morphology graph of the sample after etching of the GH3536 high-temperature nickel-based alloy in the present comparative example is shown in the figure. The etching liquid and etching method can observe the molten pool morphology under the metallographic microscope, but due to the increase of the proportion of nitric acid, the molten pool as a whole presents an over-etched appearance, which is black, and is not conducive to the subsequent study of texture or mechanism.

[0078] Comparative Example 5

[0079] An etching liquid for a nickel-based high-temperature alloy, comprising hydrochloric acid, nitric acid and an organic corrosion inhibitor, wherein the volume ratio of hydrochloric acid, nitric acid and organic corrosion inhibitor is 15:5:1, wherein the mass concentration of hydrochloric acid is 36%-38%, the mass concentration of nitric acid is 36%-38%, the organic corrosion inhibitor is a mixture of methanol and glycerol, and the volume ratio is 2:1, wherein the mass concentration of methanol is more than 99.5%, and the mass concentration of glycerol is more than 99.5%. The etching liquid in this example is prepared by mixing 30 ml of hydrochloric acid, 10 ml of nitric acid and 2 ml of organic corrosion inhibitor.

[0080] In this example, the hydrochloric acid, nitric acid, methanol and glycerol are all analytical pure.

[0081] The GH3536 nickel-based high-temperature alloy sample is prepared by SLM process, and the sample is ground to 2000# or 2500# with sandpaper and then mechanically polished with diamond polishing paste of W2.5 type until the surface is free of obvious scratches. Then the sample is chemically etched, and the specific steps are as follows: in a fume hood, clean the polished sample with alcohol, then use a glass glue dropper to absorb the etching liquid and drop it evenly on the surface to be etched, and the etching time is 5s. Then the etched sample is first washed with water, and then ultrasonically cleaned in a beaker containing absolute ethanol by an ultrasonic cleaning machine to thoroughly clean the etching liquid on the surface of the sample.

[0082] Figure 6 A metallographic morphology graph of the GH3536 high-temperature nickel-based alloy after etching in the present comparative example is shown in the figure. In the figure, a) is a metallographic microscopic morphology under 100 times perpendicular to the building direction in printing state; b) is a metallographic microscopic morphology under 200 times perpendicular to the building direction in printing state. It can be seen from the figure that the etching liquid and etching method will cause under-etching due to too short etching time, so that the molten pool line is not obvious, which is not conducive to the subsequent study of texture or mechanism.

[0083] Comparative Example 6

[0084] A kind of corrosion liquid for nickel-based superalloy, comprising hydrochloric acid, nitric acid and organic corrosion inhibitor, wherein the volume ratio of hydrochloric acid, nitric acid and organic corrosion inhibitor is 15:5:1, wherein the mass concentration of hydrochloric acid is 36%-38%, the mass concentration of nitric acid is 36%-38%, the organic corrosion inhibitor is a mixture of methanol and glycerol, and the volume ratio is 2:1, wherein the mass concentration of methanol is more than 99.5%, and the mass concentration of glycerol is more than 99.5%.The corrosion liquid in the example is prepared from 30ml of hydrochloric acid, 10ml of nitric acid and 2ml of organic corrosion inhibitor.

[0085] In the example, the hydrochloric acid, nitric acid, methanol and glycerol are all analytical pure purity levels.

[0086] GH3536 nickel-based superalloy samples were prepared using the SLM process, and the samples were ground to 2000# or 2500# with sandpaper and then mechanically polished to the surface without obvious scratches using a diamond polishing paste with a model of W2.5, and then chemically etched, the specific steps being: in a fume hood, the polished sample was cleaned with alcohol, the corrosion liquid was sucked into a glass glue head dropper and dropped evenly onto the surface to be etched, the etching time was 15s, then the etched sample was washed with clean water first, and then ultrasonically cleaned in a beaker containing absolute ethanol to thoroughly clean the corrosion liquid on the surface of the sample.

[0087] Figure 7 The metallographic morphology of the GH3536 high-temperature nickel-based alloy after etching in the present comparative example is shown in the figure. a) is the metallographic microscopic morphology perpendicular to the building direction at 100 times under the printing state; b) is the metallographic microscopic morphology parallel to the building direction at 200 times under the printing state; c) is the metallographic microscopic morphology at 500 times under the heat treatment state. As can be seen from the figure, although this corrosion liquid and corrosion method can observe the molten pool morphology under the metallographic microscope, the corrosion time is too long, and the molten pool part (such as the top of the molten pool) can be observed by metallographic microscope, which shows over-etching appearance, which is black, and the heat-treated sample is etched, and the over-etching appearance is also observed under the metallographic microscope after etching, and the grain boundary carbide can be observed, but there are over-etching traces in the grain interior, which presents dot matrix black, which is not conducive to the subsequent study of texture or mechanism.

Claims

1. A corrosion method for nickel-based superalloys: the nickel-based superalloy is selected from GH3536, GH3230, and GH4169 nickel-based superalloys, and the corrosion solution is composed of hydrochloric acid, nitric acid, and an organic corrosion inhibitor, characterized in that: The volume ratio of hydrochloric acid, nitric acid, and organic corrosion inhibitor is 12-20:4-7:1, wherein the mass concentration of hydrochloric acid is 36%-38%, the mass concentration of nitric acid is 36%-38%, and the organic corrosion inhibitor is a mixture of methanol and glycerol, wherein the volume ratio of methanol to glycerol is 1.5-3:

1. The corrosion method steps are as follows: the corrosion solution is dripped onto the cleaned and polished nickel-based superalloy surface to be corroded, the corrosion time is 8-13s, and then the corrosion solution on the surface of the nickel-based superalloy is removed by rinsing with water and ultrasonic cleaning with anhydrous ethanol.

2. The corrosion method for nickel-based superalloys according to claim 1, characterized in that: The hydrochloric acid, nitric acid, methanol, and glycerol were all of analytical purity.

3. A corrosion method for nickel-based superalloys according to claim 1 or 2, characterized in that: The volume ratio of hydrochloric acid, nitric acid, and organic corrosion inhibitor is 15:5:

1.

4. A corrosion method for nickel-based superalloys according to claim 1 or 2, characterized in that: The volume ratio of methanol to glycerol in the organic corrosion inhibitor is 2:

1.

5. The corrosion method for nickel-based superalloys according to claim 1, characterized in that: The organic corrosion inhibitor contains methanol with a mass concentration of 99.5% or higher and glycerol with a mass concentration of 99.5% or higher.

6. The corrosion method for nickel-based superalloys according to claim 1, characterized in that: The corrosion time is 10 seconds.

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