Corrosion method for low-power streamline of nickel-based superalloy forge piece

Abstract

The invention discloses a corrosion method for a low-power streamline of a nickel-based superalloy forge piece. The corrosion method comprises the following steps: providing a low-power sample with a polished surface; a macroscopic sample is used as a cathode, stainless steel is used as an anode, electrolytic corrosion is carried out, the corrosive liquid comprises HNO3, HCl and deionized water according to the volume ratio of 1: 24: 160, and 5 g of FeCl3 is correspondingly added when 1 ml of HNO3 is added; the electrolysis current is 1.5 A to 2 A, and the electrolysis time is 2 min to 4 min. By means of the method, obvious corrosion can be caused to the streamline structure in the nickel-based superalloy forge piece, the direction and structural integrity of the streamline structure can be characterized under the observation condition of naked eyes or a low-power metallographic microscope, and the quality inspection efficiency of the nickel-based superalloy forge piece is improved.

Description

Technical Field

[0001] The present invention belongs to the field of superalloys, and particularly relates to a method for etching the macrostructure streamline of a nickel-based superalloy forging. Background Art

[0002] In the field of aeroengines, nickel-based superalloy forgings are widely used to manufacture high-temperature components, such as compressor blades or disks. Nickel-based superalloy forgings are usually obtained by processing ingots. During the forging process, non-uniform structures, grain boundary impurities, and intermetallic compounds in the ingot deform or break during pressurization and deformation and rearrange along the direction of material flow during forging, forming a linearly distributed structure, i.e., a metallic fibrous structure or forging streamline. This directionality in the microstructure also leads to a significant directionality in the distribution of mechanical properties: the tensile strength is high along the streamline direction, and the shear strength is high perpendicular to the streamline direction. Therefore, when the streamline distribution matches the structure of the forged blade, the mechanical properties of the blade can be improved; if the streamline distribution does not meet the mechanical property requirements of the forged blade, or there are defects such as turbulent flow, chaotic flow, or cross flow, it will have an adverse impact on the mechanical properties of the blade.

[0003] Therefore, characterizing the streamline of nickel-based superalloy forgings is an important criterion for evaluating forging quality. Due to the high degree of alloying, low impurity element content, and strong corrosion resistance of nickel-based superalloys, conventional etching methods are difficult to effectively present the streamline morphology in nickel-based superalloy forgings. If methods such as microscopic analysis are used, the test cost will be significantly increased and the test cycle will be prolonged, affecting the quality evaluation efficiency of nickel-based superalloy forgings. Therefore, providing a method for etching the macrostructure streamline of nickel-based superalloy forgings has high practical value for improving the quality inspection efficiency of nickel-based superalloy forgings. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for etching the macrostructure streamline of a nickel-based superalloy forging to improve the etching effect of the macrostructure streamline of the nickel-based superalloy forging.

[0005] According to an embodiment of the present invention, a method for etching the macrostructure streamline of a nickel-based superalloy forging is provided. The method includes the following steps: providing an etching sample of the nickel-based superalloy forging, where the etching sample includes a target section for macrostructure streamline analysis, grinding and polishing the etching sample to obtain a macrostructure specimen; providing an electrolytic etching solution, and the components of the electrolytic etching solution include HNO 3 , HCl, deionized water, and FeCl 3 , where by volume ratio, HNO 3 :HCl:deionized water = 1:24:160, and for every 1 ml of HNO 3 added, 5 g of FeCl 3; Using the low-magnification sample as the anode and the stainless steel as the cathode, an electrolytic corrosion treatment is performed in the electrolytic corrosion solution, wherein the electrolytic current is 1.5A-2A and the electrolysis time is 2min-4min.

[0006] By utilizing the above method, effective corrosion can be formed on the nickel-based high-temperature alloy forgings, so that the corroded streamlines can be directly observed with the naked eye, effectively improving the linear efficiency of the nickel-based high-temperature alloy forgings.

[0007] Furthermore, in some embodiments, after the electrolytic corrosion treatment, the step of polishing the low-magnification sample is also included, wherein the polishing medium in the polishing step is water and the polishing time is 2s-3s. By using clean water as the polishing medium and lightly polishing on a polishing cloth, some corrosion products that interfere with observation on the surface of the low-magnification sample can be removed.

[0008] Furthermore, in some embodiments, in the step of polishing the corrosion sample, 180 mesh, 320 mesh, 800 mesh and 1200 mesh metallographic sandpaper are used for polishing in sequence, and the polishing time for each pass is 1 min-3 min.

[0009] Furthermore, in some embodiments, the step of polishing the corrosion sample uses a diamond suspension with a particle size not exceeding 3 μm for polishing, and the polishing time is 3 min-5 min.

[0010] Furthermore, in some embodiments, the electrolytic voltage in the electrolytic corrosion treatment is 4V-6V.

[0011] Furthermore, in some embodiments, a cleaning step is also included after the electrolytic corrosion treatment, and in the cleaning step, the low-magnification sample is rinsed 1-2 times with water or anhydrous ethanol.

[0012] Furthermore, in some embodiments, the nickel-based high-temperature alloy is configured as a Ni-Cr-Fe alloy or a Ni-Cr-Co alloy.

[0013] Furthermore, in some embodiments, the nickel-based high-temperature alloy is configured as IN718 alloy or GH4169D alloy.

[0014] Furthermore, in some embodiments, the nickel-based high-temperature alloy forging is configured as an aircraft engine forged blade or an aircraft engine forged blade disk. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a streamline photograph of a nickel-based high-temperature alloy blade forging in an upset state after corrosion in one embodiment;

[0016] Figure 2This is a streamline photograph of a final forged nickel-based high-temperature alloy blade forging after corrosion in an embodiment;

[0017] Figure 3 A pair of photos of the nickel-based superalloy blade forgings in the upsetting state after corrosion;

[0018] Figure 4 This is a pair of proportional photos of the final forged nickel-based high-temperature alloy blade forgings after corrosion.

[0019] The purpose of the above drawings is to explain the present invention in detail so that those skilled in the art can understand the technical concept of the present invention, but it is not intended to limit the present invention. DETAILED DESCRIPTION

[0020] The present invention is further described in detail below through specific embodiments in conjunction with the accompanying drawings.

[0021] Reference to "embodiment" herein means that a particular feature, structure or characteristic described in conjunction with the embodiment may be included in at least one embodiment of the present invention. The phrase appearing in various locations in the specification does not necessarily refer to the same embodiment, nor is it limited to mutually exclusive independent or alternative embodiments. It should be understood by those skilled in the art that the embodiments herein may be combined with other embodiments without structural conflicts. In the description herein, "multiple" means at least two.

[0022] Forging can break up the uneven structures such as dendrites formed during casting, eliminate defects such as pinholes during solidification, and promote the rearrangement of the second phase particles, thereby improving the performance of the alloy structure. Therefore, nickel-based high-temperature alloy forgings are widely used in aero-engines. For example, compressor blades are mostly made of nickel-based high-temperature alloy forgings. During the forging process, due to the directional nature of material flow, the forging structure usually exhibits significant anisotropy, and the mechanical properties in different directions will have obvious differences. Therefore, in the process of quality inspection of nickel-based high-temperature alloy forgings, corroding the forging samples and then performing low-magnification streamline characterization by naked eye or low-magnification metallographic microscope is one of the important items for evaluating the quality of forged blades. On the one hand, the morphology of the streamline can be used to judge whether the distribution characteristics of the material structure during the forging process are consistent with the design requirements of the parts. On the other hand, if the forging streamline has defects such as turbulence, turbulence or permeation, it means that there are forging defects in the material structure. Therefore, low-magnification streamline characterization can be observed by the naked eye, without the help of complex and expensive tools and equipment such as electron microscopes or X-ray diffraction equipment to achieve effective quality inspection of nickel-based high-temperature alloy forgings. However, since nickel-based high-temperature alloys themselves have a high degree of alloying, a low content of impurity elements, and the alloys used in aircraft engine manufacturing have good corrosion resistance, conventional chemical corrosion methods are difficult to be effective.

[0023] For example, when the ground and polished IN718 and GH4169D nickel-based high-temperature alloys are chemically corroded at room temperature using a mixed solution of copper sulfate, sulfuric acid, and hydrochloric acid or a mixed solution of hydrochloric acid, phosphoric acid, and ferric chloride, which are commonly used in metallographic corrosion of nickel-based alloys, no streamline structure can be observed on the polished surface, which seriously restricts the quality inspection efficiency and accuracy of nickel-based high-temperature alloy forgings.

[0024] In order to solve the above problems, an embodiment of the present invention provides a method for corrosion of low-magnification streamlines of nickel-based high-temperature alloy forgings, the method comprising the following steps:

[0025] First, a corrosion sample of a nickel-based high-temperature alloy forging is provided. The corrosion sample is cut from the nickel-based high-temperature alloy forging to be inspected by grinding wheel cutting, laser cutting or wire cutting, and the section is the surface that needs to be characterized by low-magnification streamlines. In a preferred embodiment, the section is cut along the ideal streamline extension direction. The section is ground and polished to obtain a low-magnification sample. In a preferred embodiment, the polishing step uses 180 mesh, 320 mesh, 800 mesh and 1200 mesh metallographic sandpaper for four passes, and the grinding time for each pass is 1min-3min. The polishing step uses a 3μm particle size diamond suspension as a polishing medium, and polishing is performed on the polishing flannel of a polishing machine.

[0026] Next, prepare an electrolytic etching solution. The components of the electrolytic etching solution include HNO 3 , HCl, deionized water and FeCl 3 , where by volume, HNO 3: HCl: deionized water = 1:24:160, and each time 1 ml of HNO is added 3 Corresponding to adding 5g of FeCl 3 .

[0027] The above electrolyte is added to the electrolytic cell, stainless steel is used as cathode, and the low-magnification sample is used as anode to perform electrolytic corrosion. The electrolytic corrosion parameters control the electrolytic current to be 1.5A-2A and the electrolytic time to be 2min-4min. In a preferred embodiment, the electrolytic current is regulated by controlling the electrolytic voltage to be 4V-6V.

[0028] After the electrolysis is completed, rinse the low-magnification sample with clean water or anhydrous ethanol for 1-2 times. Optionally, place the low-magnification sample on the polishing flannel of a polishing machine with water as the polishing medium and perform a light polishing treatment for 2s-3s to remove the corrosion products formed on the sample surface during the electrolysis process that are not conducive to streamline observation.

[0029] The cleaned sample is placed in an oven for drying, and the nickel-based high-temperature alloy forgings can be characterized by naked eyes or under a low-power metallographic microscope. The nickel-based high-temperature alloy forgings can be forged blades or forged blade disks of aircraft engines.

[0030] In a preferred embodiment, the corrosion method of the low-magnification streamline of the nickel-based high-temperature alloy forged blade is as follows:

[0031] The longitudinal corrosion samples of nickel-based superalloy blades in the upsetting state were cut by wire cutting. Figure 1 As shown, the sample is made of IN718 alloy, and its composition by mass ratio is: 50.0-55.0% Ni, 17.0-21.0% Cr, 2.80-3.30% Mo, 4.75-5.50% Nb, 15.0-21.0% Fe, 0.75-1.15% Ti, 0.3-0.7% Al, ≤1.0% Co, ≤0.3% Cu, ≤0.35% Si, ≤0.35% Mn. The sample section is polished with 180 mesh, 320 mesh, 800 mesh, and 1200 mesh sandpaper in turn. Each polishing is based on the consistent direction of the wear marks, the smooth polished surface and no scratches left by the previous pass. The polishing time for each pass is 1min-3min. Subsequently, the sample is polished on a polishing machine using a diamond suspension with a particle size of 3μm, and the polishing time is 3min-5min. Polishing is completed to obtain a low-magnification sample.

[0032] Next, prepare the etching solution, which includes 5 ml of analytical grade HNO 3 , 120ml analytical grade HCl, 25g FeCl 3 and 800ml of deionized water.

[0033] The above electrolyte is added to the electrolytic cell, stainless steel is used as the anode, and the low-magnification sample is used as the cathode for electrolytic corrosion treatment. During the electrolytic corrosion process, the electrolytic voltage is controlled at 4V-6V, the electrolytic current is controlled at 1.5A-2A, and the electrolytic time is controlled at 2min-4min.

[0034] After the electrolysis is completed, the low-magnification sample is placed on a polishing machine and lightly polished for 2s-3s using water as the polishing medium to remove corrosion products attached to the surface that affect streamline observation.

[0035] Rinse the low-magnification sample with clean water or anhydrous ethanol 1-2 times, dry it in an oven at 80℃-90℃ until the surface is dry, and take it out for low-magnification streamline characterization.

[0036] like Figure 1 As shown, the surface of the low-magnification sample after corrosion presents obvious streamline structure. In the blade tenon area 1, the streamline 4 has expansion along the edge plate 2, and the extension direction of the streamline 4 is generally consistent with the length direction of the blade body 3.

[0037] In another preferred embodiment, a longitudinal corrosion sample of a nickel-based high-temperature alloy blade in the final forging state is cut by wire cutting. Figure 2As shown in the figure, the sample is made of IN718 alloy. The sample section is polished with 180 mesh, 320 mesh, 800 mesh, and 1200 mesh sandpaper in sequence. Each polishing is based on the consistent direction of the grinding marks, the polished surface is flat and there are no scratches left by the previous polishing. The polishing time for each polishing is 1min-3min. Subsequently, the sample is polished on a polishing machine using a diamond suspension with a particle size of 3μm, and the polishing time is 3min-5min. After polishing, a low-magnification sample is obtained.

[0038] Next, prepare the etching solution, which includes 5 ml of analytical grade HNO 3 , 120ml analytical grade HCl, 25g FeCl 3 and 800ml of deionized water.

[0039] The above electrolyte is added to the electrolytic cell, stainless steel is used as the anode, and the low-magnification sample is used as the cathode for electrolytic corrosion treatment. During the electrolytic corrosion process, the electrolytic voltage is controlled at 4V-6V, the electrolytic current is controlled at 1.5A-2A, and the electrolytic time is controlled at 2min-4min.

[0040] After the electrolysis is completed, the low-magnification sample is placed on a polishing machine and lightly polished for 2s-3s using water as the polishing medium to remove corrosion products attached to the surface that affect streamline observation.

[0041] Rinse the low-magnification sample with clean water or anhydrous ethanol 1-2 times, dry it in an oven at 80℃-90℃ until the surface is dry, and take it out for low-magnification streamline characterization.

[0042] like Figure 2 As shown, the surface of the low-magnification sample after corrosion presents obvious streamline structure. At the end of the blade tenon area 1, the streamline 4 is distributed along the length direction of the blade body 3. In the area close to the edge plate 2, the streamline 4 expands laterally and converges to the position of the blade body 3.

[0043] In a comparative example, the same nickel-based high-temperature alloy corrosion sample in the head state as in the previous embodiment was used, and a low-magnification sample was prepared by grinding and polishing. 5 ml of analytical pure HNO 3 , 120ml analytical grade HCl, 25g FeCl 3 and 50ml of deionized water to prepare the etching solution. Use absorbent cotton to dip the etching solution and wipe the surface of the low-magnification sample for 10s. After the surface of the low-magnification sample turns gray, wash and dry it. The sample obtained is as follows Figure 3 shown.

[0044] In another comparative example, the same final forged nickel-based high-temperature alloy corrosion sample as in the previous embodiment was used and polished to prepare a low-magnification sample. 5 ml of analytical pure HNO 3, 120ml analytical grade HCl, 25g FeCl 3 and 50ml of deionized water to prepare the etching solution. Use absorbent cotton to dip the etching solution and wipe the surface of the low-magnification sample for 10s. After the surface of the low-magnification sample turns gray, wash and dry it. The sample obtained is as follows Figure 4 shown.

[0045] Depend on Figure 3 and Figure 4 It can be seen that when using conventional chemical etching liquid and following the general metallographic etching method of nickel-based alloys, the surface of the sample presents a uniform silver color, and it is impossible to form a streamline corrosion structure visible to the naked eye or under a low-magnification metallographic microscope on the target section of the low-magnification sample, which cannot meet the low-magnification streamline structure characterization requirements of nickel-based high-temperature alloy forgings.

[0046] In other embodiments, the above method may also be used to corrode the GH4169D alloy forging sample to perform low-magnification streamline characterization.

[0047] The purpose of the above embodiments is to further explain the present invention in detail in conjunction with the accompanying drawings so that those skilled in the art can understand the technical concept of the present invention. Within the scope of the present invention, the optimization or equivalent replacement of the method steps involved, and the combination of the implementation methods in different embodiments without conflict of structure and principle, all fall within the protection scope of the present invention.

Claims

1. A method for corrosion of low-magnification streamlines of nickel-based high-temperature alloy forgings. It is characterized in that The following steps are involved: Providing a corrosion sample of a nickel-based high-temperature alloy forging, wherein the corrosion sample includes a target section for low-magnification streamline analysis, and grinding and polishing the corrosion sample to obtain a low-magnification specimen; Provide an electrolytic corrosion solution, wherein the electrolytic corrosion solution comprises HNO 3 , HCl, deionized water and FeCl 3 , where by volume, HNO 3 :HCl:deionized water = 1:24:160, each time 1 ml of HNO is added 3 Corresponding to adding 5g of FeCl 3 ; The low-magnification sample is used as the anode and the stainless steel is used as the cathode. Electrolytic corrosion treatment is carried out in the electrolytic corrosion solution. The electrolytic current in the electrolytic corrosion treatment is 1.5A-2A and the electrolysis time is 2min-4min.

2. The method for corrosion of low-magnification streamlines of nickel-based high-temperature alloy forgings according to claim 1, It is characterized in that After the electrolytic corrosion treatment, the method further includes a step of polishing the low-magnification sample, wherein the polishing medium is water and the polishing time is 2s-3s.

3. The method for corrosion of low-magnification streamlines of nickel-based high-temperature alloy forgings according to claim 1 or 2, It is characterized in that In the step of polishing the corrosion sample, 180 mesh, 320 mesh, 800 mesh and 1200 mesh metallographic sandpaper are used for polishing in sequence, and the polishing time for each pass is 1 min to 3 min.

4. The method for corrosion of low-magnification flow lines of nickel-based high-temperature alloy forgings according to claim 1 or 2, It is characterized in that In the step of polishing the corrosion sample, a diamond suspension with a particle size not exceeding 3 μm is used for polishing, and the polishing time is 3 min to 5 min.

5. The method for corrosion of low-magnification streamlines of nickel-based high-temperature alloy forgings according to claim 1 or 2, It is characterized in that The electrolytic voltage in the electrolytic corrosion treatment is 4V-6V.

6. The method for corrosion of low-magnification flow lines of nickel-based high-temperature alloy forgings according to claim 1 or 2, It is characterized in that A cleaning step is also included after the electrolytic corrosion treatment, in which the low-magnification sample is rinsed 1-2 times with water or anhydrous ethanol.

7. The method for corrosion of low-magnification flow lines of nickel-based high-temperature alloy forgings according to claim 1 or 2, It is characterized in that The nickel-based high-temperature alloy is configured as a Ni-Cr-Fe alloy or a Ni-Cr-Co alloy.

8. The method for corrosion of low-magnification streamlines of nickel-based high-temperature alloy forgings according to claim 7, It is characterized in that The nickel-based high-temperature alloy is configured as IN718 alloy or GH4169D alloy.

9. The method for corrosion of low-magnification flow lines of nickel-based high-temperature alloy forgings according to claim 1 or 2, It is characterized in that The nickel-based high-temperature alloy forging is configured as an aero-engine forged blade or an aero-engine forged blisk.

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