Treatment method for inhibiting surface recrystallization of directional solidification column crystal high-temperature alloy

Abstract

The invention discloses a treatment method for inhibiting surface recrystallization of directional solidification column crystal high-temperature alloy. The treatment method comprises the following steps: respectively weighing each component according to a directional solidification column crystal high-temperature alloy group, and casting to obtain an as-cast workpiece; after the surface of the cast-state workpiece is polished to be smooth, surface hydraulic operation is conducted; and carrying out vacuum heat treatment on the treated as-cast workpiece, and cooling to room temperature. According to the technical scheme, hydraulic treatment and vacuum heat treatment are conducted on the as-cast high-temperature alloy, surface recrystallization can be effectively prevented, and meanwhile the same prevention effect is achieved on common alloys in different initial states in engineering.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of turbine blade manufacturing of aero-engine key hot end components, and particularly relates to a processing method for inhibiting surface recrystallization of directional solidification columnar crystal high-temperature alloy. BACKGROUND

[0002] Turbine blades, as key hot end components of aero-engines, work under high temperature and high pressure while suffering the influence of mechanical load and chemical corrosion. At present, the research on turbine blades mainly focuses on component design, preparation process and microstructure evolution to improve the service performance of the blades. Such extreme working conditions require high-quality materials such as nickel-based high-temperature alloy, which can meet the requirements of the above-mentioned harsh working environment. Directional solidification nickel-based high-temperature alloy is used for industrial gas turbine blades to withstand the coupling effect of high temperature and centrifugal stress during long-term use.

[0003] Directional solidification columnar crystal and single crystal high-temperature alloy have excellent high-temperature mechanical properties because the transverse grain boundaries perpendicular to the stress axis direction are eliminated, so that the grain boundaries are no longer the source of fracture initiation. They are widely used in modern engine turbine blades. Compared with single crystal high-temperature alloy, directional solidification high-temperature alloy has the advantages of low manufacturing difficulty, high yield, simple heat treatment process, etc., and is still widely used. However, recrystallization will introduce transverse grain boundaries again, resulting in a decrease in the mechanical properties of the alloy. Therefore, single crystal high-temperature alloy and directional columnar crystal blades must avoid the generation of recrystallization as much as possible.

[0004] In order to obtain good mechanical properties, a complete heat treatment method is usually used to improve the microstructure of the blade to meet the performance requirements. The plastic deformation of the turbine blade during processing, such as shrinkage stress during solidification, deformation generated during shell removal and grinding, and residual stress generated during sandblasting and shot blasting, will produce recrystallization defects during subsequent heat treatment.

[0005] During the preparation of the blade, it generally goes through processes such as casting, shell removal, riser cutting, sandblasting cleaning, etc. After vibration shell removal, a common surface treatment method is used to completely remove the shell remaining on the surface of the blade, which will introduce external stress into the blade and store it as strain energy in the blade, which will be released in the form of recrystallization during subsequent heat treatment. At the same time, the solidification stress generated during casting will also promote the generation of recrystallization. Such recrystallization is generally concentrated on the surface and has the characteristics of large size and small quantity. The presence of such recrystallization on the surface of the blade will greatly reduce the pass rate of the blade and even result in scrap processing. Surface treatment is generally essential, so it is very important to develop a method that meets the needs of shell removal and cleaning and is not prone to recrystallization. SUMMARY

[0006] The application discloses a treatment method for inhibiting surface recrystallization of a directional solidification columnar crystal high-temperature alloy.

[0007] To solve the above technical problems, the technical scheme of the application is as follows: a treatment method for inhibiting surface recrystallization of a directional solidification columnar crystal high-temperature alloy, which specifically comprises the following steps:

[0008] S1) respectively weighing each component according to a directional solidification columnar crystal high-temperature alloy group, and obtaining a cast state workpiece after casting;

[0009] S2) polishing the surface of the cast state workpiece obtained in S1) to be smooth, and then performing surface hydraulic operation;

[0010] S3) performing vacuum heat treatment on the cast state workpiece treated in S2), and cooling to room temperature.

[0011] Further, the directional solidification test bar alloy composition in S1) is C: 0.07-0.08, Cr: 8.00-8.50, Co: 9.10-9.40, W: 9.30-9.70, Mo: 0.40-0.60, Al: 5.50-5.70, Ti: 0.60-0.80, Ta: 3.10-3.30, Hf: 1.30-1.60, and Ni: balance.

[0012] Further, the specific process of S2) is as follows:

[0013] S2.1) grinding the cast state workpiece in a flowing water state by using 60#-3000# sandpaper;

[0014] S2.1) then polishing the cross section to be smooth and scratch-free by using diamond polishing paste with w0.5-2.5 in a polishing machine;

[0015] S2.3) then performing hydraulic operation on the cast state workpiece under the conditions of a water pressure of 5-30 MPa, a treatment time of ≤2 min and a distance of ≤30 cm.

[0016] Further, the specific process of vacuum heat treatment in S3) is as follows:

[0017] S3.1) placing the cast state workpiece under a vacuum degree of 10 -3 ~ 10 -5 Pa, gradually increasing the temperature from low temperature to high temperature to 1200-1300 DEG C, and performing solid solution treatment by keeping the temperature for 2-3 h;

[0018] S3.2) then gradually increasing the temperature from low temperature to high temperature to 1000-1100 DEG C, and performing stabilization treatment by keeping the temperature for 4-6 h;

[0019] S3.3) low temperature aging treatment, holding at 800-900 DEG C for 20-25h, discharging, and cooling to room temperature by argon.

[0020] Further, the S3.1) gradually increasing temperature from low temperature to high temperature process is specifically: heating from room temperature to 200-350 DEG C at a heating rate of 2-5 DEG C / min, holding for 5-30 min; heating to 1100-1200 DEG C at a heating rate of 5-10 DEG C / min, and then increasing to 1200-1300 DEG C at a heating rate of 2-10 DEG C / min.

[0021] Further, the S3.2) gradually increasing temperature from low temperature to high temperature process is specifically: heating from room temperature to 350 DEG C at a heating rate of 5 DEG C / min, holding for 30 min; heating to 1000-1100 DEG C at a heating rate of 10 DEG C / min.

[0022] Further, the treatment method further comprises the following steps: S4) polishing and observing the surface of the as-cast workpiece after the S3) treatment, and then performing electrolytic polishing and electrolytic etching treatment.

[0023] Further, the voltage of the electrolytic polishing in the S4) is 10-20V, and the time is 3-8s;

[0024] The voltage of the electrolytic etching treatment is 3-10V, and the time is 1-7s.

[0025] Further, the ratio of CH3OH:H2SO4 in the electrolytic polishing solution is 3-4.5:1.

[0026] The ratio of the electrolyte in the electrolytic etching treatment is 100-175mL H3PO4+10-25mL concentrated sulfuric acid+10-30g CrO3.

[0027] A directional solidification columnar crystal high-temperature alloy obtained by the above treatment method.

[0028] The beneficial effects of the present application are: due to the above technical scheme, the treatment method of the present application first uses a certain hydraulic process to quantitatively analyze the recrystallization pass rate of the as-cast, solid solution state, and aging state alloy commonly used in engineering practice, and verifies the effectiveness of the method for different initial states of the alloy. The results show that the method can effectively prevent the generation of alloy recrystallization under different initial states.

[0029] Under the premise of ensuring effectiveness, the parameters are explored, the as-cast blade material is subjected to hydraulic treatment, which can effectively prevent the generation of recrystallization, indicating that the series of methods can effectively prevent the generation of recrystallization. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1A flow chart of a surface recrystallization inhibiting treatment method for a directionally solidified columnar crystal high-temperature alloy.

[0031] Figure 2 A microstructure diagram of an alloy surface treated by the surface treatment method for the directionally solidified columnar crystal high-temperature alloy not prone to recrystallization according to the present application.

[0032] Figure 3 A microstructure diagram of an alloy surface treated by the surface treatment method for the directionally solidified columnar crystal high-temperature alloy not prone to recrystallization according to the present application.

[0033] Figure 4 A microstructure diagram of an alloy surface treated by the surface treatment method for the directionally solidified columnar crystal high-temperature alloy not prone to recrystallization according to the present application. Figure 2

[0034] Figure 5 A microstructure diagram of an alloy surface treated by the surface treatment method for the directionally solidified columnar crystal high-temperature alloy not prone to recrystallization according to the present application.

[0035] Figure 6 A microstructure diagram of an alloy surface treated by the surface treatment method for the directionally solidified columnar crystal high-temperature alloy not prone to recrystallization according to the present application. DETAILED DESCRIPTION

[0036] To further illustrate the present application, the present application will be described in detail below with reference to examples and drawings.

[0037] As shown in Figure 1 the present application is a surface recrystallization inhibiting treatment method for a directionally solidified columnar crystal high-temperature alloy, which specifically comprises the following steps:

[0038] S1) respectively weighing each component according to a directionally solidified columnar crystal high-temperature alloy group, and then casting to obtain a cast workpiece;

[0039] S2) polishing the surface of the cast workpiece obtained in S1) to be smooth, and then performing a surface hydraulic operation;

[0040] S3) vacuum heat treating the cast workpiece treated in S2), and cooling to room temperature.

[0041] ​Further, the directional solidification test bar alloy composition in S1) is C: 0.07-0.08, Cr: 8.00-8.50, Co: 9.10-9.40, W: 9.30-9.70, Mo: 0.40-0.60, Al: 5.50-5.70, Ti: 0.60-0.80, Ta: 3.10-3.30, Hf: 1.30-1.60, Ni: balance.

[0042] Further, the specific process of S2) is:

[0043] S2.1) grinding the as-cast workpiece with 60#-3000# sandpaper in a flow state;

[0044] S2.1) further polishing the cross section to a smooth and scratch-free finish using diamond polishing paste with w0.5-2.5 in a polishing machine;

[0045] S2.3) further performing hydraulic operation on the as-cast workpiece at a water pressure of 5-30 MPa, a treatment time of ≤2 min, and a distance of ≤30 cm.

[0046] Further, the specific process of S3) is:

[0047] S3.1) placing the as-cast workpiece in a vacuum degree of 10 -3 ~ 10 -5 Pa, gradually increasing the temperature from low to high to 1200-1300℃, and holding for 2-3h to complete the solid solution treatment;

[0048] S3.2) further adopting a process of gradually increasing the temperature from low to high to 1000-1100℃ and holding for 4-6h to complete the stabilization treatment;

[0049] S3.3) low-temperature aging treatment, holding at a temperature of 800-900℃ for 20-25h, discharging, and cooling to room temperature using argon.

[0050] Further, the process of gradually increasing the temperature from low to high in S3.1) is specifically: heating from room temperature to 200-350℃ at a heating rate of 2-5℃ / min, holding for 5-30min; heating to 1100-1200℃ at a heating rate of 5-10℃ / min, and then increasing the temperature to 1200-1300℃ at a heating rate of 2-10℃ / min.

[0051] Further, the process of gradually increasing the temperature from low to high in S3.2) is specifically: heating from room temperature to 350℃ at a heating rate of 5℃ / min, holding for 30min; and heating to 1000-1100℃ at a heating rate of 10℃ / min.

[0052] Example 1:

[0053] According to a preferred embodiment of the surface treatment method for preventing recrystallization of the directionally solidified columnar crystal high-temperature alloy according to the present application, the steps in the order include the following steps:

[0054] S1) preparing a directionally solidified columnar crystal test rod, cutting a test sample; and preparing test samples with different initial states;

[0055] S2) performing surface hydraulic operation on the test sample after polishing the surface smooth;

[0056] S3) placing the test sample in a vacuum tube in a heat treatment furnace, performing solid solution and aging heat treatment, and performing argon cooling treatment on the heat-treated test sample;

[0057] S4) performing electrolytic polishing and electrolytic etching treatment on the polished observation surface to observe the recrystallization of the alloy;

[0058] The prepared directionally solidified test rod in S1) has the following alloy composition: C 0.077, Cr 8.17, Co 9.21, W 9.51, Mo 0.47, Al 5.65, Ti 0.71, Ta 3.23, Hf 1.43, and Ni balance. Solid solution and aging state test samples are prepared using a heat treatment system.

[0059] After the alloy is ground by 60#, 240#, 600#, 1000#, and 2000# sandpaper in a flowing water state in S2), the longitudinal section is polished to a smooth and scratch-free state using a w2.5 diamond polishing paste in a PG-1A type polishing machine to eliminate the influence of grinding stress on the test sample, and then water spraying operation is performed. The water spraying parameters are: water pressure: 20 MPa, time: ≤2 min, distance: ≤30 cm. The solid solution state water spraying process is compared and analyzed with the same process. Figure 2 Figure 2 , Figure 3 The water pressure and water pressure time are changed separately, and the parameters are changed based on the whole. Figure 2

[0060] In S3), the solid solution treatment adopts a gradient heat preservation treatment from low temperature to high temperature. The specific process is as follows: heating from room temperature to 300℃ at a rate of 5℃ / min, and preserving for 10 min; heating to 1200℃ at a rate of 10℃ / min, and then heating to 1260℃ at a rate of 5℃ / min, and preserving for 2h; stabilizing treatment is heated to 1080℃ in the same way, and preserving for 4h; low-temperature aging is directly heated to 870℃, and preserving for 20h, and then taken out of the furnace. After being taken out of the furnace, they are cooled to room temperature in argon.

[0061] Test method:

[0062] ​​S4) Electrolytic polishing and electrolytic etching treatment is performed on the directionally solidified columnar crystal alloy as an anode in S4. The ratio of the electrolytic polishing solution is CH3OH:H2SO4=4:1, the voltage is 10V, and the time is 5s; the ratio of the electrolyte is 150mL H3PO4+10mL concentrated sulfuric acid+15g CrO3, the voltage is 5V, and the time is 2.5s.

[0063] Seven are selected for recrystallization comparison experiment, and the recrystallization depth and morphology of the side surface are observed after surface treatment of the cross section. As shown in the figure, after the treatment by the method, the alloy does not recrystallize, and the qualified rate reaches 100%, that is, all the experimental alloys do not recrystallize. Figures 2-4

[0064] The oxide layer attached to the treated surface is removed by sandpaper grinding to reduce the influence of uneven oxide layer on the surface treatment process. After grinding, the longitudinal cross section is polished to a smooth and scratch-free state using w2.5 diamond polishing paste on a PG-1A polishing machine to eliminate the influence of grinding stress on the sample, thereby avoiding plastic deformation during the grinding and polishing process.

[0065] Example 2:

[0066] According to a preferred embodiment of the surface treatment method for the directionally solidified columnar crystal high-temperature alloy according to the present application, the steps in the order are as follows:

[0067] S1) Preparation of directionally solidified columnar crystal test rod, cutting of test sample; and preparation of test sample with different initial states;

[0068] S2) Surface hydraulic operation after polishing the treated surface of the test sample;

[0069] S3) Vacuum sealing of the test sample in a heat treatment furnace, solid solution and aging heat treatment, and argon cooling treatment of the heat treated test sample;

[0070] S4) Electrolytic polishing and electrolytic etching treatment of the polished observation surface to observe the recrystallization of the alloy;

[0071] The prepared directionally solidified test rod in S1) has the following alloy composition: C 0.077, Cr 8.17, Co 9.21, W 9.51, Mo 0.47, Al 5.65, Ti 0.71, Ta 3.23, Hf 1.43, and Ni balance; and the test sample is prepared using a heat treatment system.

[0072] ​S2) In S2, after the alloy is ground by 60#, 240#, 600#, 1000# and 2000# sandpaper in the flowing water state, the longitudinal section is polished to be smooth and scratch-free by using w2.5 diamond polishing paste in a PG-1A type polishing grinder to eliminate the influence of grinding stress on the sample, and then the water spraying operation is performed, with the water spraying parameters being: water: 10 MPa, time ≤ 2 min, distance ≤ 30 cm,

[0073] In S3, the gradient heat preservation treatment from low temperature to high temperature is adopted in the solution treatment, and the specific process is as follows: heating from room temperature to 300℃ at a heating rate of 5℃ / min, and then heat preservation for 10 min; heating to 1200℃ at a heating rate of 10℃ / min, and then heating to 1260℃ at a heating rate of 5℃ / min, and then heat preservation for 2h; heating to 1080℃ for stabilization treatment by the same step, and then heat preservation for 4h; directly heating to 870℃ for low-temperature aging, and then heat preservation for 20h, and then discharging. After discharging, the sample is cooled to room temperature in argon.

[0074] Comparative Example 1

[0075] Example Two is not treated according to the surface treatment method of the directional solidification columnar crystal high-temperature alloy not prone to recrystallization, and the process sequence, used equipment, principle and beneficial effects thereof are basically the same as those of Example One, except that:

[0076] In Step Two, the surface treatment operation is performed by spraying corundum sand, and the sand spraying parameters are: pressure 0.1-0.7 MPa, time ≤ 5 min, distance ≤ 30 cm.

[0077] In this example, 4777DS alloy is selected, and after the cross section is treated, the recrystallization depth and morphology of the side surface are observed, so as to count the recrystallization of the alloy under the present application. As shown in Figure 5 After the treatment by the method, the experimental alloy recrystallizes.

[0078] Comparative Example 2

[0079] Example Two is not treated according to the surface treatment method of the directional solidification columnar crystal high-temperature alloy not prone to recrystallization, and the process sequence, used equipment, principle and beneficial effects thereof are basically the same as those of Example One, except that:

[0080] In Step Two, the surface treatment operation is performed by sand belt polishing, and the polishing parameters are: speed 1000-5000 r / min, mesh 100-300#, and time ≤ 60 s.

[0081] In this example, 4777DS alloy is selected, and after the cross section is treated, the recrystallization depth and morphology of the side surface are observed, so as to count the recrystallization of the alloy under the present application. As shown in Figure 6As shown, the experimental alloy is recrystallized after the treatment.

[0082] The above describes in detail the treatment method for inhibiting surface recrystallization of the directional solidification columnar crystal high-temperature alloy provided by the embodiments of the application. The above description of the embodiments is only used to help understand the method of the application and its core idea; meanwhile, for those skilled in the art, the specific implementation and application range will be changed according to the idea of the application, and the above description should not be understood as a limitation on the application.

[0083] As some terms are used in the description and claims to refer to certain components. Those skilled in the art should understand that hardware manufacturers may use different names to refer to the same component. The description and claims of the present application do not distinguish components by name, but by the functional difference between components. As mentioned throughout the description and claims, "including" and "including" are open terms, which should be interpreted as "including / including but not limited to". "Approximately" means within an acceptable error range, and those skilled in the art can solve the technical problems within a certain error range and basically achieve the technical effects. The subsequent description of the specification is a preferred embodiment of the application, which is intended to illustrate the general principles of the application, but not to limit the scope of the application. The scope of protection of the application is defined by the appended claims.

[0084] It should also be noted that the terms "include", "contain" or any other variant thereof are intended to cover non-exclusive inclusion, so that the goods or systems including a series of elements not only include those elements, but also include other elements not explicitly listed, or include elements inherent to such goods or systems. Without more limitations, the element defined by the sentence "including a…" does not exclude the existence of other identical elements in the goods or systems including the element.

[0085] It should be understood that the term "and / or" used herein is only used to describe the association relationship of the associated objects, which means that there are three relationships, for example, A and / or B, which means that there are three cases of A alone, A and B together, and B alone. In addition, the character " / " in this paper generally represents that the front and rear associated objects have an "or" relationship.

[0086] The foregoing description illustrates and describes several preferred embodiments of the present application. However, it is to be understood that the application is not limited to the precise forms described, and that changes can be made therein without departing from the scope of the present application. Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. Therefore, the specification and examples are to be considered exemplary only, with a true scope and spirit of the application being indicated by the following claims.

Claims

1. A process for inhibiting surface recrystallization of a directionally solidified columnar grain high temperature alloy characterized by, The method specifically comprises the following steps: S1) respectively taking each component according to the directional solidification columnar crystal high-temperature alloy group, casting to obtain a cast workpiece; S2) after polishing the surface of the cast workpiece obtained in S1) smooth, then performing surface hydraulic operation; S3) vacuum heat treating the cast workpiece treated in S2), and cooling to room temperature.

2. The treatment method according to claim 1, characterized in that, The directional solidification test bar alloy component in S1) is C: 0.07-0.08, Cr: 8.00-8.50, Co: 9.10-9.40, W: 9.30-9.70, Mo: 0.40-0.60, Al: 5.50-5.70, Ti: 0.60-0.80, Ta: 3.10-3.30, Hf: 1.30-1.60, and Ni balance.

3. The treatment method of claim 1, wherein, The specific process of S2) is: S2.1) grinding the cast workpiece in a flowing water state with 60#-3000# sandpaper; S2.1) then polishing the cross section to be smooth and scratch-free in a polishing machine by using diamond polishing paste with w0.5-2.5; S2.3) then performing hydraulic operation on the cast workpiece under water pressure of 5-30 MPa, treatment time of ≤2 min, and distance of ≤30 cm.

4. The treatment method of claim 1, wherein The specific process of vacuum heat treatment in S3) is: S3.1) The as-cast workpiece is placed in a vacuum furnace with a vacuum degree of 10 -3 ~ 10 -5 Pa, and a process of gradually increasing the temperature from low temperature to high temperature to 1200-1300℃ is adopted to complete the solid solution treatment, and the temperature is kept for 2-3h. S3.2) then performing stabilization treatment by gradually increasing the temperature from low temperature to high temperature to 1000-1100℃, and heat preservation for 4-6 h; S3.3) low-temperature aging treatment, heat preservation for 20-25 h at a temperature of 800-900℃, discharging, and cooling to room temperature by using argon.

5. The treatment method according to claim 4, characterized in that, The gradual temperature increasing process from low temperature to high temperature in S3.1) is specifically: heating from room temperature to 200-350℃ at a heating rate of 2-5℃ / min, and heat preservation for 5-30 min; heating to 1100-1200℃ at a heating rate of 5-10℃ / min, and then increasing the temperature to 1200-1300℃ at a heating rate of 2-10℃ / min.

6. The treatment method of claim 4, wherein The gradual temperature increasing process from low temperature to high temperature in S3.2) is specifically: heating from room temperature to 350℃ at a heating rate of 5℃ / min, and heat preservation for 30 min; heating to 1000-1100 at a heating rate of 10℃ / min.

7. The treatment method of claim 1, wherein The treatment method further comprises the following step: S4) polishing and observing the surface of the cast workpiece treated in S3), and then performing electrolytic polishing and electrolytic etching treatment.

8. The treatment method according to claim 7, characterized in that, The voltage of electrolytic polishing in S4) is 10-20 V, and the time is 3-8 s; The voltage of electrolytic etching treatment is 3-10 V, and the time is 1-7 s.

9. The processing method according to claim 8, characterized in that, The ratio of CH3OH:H2SO4 in the electrolytic polishing solution is 3-4.5:1; The ratio of the electrolyte in the electrolytic etching treatment is 100-175 mL H3PO4+10-25 mL concentrated sulfuric acid+10-30 g CrO3.

10. A directionally solidified columnar grain high temperature alloy characterized by, The directional solidification columnar crystal high-temperature alloy is obtained by the treatment method according to any one of claims 1-6.

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