CN115354133B - Method for preventing local recrystallization of monocrystalline superalloy blade - Google Patents
Method for preventing local recrystallization of monocrystalline superalloy blade Download PDFInfo
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- CN115354133B CN115354133B CN202210978837.8A CN202210978837A CN115354133B CN 115354133 B CN115354133 B CN 115354133B CN 202210978837 A CN202210978837 A CN 202210978837A CN 115354133 B CN115354133 B CN 115354133B
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/0068—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for particular articles not mentioned below
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B24—GRINDING; POLISHING
- B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
- B24B1/00—Processes of grinding or polishing; Use of auxiliary equipment in connection with such processes
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/02—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working in inert or controlled atmosphere or vacuum
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
- C23F3/00—Brightening metals by chemical means
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- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
- C25F3/00—Electrolytic etching or polishing
- C25F3/02—Etching
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
- C25F3/00—Electrolytic etching or polishing
- C25F3/16—Polishing
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Abstract
The invention discloses a method for preventing local recrystallization of a monocrystalline superalloy blade, which comprises the following steps in sequence: placing the monocrystal superalloy blade into a vacuum heat treatment furnace for recovery treatment; taking out the single-crystal superalloy blade from the vacuum heat treatment furnace, and directly mechanically polishing and grinding part of the blade; cleaning the mechanically polished single-crystal superalloy blade, and removing mechanically polished traces by adopting a local electrolytic machining or chemical corrosion mode; and carrying out solid solution aging treatment on the single-crystal superalloy blade. According to the technical scheme, the problem that the single-crystal superalloy blade is recrystallized in the subsequent solution heat treatment process due to the fact that large casting residual stress locally exists in the casting process due to the fact that the blade structure is complex can be effectively prevented.
Description
Technical Field
The invention belongs to the technical field of manufacturing of turbine blades of aeroengines, and particularly relates to a method for preventing local recrystallization of monocrystalline superalloy blades.
Background
Turbine blades are one of the most critical components in turbine engines, and are subjected to high temperatures and stresses in the harsh operating environment. Single crystal superalloys eliminate almost all grain boundaries, have good high temperature integration properties, and are considered to be critical materials for the fabrication of advanced aero-and ground-turbine blades.
For single crystal superalloys, a method of complete heat treatment is generally employed in order to obtain good mechanical properties, but the solution treatment temperature is high and the recrystallization tendency is large. On the one hand, the grain boundary strength of recrystallization is significantly lower than that of grain boundaries generated in the casting solidification process; on the other hand, the recrystallization generates a transverse grain boundary, forms a weak link of the blade, and seriously influences the performance of the blade. Therefore, single crystal superalloys and oriented columnar crystal blades must be kept from recrystallization as much as possible.
In the directional solidification process of the blade, because the shape of the blade is complex, excessive casting residual stress concentration exists in the shrinkage part in the solidification cooling process, and after the directional solidification is finished, the recrystallization defect easily occurs in the subsequent solid solution heat treatment process due to the large casting residual stress.
The formation of the recrystallization is due to the fact that the cast stress or the external stress in the blade generates a certain plastic deformation in the blade during the preparation process, a certain strain energy is stored, and the strain energy is released in a recrystallization mode during the subsequent high-temperature heat treatment process. Plastic deformation caused by casting stress due to solidification shrinkage and the like in the casting process can cause recrystallization in the heat treatment process if the density is large, and the recrystallization is usually fixed in position and has the characteristics of strong repeatability, large size, small quantity and the like. In general, if such recrystallization occurs on the surface of the blade, the entire blade is scrapped, which is also an important factor for limiting the qualification rate of the blade. Therefore, there is an urgent need to develop a method for preventing local recrystallization of single-crystal superalloy blades, so as to reduce the risk of blade recrystallization, and further improve the blade manufacturing yield.
The invention patent with the application publication number of CN107557869A discloses a method for avoiding recrystallization of a platinum wire chaplet position of a single-crystal superalloy turbine blade, wherein a sequential mode of hand-held grinding machine polishing, felt wheel low-stress polishing, chemical corrosion surface treatment and stepped heat treatment is adopted for the chaplet position of the blade, so that a plastic strain layer and residual stress of the chaplet position of the blade are reduced; the corrosive liquid of the chemical corrosion is hydrogen peroxide and hydrochloric acid, and the volume ratio of the corrosive liquid is H 2 O 2 Hcl=1:8-10; the step-type recovery heat treatment is as follows: (700-850 ℃)/(2-4 h) + (1200-1230 ℃) (0.5-1 h) + (1250-1270 ℃) (0.5-1 h) + (1200-1230 ℃)/(0.5-1 h) + (1280-1300 ℃) (0.5-1 h) + (1250-1270 ℃)/(0.5-1 h) + (1280-1300 ℃)/(0.5-1 h), the heating rate of all heating stages is less than or equal to 10 ℃/min, and after the heat preservation is completed, the furnace is cooled to below 200 ℃ and discharged. The technical proposal aims at the vortex of the monocrystal superalloyThe method for avoiding recrystallization designed at the position of the platinum wire chaplet of the wheel blade is only suitable for avoiding recrystallization at the position of the platinum wire chaplet of the blade, and is not suitable for the blade body, wherein the operation sequence, the process parameters and the like of the method are suitable for avoiding recrystallization at the position of the platinum wire chaplet of the blade; in addition, mechanical polishing and chemical etching are performed first, and then a recovery heat treatment is performed, so that the operation sequence is unfavorable for promoting recrystallization nucleation, and therefore, recrystallization still occurs in the subsequent solution aging treatment.
Disclosure of Invention
In the directional solidification process of the single-crystal superalloy blade, because the shape of the blade is complex, excessive casting residual stress concentration exists in the shrinkage part in the solidification cooling process, and after the directional solidification is finished, the recrystallization defect is easily caused in the subsequent solution heat treatment process by the larger casting residual stress. The invention aims to prevent recrystallization of a single-crystal superalloy blade in a subsequent solution heat treatment process due to the fact that large casting residual stress locally exists in the casting process due to the complicated blade structure.
In order to achieve the above object, the present invention provides a method for preventing local recrystallization of a single crystal superalloy blade, comprising the following steps in order:
step one: placing the monocrystal superalloy blade into a vacuum heat treatment furnace for recovery treatment;
step two: taking out the single-crystal superalloy blade from the vacuum heat treatment furnace, and directly mechanically polishing and grinding part of the blade;
step three: cleaning the mechanically polished single-crystal superalloy blade, and removing mechanically polished traces by adopting a local electrolytic machining or chemical corrosion mode;
step four: and carrying out solid solution aging treatment on the single-crystal superalloy blade.
The invention relates to a method for preventing local recrystallization of a monocrystalline superalloy blade, which comprises the following steps: recovery treatment, mechanical polishing, local electrolytic machining or chemical corrosion and solid solution aging treatment. It is generally recognized by those skilled in the art that mechanical direct treatment of the blade body prior to solution aging of a single crystal superalloy blade is prohibited, and that direct mechanical treatment of the blade body promotes recrystallization during solution aging. The invention overcomes the technical bias, adopts a mechanical mode to directly treat the blade body before the blade is subjected to solution aging treatment, combines the step of recovering treatment on the blade before the mechanical treatment, and finally effectively avoids the recrystallization of the monocrystal superalloy blade in the solution aging process.
The gradient recovery treatment gradually progresses from low temperature to high temperature can effectively recover casting residual stress, and when the residual stress is large, the local surface of the monocrystalline blade forms the core of recrystallized grains. However, the structural characteristics of the superalloy material determine that the migration resistance of the recrystallized grain boundary before solid solution is large, and the superalloy material is difficult to grow. The control link of the recrystallization process of the single crystal superalloy is nucleation.
The hand-held electric, pneumatic or other polishing and grinding equipment is adopted to polish and repair the blade, the area with larger surface stress of the blade is removed, and the nucleation in the solution treatment process is effectively prevented through subsequent treatment, or the recrystallized grain core formed in the recovery process is removed.
All mechanical polishing trace marks are removed by adopting non-mechanical polishing modes such as local electrolytic machining and the like, and the plastic deformation of polishing is prevented from nucleation in the solution treatment process. Because of the severe plastic deformation layer formed on the surface by mechanical polishing, the formation of recrystallized grains is promoted during solution treatment despite the thin thickness. For the mechanical polishing under the careful operation, the deformation layer is very thin, and can be effectively removed in a non-mechanical mode.
Preferably, in the first step, a gradient recovery treatment process gradually progressing from low temperature to high temperature is adopted, and the specific process is as follows: heating from room temperature to 400-600 ℃ at a heating rate of 2-5 ℃/min, and preserving heat for 5-6h; continuously heating to 650-700 ℃ at a heating rate of 2-5 ℃/min, and preserving heat for 4-5h; continuously heating to 870-900 ℃ at the heating rate of 2-5 ℃/min, and preserving heat for 1-2h; continuously heating to 1100-1150 ℃ at a heating rate of 2-5 ℃/min, and preserving heat for 1-2h; continuously heating to 1200-1250 ℃ at a heating rate of 2-5 ℃/min, and preserving heat for 0.5-1h; continuously heating to 1250-1280 ℃ at a heating rate of 2-5 ℃/min, and preserving heat for 0.5-1h; cooling to 280-300 deg.c with furnace and discharging.
In any of the above schemes, preferably, in the second step, the mechanical polishing tool is a hand-held electric grinding tool or a hand-held pneumatic grinding tool, the granularity of the grinding head is 80-120 meshes, and the polishing thickness is 0.02-0.05mm.
In any of the above schemes, preferably, in the third step, the trace of mechanical polishing is removed by adopting a local electrolytic machining mode, and electrolytic corrosion or electrolytic polishing is carried out on the local part of the blade subjected to mechanical polishing.
In any of the above embodiments, it is preferable that the blade is used as an anode and the superalloy material is used as a cathode during the partial electrolytic processing; the electrolyte is prepared from NaCl, HCl and H 2 O=1-3 g:1-5ml:100ml, voltage 5-30V, current 7-15A, electrolytic processing time 5-10s. In the electrolytic machining process, low voltage (such as 5-6V voltage) can be adopted for electrolytic corrosion, and high voltage can also be adopted for electrolytic polishing, and the voltage needs to be controlled within a safe voltage range below 36V due to manual operation. A large number of experiments prove that the proportion of the electrolyte is controlled to be NaCl, HCl and H 2 O=1-3 g:1-5ml:100ml, and the time of electrolytic processing is controlled within 5-10s, so that the processing trace can be sufficiently removed without damaging the area without the processing trace.
In any of the above schemes, preferably, in the third step, the trace of mechanical polishing is removed by chemical etching, and all the blades are immersed in the etching solution for etching. Because the mechanical polishing is performed manually, the plastic deformation depth is shallow in the processing process, and all the mechanical polishing marks can be removed by adopting a chemical corrosion mode.
In any of the above schemes, preferably, in the chemical etching process, the ratio of the etching solution is HCl to H 2 O 2 ＝100ml:10-15ml。
In any of the above schemes, preferably, in the fourth step, the solution treatment process is as follows: placing the single-crystal superalloy blade into a vacuum heat treatment furnace, heating to 1290 ℃ from room temperature at a heating rate of 10 ℃/min, and preserving heat for 1h; continuously heating to 1300 ℃ at a heating rate of 10 ℃/min, and preserving heat for 2 hours; heating to 1315 ℃ continuously at a heating rate of 10 ℃/min, and preserving heat for 4 hours.
In any of the above schemes, preferably, in the fourth step, the aging treatment process is as follows: after the solution treatment process is finished, forcibly cooling to 550 ℃; heating to 1120 ℃ at a heating rate of 10 ℃/min, preserving heat for 4 hours, and then forcibly cooling to 550 ℃; heating to 870 ℃ at a heating rate of 10 ℃/min, preserving heat for 32h, then forcedly cooling to 300 ℃, and discharging.
The method for preventing the local recrystallization of the monocrystalline superalloy blade has the following beneficial effects:
1. firstly, recovery treatment is carried out, casting residual stress at the local stress concentration position of the blade or the accumulation of the stress concentration on the surface of the blade can be effectively removed, then, a mechanical polishing mode is adopted to effectively remove the local stress concentration structure, and finally, a local electrolytic machining or other non-mechanical polishing modes are adopted to eliminate plastic deformation caused by mechanical polishing, so that recrystallization in the subsequent solution treatment process due to the fact that the local casting residual stress concentration of the blade casting is larger is effectively avoided.
2. The mechanical polishing can be used for realizing large-allowance processing, the large residual stress area existing on the part of the single crystal blade can be efficiently removed, and plastic deformation caused by mechanical polishing can be further removed by adopting non-mechanical polishing modes such as electrolytic machining and the like, so that large recrystallized grains on the part of the single crystal blade can be effectively prevented.
Drawings
FIG. 1 is a photograph of a blade from which recrystallization is eliminated in a preferred embodiment of a method for preventing localized recrystallization of a single crystal superalloy blade in accordance with the present invention, the sequence of processing being: recovery treatment, mechanical polishing and grinding, electrolytic machining and solid solution aging treatment;
FIG. 2 is a photograph of a blade in which recrystallization has occurred in a comparative example of a method for preventing localized recrystallization of a single crystal superalloy blade in accordance with the present invention, the sequence of processing being: mechanical polishing, electrolytic machining, recovery treatment and solid solution aging treatment.
The reference numerals in the drawings indicate: 1-recrystallizing the crystal grains.
Detailed Description
For a further understanding of the present invention, the present invention will be described in detail with reference to the following examples.
Embodiment one:
according to a preferred embodiment of the method for preventing local recrystallization of a single crystal superalloy blade according to the present invention, the method comprises the following steps in order:
step one: placing the monocrystal superalloy blade into a vacuum heat treatment furnace for recovery treatment;
step two: taking out the single-crystal superalloy blade from the vacuum heat treatment furnace, and directly mechanically polishing and grinding part of the blade;
step three: cleaning the mechanically polished single-crystal superalloy blade, and removing mechanically polished traces by adopting a local electrolytic machining or chemical corrosion mode;
step four: and carrying out solid solution aging treatment on the single-crystal superalloy blade.
In the first step, a gradient recovery treatment process gradually progressing from low temperature to high temperature is adopted, and the specific process is as follows: heating to 400 ℃ from room temperature at a heating rate of 2 ℃/min, and preserving heat for 6 hours; continuously heating to 650 ℃ at a heating rate of 2 ℃/min, and preserving heat for 5 hours; heating to 870 ℃ continuously at a heating rate of 2 ℃/min, and preserving heat for 2h; continuously heating to 1100 ℃ at a heating rate of 2 ℃/min, and preserving heat for 2h; continuously heating to 1200 ℃ at a heating rate of 2 ℃/min, and preserving heat for 1h; continuously heating to 1250 ℃ at a heating rate of 2 ℃/min, and preserving heat for 1h; cooling to 280 ℃ along with the furnace, and discharging.
In the second step, a hand-held electric grinding tool is adopted to mechanically polish the part of the blade, the granularity of a grinding head is 80 meshes, and the polishing thickness is 0.05mm.
Removing mechanical polishing marks by adopting a local electrolytic machining mode, wherein in the electrolytic machining process, a blade is used as an anode, and a high-temperature alloy material is used as a cathode; the electrolyte is prepared from NaCl, HCl and H 2 O=3g:5 ml:100ml, voltage 5V, current 7A, time of electrolytic processing 10s.
In the fourth step, the solution treatment process comprises the following steps: placing the single-crystal superalloy blade into a vacuum heat treatment furnace, heating to 1290 ℃ from room temperature at a heating rate of 10 ℃/min, and preserving heat for 1h; continuously heating to 1300 ℃ at a heating rate of 10 ℃/min, and preserving heat for 2 hours; heating to 1315 ℃ continuously at a heating rate of 10 ℃/min, and preserving heat for 4 hours. The aging treatment process comprises the following steps: after the solution treatment process is finished, forcibly cooling to 550 ℃; heating to 1120 ℃ at a heating rate of 10 ℃/min, preserving heat for 4 hours, and then forcibly cooling to 550 ℃; heating to 870 ℃ at a heating rate of 10 ℃/min, preserving heat for 32h, then forcedly cooling to 300 ℃, and discharging. And (5) forced cooling is carried out by adopting a mode of introducing argon after quenching.
In this embodiment, a second generation single crystal DD6 turbine blade is selected, and 100 blades are selected simultaneously for recrystallization elimination treatment, and a transition fillet region between the blade body and the flange is focused on because of a large residual stress in the region. As shown in FIG. 1, after the treatment by the method of the embodiment, the local recrystallization of the blade is completely eliminated, and the qualification rate reaches more than 98 percent, namely, 98 blades in 100 blades completely eliminate the recrystallization.
The method for preventing the local recrystallization of the single-crystal superalloy blade of the embodiment comprises the following treatment sequences in sequence: recovery treatment, mechanical polishing and grinding, electrolytic machining and solution aging treatment. It is generally recognized by those skilled in the art that mechanical direct treatment of the blade body prior to solution aging of a single crystal superalloy blade is prohibited, and that direct mechanical treatment of the blade body promotes recrystallization during solution aging. The embodiment overcomes the technical bias, adopts a mechanical mode to directly treat the blade body before the blade is subjected to solution aging treatment, and combines the step of recovering treatment of the blade before the mechanical treatment, thereby finally effectively avoiding the recrystallization of the single-crystal superalloy blade in the solution aging process.
The gradient recovery treatment gradually progresses from low temperature to high temperature can effectively recover casting residual stress, and when the residual stress is large, the local surface of the monocrystalline blade forms the core of recrystallized grains. The hand-held electric polishing and grinding equipment is adopted to polish and repair the blade, the area with larger surface stress of the blade is removed, and the nucleation in the solution treatment process is effectively prevented through subsequent treatment, or the recrystallized grain core formed in the recovery process is removed. And the trace of mechanical polishing is completely removed by adopting a local electrolytic machining mode, so that the plastic deformation of polishing is prevented from nucleation in the solid solution treatment process.
Embodiment two:
another preferred embodiment of the method for preventing local recrystallization of single crystal superalloy blades according to the present invention is essentially the same as embodiment one in the process sequence, equipment used, principle, beneficial effects, etc., except that:
in the first step, a gradient recovery treatment process gradually progressing from low temperature to high temperature is adopted, and the specific process is as follows: heating to 500 ℃ from room temperature at a heating rate of 3 ℃/min, and preserving heat for 5.5h; heating to 680 ℃ continuously at a heating rate of 3 ℃/min, and preserving heat for 4.5h; continuously heating to 885 ℃ at a heating rate of 3 ℃/min, and preserving heat for 1.5h; heating to 1125 ℃ continuously at a heating rate of 3 ℃/min, and preserving heat for 1.5h; continuously heating to 1225 ℃ at a heating rate of 3 ℃/min, and preserving heat for 0.75h; continuously heating to 1265 ℃ at a heating rate of 3 ℃/min, and preserving heat for 0.75h; cooling to 290 ℃ along with the furnace, and discharging.
In the second step, a hand-held electric grinding tool is adopted to mechanically polish the part of the blade, the granularity of a grinding head is 120 meshes, and the polishing thickness is 0.02mm.
Removing mechanical polishing marks by adopting an electrolytic machining mode, wherein in the electrolytic machining process, a blade is used as an anode, and a high-temperature alloy material is used as a cathode; the electrolyte is prepared from NaCl, HCl and H 2 O=1 g:3ml:100ml, voltage 15V, current 15A, time of electrolytic processing 8s.
Embodiment III:
another preferred embodiment of the method for preventing local recrystallization of single crystal superalloy blades according to the present invention is essentially the same as embodiment one in the process sequence, equipment used, principle, beneficial effects, etc., except that:
in the first step, a gradient recovery treatment process gradually progressing from low temperature to high temperature is adopted, and the specific process is as follows: heating from room temperature to 600 ℃ at a heating rate of 5 ℃/min, and preserving heat for 5 hours; continuously heating to 700 ℃ at a heating rate of 5 ℃/min, and preserving heat for 4 hours; continuously heating to 900 ℃ at a heating rate of 5 ℃/min, and preserving heat for 1h; continuously heating to 1150 ℃ at a heating rate of 5 ℃/min, and preserving heat for 1h; continuously heating to 1250 ℃ at a heating rate of 5 ℃/min, and preserving heat for 0.5h; continuously heating to 1280 ℃ at a heating rate of 5 ℃/min, and preserving heat for 0.5h; cooling to 300 ℃ along with the furnace, and discharging.
In the second step, a hand-held electric grinding tool is adopted to mechanically polish the part of the blade, the granularity of a grinding head is 120 meshes, and the polishing thickness is 0.03mm.
Removing mechanical polishing marks by adopting an electrolytic machining mode, wherein in the electrolytic machining process, a blade is used as an anode, and a high-temperature alloy material is used as a cathode; the electrolyte is prepared from NaCl, HCl and H 2 O=2g:1 ml:100ml, voltage 10V, current 12A, time of electrolytic processing 5s.
Embodiment four:
another preferred embodiment of the method for preventing local recrystallization of single crystal superalloy blades according to the present invention is essentially the same as embodiment one through embodiment three in the process sequence, equipment used, principle, beneficial effects, etc., except that:
in the third step, the trace of mechanical polishing and grinding is removed by adopting a chemical corrosion mode, and the blade is completely soaked in a corrosive liquid for corrosion, wherein the ratio of the corrosive liquid is HCl to H 2 O 2 ＝100ml:10ml。
In this embodiment, a second generation single crystal DD6 turbine blade is selected, and 100 blades are selected simultaneously for recrystallization elimination treatment, and a transition fillet region between the blade body and the flange is focused on because of a large residual stress in the region. After the treatment by the method of the embodiment, the local recrystallization of the blade is completely eliminated, the qualification rate reaches more than 95 percent, namely, 95 blades in 100 blades completely eliminate the recrystallization.
Fifth embodiment:
another preferred embodiment of the method for preventing local recrystallization of single crystal superalloy blades according to the present invention is essentially the same as embodiment four in process sequence, equipment used, principle, beneficial effects, etc., except that:
in the third step, the trace of mechanical polishing and grinding is removed by adopting a chemical corrosion mode, and the blade is completely soaked in a corrosive liquid for corrosion, wherein the ratio of the corrosive liquid is HCl to H 2 O 2 ＝100ml:15ml。
Comparative example one:
comparative example one was treated without the method according to the invention for preventing local recrystallization of single crystal superalloy blades, in the following order: mechanical polishing, electrolytic machining, recovery treatment and solid solution aging treatment.
In this comparative example, the process parameters and the equipment used for the four stages of mechanical polishing, electrolytic machining, recovery treatment, and solution aging treatment were exactly the same as those of the four stages of the first embodiment, except that the treatment order was different.
In the comparative example, a second-generation single crystal DD6 turbine blade is selected, 100 blades are selected simultaneously, recrystallization elimination treatment is carried out, and a transition fillet area of a blade body and a flange plate is focused on because of larger residual stress in the area. As shown in fig. 2, after the treatment by the method of this comparative example, the yield of the blade was only 48%, that is, only 48 blades out of 100 blades completely eliminated recrystallization, and it is apparent from fig. 2 that recrystallized grains 1.
Comparative example two:
comparative example two was not treated according to the method of the present invention for preventing local recrystallization of single crystal superalloy blades, the treatment sequence of comparative example two was: mechanical polishing, electrolytic machining and solid solution aging treatment.
In this comparative example, the process parameters and the equipment used in the three stages of mechanical polishing, electrolytic machining, and solution aging were exactly the same as those in example one, except that no recovery treatment was performed.
In the comparative example, a second-generation single crystal DD6 turbine blade is selected, 100 blades are selected simultaneously, recrystallization elimination treatment is carried out, and a transition fillet area of a blade body and a flange plate is focused on because of larger residual stress in the area. After the treatment by the method of the comparative example, the percent of pass of the blade is only 13%, that is, only 13 blades in 100 blades completely eliminate recrystallization.
The specific description is as follows: the technical scheme of the invention relates to a plurality of parameters, and the beneficial effects and remarkable progress of the invention can be obtained by comprehensively considering the synergistic effect among the parameters. In addition, the value ranges of all the parameters in the technical scheme are obtained through a large number of tests, and aiming at each parameter and the mutual combination of all the parameters, the inventor records a large number of test data, and the specific test data are not disclosed herein for a long period of time.
It will be appreciated by those skilled in the art that the method of preventing localized recrystallization of a single crystal superalloy blade of the present invention includes any combination of the above summary of the invention and detailed description of the invention and the various parts shown in the drawings, and is limited in scope and does not constitute a complete description of the various aspects of these combinations for brevity. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (4)
1. A method for preventing local recrystallization of a single crystal superalloy blade comprises the following steps in sequence:
step one: placing the monocrystal superalloy blade into a vacuum heat treatment furnace for recovery treatment;
step two: taking out the single-crystal superalloy blade from the vacuum heat treatment furnace, and directly mechanically polishing and grinding part of the blade;
step three: cleaning the mechanically polished single-crystal superalloy blade, and removing mechanically polished traces by adopting a local electrolytic machining or chemical corrosion mode;
step four: carrying out solid solution aging treatment on the monocrystal superalloy blade;
in the first step, a gradient recovery treatment process gradually progressing from low temperature to high temperature is adopted, and the specific process is that the temperature is heated to 400-600 ℃ from room temperature at a heating rate of 2-5 ℃/min, and the temperature is kept for 5-6h; continuously heating to 650-700 ℃ at a heating rate of 2-5 ℃/min, and preserving heat for 4-5h; continuously heating to 870-900 ℃ at the heating rate of 2-5 ℃/min, and preserving heat for 1-2h; continuously heating to 1100-1150 ℃ at a heating rate of 2-5 ℃/min, and preserving heat for 1-2h; continuously heating to 1200-1250 ℃ at a heating rate of 2-5 ℃/min, and preserving heat for 0.5-1h; continuously heating to 1250-1280 ℃ at a heating rate of 2-5 ℃/min, and preserving heat for 0.5-1h; cooling to 280-300 ℃ along with the furnace, and discharging;
in the second step, the adopted mechanical polishing tool is a hand-held electric grinding tool or a hand-held pneumatic grinding tool, the granularity of the grinding head is 80-120 meshes, and the polishing thickness is 0.02-0.05mm;
in the third step, in the local electrolytic machining process, the blade is used as an anode, and a high-temperature alloy material is used as a cathode; the electrolyte is prepared from NaCl, HCl and H 2 O=1-3 g:1-5ml:100ml, voltage 5-30V, current 7-15A, electrolytic processing time 5-10s.
2. The method for preventing localized recrystallization of single crystal superalloy blades according to claim 1, wherein: and thirdly, removing the trace of mechanical polishing by adopting a local electrolytic machining mode, and carrying out electrolytic corrosion or electrolytic polishing on the local part of the blade subjected to mechanical polishing.
3. The method for preventing localized recrystallization of single crystal superalloy blades according to claim 1, wherein: and thirdly, removing the trace of mechanical polishing and grinding by adopting a chemical corrosion mode, and completely soaking the blade in a corrosion liquid for corrosion.
4. A method of preventing localized recrystallization of a single crystal superalloy blade according to claim 3, wherein: in the chemical etching process, the ratio of the etching liquid is HCl to H 2 O 2 ＝100ml:10-15ml。
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