Method for regulating and controlling notch sensitivity of large-size GH4169 alloy bar

Abstract

The invention belongs to the technical field of metal material preparation, and particularly relates to a method for regulating and controlling the notch sensitivity of a large-size GH4169 alloy bar. According to the method, the content of the delta phase in the GH4169 alloy bar is controlled to reduce the notch lasting fracture sensitivity of the GH4169 alloy bar, specifically, 0-20% of deformation is applied at the temperature of 960-1010 DEG C, so that the delta phase is induced to be in angular distribution at the grain boundary, the grain boundary stress is released, the grain boundary strength is improved, and the phenomenon that the alloy is broken in the testing process is eliminated; in the prior art, most of the operation objects are small-size parts, and the gap sensitivity of the large-specification (phi 200mm-phi 500mm) GH4169 alloy bar is controlled through shaping treatment, so that the blank in the technical field is filled; and the unnotched large-size GH4169 alloy bar with the lasting fracture sensitivity obtained through shaping treatment meets the use requirements of aero-engine rotating parts.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal material preparation, and particularly relates to a method for regulating the notch sensitivity of large-sized GH4169 alloy bars. Background Art

[0002] GH4169 alloy is an age-hardening nickel-based wrought superalloy, which consists of a matrix γ phase, a main strengthening phase γ" phase, an auxiliary strengthening phase γ' phase, a δ phase and carbides. GH4169 alloy has excellent high-temperature strength, good corrosion resistance, oxidation resistance and good weldability at -256°C to 650°C, and is widely used in important components such as turbine disks, compressor disks, and casings for aeroengines. Since rotating components such as turbine disks and drum shafts of advanced aeroengines serve under extreme conditions such as high temperature, high stress, and high speed, higher requirements are put forward for the strength, fatigue, and notch creep properties of the materials. As an important precipitated phase in GH4169 alloy, the precipitation content, morphology and distribution of the δ phase have an important influence on the notch sensitivity of the alloy. The precipitation of the δ phase in the alloy will consume a certain amount of Nb element, and a Nb-depleted zone will be formed around it. During the subsequent double aging process, the Nb-depleted zone will become a γ"-depleted zone, forming a micro-plastic zone, which can improve the plasticity of the alloy, reduce stress concentration, and improve the notch sensitivity of the material. However, the increase in the precipitation amount of the δ phase will inevitably consume more Nb elements, resulting in a significant reduction in the main strengthening phase γ″(Ni3Nb), and reducing the service strength of the material. Therefore, many technical standards have put forward clear requirements for the precipitation amount and morphology of the δ phase.

[0003] In addition, in order to prepare an alloy with reasonable precipitation of the δ phase to reduce the notch creep fracture sensitivity while reducing the influence on improving the material strength by subsequent aging treatment, researchers have conducted in-depth research and proposed some treatment methods. The Chinese patent document (Publication No.: CN1621539A, Publication Date: 2005.06.01) discloses a method for pre-high-intensity shot peening treatment of an alloy to increase the content of the δ phase and avoid notch creep fracture sensitivity. Although researchers have proposed various treatment methods to control the precipitation content of the δ phase in the alloy to reduce the notch creep fracture sensitivity, and there are certain effects, the experimental objects are all small-sized creep tensile tests or processed parts. Regarding how to control the notch creep fracture sensitivity of large-sized GH4169 alloy bars, there has been no relevant report yet.

[0004] Therefore, there is an urgent need for a method for regulating the notch sensitivity of large-sized GH4169 alloy bars to fill the gap in the control of the notch creep fracture sensitivity of large-sized GH4169 alloy bars in the existing technology. Summary of the Invention

[0005] The object of the present invention is to overcome the above-mentioned disadvantages of the prior art and provide a method for controlling the notch sensitivity of large-sized GH4169 alloy bars.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] On the one hand, the present invention provides a method for controlling the notch sensitivity of large-sized GH4169 alloy bars. By controlling the content, morphology and distribution of δ-phase in large-sized GH4169 alloy bars, after standard heat treatment, the high-temperature notch creep performance of large-sized GH4169 alloy bars is improved. The specific control method is as follows: First, according to the δ-phase content of the large-sized GH4169 alloy bars to be processed, then determine the sizing treatment process of the large-sized GH4169 alloy bars to be processed: keep warm at a temperature of 960 °C to 1010 °C for 60 min to 240 min, and the deformation amount is 0 to 20%; the size of the large-sized GH4169 alloy bars is

[0008] Specifically, according to the δ-phase content of the GH4169 alloy bars with a size of determine the corresponding sizing treatment process parameters: the heating temperature is 970 °C, the holding time is 60 min to 120 min, and the deformation amount is 10% to 15%.

[0009] Specifically, according to the δ-phase content of the GH4169 alloy bars with a size of determine the corresponding sizing treatment process parameters: the heating temperature is 1000 °C, the holding time is 150 min to 200 min, and the deformation amount is 5% to 10%.

[0010] Specifically, according to the δ-phase content of the GH4169 alloy bars with a size of determine the corresponding sizing treatment process parameters: the heating temperature is 1010 °C, the holding time is 200 min to 240 min, and the deformation amount is 0 to 5%.

[0011] Furthermore, a method for controlling the notch sensitivity of large-sized GH4169 alloy bars according to the present invention specifically comprises the following steps:

[0012] Step 1: Take a sample of the large-sized GH4169 alloy bars to be processed;

[0013] Step 2: Determine the δ-phase content of the sample after surface pretreatment;

[0014] Step 3: According to the δ-phase content, determine the sizing treatment process parameters: the temperature is 960 °C to 1010 °C, the holding time is 60 min to 240 min, and the deformation amount is 0 to 20%;

[0015] Step 4: Shape the large-sized GH4169 alloy bar to be processed, and after completion, cool it to room temperature to finally obtain the corresponding alloy bar.

[0016] Specifically, in Step 1, the preparation process of the large-sized GH4169 alloy bar to be processed is as follows: First, prepare an ingot through a triple process of "vacuum induction melting + electroslag remelting under protective atmosphere + vacuum arc furnace remelting". Then, after multi-stage homogenization treatment of the ingot, perform free forging to break the as-cast structure, and finally obtain it through forming forging production.

[0017] Specifically, Step 2 is as follows: Rough grind → fine grind → polish → etch → metallographic observation of the specimen, and then evaluate the δ-phase content of the specimen before shape processing; the etching specifically is: Use a mixed etching solution of anhydrous ethanol, hydrochloric acid, and copper chloride to etch the surface of the specimen.

[0018] Specifically, in Step 3, an industrial heating furnace is used for heating.

[0019] Specifically, in Step 3, a free forging press is used for forging to achieve a deformation of 0 - 20%.

[0020] On the other hand, for the large-sized GH4169 alloy bar with no-notch creep fracture sensitivity obtained by the method for regulating the notch sensitivity of a large-sized GH4169 alloy bar of the present invention, a notch creep fracture sensitivity test is carried out under the conditions of a temperature of 650 °C and a loading stress of 690 MPa. The creep rupture time of the large-sized GH4169 alloy bar is greater than 25 h, and the elongation after fracture is greater than 5%.

[0021] On yet another aspect, the present invention provides an application of the method for regulating the notch sensitivity of a large-sized GH4169 alloy bar. The large-sized GH4169 alloy bar with no-notch creep fracture sensitivity obtained after regulation is applied in rotating parts of an aeroengine.

[0022] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0023] The present invention controls the δ-phase content in the GH4169 alloy bar to reduce its notch creep fracture sensitivity. Specifically, apply a deformation of 0 - 20% at a temperature of 960 °C - 1010 °C, thereby inducing the δ-phase to be angularly distributed at the grain boundaries, releasing the grain boundary stress, and improving the grain boundary strength to achieve the elimination of the phenomenon of notch fracture during the test of the alloy; in the past, the operation objects were mostly small-sized parts, and the present invention is aimed at large-sized The notch sensitivity of GH4169 alloy bars is controlled by sizing treatment, thus filling the gap in this technical field. The large-sized GH4169 alloy bars with no notch creep rupture sensitivity obtained through sizing treatment meet the service requirements of rotating parts of aeroengines and effectively avoid the problem of notch creep rupture existing in forged parts.

[0024] Furthermore, the regulation method of the present invention can greatly reduce the probability of notches in large-sized GH4169 alloy bar segments of the same batch, thereby improving the overall strength of large-sized GH4169 alloy bars. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings here are incorporated into the specification and form a part of this specification, and are used together with the specification to explain the principles of the present invention.

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0027] Figure 1 is a flowchart of the regulation method of the present invention;

[0028] Figure 2 is an embodiment of the present invention of the microstructure diagram of the GH4169 alloy bar before sizing treatment;

[0029] Figure 3 is an embodiment of the present invention of the microstructure diagram of the GH4169 alloy bar after sizing treatment;

[0030] Figure 4 is an embodiment of the present invention of the microstructure diagram of the GH4169 alloy bar before sizing treatment;

[0031] Figure 5 is an embodiment of the present invention of the microstructure diagram of the GH4169 alloy bar after sizing treatment;

[0032] Figure 6 is an embodiment of the present invention of the microstructure diagram of the GH4169 alloy bar before sizing treatment;

[0033] Figure 7 is an embodiment of the present invention of the microstructure diagram of the GH4169 alloy bar after sizing treatment. DETAILED DESCRIPTION OF THE INVENTION

[0034] Exemplary embodiments will be described in detail herein, and examples thereof are shown in the accompanying drawings. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. On the contrary, they are merely examples consistent with some aspects of the present invention detailed in the appended claims.

[0035] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0036] A method for regulating the notch sensitivity of large-sized GH4169 alloy bars according to the present invention comprises the following specific steps:

[0037] Step 1: Take a sample of the large-sized GH4169 alloy bar to be processed.

[0038] Step 2: Determine the δ-phase content of the sample after surface pretreatment.

[0039] Step 3: According to the δ-phase content, determine the sizing process parameters: the temperature is 960°C to 1010°C, the holding time is 60 min to 240 min, and the deformation amount is 0 to 20%.

[0040] Step 4: Perform sizing treatment on the large-sized GH4169 alloy bar to be processed, and after completion, cool it to room temperature to finally obtain the corresponding alloy bar.

[0041] Specifically, in Step 1, the preparation process of the large-sized GH4169 alloy bar to be processed is as follows: First, an ingot is prepared by a triple process of "vacuum induction melting + protective atmosphere electroslag remelting + vacuum arc furnace remelting", then the ingot is subjected to multi-stage homogenization treatment and then free forging is carried out to break the as-cast structure, and finally it is produced through shaping forging.

[0042] Specifically, Step 2 is as follows: The sample is subjected to rough grinding → fine grinding → polishing → etching → metallographic observation, and then the δ-phase content of the sample before sizing treatment is evaluated; the etching specifically is: etching the surface of the sample with a mixed etching solution of anhydrous ethanol, hydrochloric acid, and copper chloride.

[0043] Specifically, in Step 3, an industrial heating furnace is used for heating.

[0044] Specifically, in step 3, forging is carried out using a free forging press. To achieve a deformation amount of 0-20%, it should be noted that the standard heat treatment process adopted in the following examples is: solution treatment: (950°C - 980°C) ± 10°C, holding for 1 h, air cooling; aging treatment: 720°C ± 10°C, holding for 8 h, furnace cooling at a rate of (50 ± 10)°C / h to 620°C ± 10°C, holding for 8 h, air cooling (hereinafter referred to as "standard heat treatment"). After treatment, the high-temperature notch creep performance of the material cannot meet the requirements of the technical standards.

[0045] It should be noted that the following examples all adopt the same process to produce large-sized GH4169 alloy bars: vacuum induction melting → electroslag remelting under protective atmosphere → vacuum arc furnace remelting → homogenization diffusion annealing treatment of consumable ingots at high temperature → blooming by a cogging mill → sizing by a cogging mill → obtaining large-sized GH4169 alloy bars.

[0046] The triple process of "vacuum induction melting + electroslag remelting under protective atmosphere + vacuum arc furnace remelting" is adopted to produce alloy ingots, ensuring low gas content, high purity, and uniform composition of the alloy ingots; the chemical composition is shown in Table 1;

[0047] Table 1 Chemical composition of GH4169 alloy ingots

[0048]

[0049] In the following examples, GH4169 alloy bars with a diameter of are respectively selected to verify the regulation method of the present invention; in the following examples, corrosion is carried out using a commercially available mixed corrosion solution of anhydrous ethanol, hydrochloric acid, and copper chloride.

[0050] Example 1

[0051] As Figure 1 shown, in this example, the notch creep fracture sensitivity of the to-be-treated GH4169 alloy bars is regulated, and the specific process is as follows:

[0052] The to-be-treated GH4169 alloy bars are sawed to obtain the first sample pieces, and samples for microstructure evaluation are taken. Then, the first samples are rough ground → fine ground → polished → corroded → metallographically observed, and then the δ-phase content before sizing treatment of the first sample pieces is evaluated. As Figure 2 shown, at the same time, the first sample pieces are subjected to standard heat treatment → processing of the first sample pieces → high-temperature notch creep test, and the notch creep sensitivity of the first sample pieces without sizing treatment is evaluated, as shown in Table 2.

[0053] According to the δ-phase content before sizing treatment, the to-be-treated Straightening treatment process for GH4169 alloy bars: Insulate at 970 °C for 60 min to 120 min, with a deformation amount of 10% to 15%; the to-be-treated GH4169 alloy bars, after undergoing the straightening treatment process, are air-cooled to room temperature, and finally GH4169 alloy bars without notched creep fracture sensitivity are obtained. GH4169 alloy bars.

[0054] First, the straightened GH4169 alloy bars are sawed to obtain second specimen pieces, and then the second specimen pieces are subjected to rough grinding → fine grinding → polishing → etching → metallographic observation to evaluate the δ-phase content of the straightened GH4169 alloy bars, as Figure 3 shown; at the same time, second specimen pieces are taken for standard heat treatment → processing of the second specimen pieces → high-temperature notched creep test, and finally the notched creep sensitivity of the second specimen pieces after straightening treatment is evaluated, as shown in Table 2.

[0055] Example 2

[0056] As Figure 1 shown, in this example, the notched creep fracture sensitivity of the to-be-treated GH4169 alloy bars is regulated, and the specific process is as follows:

[0057] The to-be-treated GH4169 alloy bars are sawed to obtain third specimen pieces, and tissue evaluation specimens are taken. Then, the third specimens are successively subjected to rough grinding → fine grinding → polishing → etching → metallographic observation, and then the δ-phase content of the third specimen pieces before straightening treatment is evaluated, as Figure 4 shown; at the same time, third specimen pieces are taken for standard heat treatment → processing of the third specimen pieces → high-temperature notched creep test, and the notched creep sensitivity of the third specimen pieces without straightening treatment is evaluated, as shown in Table 2.

[0058] According to the δ-phase content before straightening treatment, the straightening treatment process for the to-be-treated GH4169 alloy bars is determined: Insulate at 1000 °C for 150 min to 200 min, with a deformation amount of 5% to 10%; the to-be-treated GH4169 alloy bars, after undergoing the straightening treatment process, are air-cooled to room temperature, and finally GH4169 alloy bars without notched creep fracture sensitivity are obtained. GH4169 alloy bars.

[0059] First, the straightened GH4169 alloy bars are sawed to obtain fourth specimen pieces, and then the fourth specimen pieces are subjected to rough grinding → fine grinding → polishing → etching → metallographic observation to evaluate the δ-phase content of the straightened The δ-phase content of the GH4169 alloy bar is as Figure 5 shown; at the same time, the fourth specimen is subjected to standard heat treatment → machining of the fourth specimen → high-temperature notched creep rupture test, and finally the notched creep rupture sensitivity of the fourth specimen after sizing treatment is evaluated, as shown in Table 2.

[0060] Example 3

[0061] As Figure 1 shown, in this example, the notched creep rupture sensitivity of the GH4169 alloy bar to be treated is regulated, and the specific process is as follows: shown, in this example, the notched creep rupture sensitivity of the GH4169 alloy bar to be treated is regulated, and the specific process is as follows:

[0062] The GH4169 alloy bar to be treated is sawed to obtain a fifth specimen, and a specimen for microstructure evaluation is taken. Then, the fifth specimen is rough ground → fine ground → polished → etched → metallographically observed, and then the δ-phase content of the fifth specimen before sizing treatment is evaluated, as Figure 6 shown; at the same time, the fifth specimen is subjected to standard heat treatment → machining of the fifth specimen → high-temperature notched creep rupture test, and the notched creep rupture sensitivity of the fifth specimen without sizing treatment is evaluated, as shown in Table 2.

[0063] According to the δ-phase content before sizing treatment, the sizing treatment process of the GH4169 alloy bar to be treated is determined: heat preservation at 1010 °C for 200 min to 240 min, and the deformation amount is 0 to 5%; the GH4169 alloy bar to be treated is air-cooled to room temperature after passing through the sizing treatment process, and finally a GH4169 alloy bar without notched creep rupture sensitivity is obtained. of the GH4169 alloy bar.

[0064] First, the GH4169 alloy bar after sizing treatment is sawed to obtain a sixth specimen, and then the sixth specimen is rough ground → fine ground → polished → etched → metallographically observed to evaluate the δ-phase content of the GH4169 alloy bar after sizing treatment as Figure 7 shown; at the same time, the sixth specimen is subjected to standard heat treatment → machining of the sixth specimen → high-temperature notched creep rupture test, and finally the notched creep rupture sensitivity of the sixth specimen after sizing treatment is evaluated, as shown in Table 2.

[0065] Table 2 High-temperature notched creep rupture life test results of the GH4169 alloy bars selected in Examples 1 and 2

[0066]

[0067] Therefore, as can be seen from Table 2, in Examples 1, 2, and 3, the The GH4169 alloy bars all had broken notches during the notch creep rupture sensitivity test conducted at a temperature of 650°C and a loading stress of 690 MPa. After sizing treatment, the GH4169 alloy bars did not have broken notches during the notch creep rupture sensitivity test conducted at a temperature of 650°C and a loading stress of 690 MPa. Moreover, the creep rupture time was greater than 25 h and the elongation after fracture was greater than 5%, meeting the requirements for subsequent use.

[0068] Furthermore, this regulation method has been verified by actual production. After sizing treatment of large-sized GH4169 alloy bars in batches, the probability of having broken notches is greatly reduced. For the same batch of large-sized GH4169 alloy bars without sizing treatment, the probability of having broken notches during the notch creep rupture sensitivity test is 50 - 60%; for the same batch of large-sized GH4169 alloy bars after sizing treatment, the probability of having broken notches during the notch creep rupture sensitivity test is 3 - 5%.

[0069] The above are only specific embodiments of the present invention, enabling those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0070] It should be understood that the present invention is not limited to the content already described above and can be modified and changed without departing from its scope. The scope of the present invention is only limited by the appended claims.

Claims

1. A method for regulating notch sensitivity of large-size GH4169 alloy bars, characterized in that: By regulating the δ phase content, morphology and distribution of large-sized GH4169 alloy bars before shaping treatment, after standard heat treatment, the high-temperature notch endurance performance of large-sized GH4169 alloy bars is improved. The specific regulation method is: according to the δ phase content of the large-sized GH4169 alloy bars to be treated, the shaping treatment process of the large-sized GH4169 alloy bars to be treated is determined: keeping warm at a temperature of 960°C to 1010°C for 60min to 240min, and the deformation amount is 0 to 20%; the size of the large-sized GH4169 alloy bars is φ200mm to φ500mm.

2. The method for controlling the notch sensitivity of large-size GH4169 alloy bars according to claim 1, characterized in that: According to the δ phase content of GH4169 alloy rod with a size of φ220mm, the corresponding shaping process parameters are determined: the heating temperature is 970℃, the holding time is 60min~120min, and the deformation amount is 10%~15%.

3. The method for controlling the notch sensitivity of large-size GH4169 alloy bars according to claim 1, characterized in that: According to the δ phase content of GH4169 alloy rod with a size of φ300mm, the corresponding shaping process parameters are determined: the heating temperature is 1000℃, the holding time is 150min~200min, and the deformation amount is 5%~10%.

4. The method for controlling the notch sensitivity of large-size GH4169 alloy bars according to claim 1 is characterized in that: According to the δ phase content of GH4169 alloy rod with a size of φ420mm, the corresponding shaping treatment process parameters are determined: the heating temperature is 1010℃, the holding time is 200min~240min, and the deformation amount is 0~5%.

5. The method for controlling the notch sensitivity of large-size GH4169 alloy bars according to claim 1 is characterized in that: The specific steps are as follows: Step 1, taking a sample of a large-size GH4169 alloy bar to be processed; Step 2, determining the δ phase content of the sample; Step 3, according to the δ phase content, determine the shaping process parameters: temperature is 960°C to 1010°C, holding time is 60min to 240min, deformation is 0 to 20%; Step 4: Perform shaping treatment on the large-size GH4169 alloy bar to be processed, and then cool it to room temperature to finally obtain the corresponding alloy bar.

6. The method for controlling the notch sensitivity of large-size GH4169 alloy bars according to claim 5, characterized in that: In step 1, the preparation process of the large-size GH4169 alloy bar to be processed is specifically as follows: first, an ingot is prepared by a triple process of "vacuum induction melting + protective atmosphere electroslag remelting + vacuum arc furnace remelting", then the ingot is subjected to multi-stage homogenization treatment and free forging to crush the cast structure, and finally the ingot is produced by forming forging.

7. The method for controlling the notch sensitivity of large-size GH4169 alloy bars according to claim 5, characterized in that: Step 2 specifically includes: rough grinding → fine grinding → polishing → corrosion → metallographic observation of the sample, and then evaluating the δ phase content of the sample before shaping treatment.

8. The method for controlling the notch sensitivity of large-size GH4169 alloy bars according to claim 7, characterized in that: The corrosion specifically includes: using a mixed corrosion solution of anhydrous ethanol, hydrochloric acid and cupric chloride to corrode the surface of the sample.

9. A large-sized GH4169 alloy bar obtained by the method for controlling the notch sensitivity of a large-sized GH4169 alloy bar according to any one of claims 1 to 8, characterized in that: The notch fracture sensitivity test was carried out under the conditions of a temperature of 650° C. and a loading stress of 690 MPa. The fracture endurance time of the large-size GH4169 alloy bars was greater than 25 hours, and the elongation after fracture was greater than 5%.

10. Application of the method for controlling notch sensitivity of large-size GH4169 alloy bars according to any one of claims 1 to 8, characterized in that: The large-sized GH4169 alloy bars with no notch-type long-term fracture sensitivity obtained after regulation are used in the rotating parts of aircraft engines.

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