Nickel-based superalloy low-welding-specification high-strength diffusion welding method

Abstract

The invention provides a nickel-based superalloy low-welding-specification high-strength diffusion welding method, and belongs to the technical field of superalloy welding. According to the method, the high-purity nickel foil is introduced between the two nickel-based high-temperature alloy to-be-welded parts to serve as the middle layer material, the middle layer material has good plastic deformation performance, the surface contact condition between the to-be-welded materials can be improved, the eutectic reaction of base metal and middle layer elements is used for promoting breaking of an oxidation film on the surface of the base metal, and the welding quality is improved. The generation of intermetallic compounds is inhibited, so that a diffusion welding joint with good performance can be obtained; by controlling the thickness of the middle layer material, the structure defects in a welding joint can be effectively reduced, the room-temperature tensile property and the high-temperature tensile property of the welding joint are improved, meanwhile, the temperature needed in the diffusion welding process can be reduced, deformation generated in the welding process is further reduced, and the welding manufacturing precision is improved.

Description

Technical Field

[0001] The invention relates to the technical field of high-temperature alloy welding, and in particular to a low-welding-specification high-strength diffusion welding method for a nickel-based high-temperature alloy. Background Art

[0002] Under the background of dual carbon, improving energy utilization and developing clean energy have become the development trend of energy consumption, and high-temperature waste heat recovery is an important means to improve energy utilization. Heat exchangers are key equipment for realizing high-temperature waste heat recovery. Compared with traditional heat exchangers, high-efficiency compact heat exchangers have obvious advantages in compact structure and heat exchange efficiency. In the future, high-efficiency compact heat exchangers have broad application prospects. Due to the compact structure of high-efficiency compact heat exchangers, diffusion welding is required to connect the fins. Although diffusion welding technology has become mature, the complex channel structure and harsh working conditions of high-efficiency compact heat exchangers pose great challenges to current diffusion welding manufacturing. For materials such as stainless steel and nickel-based alloys, in order to ensure the strength of the joints, the diffusion welding temperature is usually above 1150°C, the welding pressure is greater than 10MPa, and the insulation time is greater than 1h. Excessively high welding temperatures make it very easy for the heat exchange channel to produce large plastic and creep deformations, resulting in more defects on the welding surface, which seriously affects the manufacturing accuracy and heat exchange efficiency of the heat exchanger. However, if the welding temperature is lower than 1150°C, the welding rate will be low due to insufficient welding temperature, resulting in more welding defects, reducing the room temperature and high temperature tensile properties of the welding material, and also affecting the manufacturing accuracy and heat exchange efficiency of the heat exchanger.

[0003] Therefore, how to lower the welding temperature and reduce welding defects while ensuring the strength of the welded joint has excellent room temperature tensile properties and high temperature tensile properties has become a technical problem that needs to be urgently solved in this field. Summary of the invention

[0004] The purpose of the present invention is to provide a low welding specification high-strength diffusion welding method for nickel-based high-temperature alloys. The diffusion welding method provided by the present invention can not only reduce the welding defects of nickel-based high-temperature alloy welded joints and improve the room temperature tensile properties and high temperature tensile properties, but also the temperature during diffusion welding is only 1120°C, which significantly reduces the diffusion welding specification parameters, thereby reducing the deformation during the welding process and improving the welding manufacturing accuracy.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a nickel-based high-temperature alloy low welding specification high-strength diffusion welding method, comprising:

[0007] Placing an intermediate layer material on the welding surface of the material to be welded, and then performing diffusion welding to obtain a nickel-based high-temperature alloy welded joint;

[0008] The material to be welded includes a nickel-based high-temperature alloy;

[0009] The intermediate layer material is high-purity nickel foil, and the thickness of the intermediate layer material is 6 to 20 μm;

[0010] The diffusion welding comprises: firstly heating to 300-400°C and keeping the temperature for 120-180 minutes, then heating to 750-850°C and keeping the temperature for 60-100 minutes, then heating to 900-1000°C and keeping the temperature for 40-80 minutes, then heating to 1050-1100°C and keeping the temperature for 40-80 minutes, and finally heating to 1120°C and keeping the temperature for 200-300 minutes;

[0011] The welding pressure of the diffusion welding is 14-15 MPa.

[0012] Preferably, the material to be welded is Inconel625 nickel-based high-temperature alloy.

[0013] Preferably, the roughness of the surface to be welded is less than 0.3 μm.

[0014] Preferably, the thickness of the intermediate layer material is 10-20 μm.

[0015] Preferably, the diffusion welding comprises: first heating to 350°C and keeping warm for 150 minutes, then heating to 800°C and keeping warm for 90 minutes, then heating to 950°C and keeping warm for 60 minutes, then heating to 1100°C and keeping warm for 60 minutes, and finally heating to 1120°C and keeping warm for 260 minutes.

[0016] Preferably, the heating rate to 300-400°C is 5-6°C / min; the heating rate to 750-850°C is 3-4°C / min; the heating rate to 900-1000°C is 2-3°C / min; the heating rate to 1050-1100°C is 2-3°C / min; the heating rate to 1120°C is 1-2°C / min.

[0017] Preferably, the welding vacuum degree of the diffusion welding is less than 5×10 -2 Pa.

[0018] Preferably, the relationship between the room temperature tensile strength of the nickel-based high-temperature alloy welded joint and the diffusion welding process parameters is as shown in Formula I:

[0019] Y1=8.227H-25.951T+66.59P-0.254H 2 +0.011T 2 -2.2P 2 +15358.445 Formula I

[0020] In formula I, Y1 is the room temperature tensile strength, T is the maximum insulation temperature during diffusion welding, P is the welding pressure, and H is the thickness of the intermediate layer material.

[0021] Preferably, the relationship between the high temperature tensile strength of the nickel-based high temperature alloy welded joint and the diffusion welding process parameters is as shown in Formula II:

[0022] Y2=5.358H+294.497T-297.667P-0.128T 2 +13.667P 2 -166848 Formula II

[0023] In formula II, Y2 is the high temperature tensile strength, T is the maximum insulation temperature during diffusion welding, P is the welding pressure, and H is the thickness of the intermediate layer material.

[0024] Preferably, the relationship between the welding rate of the nickel-based high-temperature alloy welded joint and the diffusion welding process parameters is as shown in Formula III:

[0025] Y3=2.327H+14.964T+1.966P-0.058H 2 -0.007T 2 -8498.941 Formula III

[0026] In formula III, Y3 is the welding rate of the welded joint, T is the maximum insulation temperature during diffusion welding, P is the welding pressure, and H is the thickness of the intermediate layer material.

[0027] The invention provides a low welding specification high-strength diffusion welding method for a nickel-based high-temperature alloy, comprising: placing an intermediate layer material on a welding surface of a material to be welded, and then performing diffusion welding to obtain a nickel-based high-temperature alloy welded joint; the material to be welded comprises a nickel-based high-temperature alloy; the intermediate layer material is a high-purity nickel foil, and the thickness of the intermediate layer material is 6-20 μm; the diffusion welding comprises: first heating to 300-400° C. and keeping warm for 120-180 min, then heating to 750-850° C. and keeping warm for 60-100 min, then heating to 900-1000° C. and keeping warm for 40-80 min, then heating to 1050-1100° C. and keeping warm for 40-80 min, and finally heating to 1120° C. and keeping warm for 200-300 min; the welding pressure of the diffusion welding is 14-15 MPa. The present invention introduces high-purity nickel foil as an intermediate layer material between two nickel-based high-temperature alloy parts to be welded. The intermediate layer material has good plastic deformation performance, can improve the surface contact between the materials to be welded, and utilizes the eutectic reaction of the base material and the intermediate layer elements to promote the breakage of the oxide film on the surface of the base material, inhibit the formation of intermetallic compounds, and thus help to obtain a diffusion welding joint with good performance; by controlling the thickness of the intermediate layer material, the structural defects in the welded joint can be effectively reduced, and while improving the room temperature tensile properties and high temperature tensile properties of the welded joint, the temperature required for the diffusion welding process can be reduced, further reducing the structural deformation generated during the welding process, and improving the welding manufacturing accuracy.The results of the embodiment show that the low welding specification high strength diffusion welding method of nickel-based high-temperature alloy provided by the present invention has the following optimal process parameters after process optimization: the thickness of the intermediate layer material is 20 μm, the final insulation temperature during diffusion welding is 1120°C, the welding pressure during diffusion welding is 15 MPa, and the total insulation time during diffusion welding is 620 min. The tensile strength of the obtained welded joint at room temperature is 840-900 MPa, the yield strength is 480-520 MPa, the elongation after fracture is 48-60%, the deformation rate after welding is 5.6%, the high temperature tensile strength at 650°C is 580-600 MPa, the yield strength is 300-400 MPa, and the elongation after fracture is 30-50%. At the same time, the welded joint has few structural defects and the welding rate is greater than 95 %; under the conventional diffusion welding connection process (the holding temperature is 1170°C, the welding pressure during diffusion welding is 15MPa, and the total holding time during diffusion welding is 620min, that is, comparative example 5), the room temperature tensile strength of the diffusion welded joint obtained is 664-762MPa, the yield strength is 434-464MPa, the elongation after fracture is 13.3-29.3%, the deformation rate after welding is 9.28%, the tensile strength at 650°C is 482-528MPa, the yield strength is 274-296MPa, the elongation after fracture is 20.2-26.7%, and the welding rate is 73.8%, indicating that the present invention can reduce the temperature and welding specifications of diffusion welding on the premise of improving the strength of the welded joint by introducing the intermediate layer material, thereby significantly reducing the deformation rate after welding. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The room temperature tensile properties of the nickel-based high-temperature alloy welded joint prepared in Example 1;

[0029] Figure 2 The room temperature tensile properties of the nickel-based high-temperature alloy welded joint prepared in Comparative Example 1;

[0030] Figure 3 The room temperature tensile properties of the nickel-based high-temperature alloy welded joint prepared in Comparative Example 2;

[0031] Figure 4 The room temperature tensile strength of the nickel-based high-temperature alloy welded joints prepared in Example 1 and Comparative Examples 1-2;

[0032] Figure 5 The high temperature tensile properties of the nickel-based high temperature alloy welded joint prepared in Example 1;

[0033] Figure 6 The high temperature tensile properties of the nickel-based high temperature alloy welded joint prepared in Comparative Example 1;

[0034] Figure 7 The high temperature tensile properties of the nickel-based high temperature alloy welded joint prepared in Comparative Example 2;

[0035] Figure 8 The high temperature tensile strength of the nickel-based high temperature alloy welded joints prepared in Example 1 and Comparative Examples 1-2;

[0036] Fig. 9 The welding defects at the welded joint of the nickel-based high-temperature alloy prepared in Example 1;

[0037] Fig.10 The welding defects at the nickel-based high-temperature alloy welded joint prepared in Comparative Example 1;

[0038] Fig.11 The welding defects at the nickel-based high-temperature alloy welded joint prepared in Comparative Example 2;

[0039] Fig.12 The welding rate of the welded joints of the nickel-based high-temperature alloy welded joints prepared in Example 1 and Comparative Examples 1-2;

[0040] Fig.13 The room temperature tensile properties of the nickel-based high-temperature alloy welded joint prepared in Comparative Example 3;

[0041] Fig.14 The room temperature tensile properties of the nickel-based high-temperature alloy welded joint prepared in Comparative Example 4;

[0042] Fig.15 The room temperature tensile properties of the nickel-based high-temperature alloy welded joint prepared in Comparative Example 5;

[0043] Fig.16 The room temperature tensile strength of the nickel-based high-temperature alloy welded joints prepared in Comparative Example 1 and Comparative Examples 3 to 5;

[0044] Fig.17 The high temperature tensile properties of the nickel-based high temperature alloy welded joint prepared in Comparative Example 3;

[0045] Fig.18 The high temperature tensile properties of the nickel-based high temperature alloy welded joint prepared in Comparative Example 4;

[0046] Fig.19 The high temperature tensile properties of the nickel-based high temperature alloy welded joint prepared in Comparative Example 5;

[0047] Fig. 20 The high temperature tensile strength of the nickel-based high temperature alloy welded joints prepared in Comparative Example 1 and Comparative Examples 3 to 5;

[0048] Fig.21 The welding defects at the nickel-based high-temperature alloy welded joint prepared in Comparative Example 3;

[0049] Fig. 22 The welding defects at the nickel-based high-temperature alloy welded joint prepared in Comparative Example 4;

[0050] Fig.23 The welding defects at the nickel-based high-temperature alloy welded joint prepared in Comparative Example 5;

[0051] Fig.24 The welding rate of the nickel-based high-temperature alloy welded joints prepared in Comparative Example 1 and Comparative Examples 3 to 5;

[0052] Fig.25 The room temperature tensile properties of the nickel-based high-temperature alloy welded joint prepared in Comparative Example 6;

[0053] Fig.26 The room temperature tensile strength of the nickel-based high-temperature alloy welded joints prepared in Example 1 and Comparative Example 6;

[0054] Fig. 27 The high temperature tensile properties of the nickel-based high temperature alloy welded joint prepared in Comparative Example 6;

[0055] Fig.28 High temperature tensile strength of the nickel-based high temperature alloy welded joints prepared in Example 1 and Comparative Example 6. DETAILED DESCRIPTION

[0056] The present invention provides a nickel-based high-temperature alloy low welding specification high-strength diffusion welding method, comprising:

[0057] An intermediate layer material is placed on the welding surface of the material to be welded, and then diffusion welding is performed to obtain a nickel-based high-temperature alloy welded joint.

[0058] In the present invention, the material to be welded includes a nickel-based superalloy, preferably Inconel 625. The present invention has no particular limitation on the specific source of the nickel-based superalloy, and commercially available nickel-based superalloys well known to those skilled in the art can be used.

[0059] In the present invention, the roughness of the surface to be welded is preferably less than 0.3 μm. In the present invention, when the roughness of the surface to be welded does not meet the above conditions, it is preferred to process, clean and dry the surface to be welded of the material to be welded in sequence. In the present invention, the processing is preferably to use a milling machine to process the surface to be welded of the material to be welded; the cleaning agent used for the cleaning is preferably anhydrous ethanol. The present invention has no special restrictions on the temperature and time of the drying, and the surface can be dried.

[0060] In the present invention, the intermediate layer material is a high-purity nickel foil; the thickness of the intermediate layer material is 6 to 20 μm, preferably 10 to 20 μm. The present invention has no special limitation on the specific source of the high-purity nickel foil, and commercially available high-purity nickel foils well known to those skilled in the art can be used as long as the thickness meets the requirements.

[0061] The present invention preferably cleans and dries the intermediate layer material before diffusion welding. In the present invention, the cleaning agent used for the cleaning is preferably anhydrous ethanol. The present invention has no special restrictions on the specific operations of the cleaning and drying, and it only needs to remove impurities on the surface of the intermediate layer material and keep it dry. By cleaning and drying the intermediate layer material, the present invention can remove impurities such as dust attached to the surface of the intermediate layer material, thereby preventing the impurities from affecting the welding surface.

[0062] In the present invention, the intermediate layer material is preferably the same shape as the surface to be welded of the material to be welded. By controlling the shapes to be the same, the surface to be welded can be fully in contact with the intermediate layer material, avoiding missing parts and also avoiding waste of materials.

[0063] As a specific implementation of the present invention, the material to be welded is a cylindrical material; the diameter of the cylindrical material is 50 mm; the length of the cylindrical material is 55 mm; the middle layer material is a cylindrical material; the diameter of the middle layer material is 50 mm.

[0064] The present invention preferably places the intermediate layer material between the welding surfaces of the two materials to be welded, and then places it axially in a vacuum diffusion welding furnace for diffusion welding. The present invention has no special limitation on the specific source of the vacuum diffusion welding furnace, and a vacuum diffusion welding furnace well known to those skilled in the art can be used. The present invention uses the above method to assemble the welded parts, which is conducive to uniform heating.

[0065] In the present invention, the diffusion welding includes: first heating to 300-400°C and keeping for 120-180min, then heating to 750-850°C and keeping for 60-100min, then heating to 900-1000°C and keeping for 40-80min, then heating to 1050-1100°C and keeping for 40-80min, finally heating to 1120°C and keeping for 200-300min; preferably, first heating to 350°C and keeping for 150min, then heating to 800°C and keeping for 90min, then heating to 950°C and keeping for 60min, then heating to 1100°C and keeping for 60min, finally heating to 1120°C and keeping for 260min. The present invention can achieve sufficient diffusion of the material to be welded and the intermediate layer material by controlling the insulation temperature and insulation time at each stage, thereby obtaining a welded joint with excellent performance.

[0066] In the present invention, the heating rate of heating to 300-400°C is preferably 5-6°C / min, more preferably 5.5°C / min; the heating rate of heating to 750-850°C is preferably 3-4°C / min, more preferably 3.75°C / min; the heating rate of heating to 900-1000°C is preferably 2-3°C / min, more preferably 2.5°C / min; the heating rate of heating to 1050-1100°C is preferably 2-3°C / min, more preferably 2.5°C / min; the heating rate of heating to 1120°C is preferably 1-2°C / min, more preferably 1.4°C / min. The present invention can avoid uneven internal stress distribution of the material due to excessively fast heating rate by controlling the heating rate.

[0067] In the present invention, the cooling method of the diffusion welding is preferably furnace cooling. The present invention can avoid the problem of excessively fast cooling speed leading to a substantial increase in the internal stress of the welded joint and an increase in welding defects.

[0068] In the present invention, the welding pressure of the diffusion welding is 14-15 MPa, preferably 15 MPa. The present invention can improve the diffusion efficiency of the intermediate layer by controlling the welding pressure, thereby improving the surface contact between the materials to be welded.

[0069] In the present invention, the welding vacuum degree of the diffusion welding is preferably less than 5×10 -2 Pa, more preferably <3×10 - 2 Pa. The present invention can avoid oxidation reaction between the alloy and oxygen in the air at high temperature by controlling the welding vacuum degree.

[0070] In the present invention, the relationship between the room temperature tensile strength of the nickel-based high-temperature alloy welded joint and the diffusion welding process parameters is preferably as shown in Formula I:

[0071] Y1=8.227H-25.951T+66.59P-0.254H 2 +0.011T 2 -2.2P 2 +15358.445 Formula I

[0072] In formula I, Y1 is the room temperature tensile strength, T is the maximum insulation temperature during diffusion welding, P is the welding pressure, and H is the thickness of the intermediate layer material.

[0073] In the present invention, the relationship between the high temperature tensile strength of the nickel-based high temperature alloy welded joint and the diffusion welding process parameters is preferably as shown in Formula II:

[0074] Y2=5.358H+294.497T-297.667P-0.128T2 +13.667P 2 -166848 Formula II

[0075] In formula II, Y2 is the high temperature tensile strength, T is the maximum insulation temperature during diffusion welding, P is the welding pressure, and H is the thickness of the intermediate layer material.

[0076] In the present invention, the relationship between the welding rate of the nickel-based high-temperature alloy welded joint and the diffusion welding process parameters is preferably as shown in Formula III:

[0077] Y3=2.327H+14.964T+1.966P-0.058H 2 -0.007T 2 -8498.941 Formula III

[0078] In formula III, Y3 is the welding rate of the welded joint, T is the maximum insulation temperature during diffusion welding, P is the welding pressure, and H is the thickness of the intermediate layer material.

[0079] The present invention uses the above three relationship equations to characterize the relationship between the room temperature tensile strength, high temperature tensile strength and welding rate of the nickel-based high temperature alloy welded joint and the diffusion welding process parameters. After actual measurement, the p-value of the mathematical model of room temperature tensile strength, high temperature tensile strength and welding rate is less than 0.05, and the p-value of each coefficient in the model is less than 0.05, which proves that the coefficients in the relationship equation are also significant. 2 The value is close to 1, indicating that the relationship has a good fitting effect and high reliability. It means that through the above formula, the process parameters in the diffusion welding process can be adjusted and optimized according to the required performance, so as to achieve the optimal selection of the diffusion welding process and lay the foundation for subsequent diffusion welding research.

[0080] The welding joint obtained by the diffusion welding method provided by the present invention consists of two groups of nickel-based high-temperature alloys and a welding joint in the middle, and the welding joint is formed by mutual diffusion of the intermediate layer material and the nickel-based high-temperature alloy. The welding joint provided by the present invention not only has excellent tensile properties at room temperature, but also has high tensile strength, yield strength and elongation properties when the temperature is as high as 650°C.

[0081] The present invention introduces high-purity nickel foil as an intermediate layer material between two nickel-based high-temperature alloy parts to be welded. The intermediate layer material has good plastic deformation performance, can improve the surface contact between the materials to be welded, and utilizes the eutectic reaction of the base material and the intermediate layer elements to promote the breakage of the oxide film on the surface of the base material, inhibit the formation of intermetallic compounds, and thus help to obtain a diffusion welding joint with good performance; by controlling the thickness of the intermediate layer material, the structural defects in the welded joint can be effectively reduced, and while improving the room temperature tensile properties and high temperature tensile properties of the welded joint, the temperature required for the diffusion welding process can be reduced, further reducing the structural deformation generated during the welding process, and improving the welding manufacturing accuracy.

[0082] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0083] Example 1

[0084] A low welding specification high strength diffusion welding method for nickel-based high temperature alloys is:

[0085] (1) Preparation of the material to be welded: The welding surface of the material to be welded is processed by a milling machine to make the roughness of the welding surface less than 0.3 μm, and then it is cleaned with anhydrous ethanol in an ultrasonic cleaning machine, and finally dried to obtain the material to be welded; the material of the material to be welded is Inconel625 nickel-based high-temperature alloy; the shape of the material to be welded is Cylinders, two in number;

[0086] (2) Preparation of the intermediate layer material: The intermediate layer material is cleaned with anhydrous ethanol and then dried to obtain the intermediate layer material; the intermediate layer material is high-purity nickel foil, the thickness of the intermediate layer material is 20 μm, and the diameter of the intermediate layer material is 50mm;

[0087] (3) An intermediate layer material is placed between the welding surfaces of two materials to be welded for assembly, and then the materials are placed axially in a vacuum diffusion welding furnace for diffusion welding to obtain a nickel-based high-temperature alloy welded joint; the diffusion welding is as follows: firstly, the temperature is increased from room temperature to 350°C at a heating rate of 5.5°C / min and kept at this temperature for 150min, then the temperature is increased to 800°C at a heating rate of 3.75°C / min and kept at this temperature for 90min, then the temperature is increased to 950°C at a heating rate of 2.5°C / min and kept at this temperature for 60min, then the temperature is increased to 1100°C at a heating rate of 2.5°C / min and kept at this temperature for 60min, finally the temperature is increased to 1120°C at a heating rate of 1.4°C / min and kept at this temperature for 260min, and then the materials are cooled to room temperature and taken out of the furnace; the welding pressure of the diffusion welding is 15MPa, and the welding vacuum degree of the diffusion welding is less than 5×10 -2 Pa;

[0088] (4) Repeat the above steps (1) to (3) to prepare a total of 4 groups of welding joints.

[0089] The post-weld deformation rate of the nickel-based high-temperature alloy weld joint prepared in Example 1 was calculated, and the calculation method was: (1-H2 / H1)*100%, wherein H1 is the total height of the material to be welded before welding, and H2 is the height of the nickel-based high-temperature alloy weld joint after welding (the average height of the 4 groups of weld joints prepared).

[0090] After calculation, the total height H1 of the two materials to be welded before welding is 110.02 mm, the height H2 of the nickel-based high-temperature alloy weld joint after welding is 103.86 mm, and the deformation rate after welding is 5.6%.

[0091] Comparative Example 1

[0092] In the step (3), the temperature is finally raised to 1170° C. at a heating rate of 1.4° C. / min and kept at that temperature for 260 min. Other conditions are the same as those in Example 1.

[0093] Comparative Example 2

[0094] In step (3), the temperature is finally raised to 1100° C. at a heating rate of 1.4° C. / min and kept at that temperature for 260 min. Other conditions are the same as those in Example 1.

[0095] Two groups of nickel-based high-temperature alloy welded joints prepared in Example 1 and Comparative Examples 1-2 were taken, and then the room temperature tensile test was performed on the welded joints according to GB / T228. The room temperature tensile properties obtained were as follows: Figures 1 to 3 As shown, the room temperature tensile strength obtained by taking the average value of the two groups of data obtained in Example 1 and Comparative Examples 1-2 is as follows Figure 4 As shown. Figures 1 to 3From the comparison, it can be seen that although the room temperature tensile properties of the two groups of welded joints prepared in the same embodiment or comparative example are not the same, the difference in their formation parameters is not large. It is inferred that this is due to the performance of the Inconel625 nickel-based high-temperature alloy itself and the errors in the preparation process, which are within the standard error range; as the insulation temperature drops from 1170°C to 1120°C, the tensile strength of the welded joint continues to increase slightly, while the elongation at break and the yield strength remain basically unchanged, indicating that the present invention can effectively reduce the temperature during welding by introducing the intermediate layer material, and when the temperature drops from 1120°C to 1100°C, the tensile strength of the welded joint increases slightly, the elongation at break decreases, and the yield strength does not change much. Figure 4 It can be seen that as the holding temperature drops from 1170℃ to 1100℃, the room temperature tensile strength of the welded joint increases slightly, but the increase is small. When the holding temperature during diffusion welding is 1120℃, the room temperature tensile strength of the welded joint can reach above 840MPa.

[0096] Two groups of nickel-based high-temperature alloy welded joints prepared in Example 1 and Comparative Examples 1-2 were taken, and then the welded joints were subjected to high-temperature tensile tests according to GB / T228. The temperature of the welded joints during the high-temperature tensile test was 650°C. The high-temperature tensile properties obtained were as follows: Figures 5 to 7 As shown, the high temperature tensile strength obtained by taking the average value of the two groups of data obtained in Example 1 and Comparative Examples 1-2 is as follows Figure 8 As shown. Figures 5 to 7 It can be seen that when the temperature reaches 1170°C, the elongation after fracture of the welded joint at 650°C can reach more than 54%, but the requirements for the equipment are relatively high. When the temperature of diffusion welding drops to 1120°C, the elongation after fracture of the welded joint at 650°C can reach more than 30%. At this time, the high-temperature tensile performance of the welded joint can meet the technical requirements. When the temperature drops to 1100°C, the elongation after fracture of the prepared welded joint at 650°C is only 4.8-5.6%, which can no longer meet the technical requirements. This shows that after the intermediate layer material is introduced in the present invention, a welded joint with excellent high-temperature tensile performance can be obtained at a lower welding temperature. Figure 8It can be seen that the tensile strength of the welded joint at high temperature decreases with the decrease of the insulation temperature during diffusion welding. When the insulation temperature of diffusion welding is 1170°C, the tensile strength of the welded joint at 650°C is about 600MPa, and when the insulation temperature of diffusion welding is reduced to 1120°C, the tensile strength of the welded joint at 650°C only declines slightly, and can still reach about 580MPa. This shows that the present invention can reduce the temperature parameters during welding while ensuring that the high-temperature tensile properties of the welded joint are not affected by introducing an intermediate layer material. When the insulation temperature is reduced to 1100°C, the tensile strength of the welded joint at 650°C is only 400MPa, which declines greatly. Therefore, it is best to control the insulation temperature of diffusion welding to 1120°C.

[0097] The metallographic structures of the welded joints in Example 1 and Comparative Examples 1-2 were taken respectively, and the weld defects at the welded joints were observed in the following order: Figures 9-11 As shown. Figures 9-11 It can be seen that when the insulation temperature of diffusion welding is 1170°C, scattered welding defects can be seen. When the insulation temperature drops to 1120°C, the welding defects are reduced (see the welding rate for specific comparison). When the insulation temperature drops to 1100°C, the welding defects increase significantly, which is very obvious. This shows that after the intermediate layer material is introduced into the present invention, even if the insulation temperature during diffusion welding is appropriately lowered, the welding defects can be effectively reduced.

[0098] The welding rates of the welding joints of Example 1 and Comparative Examples 1 to 2 were calculated respectively, and the results obtained are as follows: Fig.12 As shown. Fig.12 It can be seen that with the decrease of the insulation temperature during diffusion welding, the welding rate at the welded joint shows a trend of first decreasing and then increasing. When the insulation temperature reaches 1120°C, the welding rate reaches the highest. At this time, there are few welding defects at the welded joint, and the performance of the welded joint is significantly improved. When the temperature continues to increase to 1170°C, the welding rate decreases, indicating that the present invention improves the welding rate while lowering the welding temperature by introducing an intermediate layer material.

[0099] Comparative Example 3

[0100] The thickness of the intermediate layer material in step (2) is 6 μm, and other conditions are the same as those in comparative example 1.

[0101] Comparative Example 4

[0102] The thickness of the intermediate layer material in step (2) is 10 μm, and other conditions are the same as those in comparative example 1.

[0103] Comparative Example 5

[0104] The intermediate layer material in step (2) was omitted, and other conditions were the same as those in Comparative Example 1.

[0105] The post-weld deformation rate of the nickel-based high-temperature alloy weld joint prepared in Comparative Example 5 was calculated using the same calculation method as in Example 1. After calculation, the total height H1 of the two materials to be welded before welding was 110 mm, the height H2 of the nickel-based high-temperature alloy weld joint after welding was 99.79 mm, and the post-weld deformation rate was 9.28%.

[0106] By comparing the post-weld deformation rates of Example 1 and Comparative Example 5, it can be seen that the present invention, by introducing the intermediate layer material, can not only reduce the temperature and welding specifications of diffusion welding, but also significantly reduce the post-weld deformation rate.

[0107] Two groups of nickel-based high-temperature alloy welded joints prepared in Comparative Examples 3 to 5 were taken, and then the room temperature tensile test was performed on the welded joints according to GB / T228. The room temperature tensile properties obtained were as follows: Figures 13-15 As shown, the room temperature tensile strength obtained by taking the average value of the two groups of data obtained from Comparative Example 1 and Comparative Examples 3 to 5 is as follows Fig.16 As shown. Figure 2 and Figures 13-15 It can be seen that when the intermediate layer material is not added to the weld joint, the elongation at break of the weld joint is only 16.7-29.3%, but when the intermediate layer material is introduced, the elongation at break of the weld joint can be significantly improved, from 16.7-29.3% to 46.4-58.9%. At the same time, when the thickness of the intermediate layer material is increased from 6μm to 20μm, the elongation at break of the weld joint does not change much. Fig.16 It can be seen that with the increase of the thickness of the intermediate layer material, the room temperature tensile strength of the welded joint shows an obvious upward trend. When the thickness of the intermediate layer material is less than 6μm, the room temperature tensile strength increases significantly. When the thickness of the intermediate layer material increases from 6μm to 20μm, the increase in the room temperature tensile strength gradually tends to be gentle, indicating that the present invention can effectively improve the room temperature tensile properties of the welded joint by introducing the intermediate layer material into the welded joint.

[0108] Two groups of nickel-based high-temperature alloy welded joints prepared in Comparative Examples 3 to 5 were taken, and then the high-temperature tensile test was performed on the welded joints according to GB / T228. The temperature of the welded joint during the high-temperature tensile test was 650°C. The high-temperature tensile properties obtained were as follows: Figures 17 to 19 As shown, the high temperature tensile strength obtained by taking the average value of the two groups of data obtained from Comparative Example 1 and Comparative Examples 3 to 5 is as follows Fig. 20 As shown. Figures 17 to 19 It can be seen that by Fig.17 and Fig.19 It can be seen that when the thickness of the intermediate layer material is less than 6 μm, the tensile strength, yield strength and elongation of the welded joint at high temperature increase slightly. Figure 6 , Fig.18 and Fig.19 It can be seen from the comparison that when the thickness of the middle layer material increases from 6μm to 20μm, the tensile strength, yield strength and elongation of the welded joint at high temperature are significantly improved, and the strength increases with the increase of the thickness of the middle layer material. Fig. 20 It can be seen that with the increase of the thickness of the intermediate layer material, the high-temperature tensile strength of the welded joint shows an obvious upward trend. When the thickness of the intermediate layer material is less than 6μm, the increase in high-temperature tensile strength is small. When the thickness of the intermediate layer material is increased from 6μm to 20μm, the increase in high-temperature tensile strength gradually increases. This shows that the present invention can effectively improve the high-temperature tensile properties of the welded joint by introducing the intermediate layer material into the welded joint, thereby laying the foundation for lowering the welding temperature.

[0109] The metallographic structures of the welded joints in Comparative Examples 3 to 5 were taken respectively, and the welding defects at the welded joints were observed in order as follows: Figures 21 to 23 As shown. Figures 21 to 23 It can be seen that when the intermediate layer material is not added, there are obvious cracks at the welding joint of the welding joint. With the addition of the intermediate layer material and the gradual increase in the thickness of the intermediate layer material, the welding defects become smaller and smaller. When the thickness of the intermediate layer material reaches 20μm, the welding defects are almost not obvious, indicating that the intermediate layer material can effectively eliminate the welding defects at the welding joint.

[0110] The welding rates of the welding joints of comparative examples 3 to 5 were calculated respectively, and the results obtained by combining the welding rate of comparative example 1 are as follows: Fig.24 As shown. Fig.24 It can be seen that with the increase of the thickness of the intermediate layer material, the welding rate at the welding joint shows a significant increasing trend, and reaches the highest value when the thickness of the intermediate layer material reaches 20μm. At this time, the welding rate reaches more than 95%. At this time, there are very few welding defects at the welding joint, and the performance of the welding joint is significantly improved. This shows that the present invention can significantly improve the welding deformation problem by introducing the intermediate layer material even when the diffusion welding temperature reaches 1170°C, which is helpful to obtain a diffusion welding joint with good performance and lays a foundation for reducing the diffusion welding temperature.

[0111] Comparative Example 6

[0112] The welding pressure of the diffusion welding in step (3) is 13 MPa, and other conditions are the same as those in Example 1.

[0113] Take two groups of nickel-based high-temperature alloy welded joints prepared in Comparative Example 6, and then perform room temperature tensile tests on the welded joints according to GB / T228. The room temperature tensile properties are as follows: Fig.25 As shown, the room temperature tensile strength obtained by taking the average value of the two groups of data obtained in Example 1 and Comparative Example 6 is as follows Fig.26 As shown. Figure 1 and Fig.25 It can be seen that as the welding pressure of diffusion welding increases from 13MPa to 15MPa, the elongation at break of the welded joint increases slightly, while the yield strength changes slightly. Fig.26 It can be seen that as the welding pressure of diffusion welding increases from 13 MPa to 15 MPa, the room temperature tensile strength of the welded joint increases slightly, indicating that controlling the welding pressure can regulate the room temperature tensile properties of the welded joint.

[0114] Take two groups of nickel-based high-temperature alloy welded joints prepared in Comparative Example 6, and then perform high-temperature tensile tests on the welded joints according to GB / T228. The temperature of the welded joints during the high-temperature tensile test is 650°C. The high-temperature tensile properties are as follows: Fig. 27 As shown, the high temperature tensile strength obtained by taking the average value of the two sets of data obtained in Example 1 and Comparative Example 6 is as follows Fig.28 As shown. Figure 1 and Fig. 27 It can be seen that as the welding pressure of diffusion welding increases from 13MPa to 15MPa, the yield strength of the prepared welded joint at 650℃ changes slightly, while the tensile strength and elongation after fracture of the welded joint are significantly improved, indicating that increasing the welding pressure during welding can effectively improve the tensile strength and toughness of the welded joint at high temperature. Fig.28 It can be seen that the tensile strength of the welded joint at high temperature increases with the increase of welding pressure. When the welding pressure increases from 13MPa to 15MPa, the tensile strength increases from 400MPa to more than 550MPa, and the increase exceeds 150MPa. The high temperature strength of the welded joint is significantly improved.

[0115] The diffusion welding process parameters of Example 1 and Comparative Examples 1 to 6 and the properties of the obtained welded joints are summarized, and the obtained results are shown in Tables 1 to 3 respectively:

[0116] Table 1 Diffusion welding process parameters of Example 1 and Comparative Examples 1 to 6

[0117] Example Maximum holding temperature during diffusion welding / ℃ Welding pressure / MPa Thickness of the middle layer material / μm Example 1 1120 15 20 Comparative Example 1 1170 15 20 Comparative Example 2 1170 15 20 Comparative Example 3 1170 15 6 Comparative Example 4 1170 15 10 Comparative Example 5 1170 15 0 Comparative Example 6 1120 13 20

[0118] Table 2 Room temperature properties of welded joints obtained in Example 1 and Comparative Examples 1 to 6

[0119]

[0120]

[0121] Table 3 High temperature (650°C) performance of welded joints obtained in Example 1 and Comparative Examples 1 to 6

[0122] Example Tensile strength / MPa Yield strength / MPa Elongation after break / % Example 1 Group 1 589 323 31.3 Example 1 Group 2 581 316 30.7 Comparative Example 1 Group 1 614 335 61.3 Comparative Example 1 Group 2 596 324 54.7 Comparative Example 2 Group 1 403 324 5.6 Comparative Example 2 Group 2 393 318 4.8 Comparative Example 3 Group 1 526 292 28.3 Comparative Example 3 Group 2 490 286 23.3 Comparative Example 4 Group 1 576 334 46.2 Comparative Example 4 Group 2 535 308 32.7 Comparative Example 5 Group 1 482 274 20.2 Comparative Example 5 Group 2 528 296 26.7 Comparative Example 6 Group 1 394 312 5.2 Comparative Example 6 Group 2 407 310 5.9

[0123] Based on the above process parameters and performance analysis, it is determined that when the thickness of the intermediate layer material is 20μm, the final insulation temperature during diffusion welding is 1120℃, the welding pressure during diffusion welding is 15MPa, and the total insulation time during diffusion welding is 620min, the prepared welded joint has the best performance.

[0124] According to the performance of the welded joints prepared in Example 1 and Comparative Examples 1 to 6, a multivariate nonlinear fitting Y=f(H, T, P) was performed on the process parameters of diffusion welding (including the three factors of holding temperature, welding pressure and thickness of the intermediate layer material) and the room temperature tensile strength, high temperature tensile strength and welding defects of the welded joint, and a relationship between the process parameters and the welded joint strength and welding defects was established, thereby establishing a multivariate nonlinear regression model, which is specifically as follows:

[0125] The relationship between the diffusion welding process parameters and the room temperature tensile strength of the welded joint is shown in Formula I:

[0126] Y1=8.227H-25.951T+66.59P-0.254H 2 +0.011T 2 -2.2P 2 +15358.445 Formula I

[0127] In formula I, Y1 is the room temperature tensile strength, T is the maximum holding temperature during diffusion welding, P is the welding pressure, and H is the thickness of the intermediate layer material;

[0128] The variance analysis of diffusion welding process parameters and room temperature tensile strength of welded joints is shown in Table 4:

[0129] Table 4 Variance analysis of diffusion welding process parameters and room temperature tensile strength of welded joints

[0130] factor Degrees of Freedom Mean Square P-value Mathematical model 6 1358.66 0.0050 H 1 516.67 0.0067 T 1 1015.61 0.0048 P 1 1682.00 0.0037 <![CDATA[H 2 ]]> 1 545.77 0.0065 <![CDATA[T 2 ]]> 1 78.12 0.0172 <![CDATA[P 2 ]]> 1 114.63 0.0142

[0131] After numerical fitting, we get: R 2 =0.9983, Adj R 2 =0.9949, Pre R 2 =0.7515

[0132] As shown in Table 4, the p-value of the mathematical model of the room temperature tensile strength Y of the joint is less than 0.05, which proves that the model is significant. The p-values ​​of the coefficients in the model are all less than 0.05, which proves that the coefficients in the relationship are also significant. 2 The value is close to 1, indicating that the relationship has a good fitting effect and high reliability.

[0133] The relationship between the diffusion welding process parameters and the high temperature tensile strength of the welded joint is shown in Formula II:

[0134] Y2=5.358H+294.497T-297.667P-0.128T 2 +13.667P 2 -166848 Formula II

[0135] In formula II, Y2 is the high temperature tensile strength, T is the maximum holding temperature during diffusion welding, P is the welding pressure, and H is the thickness of the intermediate layer material;

[0136] The variance analysis of diffusion welding process parameters and high temperature tensile strength of welded joints is shown in Table 5:

[0137] Table 5 Variance analysis of diffusion welding process parameters and high temperature tensile strength of welded joints

[0138] factor Degrees of Freedom Mean Square P-value Mathematical model 5 11289.02 0.0199 H 1 6087.25 0.0354 T 1 23098.34 0.0097 P 1 24200.22 0.0093 <![CDATA[T 2 ]]> 1 10460.31 0.0211 <![CDATA[P 2 ]]> 1 4423.68 0.0477

[0139] After numerical fitting, we get: R 2 =0.9920, Adj R 2 =0.9720, Pre R 2 =0.8235

[0140] It can be seen from Table 5 that the p-value of the mathematical model of the high-temperature tensile strength Y of the joint is less than 0.05, which proves that the model is significant. The p-values ​​(i.e., P values) of the coefficients in the model are all less than 0.05, which proves that the coefficients in the relationship are also significant. 2 The value is close to 1, indicating that the relationship has a good fitting effect and high reliability.

[0141] The relationship between the process parameters of diffusion welding and the welding defects of the welded joint (i.e., the welding rate) is shown in Formula III:

[0142] Y3=2.327H+14.964T+1.966P-0.058H 2 -0.007T 2 -8498.941 Formula III

[0143] In formula III, Y3 is the welding rate of the welded joint, T is the maximum holding temperature during diffusion welding, P is the welding pressure, and H is the thickness of the intermediate layer material;

[0144] The variance analysis of diffusion welding process parameters and welding defects of welding joints is shown in Table 6:

[0145] Table 6 Variance analysis of diffusion welding process parameters and welding defects of welded joints

[0146] factor Degrees of Freedom Mean Square P-value Mathematical model 5 86.09 0.0111 H 1 113.77 0.0087 T 1 24.07 0.0391 P 1 51.04 0.0190 <![CDATA[H 2 ]]> 1 30.18 0.0316 <![CDATA[T 2 ]]> 1 33.03 0.0290

[0147] After numerical fitting, we get: R 2 =0.9956, Adj R 2 =0.9845, Pre R 2 =0.8354

[0148] It can be seen from Table 6 that the p-value of the mathematical model of welding joint welding rate Y is less than 0.05, which proves that the model is significant. The p-value of each coefficient in the model is less than 0.05, which proves that the coefficients in the relationship are also significant. 2 The value is close to 1, indicating that the relationship has a good fitting effect and high reliability.

[0149] In summary, Formula I, Formula II and Formula III are proposed as process-performance-defect prediction models, which can provide guidance for the selection of welding process parameters.

[0150] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A nickel-based high-temperature alloy low welding specification high-strength diffusion welding method, comprising: Placing an intermediate layer material on the welding surface of the material to be welded, and then performing diffusion welding to obtain a nickel-based high-temperature alloy welded joint; The material to be welded includes a nickel-based high-temperature alloy; The intermediate layer material is high-purity nickel foil, and the thickness of the intermediate layer material is 6 to 20 μm; The diffusion welding comprises: firstly heating to 300-400°C and keeping the temperature for 120-180 minutes, then heating to 750-850°C and keeping the temperature for 60-100 minutes, then heating to 900-1000°C and keeping the temperature for 40-80 minutes, then heating to 1050-1100°C and keeping the temperature for 40-80 minutes, and finally heating to 1120°C and keeping the temperature for 200-300 minutes; The welding pressure of the diffusion welding is 14-15 MPa.

2. The diffusion welding method according to claim 1, characterized in that: The material to be welded is Inconel625 nickel-based high-temperature alloy.

3. The diffusion welding method according to claim 1, characterized in that: The roughness of the surface to be welded is less than 0.3 μm.

4. The diffusion welding method according to claim 1, characterized in that: The thickness of the intermediate layer material is 10-20 μm.

5. The diffusion welding method according to claim 1, characterized in that: The diffusion welding comprises: first heating to 350° C. and keeping the temperature for 150 minutes, then heating to 800° C. and keeping the temperature for 90 minutes, then heating to 950° C. and keeping the temperature for 60 minutes, then heating to 1100° C. and keeping the temperature for 60 minutes, and finally heating to 1120° C. and keeping the temperature for 260 minutes.

6. The diffusion welding method according to claim 1, characterized in that: The heating rate to 300-400°C is 5-6°C / min; the heating rate to 750-850°C is 3-4°C / min; the heating rate to 900-1000°C is 2-3°C / min; the heating rate to 1050-1100°C is 2-3°C / min; the heating rate to 1120°C is 1-2°C / min.

7. The diffusion welding method according to claim 1, characterized in that: The welding vacuum degree of the diffusion welding is less than 5×10 -2 Pa.

8. The diffusion welding method according to claim 1, characterized in that: The relationship between the room temperature tensile strength of the nickel-based high-temperature alloy welded joint and the diffusion welding process parameters is shown in Formula I: Y1=8.227H-25.951T+66.59P-0.254H 2 +0.011T 2 -2.2P 2 +15358.445 Formula I In formula I, Y1 is the room temperature tensile strength, T is the maximum insulation temperature during diffusion welding, P is the welding pressure, and H is the thickness of the intermediate layer material.

9. The diffusion welding method according to claim 1, characterized in that: The relationship between the high temperature tensile strength of the nickel-based high temperature alloy welded joint and the diffusion welding process parameters is shown in Formula II: Y2=5.358H+294.497T-297.667P-0.128T 2 +13.667P 2 -166848 Formula II In formula II, Y2 is the high temperature tensile strength, T is the maximum insulation temperature during diffusion welding, P is the welding pressure, and H is the thickness of the intermediate layer material.

10. The diffusion welding method according to claim 1, characterized in that: The relationship between the welding rate of the nickel-based high-temperature alloy welded joint and the diffusion welding process parameters is shown in Formula III: Y3 = 2.327H + 14.964T + 1.966P - 0.058H 2 - 0.007T 2 - 8498.941 Formula III In formula III, Y3 is the welding rate of the welded joint, T is the maximum insulation temperature during diffusion welding, P is the welding pressure, and H is the thickness of the intermediate layer material.

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