A homogenization preparation method of a homogeneous high-w nickel-based superalloy K465

Abstract

The application discloses a homogenization preparation method of a homogenized high-W nickel-based high-temperature alloy K465 and belongs to the technical field of alloy component design and preparation. The method controls the (Al+Ti) / W ratio in the alloy, smelting and pouring processes and solidification environment to obtain a homogenized product. In order to avoid high-W phase or large-size eutectic from being precipitated from the alloy during solidification, the (Al+Ti) / W ratio should be within the range of 0.76 to 0.80. In order to ensure the consistency of the cooling environment of different alloy ingots in a mold, the pouring rate of the alloy ingots at different positions and the heat storage capacity of the mold pipe are controlled, the cooling environment of the alloy ingots at different positions is accurately controlled, and the effect that the components of the alloy ingots at different positions are uniform is achieved. The prepared alloy ingots are uniform in component, the concentration difference of main elements of different alloy ingots is less than or equal to 0.2%, and the concentration difference of trace elements is less than or equal to 0.02%.

Description

Technical Field

[0001] This invention relates to the field of alloy composition design and preparation technology, and specifically to a homogenization preparation method for a homogeneous high-W nickel-based superalloy K465. Background Technology

[0002] Nickel-based superalloys possess excellent high-temperature structural stability, oxidation resistance, hot corrosion resistance, and resistance to high-temperature creep and fatigue, making them widely used in the manufacture of advanced aerospace engines and hot-end components of gas turbines. With the increasing demands on the heat-bearing capacity of superalloy components, high alloying and high proportions of refractory elements are generally pursued in the composition design of superalloys to improve the solid solution strengthening level. Compared with currently widely studied additive elements such as Re and Ru, W is cheaper and has excellent strengthening effects in nickel-based superalloys, and can replace Re and Ru to a certain extent. Therefore, the research and application of high-W alloyed nickel-based superalloys has attracted widespread attention from researchers worldwide.

[0003] However, W has a relatively high density, approximately 19.35 g / cm³. 3 It is much higher than the average density of nickel-based superalloys (approximately 8.4 g / cm³). 3 Therefore, high-W alloy ingots are prone to gravity segregation during preparation, resulting in uneven composition and consequently poor performance consistency in the cast parts after quantitative cutting. On the other hand, W has a high melting point and solidifies relatively early in the alloy's solidification process, leading to a greater tendency for W-rich phases to precipitate. These W-rich phases can still exist in the melt as short-range ordered clusters even during secondary remelting, exhibiting high microstructural inheritance. Therefore, preparing homogenized high-W nickel-based superalloy ingots helps improve the performance stability of this type of alloy, expanding its application potential and range.

[0004] The homogeneity of an alloy depends primarily on the compositional uniformity of the melt before casting and the microstructure uniformity during solidification. While a vacuum induction furnace coupled with electromagnetic stirring can ensure uniform melt composition, the difference in solidification sequence at different locations after casting leads to the growth of high-melting-point phases that precipitate first, consuming a large amount of refractory elements in the melt and resulting in poor compositional uniformity. Furthermore, in industrial production, multiple alloy ingots are often cast simultaneously. The outer ingots typically solidify faster and have relatively uniform composition, while the inner ingots solidify more slowly and are more prone to compositional segregation, reducing the yield rate of that batch of ingots.

[0005] Previous studies have found that during the casting of large-size alloy ingots, the casting and solidification processes occur simultaneously. Furthermore, in large modules used in engineering applications, the solidification microstructure of alloy ingots in different locations is mainly related to the heat storage capacity at that location and the system's temperature rise rate. The dynamic solidification behavior of the alloy during casting can be controlled by adjusting the casting rate at different locations and the thickness of the metal mold tube, thereby obtaining alloy ingots with better overall microstructure consistency. When the casting rate is too fast, the mold tube is quickly filled, resulting in less heat exchange between the mold tube and the molten alloy, easily leading to a hot core phenomenon and a significantly increased probability of W-rich phase precipitation in the core. When the casting rate is too slow, the high-melting-point phases in the lower, pre-solidified parts tend to grow, leading to uneven alloy microstructure and composition distribution. When the mold tube wall is thin, the heat storage capacity is low and the heating rate is fast, easily causing a hot core to appear in the middle of the alloy ingot. Conversely, when the mold tube wall is thick, the heat storage capacity is high, the initial solidification rate of the alloy ingot is fast, the growth time of high-melting-point phases is long, and the thick-walled mold tube occupies a large casting area, affecting alloy yield.

[0006] Therefore, this invention designs a simple, economical, and practical engineering preparation method for homogenized high-W nickel-based superalloy ingots, which not only helps improve alloy quality but also enhances the performance stability of such alloy castings, promoting the preparation and application of low-cost high-W alloys in my country, and has significant social and economic implications. Summary of the Invention

[0007] The purpose of this invention is to provide a homogenization preparation method for homogenized high-W nickel-based superalloy K465, thereby solving the problem of homogenization of high-W nickel-based superalloy K465 ingots.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A homogenization preparation method for a homogeneous high-W nickel-based superalloy K465 includes the following steps:

[0010] (1) The content of Al, Ti and W is designed according to the chemical composition of the high W nickel-based high temperature alloy K465. The ratio of (Al+Ti) to W should be in the range of 0.76 to 0.80 to avoid the precipitation of a large amount of large W-rich phase and eutectic structure in the alloy ingot.

[0011] (2) Alloy smelting: Ultra-high temperature melt treatment and low temperature refining are carried out in sequence to ensure uniform melt composition; wherein: the ultra-high temperature melt treatment temperature is not lower than 1500℃, and the low temperature refining temperature is between 1380 and 1420℃.

[0012] (3) Assemble the casting module: According to the number of alloy ingots prepared, it is divided into several 4×4 module units. The module unit consists of 4 mold tubes with a wall thickness of 30mm and 12 mold tubes with a wall thickness of 20mm. The height of the mold tube is about 1000mm.

[0013] (4) Place the assembled module into a muffle furnace for preheating.

[0014] (5) Casting: The melt temperature is about 1420℃ during casting. After casting, the melt is kept in the furnace for 5 to 10 minutes before being taken out of the furnace. This will allow for the batch production of homogeneous high-W nickel-based high-temperature alloy ingots.

[0015] The chemical composition of the high-W nickel-based superalloy K465, by weight percentage, is as follows:

[0016] C: 0.13–0.2%, Cr: 8.0–9.5%, Co: 9.5–10.5%, W: 9.5–11.0%, Mo: 1.2–2.4%, Al: 5.1–6.0%, Ti: 2.0–2.9%, Nb: 0.8–1.2%, Zr ≤ 0.04%, B ≤ 0.035%, Ni balance.

[0017] The chemical composition of the high-W nickel-based superalloy K465, by weight percentage, should have an (Al+Ti) to W ratio in the range of 0.76 to 0.80 to avoid the precipitation of large-sized W-rich phases and eutectic structures in the alloy ingot.

[0018] In step (3) above, the 30mm thick wall tube is located in the center and four corners, and the 20mm thick wall tube is located in other positions on the outside. The bottom of the tube is sealed with a graphite pad, and the top is equipped with an 80-120mm high aluminum silicate riser. The pouring rate is controlled by a pouring distributor. The pouring rate distribution is as follows: the pouring gate diameter corresponding to the 20mm thick wall tube is about φ13mm, and the pouring gate diameter corresponding to the 20mm thick wall tube is about φ10mm.

[0019] In step (4) above, the preheating process parameters are: preheating temperature 650℃ and preheating time 3h, so as to ensure that the temperature of the mold tubes at different positions in the module is basically the same.

[0020] The advantages and beneficial effects of this invention are as follows:

[0021] 1. To avoid the precipitation of high W phase or large-sized eutectic during solidification, the ratio of (Al+Ti) to W in the alloy composition should be in the range of 0.76 to 0.80.

[0022] 2. To ensure the consistency of the cooling environment for different alloy ingots within the module, the pouring rate of alloy ingots at different locations and the heat storage method of the mold tube are controlled. By precisely controlling the cooling environment of ingots at different locations, the uniform composition of each alloy ingot at different locations is achieved.

[0023] 3. The alloy ingots prepared by the process of this invention have uniform composition, with the concentration difference of main elements between different alloy ingots ≤0.2% and the concentration difference of trace elements ≤0.02%. The preparation method of the homogeneous high-W nickel-based superalloy K465 involved in this invention is suitable for engineering production applications, with low implementation difficulty and significant effects. Attached Figure Description

[0024] Figure 1 The invention relates to a mold tube assembly method and a pouring distributor structure; wherein: (a) a schematic diagram of the mold tube arrangement, and (b) a schematic diagram of the main structure of the pouring distributor. Detailed Implementation

[0025] To further understand the present invention, the present invention is described below with reference to examples. However, the examples are only for further illustrating the features and advantages of the present invention, and are not intended to limit the scope of the claims of the present invention.

[0026] This invention provides a homogenization preparation method for high-W nickel-based superalloy K465. The chemical composition of the nickel-based superalloy K465, by weight percentage, is as follows:

[0027] C: 0.13~0.20, Cr: 8.0~9.5, Co: 9.5~10.5, W: 9.5~11.0, Mo: 1.2~2.4, Al: 5.1~6.0, Ti: 2.0~2.9, Nb: 0.8~1.2, Zr: ≤0.04, B: ≤0.035, Ni balance.

[0028] The homogenization preparation method of this nickel-based superalloy K465 includes the following steps:

[0029] (1) The content of Al, Ti and W should be designed according to the composition line range. The ratio of (Al+Ti) to W should be in the range of 0.76 to 0.80 to avoid the precipitation of large-sized W-rich phase and eutectic structure in the alloy ingot.

[0030] (2) The alloy smelting is carried out by using ultra-high temperature melt treatment and low temperature refining methods to ensure uniform melt composition. The ultra-high temperature melt treatment temperature is not lower than 1500℃, and the low temperature refining temperature is between 1380 and 1420℃.

[0031] (3) Assemble the casting module. Based on the number of alloy ingots to be prepared, divide it into several 4×4 module units. Each module unit consists of 4 30mm thick mold tubes and 12 20mm thick mold tubes. The height of the mold tubes is approximately 1000mm. Among them, the 30mm thick mold tubes are located in the center and four corners, and the 20mm thick mold tubes are located in other positions on the outside. The bottom of the mold tubes is sealed with graphite pads, and the top is equipped with risers made of 80-120mm high-alumina silicate material. The casting rate is controlled by a casting distributor. The casting rate distribution is as follows: the diameter of the casting port corresponding to the 20mm thick mold tube is approximately φ13mm, and the diameter of the casting port corresponding to the 20mm thick mold tube is approximately φ10mm.

[0032] A schematic diagram of mold tube placement and distributor pouring speed distribution is shown below. Figure 1 As shown in the diagram; where position A is the placement location for 30mm wall thickness mold tubes, and position B is the placement location for 20mm wall thickness mold tubes. In the distributor diagram, C is the guide wall, with a height of approximately (1 / 3) to (1 / 2) of the outer wall height, D is the sprue with a diameter of φ13mm, and E is the sprue with a diameter of φ10mm.

[0033] (4) The assembled module is placed in a muffle furnace for preheating. The preheating process parameters are: 650℃×3h, to ensure that the temperature of the mold tubes at different positions in the module is basically the same.

[0034] (5) Based on the heat absorption of the tundish and distributor, the pouring temperature is determined to ensure that the melt temperature is about 1420℃ during pouring. When pouring, try to fill the mold in the order of center → four corners → side. After pouring, keep the furnace warm for 5 to 10 minutes and then take it out of the furnace. This will allow you to obtain homogeneous high W nickel-based high temperature alloy ingots in batches.

[0035] Example 1:

[0036] 700 kg of the high-W nickel-based superalloy ingot was smelted using a 1.0T vacuum induction furnace. The composition control points of the alloy ingot were (mass fraction): C: 0.15%, Cr: 8.8%, Co: 10%, W: 10%, Mo: 1.8%, Al: 5.4%, Ti: 2.3%, Nb: 1.0%, Zr: 0.015%, B: 0.015%. Among them, (Al+Ti):W = 0.77.

[0037] The process parameters used for alloy smelting are: high-temperature refining at 1550℃ for 30 minutes and low-temperature refining at 1400℃ for 50 minutes. Based on production experience, the heat absorbed by the tundish and distributor during casting is about 30 to 40℃. Therefore, the casting temperature is set at 1460℃.

[0038] The casting mold tube is a cylindrical metal ingot mold with an inner diameter of φ85mm and a height of 1200mm, made of 45# steel, according to... Figure 1After the modules are arranged and combined with the distributor, they are placed in a muffle furnace for preheating at 650℃ for 3 hours, ensuring that the module temperature is not lower than 600℃ before being moved into the vacuum furnace casting chamber for casting. After casting, alloy ingots from the outer side, top corner, and center are taken respectively, and their upper and lower chemical compositions are analyzed. The test results are shown in Table 1.

[0039] Table 1 Chemical composition of alloy ingots in different parts, wt.%

[0040]

[0041]

[0042] 4.2 kg of each from the upper, middle, and lower parts of different alloy ingots were used for casting test bars to examine the consistency of their mechanical properties. The casting process was as follows: high-temperature refining at 1550℃ for 3 min, casting at 1500℃, preheating of the mold shell at 900℃, and sand-buried cooling. After heat treatment (1210℃ for 4 h, air cooling), the test bars were processed into standard cylindrical tensile and creep rupture test bars, and room temperature tensile and 975℃ / 225MPa creep rupture performance tests were conducted. The performance test results are shown in Table 2.

[0043] Table 2 Mechanical properties of alloy ingots at different locations

[0044]

[0045] It can be seen that the high-W nickel-based superalloy K465 produced by the engineering preparation method of this invention has a uniform chemical composition, stable mechanical properties, and high engineering application value.

Claims

1. A method for homogenizing and preparing a homogeneous high-W nickel-based superalloy K465, characterized in that: The preparation method includes the following steps: (1) The content of Al, Ti and W is designed according to the chemical composition of the high W nickel-based high temperature alloy K465. The ratio of (Al+Ti) to W should be in the range of 0.76~0.80 to avoid the precipitation of a large amount of large W-rich phase and eutectic structure in the alloy ingot; (2) Alloy smelting: Ultra-high temperature melt treatment and low temperature refining are carried out in sequence to ensure uniform melt composition; wherein: the ultra-high temperature melt treatment temperature is not lower than 1500℃, and the low temperature refining temperature is between 1380 and 1420℃. (3) Assemble the casting module: According to the number of alloy ingots to be prepared, it is divided into several 4x4 module units. The module unit consists of 4 30mm thick mold tubes and 12 20mm thick mold tubes. The height of the mold tube is 1000mm. The 30mm thick mold tubes are located in the center and four corners, and the 20mm thick mold tubes are located in other positions on the outside. The bottom of the mold tube is sealed with a graphite pad, and the top is equipped with an 80-120mm high aluminum silicate riser. The casting rate is controlled by a casting distributor. The casting rate distribution is as follows: the diameter of the casting port corresponding to the 20mm thick mold tube is 13mm, and the diameter of the casting port corresponding to the 30mm thick mold tube is 10mm. (4) Place the assembled module into a muffle furnace for preheating treatment; (5) Casting: The melt temperature is 1420℃ during casting. After casting, the melt is kept in the furnace for 5 to 10 minutes before being taken out of the furnace. This will allow for the batch production of homogeneous high-W nickel-based high-temperature alloy ingots.

2. The homogenization preparation method of homogeneous high-W nickel-based superalloy K465 according to claim 1, characterized in that: The chemical composition of the high-W nickel-based superalloy K465, by weight percentage, is as follows: C: 0.13~0.2%, Cr: 8.0~9.5%, Co: 9.5~10.5%, W: 9.5~11.0%, Mo: 1.2~2.4%, Al: 5.1~6.0%, Ti: 2.0~2.9%, Nb: 0.8~1.2%, Zr≤0.04%, B≤0.035%, Ni balance.

3. The homogenization preparation method of homogeneous high-W nickel-based superalloy K465 according to claim 1, characterized in that: In step (4), the preheating process parameters are: preheating temperature 650℃ and preheating time 3h, so as to ensure that the temperature of the mold tubes at different positions in the module is basically the same.

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