High-temperature alloy material and preparation method thereof

Abstract

The invention discloses a high-temperature alloy material which is composed of 0.022 wt% of C, 0.0056 wt% of Cr, 98.41 wt% of Ni, 14.29 wt% of Co, 0.175 wt% of Al, 1.72 wt% of Ti, 4.99 wt% of Nb, 0.0037 wt% of B, 0.3 wt% of Si, 0.012 wt% of Mn, 0.0011 wt% of P, 0.001 wt% of S, 0.025 wt% of Cu and the balance Fe, a Laves phase exists at the grain boundary of alloy grains, and the volume fraction of the Laves phase in the whole alloy is 1-2%. The alloy bar has excellent combination durability and is free of notch sensitivity. And compared with other methods, the process has the advantages of convenience, flexibility and low cost.

Description

Technical Field

[0001] The invention belongs to the field of metal material manufacturing, and specifically relates to a high-temperature alloy material and a preparation method thereof. Background Art

[0002] The operating temperature of Fe-Ni-Co-Nb based precipitation hardening deformable high-temperature alloy is below 650 ℃. This type of alloy has high strength, high thermal fatigue resistance, low expansion coefficient and excellent welding performance. It is widely used in the manufacture of turbine engine parts, such as high-pressure compressor rear casing, load-bearing ring, thermal insulation ring, combustion chamber sealing ring, etc. It is also extended to gun barrels, artillery parts, glass-metal sealing materials, measuring tools and molds, and components for high-pressure hydrogen environments.

[0003] Since the Cr content of this alloy is very low, there is a tendency for stress to accelerate grain boundary oxidation brittleness, so the alloy is extremely sensitive to notch brittleness. The original intention of the design of Fe-Ni-Co-Nb-based high-temperature alloys was to increase the Si content so that more granular Laves phases would precipitate during the thermal deformation process to eliminate notch endurance sensitivity and ensure endurance performance. However, this type of alloy bar has often shown unqualified combined endurance performance, which is mainly reflected in the problems of short endurance life and notch sensitivity. Despite a lot of research, it has not been completely solved, which greatly limits the application prospects of this alloy. Summary of the invention

[0004] The purpose of the present invention is to solve the problem of notch sensitivity in Fe-Ni-Co-Nb-based high-temperature alloy bars, and to provide a high-temperature alloy material and a preparation method thereof by changing the heat treatment process. The specific technical scheme is as follows: A high-temperature alloy material comprises: 0.022wt% C, 0.0056wt% Cr, 98.41wt% Ni, 14.29wt% Co, 0.175wt% Al, 1.72wt% Ti, 4.99wt% Nb, 0.0037wt% B, 0.3wt% Si, 0.012wt% Mn, 0.0011wt% P, 0.001wt% S, 0.025wt% Cu and the balance Fe. A Laves phase exists at the grain boundary of the alloy, and the volume fraction of the Laves phase in the whole alloy is 1-2%.

[0005] The volume fraction of the Laves phase in the whole alloy is 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, or can be a value within a numerical range consisting of any two of the above specific values ​​as endpoints; The Laves phase is in the form of short rods or / and particles.

[0006] When the Laves phase is in the form of short rods, its aspect ratio is 3:1-5:1; when the Laves phase is in the form of particles, its particle size is about 2-3 μm.

[0007] Preferably, when the Laves phase is in the form of short rods, its aspect ratio is 3:1, 4:1, 5:1 or can be a value within a numerical range consisting of any two of the above specific values ​​as endpoints; when the Laves phase is in the form of particles, its particle size is about 2 μm, 2.5 μm, 3 μm or can be a value within a numerical range consisting of any two of the above specific values ​​as endpoints; The short rod-shaped Laves phase has a length of 7-9 μm and a diameter of 1-3 μm.

[0008] Preferably, the length of the short rod-shaped Laves phase is 7 μm, 8 μm, 9 μm, or a value within a numerical range consisting of any two of the above specific values ​​as endpoints; the diameter is 1 μm, 2 μm, 3 μm, or a value within a numerical range consisting of any two of the above specific values ​​as endpoints; A method for preparing a high-temperature alloy material comprises the following steps: Step 1: The basic bar is obtained by hot processing. The specific processing technology is as follows: the steel ingot is first forged and then hot processed into the required basic bar by a fast forging machine or a rolling mill; Step 2: pretreat the base rod by keeping it at 940-960°C for not less than 1h, and then air-cool; preferably, the pretreatment temperature is 940-960°C, and the holding time is 1-10 hours; in some embodiments, the pretreatment temperature is 940°C, 950°C, 960°C or can be a value within the numerical range formed by any two of the above specific values ​​as endpoints; the holding time is 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h or can be a value within the numerical range formed by any two of the above specific values ​​as endpoints.

[0009] Step 3: Perform standard solution aging treatment on the rod obtained in step 2. The treatment process is to keep it at 980℃±15℃ for 1h and then air cool it, then keep it at 720℃±10℃ for 8h, reduce the temperature in the furnace to 620℃±10℃ within 2 hours, keep it at 620℃±10℃ for 8h and then air cool it, and then process it into a notched durable rod.

[0010] Furthermore, the bar in step 1 is processed by hot working methods such as forging and rolling.

[0011] Furthermore, the pretreatment in step 2 is performed using an electric furnace or an atmosphere furnace, and air cooling is performed after the pretreatment is completed.

[0012] Furthermore, the pretreatment temperature in step 2 is 940-960°C, and the holding time is ≥1h. At the same time, the soaking time is considered according to the furnace load, cross-section thickness, etc.

[0013] Furthermore, in step 3, it is necessary to process into a notched durability test bar according to relevant technical standards.

[0014] The technical principle of the present invention is: the precipitation phase at the grain boundary of the Fe-Ni-Co-Nb-based high-temperature alloy will be enriched with alloy elements such as Cr and Nb, and the corresponding matrix near it will lack these necessary solid solution elements, which will reduce the strength of the alloy, improve the plasticity, and cause stress relaxation, which is conducive to eliminating the notch sensitivity of the material; the precipitation phase can increase the resistance to grain boundary sliding, improve the grain boundary bonding force, and thus improve the notch sensitivity of the material; at the same time, the pinning effect of the precipitation phase on the grain boundary can refine the grains, improve the plasticity of the alloy, and reduce the notch sensitivity; the precipitation phase can also reduce the oxidation tendency of the grain boundary, prevent the diffusion of oxygen elements along the grain boundary, ensure the strength of the grain boundary, and reduce the notch sensitivity. However, excessive carbide precipitation will hinder dislocation sliding, making cracks easier to initiate and expand. In addition, the precipitation morphology of the precipitation phase also has an important influence on the notch sensitivity of the material. The larger short rod-shaped and needle-shaped precipitation phases will increase the stress concentration effect, which is not conducive to coordinating the deformation of the alloy as a whole. The smaller spherical precipitation phase can inhibit the initiation and expansion of cracks and reduce the notch sensitivity of the alloy.

[0015] The beneficial technical effect of the present invention is that by pre-treating the alloy at low temperature, the Laves phase is supplemented and precipitated to ensure that the size and quantity of the Laves phase are within a reasonable range. After normal solution aging, the alloy bar has excellent combined durability and no notch sensitivity. Compared with other methods, the process has the advantages of convenience, flexibility and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a tissue photograph of the product obtained in Example 1 of the present invention; Figure 2 This is a tissue photograph of the product obtained in Example 2 of the present invention; Figure 3 This is a tissue photograph of the product obtained in Example 3 of the present invention. DETAILED DESCRIPTION Example 1

[0017] The Fe-Ni-Co-Nb based high temperature alloy rods were prepared by the following steps: (1) Referring to the raw material element contents listed in Table 1, a 250 mm Ø bar was obtained by rapid forging hot working.

[0018] (2) The forged bars are directly subjected to standard solution aging treatment, which is carried out by keeping the temperature at 980℃±15℃ for 1 h and then air cooling. Then, the temperature is kept at 720℃±10℃ for 8 h. The temperature in the furnace is reduced to 620℃±10℃ within 2 hours, and then the temperature is kept at 620℃±10℃ for 8 h and then air cooling.

[0019] (3) The heat-treated bars are processed into notch endurance test bars according to relevant technical standards.

[0020] A small amount of fine granular Laves phase is precipitated along the grain boundaries of the Fe-Ni-Co-Nb-based high-temperature alloy rod prepared by the above process. The volume fraction of the Laves phase is about 0.29%. Figure 1 The specimen combination has a short durability life and the fracture position is at the notch, which indicates notch durability sensitivity. The results of two parallel tests are shown in Table 2. Example 2

[0021] The Fe-Ni-Co-Nb based high temperature alloy rods were prepared by the following steps: (1) Referring to the raw material element contents listed in Table 1, a 250 mm Ø bar was obtained by rapid forging hot working.

[0022] (2) The rods are pretreated at 950 °C in a resistance furnace for 24 h and air-cooled to allow the Laves phase to precipitate and ensure that the amount of the Laves phase is within a reasonable range.

[0023] (3) The pretreated bars are subjected to standard solution aging treatment, which is carried out at 980℃±15℃ for 1 hour and then air-cooled. Then, the temperature is kept at 720℃±10℃ for 8 hours. The temperature in the furnace is reduced to 620℃±10℃ within 2 hours, and then kept at 620℃±10℃ for 8 hours and then air-cooled. (4) The heat-treated bars are processed into notch endurance test bars according to relevant technical standards.

[0024] The Fe-Ni-Co-Nb-based high-temperature alloy rod prepared by the above process precipitates an appropriate amount of short rod-shaped Laves phase along the grain boundary. The volume fraction of the Laves phase is about 1.9% according to statistics. Figure 2 The sample has good combined durability performance and no notch durability sensitivity. The results of two parallel tests are shown in Table 2. Example 3

[0025] The Fe-Ni-Co-Nb based high temperature alloy rods were prepared by the following steps: (1) Referring to the raw material element contents listed in Table 1, a 250 mm Ø bar was obtained by rapid forging hot working.

[0026] (2) The rods are pretreated at 950 °C in a resistance furnace for 8 h and then air-cooled to allow the Laves phase to precipitate and ensure that the amount of the Laves phase is within a reasonable range.

[0027] (3) The pretreated bars are subjected to standard solution aging treatment, which is carried out at 980℃±15℃ for 1 h and then air-cooled. Then, the temperature is kept at 720℃±10℃ for 8 h. The temperature in the furnace is reduced to 620℃±10℃ within 2 hours, and then kept at 620℃±10℃ for 8 h and then air-cooled.

[0028] (4) The heat-treated bars are processed into notched endurance test bars in accordance with relevant technical standards.

[0029] The Fe-Ni-Co-Nb-based high-temperature alloy rod prepared by the above process precipitates an appropriate amount of granular Laves phase along the grain boundary. The volume fraction of the Laves phase is about 1.2% according to statistics. Figure 3 The sample has good combined durability performance and no notch durability sensitivity. The results of two parallel tests are shown in Table 2.

[0030] Table 1 Chemical composition of Fe-Ni-Co-Nb based high temperature alloy bars in Examples 1-3 element C Cr Ni Co Al Ti Fe wt% ≤0.06 ≤1.00 35.00~40.00 12.00~16.00 ≤0.15 1.30~1.80 Remain element Nb B Si Mn P S Cu wt% 4.30~5.20 ≤0.012 0.25~0.50 ≤1.00 ≤0.015 ≤0.015 ≤0.500 Table 2 Combination durability performance table in Examples 1-3 Combined endurance test specimen Durable life / h Fracture location Sectional shrinkage / % Elongation / % Example 1 (1) 15.24 gap 2.5 5.6 Example 1 (2) 9.98 gap 1.3 4.9 Example 2 (1) 77.29 smooth 14.0 39.8 Example 2 (2) 89.53 smooth 15.6 40.3 Example 3 (1) 203.38 smooth 19.0 59.1 Example 3 (2) 181.44 smooth 16.5 55.2

Claims

1. A high temperature alloy material, characterized in that: Its composition is: 0.022wt% C, 0.0056wt% Cr, 98.41wt% Ni, 14.29wt% Co, 0.175wt% Al, 1.72wt% Ti, 4.99wt% Nb, 0.0037wt% B, 0.3wt% Si, 0.012wt% Mn, 0.0011wt% P, 0.001wt% S, 0.025wt% Cu and the balance Fe. Laves phase exists at the grain boundaries of the alloy, and the volume fraction of the Laves phase in the whole alloy is 1-2%.

2. The high temperature alloy material according to claim 1, characterized in that: The Laves phase is in the form of short rods or / and particles.

3. The high temperature alloy material according to claim 2, characterized in that: When the Laves phase is in the form of short rods, its aspect ratio is 3:1-5:1; when the Laves phase is in the form of particles, its particle size is about 2-3 μm.

4. The high temperature alloy material according to claim 3, characterized in that: The dimensions of the short rod-shaped Laves phase are: 7-9 μm in length and 1-3 μm in diameter.

5. A method for preparing a high temperature alloy material, characterized in that: The following steps are involved: Step 1: The basic bar is obtained by hot processing. The specific processing technology is as follows: the steel ingot is first forged and then hot processed into the required basic bar by a fast forging machine or a rolling mill; Step 2: Pre-treat the base bar by keeping it at 940-960℃ for not less than 1h, and then air-cool it; Step 3: Perform standard solution aging treatment on the rod obtained in step 2. The treatment process is to keep it at 980℃±15℃ for 1h and then air cool it, then keep it at 720℃±10℃ for 8h, reduce the temperature in the furnace to 620℃±10℃ within 2 hours, and then keep it at 620℃±10℃ for 8h and then air cool it, and then process it into a notched durable rod.

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