CN100482824C - Single crystal high temperature nickel base alloy containing rhenium and its preparing process - Google Patents

Abstract

The invention relates to the preparation technology of a rhenium-containing single-crystal superalloy and heat treatment, in particular to a rhenium-containing nickel-based single-crystal superalloy and a preparation process thereof. In terms of weight percentage, the alloy composition includes: C 0.12～0.18, Cr 4.3～5.6, Al 5.6～6.3, Co 8.0～10.0, Mo 0.8～1.4, W 7.7～9.3, Nb 1.4～1.8, Ta 3.5～4.5, Re 3.5 to 4.5, Y 0.001 to 0.005, RE 0.005 to 0.025, more than Ni. Use a vacuum induction furnace to melt the master alloy, prepare single crystal blades or test rods in the temperature gradient range of the single crystal growth furnace 60K/cm～100K/cm, and the single crystal growth rate within the range of 2～10mm/min; then carry out solid melting and homogenization treatment, high temperature aging treatment, low temperature aging treatment. Adopting the present invention has the following advantages: the material has high enduring strength limit and creep limit; good high temperature oxidation resistance and thermal corrosion resistance, high thermal stability; good tensile and long-lasting plasticity; good thermal fatigue and mechanical fatigue resistance ; The heat treatment window is wide, and the solid solution treatment is easy to control; the preparation process of the invention is reasonable, and the production efficiency is high.

Description

A rhenium-containing nickel-based single crystal superalloy and its preparation process

technical field

The invention relates to the preparation technology of rhenium-containing single crystal superalloy and heat treatment, etc., and particularly provides a rhenium (Re) nickel-based single crystal high-temperature turbine working blade material with high creep resistance and long high-temperature durability and a process for preparing the material system.

Background technique

With the increase of the temperature before the turbine of the engine, higher and higher requirements are put forward for the high temperature resistance and strength performance level of the turbine blades, especially the high pressure turbine blades. Since the 1980s, the development of single crystal superalloy turbine blades has become one of the key technologies in the design and manufacture of modern aero-engines. At present, the aeroengines F119 (US), F120 (US), GE90 (US), EJ200 (British, German, Italian, Spanish), M88-2 (French), P2000 (Russian) with a thrust-to-weight ratio of 10 have all selected A single crystal alloy is used as the blade material. The second-generation and third-generation single-crystal alloys that have been researched and applied successively have a temperature-bearing capacity that is about 30°C and 60°C higher than that of the first-generation single-crystal superalloy. The fourth-generation single-crystal alloy RR3010, which has appeared in recent years, has a temperature-bearing capacity of 1180°C and is used in the latest Trent engine developed by the British RR company.

American Howmet Company, GE Company, PCC Company, Allison Company, British RR Company, French CNECMA Company, Russian SALUT Engine Factory and other manufacturers all produce large quantities of single crystal parts, including turbine working blades, guide vanes, inner and outer rings of blades , nozzle segments, sealing blocks, fuel nozzles, etc., for military and commercial aircraft, tanks, ships, industrial gas turbines, missiles, rockets, space shuttles, etc. The application range of single crystal superalloys is becoming more and more extensive, especially the use of single crystal alloys to prepare turbine rotor blades has become the main trend in the development of advanced aero-engines.

Heat treatment has a significant impact on the durable strength of single crystal alloys. For example, in MC2 single crystal alloys, solution treatment only needs to be kept at 1300°C for 3 hours. The first generation of single crystal superalloys, except PWA1480, are easier to homogenize deal with. The third generation single crystal superalloy contains a large amount of alloying elements, especially Ta and W, which promote the formation of (γ+γ′) eutectic phase, so the solidified structure without heat treatment contains quite a lot of (γ+ γ') eutectic. Experiments show that it is impossible to eliminate these eutectic phases by simple isothermal solution heat treatment, and complex heat treatment processes must be used to basically eliminate eutectic phases. For example: In order to completely eliminate these (γ+γ′) eutectics in CMSX-10M single crystal superalloy, it is first pretreated at 1337°C/3h, then raised to 1367°C at a rate of 3°C/h, and kept for 3 hours in air cooling. Erikson used 1366°C holding time for 30-35h during CMSX-10 solution heat treatment. Therefore, the heat treatment regime of single crystal alloys must be carefully studied in order to fully develop the potential of the alloy. The correct heat treatment system will enable the cubic γ′ phase to obtain the ideal creep strength, because it is necessary to promote a uniform deformation structure to ensure a low creep rate.

Contents of the invention

The object of the present invention is to provide a Re-containing single crystal superalloy and its preparation process, which are used for high-temperature turbine working blade materials that require high creep resistance and long high-temperature durability and a process system for preparing the material.

Technical scheme of the present invention is:

The present invention contains Re-containing nickel-based single crystal superalloy (hereinafter referred to as DD32) comprising the following alloy components (weight percent):

C 0.12～0.18, Cr 4.3～5.6, Al 5.6～6.3, Co 8.0～10.0, Mo 0.8～1.4, W 7.7～9.3, Nb 1.4～1.8, Ta 3.5～4.5, Re 3.5～4.5, Y 0.001～0.005, Ni Yu.

It also includes adding 0.005-0.025% RE (mixed rare earth). The allowable impurity and gas content ranges of the alloy of the present invention are shown in Table 1.

Table 1 DD32 single crystal impurity content (wt%)

Design principle of the present invention is as follows:

The invention mainly adds more aluminum to form a high volume fraction of γ' phase to increase its strength; the addition of Re has a great effect on the improvement of the temperature resistance of the single crystal alloy and the oriented alloy. Re mainly enters the γ matrix to form a short-range ordered Re atomic group with a size of ~1nm, which can effectively hinder the movement of dislocations, reduce the diffusion rate of alloying elements, prevent the coarsening of the γ′ phase, and increase the γ/γ′ mismatch Spend. In addition, about 20% of Re enters the γ′ phase, directly strengthening the γ′ phase. The addition of Re helps to reduce the grain defects and surface recrystallization of single crystal castings, and is also beneficial to the environmental resistance of the alloy. The addition of Re to the superalloy can effectively hinder the coarsening of the γ′ phase and increase the activation energy of the coarsening of the γ′ phase, thereby improving the high-temperature mechanical properties of the single crystal superalloy. By adding niobium to further increase the number of γ′ phases, improve the lattice mismatch of γ-γ′, enhance the strengthening effect of γ′ phase, and form γ″ phase to enhance its mechanical properties at room temperature and medium temperature; adding a certain amount of Carbon, on the one hand, strengthens the grain boundary, and on the other hand forms more carbides with tantalum, niobium, chromium, etc. to strengthen the alloy; alloying elements such as tungsten and molybdenum mainly play an important role in solid solution strengthening alloys, and the W+Mo content is An important parameter to increase the creep life, and the creep life increases with the increase of their content. Co has little effect on the thermal strength of the alloy, but it can significantly improve the plasticity of the alloy, and Co can improve the creep under high stress. Variable life. The addition of Y (200ppm) can significantly improve the oxidation resistance of single crystal alloys, and is also good for thermal fatigue performance. Adding RE to the alloy for microalloying is conducive to the refinement of dendrite structure and strengthening of grain boundaries, control The sulfur content in the alloy improves the durable life. The alloy sample of the invention is prepared by the internationally accepted directional solidification technology, which eliminates the transverse and longitudinal grain boundaries and improves the initial melting temperature of the alloy.

The preparation process of the Re-containing nickel-based single crystal superalloy of the present invention adopts a vacuum induction furnace to melt the master alloy, the temperature gradient of the single crystal growth furnace is in the range of 60K/cm-100K/cm, and the single crystal growth rate is in the range of 2-10mm/min Preparation of single crystal blades or test rods; then solution treatment at 1270-1300°C for 2-6 hours, followed by air cooling, followed by homogenization treatment at 1260-1290°C for 2-6 hours, followed by air cooling; then High temperature aging treatment is carried out in the range of 1100-1150°C for 3-6 hours, followed by low-temperature aging treatment in the range of 850-890°C for 16-36 hours, followed by air cooling.

The present invention has the following advantages:

1. The material obtained by the present invention has high endurance strength limit and creep limit.

2. The material obtained by the present invention has good high temperature oxidation resistance and thermal corrosion resistance, and high thermal stability.

3. The material obtained by adopting the present invention has good stretchability and long-lasting plasticity.

4. The material obtained by adopting the present invention has good thermal fatigue resistance and mechanical fatigue resistance.

5. The heat treatment window of the present invention is wide, and the solution treatment is easy to control.

6. The preparation process of the present invention is reasonable and the production efficiency is high.

7. Adopting the heat treatment system of the present invention can dissolve more than 99% of the as-cast γ′, and precipitate evenly distributed and regularly arranged fine (0.4-0.5 μm) cubic γ′ phases, and precipitate finer (～0.3 μm) phases on the γ matrix. μm) of the γ′ phase, and stabilize the single crystal structure, which is easy to control and enhances the effect of hindering dislocation movement, and improves the creep strength.

Description of drawings

Fig. 1 is a Larson-Miller (Larson-Miller) curve. The parameter P in the figure is a relational expression without specific meaning, T is temperature (K), and t is time (hour).

Detailed ways

The present invention is described in detail below by way of examples.

The experimental master alloy of the present invention is smelted in a ZG-0.025B vacuum induction furnace, and the sintered Ni-Re prefabricated block is placed at the bottom of the crucible, and then other elements are put in order. Vacuum up to the maximum vacuum before heating up, turn off the vacuum pump and fill with argon when the temperature rises to about 1300°C, continue to heat up until it is completely melted, then vacuumize, refine, and come out of the furnace. Cast into a master alloy ingot with a size of φ80×500mm, and then grind to remove scale and cut into suitable blocks for preparing single crystal samples.

The single crystal sample of the present invention is prepared on a ZGG-0.02 vacuum induction furnace by a spiral crystal selection method. The power of the heating system of the directional solidification furnace is 30KW, and it is heated by a low-voltage, high-current, high-purity graphite induction heating element. SCR is used to control the drawing rate, and the drawing rate of the crystallizer is steplessly adjustable within the range of 0.1-1000mm/min. The vacuum system consists of a diffusion pump and a front mechanical pump, the pumping rate is 30mm/min, and the working vacuum is 10 ^-5 Torr. The preparation of the directional solidification sample is carried out on the directional solidification furnace. The mold shell for the experiment is a corundum shell. The mold shell is placed on the copper water crystallizer, and the prepared master alloy is put into the CaO crucible, and the directional solidification furnace is evacuated. State, heating by power transmission, after the alloy is melted, measure the temperature of the alloy melt with a W-Re galvanic couple, cast at 1600°C, keep warm for 10 minutes, and pull at a predetermined speed to prepare an oriented sample.

Example 1

The composition of this example is shown in Table 2. The temperature gradient range of the single crystal growth furnace is 80K/cm, the single crystal growth rate is 4mm/min, and the sample is subjected to 1295°C/4h AC. +1150°C/4h AC.+850°C/24h AC. heat treatment, the properties of single crystal alloy are shown in Table 3 and Figure 1. The present invention cites that the mechanical property data of alloys such as DZ4, DZ22, Rene N4, DD3, SRR99 and DD6 are published publicly.

Table 2 Alloy composition, wt%

C Cr al co Mo Nb W Ta Re Y RE Ni 0.16 4.4 5.65 9.4 1.3 1.4 8.8 4.0 3.8 0.003 0.008 balance margin

Table 3 100 hours lasting strength/MPa

alloy 760°C 980°C 1100°C DD6 807 303 148 DD32 785 315 160

As shown in Fig. 1, the high temperature resistance of the DD32 single crystal alloy of the present invention has an advantage of 30°C under low stress conditions and 60°C under high stress conditions compared with the first generation single crystal alloy SRR99. At 980℃～1100℃, the durability strength is about 10MPa higher than that of the current domestic typical second-generation single crystal alloy DD6.

Example 2

The difference from Example 1 lies in the alloy composition of this example (shown in Table 4). The temperature gradient range of the single crystal growth furnace is 70K/cm, and the single crystal growth rate is 6mm/min. Heat treatment at 1285℃/4hAC.+1275℃/4hAC.+1100℃/4hAC.+870℃/24hAC. Compared with DZ4, DZ22, Rene N4 and DD3 alloys for durable strength, the results are shown in Table 5.

Table 4 Alloy composition, wt%

C Cr al co Mo Nb W Ta Re Y RE Ni 0.18 4.8 5.6 9.5 1.2 1.6 8.0 3.6 4.0 0.005 0.005 margin

Table 5 100-hour endurance strength of some alloys/MPa

alloy 760°C 800℃ 900°C 980°C 1000℃ 1040°C DZ4 804 677 353 206 181 142 DZ22 804 653 375 213 181 137 Rene N4 853 709 415 247 215 161 DD3 814 706 368 226 201 177 DD32 785 620 420 310 280 200

It can be seen from Table 5 that the durability strength of the DD32 single crystal alloy of the present invention above 900°C has a very obvious advantage over typical directional superalloys (DZ4, DZ22) and first-generation single crystal alloys (DD3, ReneN4).

Example 3

The difference from Example 1 is that the alloy composition of this example is shown in Table 6. The temperature gradient range of the single crystal growth furnace is 70K/cm, and the single crystal growth rate is 6mm/min. After 1290°C/4h AC.+1280 ℃/4hAC.+1100℃/4hAC.+870℃/24h AC. After heat treatment, the comparison results of tensile properties of DD32 single crystal and SRR99 at various typical temperatures are shown in Table 7. The tensile properties of DD32 single crystal at various typical temperatures below 900°C are not much different from those of SRR99, but the tensile strength at 1000°C and 1100°C has obvious advantages.

Table 6 Alloy composition, wt%

C Cr Al co Mo Nb W Ta Re Y RE Ni 0.14 5.0 5.65 9.4 0.98 1.8 7.8 4.4 3.6 0.006 0.02 balance margin

Table 7 Comparison of tensile properties of DD32 single crystal and SRR99 at various typical temperatures

Example 4

The difference from Example 1 is that the alloy composition of this example is shown in Table 8. The temperature gradient range of the single crystal growth furnace is about 80K/cm, after 1290°C/4h AC.+1280°C/4h AC.+1100°C /4hAC.+890°C/16h AC. After heat treatment, the creep results of DD32 single crystal at 1000°C are shown in Table 9; Table 10 shows the creep strength of some first-generation single crystals at 1000°C.

Table 8 Alloy composition, wt%

C Cr al co Mo Nb W Ta Re Y RE Ni 0.12 5.2 5.6 9.6 1.4 1.6 9.2 3.6 4.2 0.001 0.01 balance margin

The experimental master alloy is smelted in a vacuum induction furnace. The smelting crucible is a CaO crucible. The temperature measurement system is a W-Re galvanic couple and a JH-5 infrared photoconductive temperature/vacuum tester. The temperature measurement protection sleeve is coated with ZrO ₂ on the outside. (CeO stabilized) and BN Mo-Al ₂ O ₃ cermet tubes. The operation process is as follows: put carbon, nickel-boron intermediate alloy, chromium, tungsten, molybdenum, niobium alloy elements and nickel plate into the crucible; vacuumize the small current oven to remove the attached gas, when the vacuum reaches 10 ^-3 Pa , increase the power to melt the alloy; after the melting is completed, refine at 1600°C for 5-7 minutes, add Al and Al-Y intermediate alloys and mixed rare earth RE after power failure, conjunctiva, and membrane rupture, and then stir with high power. After stirring, power off to cool down, and high current impact The membrane is broken and cast into a master alloy ingot at 1450°C.

Table 9 Creep of DD32 single crystal under different stress conditions at 1000℃

t(h) 152.1MPa t(h) 186.4 MPa t(h) 215.8 MPa t(h) 245.3 MPa t(h) 343.4 MPa 10 0.70 20 0.25 10 0.25 6 0.90 2 1.00 20 0.85 50 0.40 20 0.50 10 1.2 3 2.00 50 1.00 100 0.55 50 1.8 20 1.65 4 3.00 100 1.20 150 0.80 70 2.00 30 2.15 6 4.00 200 1.50 200 1.20 100 3.60 40 3.10 7 5.00 300 1.85 250 1.70 110 5.00 50 5.00 8 6.00 400 2.20 300 2.40 124 7.50 55 7.00 10 8.75

Table 10 Creep strength of some single crystal alloys at 1000℃

alloy σ_0.1/100/MPa σ_0.2/100/MPa σ_1.0/100/MPa DD402 88 115 208 alloy σ_0.2/100/MPa - σ_1.0/100/MPa DD3 78.5 - 196

It can be seen from Table 9 and Table 10 that the DD32 single crystal alloy has very obvious advantages over the first generation single crystal alloy, and has excellent creep resistance.

Claims (2)

1. A rhenium-containing nickel-based single crystal superalloy, characterized in that the alloy composition includes: C 0.12-0.18, Cr 4.3-5.6, Al 5.6-6.3, Co 8.0-10.0, Mo 0.8-1.4, by weight percentage, W 7.7～9.3, Nb 1.4～1.8, Ta 3.5～4.5, Re 3.5～4.5, Y 0.001～0.003, RE 0.005～0.020%, Ni surplus. 2. According to the preparation process of rhenium-containing nickel-based single crystal superalloy according to claim 1, the master alloy is smelted in a vacuum induction furnace, which is characterized in that: the temperature gradient range of the single crystal growth furnace is 60K/cm～100K/cm, and the single crystal growth rate Prepare single crystal blades or test rods in the range of 2-10mm/min; then solid solution treatment in the range of 1270-1300°C for 2-6 hours, followed by air cooling, and then homogenization in the range of 1260-1290°C for 2-6 hours Chemical treatment followed by air cooling; then high temperature aging treatment at 1100-1150°C for 3-6 hours, followed by low-temperature aging treatment at 850-890°C for 16-36 hours, followed by air cooling.

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