阅读说明：本技术 一种mc碳化物晶须强化的定向凝固镍基高温合金及其制备方法 (MC carbide whisker reinforced directional solidification nickel-based high-temperature alloy and preparation method thereof ) 是由 于金江 孙晓峰 周亦胄 王新广 于 2020-11-30 设计创作，主要内容包括：本发明公开了一种MC碳化物晶须强化的定向凝固镍基高温合金及其制备方法,属于高温合金技术领域。该合金成分(wt.％)：C 0.1～1.0％,Cr 6.0～12.0％,Co 4.0～12.0％,Al 4.0～6.5％,W 6.0～12.0％,Mo 1.0～5.0％,Nb 1.0～5.0％,Ta 11.0～15.0％,B≤0.02wt.％,Ni余。制备方法：采用真空感应炉冶炼母合金,然后在定向凝固炉内真空度0.5Pa～10～(-3)Pa熔化合金,1500～1650℃时浇铸,保温10～20min后定向抽拉凝固得到定向凝固试样及叶片。本发明合金初熔温度高,综合性能优异,持久性能好,使用寿命长,合金成本低。(The invention discloses an MC carbide whisker reinforced directional solidification nickel-based high-temperature alloy and a preparation method thereof, belonging to the technical field of high-temperature alloys. The alloy composition (wt.%): 0.1-1.0% of C, 6.0-12.0% of Cr, 4.0-12.0% of Co, 4.0-6.5% of Al, 6.0-12.0% of W, 1.0-5.0% of Mo, 1.0-5.0% of Nb, 11.0-15.0% of Ta, less than or equal to 0.02 wt% of B and the balance of Ni. The preparation method comprises the following steps: smelting mother alloy in a vacuum induction furnace, and then in a directional solidification furnace, keeping the vacuum degree at 0.5 Pa-10 ‑3 Pa melting alloy, casting at 1500-1650 ℃, preserving heat for 10-20 min, and then performing directional drawing solidification to obtain a directional solidification sample and a blade. The alloy of the invention has high initial melting temperature, excellent comprehensive performance and durabilityGood performance, long service life and low alloy cost.)

1. A MC carbide whisker reinforced directional solidification nickel-based superalloy is characterized in that: the alloy comprises the following chemical components in percentage by weight:

0.1-1.0% of C, 6.0-12.0% of Cr, 4.0-12.0% of Co, 4.0-6.5% of Al, 6.0-12.0% of W, 1.0-5.0% of Mo, 1.0-5.0% of Nb, 11.0-15.0% of Ta and the balance of Ni.

2. The MC carbide whisker reinforced directionally solidified nickel-base superalloy as in claim 1, wherein: the alloy also contains B element, B≤0.02wt.％。

3. The method for preparing the MC carbide whisker reinforced directional solidification nickel-base superalloy according to claim 1 or 2, wherein the method comprises the following steps: the method comprises the following steps:

1) smelting the master alloy by using a vacuum induction furnace, wherein a CaO or MgO crucible is selected as a smelting crucible;

2) preparing directional solidification alloy on a directional solidification furnace, comprising the following steps: putting the master alloy prepared in the step (1) into a CaO or MgO crucible, and keeping the vacuum degree at 5 multiplied by 10^-1～10^-3Melting the alloy under the Pa condition, casting at 1500-1650 ℃, and carrying out directional drawing solidification after heat preservation for 10-20 min.

4. The method of making the MC carbide whisker reinforced directionally solidified nickel-base superalloy as in claim 3, wherein: the process of smelting the master alloy in the step (1) comprises the following steps: firstly, according to the alloy components, other raw materials (carbon, nickel, chromium, cobalt, tungsten, molybdenum, niobium and tantalum alloy elements) except aluminum are filled into a crucible, and the vacuum degree is 5 multiplied by 10^-1～10^－2Melting the alloy between Pa; after melting, refining at 1550-1650 ℃ for 1-5 min, and then cutting off power, forming a film and breaking the filmAdding aluminum into the film, uniformly stirring, and casting into a master alloy ingot at 1450-1600 ℃.

5. The method of making the MC carbide whisker reinforced directionally solidified nickel-base superalloy as in claim 4, wherein: in the step (1), when B is contained in the alloy composition, B is charged into the crucible in the form of a nickel-boron intermediate alloy.

Technical Field

The invention relates to the technical field of high-temperature alloys, in particular to an MC carbide whisker reinforced directional solidification nickel-based high-temperature alloy and a preparation method thereof.

Background

The nickel-based high-temperature alloy has excellent high-temperature oxidation resistance and high-temperature corrosion resistance, hardly oxidizes at the temperature of below 500 ℃, is not easily corroded by moisture, water and certain salt aqueous solutions at normal temperature, and has better oxidation resistance than the cobalt-based high-temperature alloy. Due to the appearance of jet engines, the application of vacuum smelting technology, the progress of alloying theory research and the innovation of process technology, casting high-temperature alloy is developed rapidly from the beginning of sixties, and various types of alloy are widely applied to various engines. However, as the strength of the cast superalloy is improved, the plasticity is reduced, and the elongation rate before creep rupture is obviously reduced, mainly because creep cracks are initiated and propagated along the grains. Grain boundaries in the turbine blade structure, particularly transverse grain boundaries perpendicular to the stress axis, are weak links, and under the action of high temperature and stress, cracks first initiate on the transverse grain boundaries perpendicular to the stress axis and then develop to complete fracture. It is therefore necessary to strengthen grain boundaries or eliminate transverse grain boundaries to extend creep life, which has led to the development of directionally solidified superalloys.

In the directionally solidified high-temperature alloy blade, on one hand, grain boundaries parallel to the stress axial direction are directionally arranged and are parallel to the solidification direction, so that the grain boundaries do not become fracture sources any more; on the other hand, in the directional solidification process, the solidification direction of the alloy is the [001] direction of the preferred growth of low modulus, so that the thermal fatigue resistance of the part is obviously improved; meanwhile, the blade with the columnar crystal structure, which is prepared by adopting the directional solidification technology and has the growth direction parallel to the stress axis, is usually added with crystal boundary strengthening elements such as C, Ta, B, Zr, Hf and the like to strengthen the crystal boundary state, so that the transverse plasticity and the thermal fatigue performance of the part are also improved.

Oriented eutectic autogenous technology has been the focus of attention in the development of nickel-based superalloys. Directional eutectic superalloys are alloys that grow simultaneously with directional whiskers or lamellar strengthening phases from the alloy melt under directional solidification conditions and that remain regularly arranged after solidification. The reinforcement phase and the matrix phase are formed simultaneously during the solidification process, so the composite material is also called as a primary composite material. Lemkey et Al demonstrated for the first time that 11% Al by volume was obtained by directional solidification₃Ni oriented crystalThe aluminum-based eutectic composite material which needs to be a strengthening phase has better high-temperature strength and structural stability, and the feasibility of the application of the material in the field of high-temperature components is confirmed by the experimental result on Ni-based and Co-based eutectic alloys.

The directional crystal whisker with high strength and high modulus at high temperature is used as a reinforcing phase, and the high-temperature nickel-based or iron-based high-temperature alloy is used as a matrix, so that a new material with higher strength and modulus at higher temperature can be prepared, and the method is an important direction for developing high-temperature component materials such as gas turbine blades, combustion chambers and the like, and is one of the most active fields of research and development of the directional eutectic high-temperature alloy at present. When the eutectic high-temperature alloy is used for manufacturing turbine blades (the working temperature is more than 900 ℃, and the stress can reach 300MPa), the eutectic high-temperature alloy has great advantages compared with common cast high-temperature alloy, the high-strength reinforcing phase is directionally compounded with the plastic matrix, and the periodic alternate arrangement can obtain ideal combination of strength and plasticity; meanwhile, the extension direction of the strengthening phase is consistent with the working load direction, and the strengthening effect is exerted to the maximum extent. Because the eutectic compound directly grows from the alloy melt under the condition close to thermodynamic equilibrium, the structural stability of the eutectic compound can be kept to a higher temperature, which exceeds the limit temperature of solid solution strengthening, precipitation strengthening and grain boundary strengthening of common alloys by 0.6-0.7 Tm, and the use temperature of the eutectic compound is increased to 0.85-0.9 Tm. Various famous aircraft engine companies around the world have focused on developing high temperature eutectic composite engine blades.

Disclosure of Invention

The invention aims to provide an MC carbide whisker reinforced directional solidification nickel-based high-temperature alloy and a preparation method thereof. .

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

the MC carbide whisker reinforced directional solidification nickel-based high-temperature alloy comprises the following chemical components in percentage by weight:

0.1-1.0% of C, 6.0-12.0% of Cr, 4.0-12.0% of Co, 4.0-6.5% of Al, 6.0-12.0% of W, 1.0-5.0% of Mo, 1.0-5.0% of Nb, 11.0-15.0% of Ta and the balance of Ni.

The alloy may also contain B element, B ≦ 0.02 wt.%.

The preparation method of the MC carbide whisker reinforced directional solidification nickel-based superalloy comprises the following steps:

1) smelting the master alloy by using a vacuum induction furnace, wherein a CaO or MgO crucible is selected as a smelting crucible;

2) preparing directional solidification alloy on a directional solidification furnace, comprising the following steps: putting the master alloy prepared in the step (1) into a CaO or MgO crucible, and keeping the vacuum degree at 5 multiplied by 10^-1～10^-3Melting the alloy under the Pa condition, casting at 1500-1650 ℃, and carrying out directional drawing solidification after heat preservation for 10-20 min.

The process of smelting the master alloy in the step (1) comprises the following steps: firstly, according to the alloy components, other raw materials (carbon, nickel, chromium, cobalt, tungsten, molybdenum, niobium and tantalum alloy elements) except aluminum are filled into a crucible, and the vacuum degree is 5 multiplied by 10^-1～10^－2Melting the alloy between Pa; and after melting, refining at 1550-1650 ℃ for 1-5 min, then powering off, forming a film, breaking the film, adding aluminum, uniformly stirring, and casting at 1450-1600 ℃ to obtain a master alloy ingot.

In the step (1), when B is contained in the alloy composition, B is charged into the crucible in the form of a nickel-boron intermediate alloy.

The alloy of the invention has the following design mechanism:

1. the invention mainly adds more aluminum to form a gamma' phase with high volume fraction to improve the strength; by adding a proper amount of niobium and tantalum, the volume fraction of the gamma ' phase can be increased, the lattice mismatching degree of gamma-gamma ' is improved, the strengthening effect of the gamma ' phase is further enhanced, and meanwhile, a gamma ' phase is formed to enhance the room temperature and middle temperature performance of the gamma ' phase. A small amount of carbon and boron are added into the alloy, so that the grain boundary is strengthened on one hand; on the other hand, carbon forms MC carbide with niobium, tantalum and the like, and generates a crystal whisker in the [001] direction by coupling under the condition of directional solidification, thereby improving the mechanical property of the alloy. Alloy elements such as chromium, cobalt, tungsten, molybdenum and the like can also be subjected to solid solution strengthening to improve the volume fraction of the gamma' phase; the alloy has low boron content and no titanium, so that the alloy has high initial melting temperature and good cold and hot fatigue performance; in addition, the alloy sample is prepared by adopting a directional solidification technology, so that a transverse crystal boundary is eliminated, and the strength and the initial melting temperature of the alloy are improved.

The invention has the following advantages:

1. the alloy of the invention has high initial melting temperature. Differential Thermal Analysis (DTA) showed: the initial melting temperature of the alloy is 1362 ℃, which is higher than that of the alloys DZ411, DZ417G and DZ422, and reaches 65 ℃, 76 ℃, 55 ℃, which is also higher than that of the alloys DZ40M, K640, and the like.

2. The alloy of the invention has good oxidation resistance. The alloy of the invention reaches the complete oxidation resistance level at 1100 ℃.

3. The invention has good cold and hot fatigue performance. The crack propagation rate of the alloy of the invention does not exceed 1/2 of DZ 40M.

4. The alloy of the invention has good processing property. The alloy can be cast into a zero-allowance directional solidification blade with a complex inner cavity and the wall thickness of which is as small as 0.4 mm.

5. The alloy of the invention has low cost. The alloy of the invention does not contain precious elements such as rhenium, hafnium and the like, and the price is far lower than that of the second generation directional high-temperature alloy.

6. The alloy of the invention has high strength. The alloy of the invention has much higher tensile and permanent strength than the typical second generation directional high temperature alloy at all temperatures.

7. The alloy of the invention has wide application prospect in turbine blades of military high thrust-weight ratio aircraft engines or land industrial gas turbines.

Drawings

FIG. 1 shows the microstructure of MC carbide whisker reinforced directionally solidified alloy.

Detailed Description

Example 1

The alloy composition of the present example is shown in Table 1:

table 1 example 1 alloy chemistry (wt.%)

	C	Cr	Co	Al	W	Mo	Nb	Ta	B	Ni
											Example 1	0.1	12.0	4.0	6.5	6.0	1.0	5.0	11.0	0.01	Surplus

The master alloy for the experiment is smelted by a vacuum induction furnace, a CaO crucible is selected as a smelting crucible, a temperature measuring system is a W-Re galvanic couple and a JH-5 type infrared light-guide temperature/vacuum degree tester, and a temperature measuring protective sleeve is a ZrO coated outer layer₂Mo-Al of BN₂O₃A cermet tube. The operation process is as follows: putting carbon, nickel-boron intermediate alloy, chromium, tungsten, molybdenum and niobium alloy elements and a nickel plate into a crucible; vacuumizing, drying the crucible with low power (10KW) to remove attached gas, and increasing power to melt the alloy when the vacuum degree reaches 0.5 Pa; after melting, refining at 1550 +/-10 ℃ for 5min, cutting off power, forming films and breaking films, adding Al, then stirring at high power (50KW), cutting off power and cooling after stirring, breaking films at high power (40KW), and casting into master alloy ingots at 1600 +/-10 ℃; the preparation of the directional solidification sample is carried out on a directional solidification furnace, the experimental mould shell is a corundum shell, the mould shell is placed on a water-cooled copper crystallizer, the prepared master alloy is placed in a CaO crucible, the directional solidification furnace is pumped into a vacuum state, when the vacuum degree reaches 0.1Pa, the mould shell is electrified and heated, after the alloy is melted, the temperature of an alloy melt is measured by a W-Re galvanic couple, the directional casting is carried out at 1500 +/-10 ℃, the temperature of the mould shell is the same as the casting temperature, after the heat preservation is carried out for 20 minutes, the drawing is carried out at a preset speed (0.8mm/min), the directional crystallization sample is prepared, and the microstructure of the MC carbide whisker reinforced directional solidification alloy is shown as figure 1.

The initial melting temperature of the alloy of the invention is 1362 ℃, which is higher than that of the high-temperature alloys DZ411, DZ417G and DZ422 respectively to 65 ℃, 76 ℃, 55 ℃, which is also higher than that of the alloys DZ4125 and K640, and the melting temperature range of the turbine blade material is shown in Table 2.

TABLE 2

The alloy of the invention has good oxidation resistance, and the oxidation weight gain rate of 1100 ℃ is 0.035g/m²h, toTo a complete oxidation resistance level. The alloy has good cold and hot fatigue performance, and the crack propagation rate does not exceed 1/2 of DZ 40M.

The alloy of the invention has high strength. The tensile properties of the turbine blade material at both typical temperatures of 20 c and 900 c are shown in table 3, with the example 1 alloy being the highest of several typical guide blade materials, above 50% strength of the DZ40M and K640 alloys, and only less plastic than the DZ40M alloy.

Table 3 comparison of strength of example 1 alloy with existing alloy

Example 2

The difference from example 1 is that the alloy composition of this example is shown in table 4:

table 4 example 2 alloy chemistry (wt.%)

	C	Cr	Co	Al	W	Mo	Nb	Ta	B	Ni
											Example 2	1.0	8.0	12.0	4.0	12.0	5.0	1.0	15.0	0.004	Surplus

A master alloy for a vacuum induction furnace smelting experiment is adopted, a MgO crucible is selected as a smelting crucible, a temperature measuring system is a W-Re couple and a JH-5 type infrared light-guide temperature/vacuum degree tester, and a temperature measuring protective sleeve is Mo-Al coated with CeO and BN on the outer layer₂O₃A cermet tube. The operation process is as follows: putting carbon, nickel-boron intermediate alloy, chromium, cobalt, tungsten, molybdenum and niobium alloy elements and a nickel plate into a crucible; vacuumizing, drying the crucible with low power (20KW) to remove attached gas, and increasing power to melt the alloy when the vacuum degree reaches 0.1 Pa; after melting, refining at 1650 +/-10 deg.C for 7min, cutting off power, filming and breaking film, adding Al alloy, stirring at 70KW, cutting off power, cooling, breaking film at 60KW, and casting at 1450 +/-10 deg.C to obtain mother alloy ingot.

The preparation of the directional solidification sample is carried out on a directional solidification furnace, a mould shell for experiments is a corundum shell, the mould shell is placed on a water-cooled copper crystallizer, the prepared master alloy is filled into an MgO crucible, and the directional solidification furnace is pumped into a vacuum state; when the vacuum degree reaches 0.1Pa, the alloy is electrified and heated, after the alloy is melted, the temperature of the alloy melt is measured by a W-Re galvanic couple, casting is carried out at 1500 ℃ plus or minus 10 ℃, the temperature of the mould shell is the same as the casting temperature, after heat preservation is carried out for 15 minutes, drawing is carried out at a preset speed (0.5mm/min), and the directional crystallization sample is prepared. The 100h endurance strength of the alloy is shown in Table 5, compared to the performance of the DZ40M, K640 and K403 alloys (Table 6).

As shown in Table 5 for the turbine blade material endurance life, the inventive alloy endurance life is highest in Table 5. The 100-hour endurance strength of the alloy is 2-3 times that of the DZ40M and K640 alloys.

TABLE 5 comparison of the durability of the alloy of example 2 with that of the prior art alloy

Table 6 comparison of the properties of the alloy of example 2 with those of the prior art alloys

Example 3

The alloy composition of the present example is shown in Table 7:

table 7 example 3 alloy chemistry (wt.%)

	C	Cr	Co	Al	W	Mo	Nb	Ta	B	Ni
											Example 3	0.06	10.0	10.0	5.5	9.0	3.0	3.0	13.0	0.02	Surplus

The master alloy for the experiment is smelted by adopting a vacuum induction furnace, a CaO crucible is selected as a smelting crucible, and W-Re galvanic couple and JH-5 type infrared light guide temperature/vacuum are adopted as temperature measuring systemsThe measuring temperature protective sleeve of the hollow degree tester is coated with ZrO₂Mo-Al of BN₂O₃A cermet tube. The operation process is as follows: putting carbon, chromium, cobalt, tungsten, molybdenum, niobium and tantalum alloy elements and a nickel plate into a crucible; vacuumizing, baking the crucible at low power (15KW) to remove attached gas, and when the vacuum degree reaches 10^－2When Pa, increasing power to melt the alloy; after melting, refining at 1600 +/-10 ℃ for 5min, cutting off power, forming films and breaking films, adding Al ingots, stirring at high power (60KW), cutting off power and cooling after stirring, breaking films at high power (50KW), and casting into master alloy ingots at 1550 +/-10 ℃; the preparation of the directional solidification sample is carried out on a directional solidification furnace, the experimental mould shell is a corundum shell, the mould shell is placed on a water-cooled copper crystallizer, the prepared master alloy is put into a CaO crucible, the directional solidification furnace is pumped into a vacuum state, and when the vacuum degree reaches 10^－2And when Pa, transmitting electricity for heating, after the alloy is melted, measuring the temperature of the alloy melt by using a W-Re galvanic couple, casting at 1550 +/-10 ℃, keeping the temperature of the mould shell the same as the casting temperature for 10 minutes, and drawing at a preset speed (1mm/min) to prepare the directional sample. The melting temperature range of example 3 is compared with other superalloys in Table 8. Example 3 was compared to DZ40M, K640, K403, and DZ4 alloys (Table 9) for performance and alloy 100h endurance strength is shown in Table 10.

Table 8 comparison of the melting temperature ranges of the alloy of example 3 with those of the prior art alloys

TABLE 9 comparison of the properties of the alloy of example 3 with those of the prior art alloys

TABLE 10 100h proof strength of the alloy of example 3 with the prior art alloy