CN1317095C - Single crystal and oriented columnar crystal compound crystallization blade and manufacturing method thereof - Google Patents

Abstract

The invention belongs to the category of high-temperature alloy precision casting, new materials and new technology fields, and specifically relates to a novel single crystal and directional columnar crystal compound crystallization blade and its manufacturing technology, which are used to develop and produce various types of materials and blades for directional solidification of high-temperature alloys . The blade is composed of two crystal types: oriented columnar crystals in the middle of the blade, and single crystals on the inlet and exhaust sides of the blade; the manufacturing method is to install the composite crystallizer on the crystallizer of the directional crystallization furnace, heat and melt The superheating degree is 100-150°C, the heating temperature of the mold heater is adjusted to 1500-1530°C in the upper zone, and 1550-1580°C in the lower zone; when the liquid alloy is poured into the mold, the mold starts to move downward, and the mold The speed of moving down is 5-7mm/min. The single crystal and oriented columnar crystal compound crystallization blade of the invention has high comprehensive performance, and its manufacturing method is simple and easy to implement, and can be applied to the production of gas turbine blades from superalloys.

Description

Single crystal and oriented columnar crystal compound crystallization blade and manufacturing method thereof

technical field

The invention belongs to the category of high-temperature alloy precision casting, new materials and new technology fields, and specifically relates to a novel single-crystal and directional columnar-crystal compound crystallization blade and its manufacturing technology, which are used to develop and produce various types of materials and blades for directional solidification of high-temperature alloys .

Background technique

Energy is the driving force of national economic construction. The research and development of high-performance gas turbines is an ideal power system required for sustainable development. All developed countries attach great importance to the research and development of gas turbines as a priority development strategy of science and technology, and have received key and rapid development. develop. In order to realize my country's energy sustainable development strategy, the country's energy policy has also made important adjustments, and it is necessary to vigorously develop clean coal-fired technology, develop oil and gas fields, and transport gas from west to east. Therefore, the country also regards gas turbines as a key development direction. One of the key technologies for the development of gas turbines is the turbine blade material and its manufacturing process. The development project is included in the plan and will be developed in the Metal Research Institute.

The development of gas turbine blade materials and processes usually absorbs the successful experience and technology of aeroengine blades. Therefore, advanced superalloy directional solidification technology is also included in the development of directional crystallization blades for industrial gas turbines. The directional crystallization of the blade means that the blade controls the heat flow direction during the solidification process, so that the crystal grows along the direction parallel to the principal stress axis of the blade, forming a directional growth columnar crystal structure. Because the directional crystal blade eliminates the transverse grain boundary, its performance and service life are significantly improved compared with the equiaxed crystal blade. If in the process of directional solidification, it is further tried to make only one grain grow directionally, and finally obtain a single crystal blade, its performance will be further improved, because the single crystal not only eliminates the transverse grain boundary, but also the vertical grain boundary does not exist.

However, blades for aero-engines are quite different in size from blades for industrial gas turbines. The former is generally only about 100mm in length and weighs about 250 grams; while the gas turbine blades are several hundred millimeters long and weigh at least a few kilograms. Due to the large size, heavy weight and high heat of gas turbine blades, it is quite difficult to develop the directional crystallization process for such large blades, and it is even more difficult to produce single crystal blades.

Contents of the invention

The purpose of the present invention is to provide a novel single crystal and oriented column crystal compound crystallization blade with high comprehensive performance and its manufacturing method.

Technical scheme of the present invention is:

A compound crystallization blade of single crystal and oriented columnar crystal, the blade is composed of two crystal types: oriented columnar crystal in the middle of the blade, and single crystal in the inlet and outlet sides of the blade.

The width of the single crystal may be 20-30mm.

The specific steps of the manufacturing method of the above single crystal and oriented columnar crystal compound crystallization blade are as follows:

1) Install the composite crystallizer on the crystallizer of the directional crystallization furnace. The composite crystallizer includes a single crystal selector, a directional column crystal selector and a directional solidification initial section, a single crystal selector, and a directional column crystal selector Both ends of the device are connected with the leaf crown and the initial section of directional solidification, and the number of single crystal selectors is two, which correspond to the inlet and exhaust sides of the blade respectively, and the directional column crystal selector corresponds to the middle part of the blade, and The solidification initiation section communicates with the directional crystallization furnace;

2) Process conditions:

The degree of superheat for heating and melting is 100-150°C, and the heating temperature of the mold heater is adjusted to 1500-1530°C in the upper zone and 1550-1580°C in the lower zone;

3) After the liquid alloy is poured into the mold, the mold starts to move downward, and under the above-mentioned directional solidification condition, the mold moves down at a speed of 5-7 mm/min.

4. The method for manufacturing a composite crystal blade of single crystal and oriented columnar crystal according to claim 3, characterized in that: the material of the blade is superalloy.

The single crystal selector may be a single crystal spiral selector.

The directional columnar crystal selector can be block or columnar, and the number of columnar crystal selectors is 3-5.

The beneficial effects of the present invention are:

1. The compound crystallization blade of single crystal and oriented columnar crystal of the present invention has higher comprehensive performance. The blade is composed of two crystal forms: oriented columnar crystals in the middle of the blade, and single crystals with a certain width at the inlet and outlet sides of the blade. The directional crystallization blade eliminates the transverse grain boundary, and its performance and service life are significantly improved compared with the equiaxed crystal blade. If only one grain is oriented to grow in the directional solidification process, and finally a single crystal blade is obtained, its performance will be further improved. Improvement, because the single crystal not only eliminates the transverse grain boundary, but also the vertical grain boundary does not exist. The organizational structure of the material determines the performance of the material, and the performance of the material reflects the state of its organization. The performance of the blade and its organizational structure together reflect the excellent quality of the blade.

2. The manufacturing method of the single crystal and oriented columnar crystal compound crystallization blade of the present invention is simple and easy to implement. This method adopts the corresponding directional solidification process conditions plus a specially designed "composite crystallizer", and installs the composite crystallizer on the crystallizer of the directional crystallization furnace. The composite crystallizer includes a single crystal selector and a directional column crystal selector. and the initial section of directional solidification, the two ends of the single crystal selector and the directional column crystal selector are connected with the leaf crown and the initial section of directional solidification, and the number of single crystal selectors is two, corresponding to the On the inlet and exhaust sides, the directional columnar crystal selector corresponds to the middle of the blade, and the directional solidification initiation section is connected to the directional crystallization furnace. The "composite crystallizer" plays a catalytic role in the single crystal and directional columnar crystal blades.

3. The present invention can be applied to the production of gas turbine blades from superalloys.

Description of drawings

Figure 1 is a photo of the comparison of the shape and size of the blades of the aero-engine and the industrial gas turbine.

Fig. 2 is a real photo of the directional crystallization large blade of the present invention.

Fig. 3 is a photograph of the single crystal and column crystal compound crystal structure of the blade of the present invention.

Fig. 4 is a schematic diagram of the sampling location for the performance test of the blade of the present invention.

Figures 5a-d are pictures of the distribution of dendrites at sampling sites 6, 5, 4, and 2 in Figure 4, respectively.

Figures 6a-d are pictures of the distribution of eutectic structures at sampling sites 6, 5, 4, and 2 in Figure 4, respectively.

Figures 7a-d are pictures of the distribution of carbides at sampling sites 6, 5, 4, and 2 in Figure 4, respectively.

Fig. 8 is a picture of a compound crystallization blade of single crystal and oriented columnar crystal with compound crystallizer of the present invention.

Fig. 9 is a schematic diagram of the structure of the compound crystallizer of the present invention and its connection with the blades.

FIG. 10 is a cross-sectional view along line A-A of FIG. 9 .

Fig. 11 is a sectional view along line B-B of Fig. 9 .

Fig. 12 is a photograph of a compound crystallization blade of single crystal and oriented columnar crystal in another compound crystallizer of the present invention.

Detailed ways

In this embodiment, the large blade (300 mm, weighing 2500 grams) of a 5000 series gas turbine is selected as the research object, and the research work is carried out. The material of the blade is directionally solidified superalloy GTD-111. Figure 1 shows a photo of the comparison of the shape and size of the aeroengine and the selected industrial gas turbine blades.

The present invention not only completes the research on the directional crystallization process of large blades, but also develops large blades with directional crystallization during the development process of the gas turbine blade directional crystallization process, as shown in FIG. 2 . At the same time, a new type of blade with single crystal and directional compound crystal has been successfully developed. The blade is composed of two crystal forms: oriented columnar crystals in the middle of the blade, and single crystals with a certain width (20-30 mm in this embodiment) at the inlet and outlet sides of the blade. Figure 3 shows the crystalline structure of this new blade. It can be seen from the photos that this is a new type of composite crystallization leaf formed by the symbiosis, co-growth and coexistence of single crystals and oriented columnar crystals during the solidification process.

1. The properties of single crystal and oriented column crystal compound crystallization blades. In order to understand the performance of single crystal and oriented columnar composite crystal blades, different samples were cut from different parts of the blade for performance testing. Figure 4 shows the sampling location of the blade.

(1) Cold and heat fatigue. The cold and hot fatigue samples were cut from the single crystal region at the air inlet edge of the blade and the oriented columnar crystal region in the middle of the blade for testing and comparison. The cold and hot fatigue test is to use the sharp change of temperature to cause cracks in the material to test the cold and hot fatigue strength of the material. This test is similar to the changes in the rapid cooling and heating of the blades during use. Therefore, the purpose of choosing the cold and heat fatigue test is also to simulate the service condition of the blade and compare the materials. The test results are shown in the table. No cracks were found in the single crystal sample after 66 thermal and thermal fatigue tests, and there is still no sign of cracks. The oriented columnar crystal sample has undergone 19 thermal and thermal fatigue tests, and a crack occurs at the edge of the sample, and extends along the grain boundary through the loose and oxidized zone. This comparison shows the superiority of the single crystal structure.

(2) Long-lasting and transient performance at high temperature. Φ3mm high-temperature persistent and high-temperature transient samples were cut from the oriented columnar crystal region in the middle of the blade for testing. The test results are shown in Table 1. It can be seen from the test results that whether it is in the upper part of the blade or in the lower part of the blade, the sampling performance meets or exceeds the requirements specified by the material. For the samples that have been tested for performance, the metallographic inspection is carried out, and the size and distribution of dendrites, eutectics and carbides on the upper and lower parts of the blade are relatively good. As shown in Figures 5, 6, and 7, the organizational structure of the material determines the performance of the material, and the performance of the material reflects its organizational status. The performance of the blade and its organizational structure reflect the excellent quality of this blade.

(3) Properties of plate samples. The inlet and exhaust edges of the blade are relatively thin. In order to understand the performance of the single crystal region on the exhaust edge, a plate-shaped sample with a thickness of 2mm was cut from the single crystal region of the blade exhaust edge for high-temperature transient performance test. The results are shown in Table 1. As shown, the measured data is much higher than the required value, which also reflects the superiority of the single crystal structure.

Table 1 Performance of single crystal and oriented columnar composite crystal blades serial number Crystalline state performance requirements results of testing Remark 1 single crystal hot and cold fatigue No cracks after 66 times of water quenching at 1100°C The sample maintains the shape of the blade inlet edge 2 Pillar crystal hot and cold fatigue 1100℃ water quenching 19 times intergranular cracking The sample is made into the shape of the blade inlet edge 3 single crystal 980℃σb≥400MPaδ%≥10% 980℃σb=492MPaδ%=28% Plate sample thickness 2mm 4 Pillar crystal 816℃483MPa≥60h 816℃483MPa≥200h Φ3mm small test rod 5 Pillar crystal 980℃σb≥400MPaδ%≥10% 980℃σb=521MPaδ%=19% Φ3mm small test rod 6 Pillar crystal 980℃190MPa≥50h 980℃190MPa≥62h Φ3mm small test rod 7 Pillar crystal Room temperature σb≥900MPaδ%≥5% Room temperature σb≥1189MPaδ%≥6.7% Φ3mm small test rod 8 Column crystal (horizontal) - 980℃190MPa＝48.9h Φ3mm small test rod

2. A method for manufacturing single crystal and oriented columnar composite crystal blades. According to the crystallization principle of single crystal and directional column crystal, in addition to the necessary adjustment of its directional solidification process parameters, a "composite crystallizer" is specially designed for this purpose. The "composite crystallizer" consists of three parts, that is, a single crystal spiral crystal selector, a directional column crystal selector and a directional solidification initiation section. When in use, the "composite crystallizer" is connected to the crown of the blade, the two single crystal selectors on the "composite crystallizer" are respectively aligned with the inlet and exhaust sides of the blade, and the directional column crystal selection of the "composite crystallizer" Align the tool with the center of the blade. Figure 8 shows the successfully developed compound crystallization blade with single crystal and oriented columnar crystal with "composite crystallizer".

The successful development of the new single crystal and oriented columnar crystal compound crystallization blade is the result of clever use of single crystal and directional crystallization laws. During the directional solidification process of the blade, what type of crystals the crystals grow into mainly depends on the temperature gradient distribution of the liquid phase alloy in the solidification region. When the large blade is directional solidified, due to its relatively thin inlet and exhaust edges, less liquid volume, faster solidification, and large solid-phase thermal conductivity, the temperature gradient of the liquid-phase alloy in the solidification zone is higher than that of the directional column with the same cross-section. Crystal growth in the middle of the leaves. Thus, the conditions for growing single crystals at the inlet and outlet sides of the blades and oriented columnar crystals at the middle of the blades are formed. That is to say, the conditions for co-growth and co-growth of single crystals and oriented columnar crystals are met in the same section of the blade. As long as the crystal nucleus is provided, two kinds of crystals can be grown simultaneously. Single crystal and oriented columnar crystal "composite crystallizers" can play this role. In this way, under the process conditions of directional solidification, it can be crystallized into this new type of blade.

1. The "composite crystallizer" structure and its connection to the blade 1. The "composite crystallizer" is formed by combining the single crystal spiral crystal selector 3 and the directional column crystal selector 4 . It includes three parts: a single crystal selector 3 , a directional column crystal selector 4 and a directional solidification initiation section 5 . Figure 9 shows its structure and its connection to the blades.

FIG. 10 shows the connection positions of the single crystal spiral crystal selector 3 and the directional column crystal selector 4 of the "composite crystallizer" and the blade shroud 2 of the blade 1 . Figure 11 shows the combination of the single crystal selector 3, the directional column crystal selector 4 and the directional solidification initiation section 5 on the "composite crystallizer".

2. The role of "composite crystallizer"

The "composite crystallizer" of the compound crystallization blade of single crystal and directional columnar crystal is directly installed on the crystallizer of the directional crystallization furnace. In the early stages of directional solidification, when the liquid alloy is poured into the mold, the mold begins to move downward. Under the quenching of the crystallizer, the liquid alloy forms a layer of fine equiaxed crystals at the beginning of the "composite crystallizer". During the continuous solidification process, under the control of heat flow, the small equiaxed crystals quickly grow into small oriented columnar crystals, and then enter the single crystal selector and the oriented columnar crystal selector respectively. In the single crystal selector, the redundant columnar crystals are restricted, and finally only one crystal grain enters the blade, which provides a crystal nucleus that can grow into a single crystal for the inlet and exhaust sides of the blade. In the crystal selector for oriented columnar crystals, the directionally solidified columnar crystal groups will be further arranged and combined, and the direction will be rectified. The thin and straight columnar crystals with the preferential growth (001) crystal direction will first enter the blade, which is the oriented columnar crystal in the middle of the blade. Solidification provides straighter columnar nuclei. In this way, under the corresponding directional solidification process, the "composite crystallizer" plays a catalytic role in the single crystal and directional column crystal blades.

The implementation of single crystal and directional column crystal compound blade is the corresponding directional solidification process conditions plus a specially designed "composite crystallizer".

1. Process conditions. The implementation of single crystal and directional columnar crystal compound crystallization blade must have the minimum directional solidification process conditions. In order to facilitate the growth of single crystal, the pouring temperature and the heating temperature of the mold heater were further adjusted on this basis. For this reason, the pouring temperature was increased from 1520°C to 1550°C. The heating temperature of the mold heater is adjusted to 1500°C in the upper zone and 1550°C in the lower zone.

2. The connection between the "composite crystallizer" and the blade. It must meet the crown end of the blade. That is to say, the crystallization of single crystal and oriented columnar composite crystallization leaves starts from the tip of the leaf crown.

3. Mold moving speed. Under the above-mentioned directional solidification conditions, the new type of blade can be obtained by adopting the downward movement speed of the mold of 5-7mm/min.

Under the above-mentioned directional solidification conditions, using another "composite crystallizer", only changing the directional column crystal selector on the above-mentioned "composite crystallizer" from a block shape to three column shapes, such blades can also be obtained, as shown in the figure As shown in 12, it shows that the single crystal selector on the "composite crystallizer" is the key to implementation.

Claims (6)

1. A compound crystallization blade of single crystal and oriented columnar crystal, characterized in that the blade is composed of two crystal forms: oriented columnar crystal in the middle of the blade, and single crystal in the inlet and exhaust sides of the blade. 2. The compound crystal blade of single crystal and oriented columnar crystal according to claim 1, characterized in that the width of the single crystal is 20-30 mm. 3. According to the manufacturing method of single crystal and oriented columnar crystal compound crystallization blade according to claim 1, it is characterized in that the specific steps are as follows: 1) Install the composite crystallizer on the crystallizer of the directional crystallization furnace. The composite crystallizer includes a single crystal selector, a directional column crystal selector and a directional solidification initial section, a single crystal selector, and a directional column crystal selector Both ends of the device are connected with the leaf crown and the initial section of directional solidification, and the number of single crystal selectors is two, which correspond to the inlet and exhaust sides of the blade respectively, and the directional column crystal selector corresponds to the middle part of the blade, and The solidification initiation section communicates with the directional crystallization furnace; 2) Process conditions: The degree of superheat for heating and melting is 100-150°C, and the heating temperature of the mold heater is adjusted to 1500-1530°C in the upper zone and 1550-1580°C in the lower zone; 3) After the liquid alloy is poured into the mold, the mold starts to move downward, and under the above-mentioned directional solidification condition, the mold moves down at a speed of 5-7mm/min. 4. The method for manufacturing a composite crystal blade of single crystal and oriented columnar crystal according to claim 3, characterized in that: the material of the blade is superalloy. 5. The manufacturing method of single crystal and oriented columnar crystal compound crystallization blade according to claim 3, characterized in that: said single crystal selector is a single crystal spiral selector. 6. According to the manufacturing method of single crystal and oriented columnar crystal compound crystallization blade according to claim 3, it is characterized in that: the oriented columnar crystal selector is block or columnar, and the number of columnar crystal selectors is 3 to 5 .

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