阅读说明：本技术 一种定向叶片及其柱状晶组织优化方法 (Directional blade and columnar crystal structure optimization method thereof ) 是由 赵运兴 马德新 徐维台 皮立波 李重行 于 2021-06-28 设计创作，主要内容包括：本发明公开了一种定向叶片及其柱状晶组织优化方法,旨在优化定向叶片柱状晶组织,使晶粒生长方向垂直,降低叶片露头晶数量,提高定向叶片的合格率。为此,本发明实施例一方面提供的定向叶片柱状晶组织优化方法,通过对原有定向叶片起晶段作加厚处理,使得受横向温度梯度影响生长发生倾斜的晶粒主要位于外侧的加厚区域内,并且保证加厚区域内晶粒不会长入铸件内部,从而淘汰掉表面受横向温度梯度影响发生倾斜的晶粒,使得起晶段中间区域未受影响的笔直晶粒长入铸件中,以此实现定向叶片柱状晶组织优化。(The invention discloses an oriented blade and a columnar crystal structure optimization method thereof, and aims to optimize the columnar crystal structure of the oriented blade, so that the growth direction of crystal grains is vertical, the quantity of exposed crystals of the blade is reduced, and the qualification rate of the oriented blade is improved. Therefore, according to the directional blade columnar crystal structure optimization method provided by the embodiment of the invention, the original directional blade crystallization section is thickened, so that the crystal grains which are influenced by the transverse temperature gradient and grow and incline are mainly positioned in the thickened area at the outer side, and the crystal grains in the thickened area are ensured not to grow into the casting, so that the crystal grains with the surfaces influenced by the transverse temperature gradient and incline are eliminated, and the straight crystal grains which are not influenced in the middle area of the crystallization section are grown into the casting, so that the directional blade columnar crystal structure optimization is realized.)

1. A directional blade columnar crystal structure optimization method is characterized by comprising the following steps: the crystallization section of the original directional blade is thickened, so that the crystal grains which are influenced by the transverse temperature gradient and are inclined are mainly located in the thickening area (1) on the outer side, and the crystal grains in the thickening area (1) can not grow into the casting, so that the crystal grains with the inclined surfaces influenced by the transverse temperature gradient are eliminated, the straight crystal grains which are not influenced in the middle area (2) of the crystallization section are grown into the casting, and the columnar crystal texture optimization of the directional blade is realized.

2. The method for optimizing the columnar crystal structure of the directional blade according to claim 1, wherein: the orthographic projection of the blade body of the directional blade on the crystallization section is completely coincided with the middle area (2) of the crystallization section.

3. The method for optimizing the columnar crystal structure of the directional vane according to claim 2, wherein: the thickness of each part of the thickened area (1) is equal.

4. The method for optimizing the columnar crystal structure of the directional vane according to claim 2, wherein: when the directional blade mold is designed, the crystallization section of the blade is designed according to the blade structure, the shape and the size of the crystallization section are ensured to be matched with the blade structure, and the directional blade and the crystallization section are directly extruded together when wax is pressed.

5. The method for optimizing the columnar crystal structure of the directional blade according to any one of claims 1 to 4, wherein: the height of the thickened area (1) is smaller than that of the crystal pulling section, and the bottom end of the thickened area is flush with the crystal pulling section.

6. The method of directional blade columnar crystal texture optimization according to claim 5, wherein: the height of the thickened area (1) is controlled to be 10-40 mm.

7. The method of directional blade columnar crystal texture optimization according to claim 5, wherein: the thickness of the thickened area (1) is controlled to be 1-4 mm.

8. A directional blade, characterized by: the method is optimized by the directional blade columnar crystal structure optimization method of any one of claims 1 to 7.

Technical Field

The invention belongs to the technical field of high-temperature alloy preparation, and particularly relates to a directional blade and a columnar crystal structure optimization method thereof.

Background

For the high-temperature alloy directional blade, in the directional solidification process of the blade, besides the vertical temperature gradient from bottom to top, the blade also has the temperature gradient in the transverse direction from outside to inside, and the existence of the transverse temperature gradient enables the growth of crystal grains in a region with a certain thickness on the surface of the directional blade in the solidification process to be influenced, so that the directional blade inclines inwards, and the inclined crystal grains with a certain thickness on the surface grow into the casting to become inclined crystal grains and often expose to form exposed crystals. For a high-temperature alloy directional blade, the deviation of grain growth and outcrop have great influence on the service performance of the blade, and especially outcrop crystals with great influence on the performance of the blade often cause the blade to be scrapped, so the service performance and the qualification rate of the blade are greatly reduced. However, the problems that the surface crystal grains of a blade casting are large, the crystal grain growth is inclined, the number of outcrop crystals is large and the like still exist in the directional blade prepared under the existing casting process conditions.

Disclosure of Invention

The invention mainly aims to provide an oriented blade and a columnar crystal structure optimization method thereof, aiming at optimizing the columnar crystal structure of the oriented blade, enabling the growth direction of crystal grains to be vertical, reducing the quantity of outcrop crystals of the blade and improving the qualification rate of the oriented blade.

Therefore, according to the directional blade columnar crystal structure optimization method provided by the embodiment of the invention, the crystallization starting section of the original directional blade is thickened, so that the crystal grains which are influenced by the transverse temperature gradient and grow to be inclined are mainly positioned in the thickened area at the outer side, and the crystal grains in the thickened area are ensured not to grow into the casting, so that the crystal grains with the surfaces influenced by the transverse temperature gradient and inclined are eliminated, and the straight crystal grains which are not influenced in the middle area of the crystallization starting section grow into the casting, so that the directional blade columnar crystal structure optimization is realized.

Specifically, the orthographic projection of the blade body of the directional blade on the crystallization section is completely coincided with the middle area of the crystallization section.

Specifically, the thickness of the thickened area is equal.

Specifically, when the directional blade mold is designed, the crystallization section of the blade is designed according to the blade structure, the shape and the size of the crystallization section are ensured to be matched with the blade structure, and the directional blade and the crystallization section are directly pressed together during wax pressing.

Specifically, the height of the thickened region is smaller than that of the crystallization segment, and the bottom end of the thickened region is flush with the crystallization segment.

Specifically, the height of the thickened area is controlled to be 10-40 mm.

Specifically, the thickness of the thickened area is controlled to be 1-4 mm.

The embodiment of the invention also provides a directional blade obtained by optimizing the directional blade columnar crystal structure optimization method.

Principle analysis

According to the method, a thickening layer with a certain height is added on the outer side of the crystallization section of the directional blade, crystal grains in a thickening area are influenced by a transverse temperature gradient to grow to be inclined but cannot grow into the casting, so that inclined crystal grains with the influenced surfaces are eliminated, the crystal grains are prevented from growing into the casting, straight crystal grains which are not influenced in the middle area of the crystallization section are grown into the casting, and the columnar crystal structure of the directional blade is optimized.

Compared with the prior art, at least one embodiment of the invention has the following beneficial effects: 1) the change point is only the oriented blade crystallization section, the original process and structure are not required to be changed too much, and the method has the advantages of easy operation and low cost; 2) the columnar crystal structure of the directional blade can be obviously optimized, the quantity of the exposed crystals of the blade is reduced, and the qualification rate of the directional blade is improved.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

FIG. 1 is a front view of a crystallization segment according to an embodiment of the present invention;

FIG. 2 is a sectional view taken along line A-A of FIG. 1;

FIG. 3 is a surface grain topography of a blade body after the directional blade manufactured by the original process is corroded;

FIG. 4 is a surface grain topography of a blade body after erosion of a directional blade fabricated in accordance with an embodiment of the present invention;

wherein: 1. a thickened region; 2. a middle region.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be considered limiting of the invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.

Referring to fig. 1 and 2, a directional blade columnar crystal structure optimization method is characterized in that a crystallization starting section of an original directional blade is thickened, so that crystal grains which grow and incline under the influence of a transverse temperature gradient are mainly located in a thickened area 1 on the outer side, and the crystal grains in the thickened area 1 are ensured not to grow into a casting, so that the crystal grains with surfaces inclined under the influence of the transverse temperature gradient are eliminated, straight crystal grains which are not influenced in a middle area 2 of the crystallization starting section grow into the casting, and the directional blade columnar crystal structure optimization is realized.

In the embodiment, the thickening layer with a certain height is added on the outer side of the crystallization section of the original directional blade, so that the crystallization section of the directional blade is thickened, the change point of the whole invention is only the crystallization section of the directional blade, the columnar crystal structure of the directional blade is obviously optimized, the quantity of the exposed crystals of the blade is reduced, the qualification rate of the directional blade is improved, the original process and structure are not required to be changed too much, and the method has the advantages of easiness in operation and low cost.

In some embodiments, the blade crystallization section may be designed as a crystallization-following section, which means that the shape of the crystallization-following section middle area 2 is consistent with the shape of the blade body of the orientation blade, that is, the orthographic projection of the blade body of the orientation blade on the crystallization section is completely coincident with the crystallization-following section middle area 2. Such design structure can guarantee on the one hand that the crystalline grain can not grow into inside the foundry goods in thickening region 1, and on the other hand the crystallization section is along with the type design can guarantee the more excellent growth route of crystalline grain, avoids because of the interference that the shape difference brought, and the columnar crystal tissue can obtain further optimization.

It can be understood that, in practical application, when the directional blade mold is designed, the crystallization section of the blade is designed according to the blade structure, the crystallization section is connected with the root part of the blade body of the directional blade, the shape and the size of the crystallization section are ensured to be adaptive to the blade structure, and the directional blade and the crystallization section are directly pressed out together during wax pressing. In this embodiment, directional blade and seeding section integrated into one piece, not only directional blade is high with seeding section connection accuracy, can effectively avoid the connection defect that the concatenation formula structure brought moreover.

Referring to fig. 1, in some embodiments, both ends of the thickened region 1 may be designed to be flush with the central region 2, but such a design may risk that the thickened region 1 contacts other parts of the blade, such as the tip shroud, so that the grains grown obliquely in the thickened region 1 grow into the blade from other parts of the blade, such as the tip shroud. Therefore, in actual design, the height of the thickening region 1 is smaller than that of the seeding section, and the bottom end is flush with the bottom of the seeding section, so that the thickening region 1 can be completely separated from each part of the blade, and the problem that the obliquely-grown crystal grains grow into the blade from other parts such as the blade crown of the blade can be solved.

In the actual design, the crystallization section of the original directional blade can be uniformly thickened, namely the thickness of each part of the thickened area 1 is equal; specifically, the height of the thickened area 1 can be controlled to be 10-40 mm, and the thickened thickness can be controlled to be 1-4 mm.

The present invention will be further described with reference to specific examples.

Examples

The present example uses a nickel-based directionally superalloy DZ125 with the alloy composition shown in Table 1.

TABLE 1 weight percents of alloying elements

In the embodiment, taking the directional superalloy blade crystallization section for the aviation turbine engine as an example, molten paraffin is injected into a directional blade metal mold containing the crystallization section with the optimized structure through a paraffin injection machine, and a blade wax mold with the optimized structure of the crystallization section is extruded. And simultaneously, extruding the directional blade wax mold with the crystal pulling section structure which is not optimized by the same method. Forming a wax pattern by the two blade wax patterns, coating the combined wax pattern with slurry, spraying sand, drying, coating the slurry for multiple times to ensure that the thickness of the wax pattern is 7-9mm, and then dewaxing and sintering to prepare the corundum mould shell. And (3) performing directional solidification in a vacuum directional furnace to prepare the high-temperature alloy directional blade, wherein the heating temperature of an upper area is 1515 ℃, the heating temperature of a lower area is 1515 ℃, and the directional solidification is performed under the condition that the pulling speed is 5mm/min, after the directional solidification is finished, the structure appearance of the directional columnar crystal of the directional blade with the crystal pulling section structure which is not optimized is shown in figure 3, and the structure appearance of the directional columnar crystal of the directional blade with the crystal pulling section which is optimized is shown in figure 4.

From fig. 3, it can be found that the blade body of the directional blade prepared by the original process has coarse grains, the grain growth is inclined, and more outcrop crystals exist. After the blade crystallization section is optimized by adopting the method, the crystal grains of the blade body of the oriented blade are obviously refined, the crystal grains grow straightly, and the quantity of outcrop crystals is also obviously reduced, which is shown in figure 4.

Any embodiment disclosed herein above is meant to disclose, unless otherwise indicated, all numerical ranges disclosed as being preferred, and any person skilled in the art would understand that: the preferred ranges are merely those values which are obvious or representative of the technical effect which can be achieved. Since the numerical values are too numerous to be exhaustive, some of the numerical values are disclosed in the present invention to illustrate the technical solutions of the present invention, and the above-mentioned numerical values should not be construed as limiting the scope of the present invention.

Meanwhile, if the invention as described above discloses or relates to parts or structural members fixedly connected to each other, the fixedly connected parts can be understood as follows, unless otherwise stated: a detachable fixed connection (for example using bolts or screws) is also understood as: non-detachable fixed connections (e.g. riveting, welding), but of course, fixed connections to each other may also be replaced by one-piece structures (e.g. manufactured integrally using a casting process) (unless it is obviously impossible to use an integral forming process).

In addition, terms used in any technical solutions disclosed in the present invention to indicate positional relationships or shapes include approximate, similar or approximate states or shapes unless otherwise stated. Any part provided by the invention can be assembled by a plurality of independent components or can be manufactured by an integral forming process.

The above examples are merely illustrative for clearly illustrating the present invention and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. Nor is it intended to be exhaustive of all embodiments. And obvious variations or modifications of the invention may be made without departing from the scope of the invention.