CN114544631B - Method for evaluating recrystallization formation tendency of turbulence column of single crystal high-temperature alloy hollow blade - Google Patents

Abstract

The invention relates to the technical field of single crystal superalloys, in particular to a method for evaluating the recrystallization formation tendency of single crystal superalloy hollow vane spoiler columns, comprising the following steps: Step 1, core preparation: using a designed ceramic core mold, pressing ceramics Core; step 2, wax mold pressing: press into a wax mold in the shape mold, and combine the wax molds into a module. The invention can quantitatively evaluate the recrystallization tendency of the spoiler column of the single-crystal superalloy, and provide a basis for alloy material selection. For different alloys, the more the number of recrystallization found, the larger the diameter of the recrystallized spoiler, and the larger the radius of the fillet, the greater the recrystallization tendency of the spoiler of this alloy.

Description

Evaluation method for recrystallization formation tendency of single crystal superalloy hollow blade spoiler column

technical field

The invention relates to the technical field of single-crystal high-temperature alloys, in particular to a method for evaluating the recrystallization formation tendency of single-crystal high-temperature alloy hollow vane spoiler columns.

Background technique

Nickel-based single crystal superalloys are widely used in advanced aviation gas turbine blades due to their excellent high temperature properties. Single crystal superalloy is currently the preferred material for the turbine blades of high thrust-to-weight ratio and high power-to-weight ratio aeroengines. It can even be said that single crystal blades are an important symbol of the advanced level of the engine and a significant symbol of the level of a country's aviation industry. The working conditions of single crystal blades are extremely harsh, and they are subjected to complex aerodynamic, thermal and mechanical loads. Blade materials and complex structures will also bring matching problems between materials, processes, and structures in engineering applications.

As the working environment temperature of aeroengine turbine blades is getting higher and higher, how to ensure the safe and reliable operation of turbine blades is a very critical issue. The cooling principle of the hollow blade is that the cold air inhaled by the aero-engine flows from the bottom of the turbine blade into the internal cavity of the blade, along the internal cooling channel of the blade, and effectively cools the inner surface of the hollow blade from bottom to top. Part of the cooling air flow passes through the impingement hole at the front edge of the blade edge to cool the inner surface of the blade edge edge in the form of impingement cooling, and the other part of the gas passes through the spoiler column near the exhaust edge of the hollow blade, which is disturbed and slows down the flow velocity to make it collide with the blade. After the forced heat exchange, it flows out from the tail of the exhaust side, and the last part of the cooling gas flows out through the air film holes of the blade platform and the blade body, forming a thin-walled cold air diaphragm on the outer surface of the blade, so that the blade as a whole is effectively protected and cooled. In recent years, a series of studies have been carried out on the cooling technology of turbine blades, and the relationship between the cooling efficiency and the arrangement of the spoiler columns has been obtained.

Single crystal superalloys are very sensitive to recrystallization because they contain no or few grain boundary strengthening elements. Once the single crystal blade recrystallizes in a certain area, cracks are easy to initiate at the interface between the crystal and the matrix, and along the grain boundary. Expansion, and lead to fracture, causing significant economic losses. Many studies have shown that the existence of recrystallization seriously affects the service performance of single crystal blades, especially the high temperature fatigue and durability performance. The higher the operating temperature of the single crystal hollow blade, the greater the influence of recrystallization on it.

Therefore, in some advanced engines with high design working temperature, the key parts of single crystal turbine hollow blades are very strict, and recrystallization is almost not allowed. Surface recrystallization can be accomplished by visual inspection, but recrystallization inspection of lumen spoiler columns can only be found after dissection and destruction, so it is critical to ensure that the lumen structure does not form recrystallization.

Contents of the invention

Aiming at the defects of the prior art, the object of the present invention is to provide a method for evaluating the recrystallization formation tendency of the single crystal superalloy hollow vane spoiler column.

The present invention solves technical problem and adopts following technical scheme:

The invention provides a single crystal superalloy hollow blade spoiler post recrystallization formation tendency evaluation method, comprising the following steps:

Step 1, core preparation: use the designed ceramic core mold to press the ceramic core;

Step 2, wax mold pressing: press into a wax mold in a shape mold, and combine the wax molds into a module;

Step 3, mold shell preparation: coat the module with refractory material, dry and sinter to obtain the shell mold, the shell mold has a multi-layer structure, and dewax and sinter the shell mold after coating and hanging;

Step 4, directional solidification: use a single crystal furnace to pour different single crystal superalloys to prepare single crystal superalloy castings, and after cutting, perform shelling and core removal;

Step 5, vacuum heat treatment: according to the heat treatment specifications of different alloys, the single crystal superalloy casting is subjected to vacuum heat treatment;

Step 6, recrystallization inspection: After dissecting the casting along the height direction of the spoiler column, perform macroscopic corrosion, and visually inspect the recrystallization.

Preferably, the ceramic core is a plate-like structure with a thickness of 2mm, and 16 groups of through holes are evenly distributed to form the spoiler structure of the casting.

Preferably, each of the 16 groups of through holes is composed of 5 through holes with the same diameter, the 5 through holes have the same diameter, and the radius of the transition fillet is the same.

Preferably, the specific arrangement rules for each group of holes are: one through hole at the center, four through holes evenly distributed on the outside with the center of the center hole as the center; the minimum distance between the four holes on the outside and the center hole is the aperture; 4 groups of through-holes, each with different hole diameters, 1, 1.5, 2, 2.5 mm, and the same transition fillet; 4 sets of through-holes in the vertical direction, with the same hole diameter, and the transition fillet radius of each group of through-holes is different, respectively 0.1, 0.3, 0.5, 0.7mm.

Preferably, the wall thickness of the wax model in the second step is 1-3mm.

Preferably, the specific process steps in the step four directional solidification are:

Put the prepared shell into the single crystal furnace, melt and refine the vacuum pressure <4Pa; the temperature of the upper heater is 1500-1520°C; the temperature of the lower heater is 1520-1540°C; The sprue cup of the pouring system is poured into the shell mold, and the drawing rate is 3-4mm/min. After the completion, the vacuum is broken and cooled.

Preferably, the heat treatment regime in step five vacuum heat treatment is: heating to 1315-1320°C, holding the temperature for 4 hours, filling with argon for cooling, and cooling the casting at a rate of not lower than 40°C/min when the casting is cooled to 500°C or below.

Preferably, one of hydrochloric acid etchant or ferric chloride etchant is used for macro corrosion in the step 6 to perform macro corrosion on the casting.

Preferably, the shell-type multilayer structure has 6-8 layers; the alloy includes DD6 alloy or DD419 alloy.

Preferably, the refractory material is formed by mixing white corundum powder and silica sol, and the weight ratio of white corundum powder and silica sol is (2~3):1.

Compared with the prior art, the present invention has the following beneficial effects:

1. The present invention can quantitatively evaluate the recrystallization tendency of spoiler columns of single crystal superalloys, and provide a basis for alloy material selection. For different alloys, the more the number of recrystallization found, the larger the diameter of the recrystallized spoiler, and the larger the radius of the fillet, the greater the recrystallization tendency of the spoiler of this alloy.

2. The present invention can realize the evaluation of the design rationality of the spoiler column structure of the single crystal hollow turbine blade. For a specific material, through this experiment, the threshold value of the structure design of the blade spoiler can be obtained, and the repeated modification of the structure due to recrystallization and scrapping can be avoided.

3. The single crystal casting designed by the present invention has a simple structure, is easy to cast, and can quickly and accurately evaluate the recrystallization tendency of the spoiler column structure of the single crystal superalloy; the method is low in cost and easy to be popularized and applied.

Description of drawings

Fig. 1 is a schematic diagram of the present invention;

Fig. 2 is a schematic diagram of the ceramic core of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with specific embodiments. Apparently, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Example 1

In this example,

The evaluation method for recrystallization formation tendency of single crystal superalloy hollow blade spoiler column in this embodiment includes the following steps:

Step 1, core preparation: use the designed ceramic core mold to press the ceramic core;

Step 2, wax mold pressing: press into a wax mold in a shape mold, and combine the wax molds into a module;

Step 3, shell preparation: coat the module with refractory material, dry and sinter to obtain the shell shape, the shell shape is a multi-layer structure of 6 and a half layers, the slurry is made of silica sol and white corundum powder, white corundum The weight ratio of powder and silica sol is 2:1, and the sanding material is white corundum powder, and the shell mold is dewaxed and sintered after coating and hanging;

Step 4, directional solidification: use a single crystal furnace to pour different single crystal superalloys to prepare single crystal superalloy castings, and after cutting, perform shelling and core removal;

Step 5, vacuum heat treatment: according to the heat treatment specifications of different alloys, the single crystal superalloy casting is subjected to vacuum heat treatment;

Step 6, recrystallization inspection: After dissecting the casting along the height direction of the spoiler column, perform macroscopic corrosion, and visually inspect the recrystallization.

In this embodiment, the ceramic core is pressed according to the designed mold. As shown in FIG. 1 , the ceramic core is composed of 16 groups of through holes, and each group includes 5 through holes. The arrangement rule of each group of holes is: the 5 through holes have the same diameter and the same radius of the transition fillet. The specific arrangement is one through hole at the center, and four through holes evenly distributed on the outside with the center of the center hole as the center. The minimum distance between the outer 4 holes and the center hole is the hole diameter. There are 4 groups of through holes in the horizontal direction, each group of holes has a different diameter of 1, 1.5, 2, and 2.5 mm, and the transition fillets are the same. There are 4 groups of through holes in the vertical direction with the same diameter, and the transition fillet radius of each group of through holes is different, which are 0.1, 0.3, 0.5, and 0.7mm respectively.

In this embodiment, the prepared ceramic core is put into a shape mold and pressed into a wax mold with a wall thickness of 1mm, and the wax molds are combined to form a module set.

The module is coated with refractory material, and after drying and sintering, the shell shape is obtained; the shell shape is generally a multi-layer structure, the slurry is made of silica sol and white steel jade powder, and the sanding material is white steel jade powder; the shell shape is coated and hung. After that, dewaxing, sintering and other treatments are carried out.

Put the prepared mold shell into the single crystal furnace, melting and refining the vacuum pressure <4Pa; the temperature of the upper heater is 1500°C; the temperature of the lower heater is 1520°C; the DD6 alloy is refined from the gate of the pouring system The cup is poured into the shell mold, the drawing speed is 3mm/min, and after the completion, the vacuum is broken and cooled.

After the riser of the module is cut, shelling and core removal are performed. After cleaning and drying, put it into a vacuum heat treatment furnace for solid solution treatment. The heat treatment system is as follows: heat to 1315°C, keep it warm for 4 hours, fill it with argon to cool, and take out the casting. When it is cooled to 500°C or below, the cooling rate of the casting should not be lower than At 40°C/min, the spoiler column was cut along the height direction with a wire cutting machine, and then the casting was macroscopically corroded with ferric chloride etchant, and the recrystallization around the spoiler column was observed.

Example 2

In this example

The evaluation method for recrystallization formation tendency of single crystal superalloy hollow blade spoiler column in this embodiment includes the following steps:

Step 1, core preparation: use the designed ceramic core mold to press the ceramic core;

Step 2, wax mold pressing: press into a wax mold in a shape mold, and combine the wax molds into a module;

Step 3, shell preparation: coat the module with refractory material, dry and sinter to obtain the shell shape, the shell shape is a multi-layer structure of 7 and a half layers, the slurry is made of silica sol and white corundum powder, white corundum The weight ratio of powder and silica sol is 3:1, and the sanding material is white corundum powder. After the shell mold is coated and hung, it is dewaxed and sintered;

Step 4, directional solidification: use a single crystal furnace to pour different single crystal superalloys to prepare single crystal superalloy castings, and after cutting, perform shelling and core removal;

Step 5, vacuum heat treatment: according to the heat treatment specifications of different alloys, the single crystal superalloy casting is subjected to vacuum heat treatment;

Step 6, recrystallization inspection: After dissecting the casting along the height direction of the spoiler column, perform macroscopic corrosion, and visually inspect the recrystallization.

Press the ceramic core according to the designed mold, as shown in Figure 1, the ceramic core consists of 16 groups of through holes, each group contains 5 through holes. The arrangement rule of each group of holes is: the 5 through holes have the same diameter and the same radius of the transition fillet. The specific arrangement is one through hole at the center, and four through holes evenly distributed on the outside with the center of the center hole as the center. The minimum distance between the outer 4 holes and the center hole is the hole diameter. There are 4 groups of through holes in the horizontal direction, each group of holes has a different diameter of 1, 1.5, 2, and 2.5 mm, and the transition fillets are the same. There are 4 groups of through holes in the vertical direction with the same diameter, and the transition fillet radius of each group of through holes is different, which are 0.1, 0.3, 0.5, and 0.7mm respectively.

Put the prepared ceramic core into the shape mold, press it into a wax mold, the wall thickness of the wax mold is 1mm, and combine the wax molds into a mold set.

The module is coated with refractory material, dried and sintered to obtain the shell shape; the shell shape is generally a multi-layer structure, the slurry is made of silica sol and white steel jade powder, and the sanding material is white steel jade powder. After the shell coating is completed, dewaxing, sintering and other treatments are carried out.

Put the prepared mold shell into the single crystal furnace, melting and refining the vacuum pressure <4Pa; the temperature of the upper heater is 1520°C; the temperature of the lower heater is 1540°C; the DD419 alloy is refined from the gate of the pouring system The cup is poured into the shell mold, the drawing speed is 4mm/min, and after the completion, the vacuum is broken and cooled.

After cutting the riser of the module, perform shelling, core removal and other treatments, after cleaning and drying, put it into a vacuum heat treatment furnace for solid solution treatment. The heat treatment system is: heating to 1320 ° C, holding for 4 hours, and cooling with argon Finally, the casting is taken out, and the spoiler column is cut along the height direction with a wire cutting machine, and then the casting is macroscopically corroded with hydrochloric acid etchant to check the recrystallization around the spoiler column.

Example 3

The only difference from Example 2 is that the prepared mold shell is put into a single crystal furnace, and the melting and refining vacuum pressure is <4Pa; the temperature of the upper heater is 1510°C; the temperature of the lower heater is 1530°C; After refining at ℃, it is poured into the shell mold from the sprue cup of the pouring system, and the drawing rate is 3.5mm/min. After the completion, the vacuum is broken and cooled.

Step 5 The heat treatment system in the vacuum heat treatment is: heating to 1315°C, holding the heat for 4 hours, filling with argon and cooling, then taking out the casting, and the rest of the operation steps are the same.

Example 4

The only difference from Embodiments 1 to 3 is that the wall thickness of the wax model is 3mm, and the rest of the operation steps are the same.

Comparative example 1

For different alloys, the more the number of recrystallization found, the larger the diameter of the recrystallized spoiler, and the larger the radius of the fillet, the greater the recrystallization tendency of the spoiler of this alloy.

For example, Example 1 and Example 2, which are DD6 alloy and DD419 alloy respectively, adopt their typical process parameters. If the number of recrystallization found in a certain alloy is larger, the diameter of the turbulent flow caused by recrystallization is larger, and the rounded corners are larger. The larger the radius, the greater the alloy's propensity for spoiler recrystallization.

For a specific material, through this experiment, the threshold value of the structure design of the blade spoiler can be obtained, and the repeated modification of the structure due to recrystallization and scrapping can be avoided.

For the DD419 alloy, the heat treatment temperatures of Examples 2 and 3 are different. If the number of recrystallization at 1320°C is significantly greater than the number of recrystallization at 1315°C, the heat treatment temperature must be lowered during the blade development process to reduce the scrap rate of recrystallization , to ensure that the product meets the design requirements.

It will be apparent to those skilled in the art that the invention is not limited to the details of the above-described exemplary embodiments, but that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Accordingly, the embodiments should be regarded in all points of view as exemplary and not restrictive, the scope of the invention being defined by the appended claims rather than the foregoing description, and it is therefore intended that the scope of the invention be defined by the appended claims rather than by the foregoing description. All changes within the meaning and range of equivalents of the elements are embraced in the present invention.

In addition, it should be understood that although this specification is described according to implementation modes, not each implementation mode only contains an independent technical solution, and this description in the specification is only for clarity, and those skilled in the art should take the specification as a whole , the technical solutions in the various embodiments can also be properly combined to form other implementations that can be understood by those skilled in the art.

Claims (5)

1. The method for evaluating the recrystallization forming tendency of the turbulence column of the single crystal superalloy hollow blade is characterized by comprising the following steps:

step one, core preparation: pressing a ceramic core by adopting a designed ceramic core mold;

step two, pressing a wax mould: pressing wax patterns in the external mold, and combining the wax patterns into a module;

step three, shell mold preparation: coating a refractory material on the module, drying and sintering to obtain a shell mold, wherein the shell mold is of a multilayer structure, and dewaxing and sintering treatment are carried out after the shell mold is coated;

step four, directional solidification: pouring different single-crystal high-temperature alloys by using a single-crystal furnace to prepare single-crystal high-temperature alloy castings, and carrying out shelling and depoling treatment after cutting;

step five, vacuum heat treatment: carrying out vacuum heat treatment on the single-crystal high-temperature alloy casting according to the heat treatment specifications of different alloys;

step six, recrystallization inspection: dissecting the casting along the height direction of the turbulence column, performing macroscopic corrosion, and performing visual inspection and recrystallization; the specific process steps in the directional solidification in the fourth step are as follows:

putting the prepared shell mold into a single crystal furnace, and melting and refining the shell mold under the vacuum pressure of less than 4Pa; the temperature of the upper heater is 1500-1520 ℃; the temperature of the lower heater is 1520-1540 ℃; refining the alloy at 1550-1560 ℃, pouring the refined alloy into a shell mold from a pouring cup of a pouring system, wherein the drawing speed is 3-4mm/min, and cooling after breaking vacuum after finishing the drawing; the heat treatment specification in the step five vacuum heat treatment is as follows: heating to 1315-1320 ℃, preserving heat for 4h, filling argon for cooling, and when the temperature is cooled to 500 ℃ or below, the cooling speed of the casting is not lower than 40 ℃/min;

the ceramic core is of a plate-shaped structure with the thickness of 2mm, and 16 groups of through holes are uniformly distributed and used for forming a turbulence column structure of a casting; each group of the 16 groups of through holes consists of 5 through holes with the same diameter, the apertures of the 5 through holes are the same, and the radiuses of transition fillets are the same;

the specific arrangement rule of each group of holes is as follows: a through hole is arranged at the center, and 4 through holes are uniformly distributed on the outer side by taking the center of the center hole as the center; the minimum distances between the outer 4 holes and the central hole are the hole diameters; 4 groups of transverse through holes are arranged, the aperture of each group is different and is respectively 1mm, 1.5 mm, 2mm and 2.5mm, and the transition fillets are the same; the diameter of each longitudinal 4 groups of through holes is the same, and the radius of the transition fillet of each group of through holes is different and is respectively 0.1 mm, 0.3 mm, 0.5 mm and 0.7mm.

2. The method for evaluating the recrystallization forming tendency of the turbulence column of the single-crystal superalloy hollow blade according to claim 1, wherein the wall thickness of the wax mold in the second step is 1-3mm.

3. The method for evaluating the tendency of the turbulence column of the single-crystal superalloy hollow blade to recrystallize and form, according to claim 1, wherein in the sixth step, the macro-etching is performed on the casting by using one of a hydrochloric acid etchant and a ferric trichloride etchant.

4. The method for evaluating the recrystallization forming tendency of the turbulence column of the single-crystal superalloy hollow blade according to claim 1, wherein: the shell-type multilayer structure is 6~8 layers; the alloy comprises a DD6 alloy or a DD419 alloy.

5. The method for evaluating the tendency of the turbulence column of the single-crystal high-temperature alloy hollow blade to recrystallize and form according to claim 1, wherein the refractory material is formed by mixing white corundum powder and silica sol, and the weight ratio of the white corundum powder to the silica sol is (2~3): 1.

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