CN114544631A - Evaluation method for recrystallization tendency of spoiler column in single crystal superalloy 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 tendency of a single-crystal superalloy hollow blade spoiler column, comprising the following steps: Step 1, core preparation: using a designed ceramic core mold, press ceramic Core; step 2, wax mold pressing: pressing into a wax mold in a shape mold, and combining the wax mold 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 the selection of alloy materials. For different alloys, the greater the number of recrystallizations found, the larger the diameter of the turbulent injector and the larger the radius of the fillet, the greater the recrystallization tendency of the turbulent column of this alloy.

Description

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

technical field

The invention relates to the technical field of single crystal superalloy, in particular to a method for evaluating the recrystallization formation tendency of a single crystal superalloy hollow blade spoiler column.

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 superalloys are currently the preferred materials for turbine blades of aero-engines with high thrust-to-weight ratio and high power-to-weight ratio. It can even be said that single crystal blades are an important symbol of the advanced degree of the engine and a significant symbol of the level of a national 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 problems of matching materials, processes, and structures to engineering applications.

As the working environment temperature of aero-engine 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 into the inner cavity of the blade from the bottom of the turbine blade, along the cooling flow channel inside the blade, and effectively cools the inner surface of the hollow blade from bottom to top. Part of the cooling airflow passes through the impact hole at the front of the blade edge to cool the inner surface of the blade edge by means of impact 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 rate to make it match the blade. After 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 whole blade can be 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 do not contain or less 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 working temperature of the single crystal hollow blade, the greater the effect 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 demanding, and recrystallization is almost not allowed. Surface recrystallization can be accomplished by visual inspection, but recrystallization inspection of the lumen spoiler column can only be found after dissection and destruction, so it is very important to ensure that the lumen structure does not form recrystallization.

SUMMARY OF THE INVENTION

In view of the defects of the prior art, the purpose of the present invention is to provide a method for evaluating the recrystallization tendency of a single crystal superalloy hollow blade spoiler column.

The present invention solves the technical problem by adopting the following technical solutions:

The invention provides a method for evaluating the recrystallization tendency of a single crystal superalloy hollow blade spoiler column, comprising the following steps:

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

Step 2, wax mold pressing: pressing into a wax mold in a shape mold, and combining the wax mold into a module;

Step 3, shell preparation: coating and hanging refractory material on the module, drying and sintering to obtain a shell shape, the shell shape is a multi-layer structure, and the shell shape is dewaxed and sintered after coating and hanging;

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

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

Step 6: Recrystallization inspection: After dissecting the casting along the height direction of the spoiler column, macroscopic corrosion is performed, and recrystallization is visually inspected.

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

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

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

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

Preferably, the specific process steps in the directional solidification of the step 4 are:

Put the prepared mold shell into the single crystal furnace, melt and refine the vacuum pressure <4Pa; the upper heater temperature is 1500-1520 ℃; the lower heater temperature is 1520-1540 ℃; the alloy is refined at 1550-1560 ℃ from The pouring cup of the pouring system is poured into the shell mold, and the pulling rate is 3-4mm/min. After the completion, the vacuum is broken and then cooled.

Preferably, the heat treatment system in the vacuum heat treatment in step 5 is: heating to 1315-1320°C, holding for 4 hours, cooling with argon gas, and cooling to 500°C or below, the cooling rate of the casting is not lower than 40°C/min.

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

Preferably, the shell-type multi-layer structure is 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 the spoiler column of the single crystal superalloy, and provide a basis for the selection of alloy materials. For different alloys, the greater the number of recrystallizations found, the larger the diameter of the turbulent injector and the larger the radius of the fillet, the greater the recrystallization tendency of the turbulent column of this alloy.

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

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 single crystal superalloy spoiler column structure; the method has low cost and is easy to popularize and apply.

Description of drawings

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

Figure 2 is a schematic view 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 with reference to specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Example 1

In this embodiment,

The method for evaluating the recrystallization tendency of a 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: pressing into a wax mold in a shape mold, and combining the wax mold into a module;

Step 3, shell preparation: coating the module with refractory material, drying and sintering to obtain a shell shape, the shell shape is a multi-layer structure of 6 and a half layers, the slurry is a mixture of silica sol and white steel jade powder, white corundum The weight ratio of powder and silica sol is 2:1, and the sanding material is white steel jade powder. After the shell-shaped coating is completed, dewaxing and sintering are carried out;

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

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

Step 6: Recrystallization inspection: After dissecting the casting along the height direction of the spoiler column, macroscopic corrosion is performed, and recrystallization is visually inspected.

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 contains 5 through holes. The arrangement rule of each group of holes is: the 5 through holes have the same diameter and the same transition fillet radius. The specific arrangement is one through hole in the center, and four through holes are evenly distributed on the outside with the center of the center hole as the center. The minimum distances of the outer 4 holes and the center hole are all diameters. There are 4 sets of lateral through holes, each set of diameters is different, 1, 1.5, 2, 2.5mm, respectively, and the transition fillet is the same. There are 4 groups of longitudinal through holes with the same diameter, and the transition radius of each group of through holes is different, which are 0.1, 0.3, 0.5, and 0.7mm respectively.

In this example, the prepared ceramic core is put into a shape mold, and pressed into a wax mold. The wall thickness of the wax mold is 1 mm, and the wax mold is combined into a module.

Coating and hanging refractory material on the module, after drying and sintering, the shell shape is obtained; the shell shape is generally a multi-layer structure, the slurry is a mixture of silica sol and white steel jade powder, and the sanding material is white steel jade powder; the shell shape coating is completed. After dewaxing, sintering and other treatments.

Put the prepared mold shell into the single crystal furnace, melt and refine the vacuum pressure <4Pa; the upper heater temperature is 1500 ℃; the lower heater temperature is 1520 ℃; DD6 alloy is refined at 1550 ℃ from the gate of the pouring system The cup is poured into the shell mold, and the pulling rate is 3mm/min. After the completion, the vacuum is broken and then cooled.

After cutting the module riser, etc., it is processed such as shelling and core removal. After cleaning and drying, put it into a vacuum heat treatment furnace for solution treatment. The heat treatment system is: heating to 1315 ° C, holding for 4 hours, and then taking out the casting after cooling with argon. When it is cooled to 500 ° C or below, the cooling rate of the casting is not lower than At 40 °C/min, use a wire cutting machine to cut the spoiler column in the height direction, and then use ferric chloride etchant to perform macro-etching on the casting to observe the recrystallization around the spoiler column.

Example 2

In this example

The method for evaluating the recrystallization tendency of a 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: pressing into a wax mold in a shape mold, and combining the wax mold into a module;

Step 3, shell preparation: coating the module with refractory material, drying and sintering to obtain a shell shape, the shell shape is a multi-layer structure of 7 and a half layers, the slurry is a mixture of silica sol and white steel jade powder, and white corundum is formed. The weight ratio of powder and silica sol is 3:1, the sanding material is white steel jade powder, and the shell shape is dewaxed and sintered after the coating is completed;

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

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

Step 6: Recrystallization inspection: After dissecting the casting along the height direction of the spoiler column, macroscopic corrosion is performed, and recrystallization is visually inspected.

According to the designed mold, the ceramic core is pressed. As shown in Figure 1, the ceramic core is composed of 16 groups of through holes, and 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 transition fillet radius. The specific arrangement is one through hole in the center, and four through holes are evenly distributed on the outside with the center of the center hole as the center. The minimum distances of the outer 4 holes and the center hole are all diameters. There are 4 groups of through holes in the transverse direction, each group has a different hole diameter, 1, 1.5, 2, 2.5mm, respectively, and the transition fillet is the same. There are 4 groups of longitudinal through holes with the same diameter, and the transition 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 a shape mold, press it into a wax mold, the wall thickness of the wax mold is 1 mm, and combine the wax mold into a module.

The module is coated with refractory material, dried and sintered to obtain a shell shape; the shell shape is generally a multi-layer structure, the slurry is a mixture 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 a single crystal furnace, melt and refine the vacuum pressure <4Pa; the upper heater temperature is 1520 ℃; the lower heater temperature is 1540 ℃; DD419 alloy is refined at 1560 ℃ from the gate of the pouring system The cup is poured into the shell mold, and the pulling rate is 4mm/min. After the completion, the vacuum is broken and then cooled.

After cutting the riser of the module, carry out shelling, core removal and other treatments, after cleaning and drying, put it into a vacuum heat treatment furnace for solid solution treatment. Then take out the casting, use a wire cutting machine to cut the spoiler column in the height direction, and then use hydrochloric acid etchant to perform macro-etching on the casting to check the recrystallization around the spoiler column.

Example 3

The only difference from Example 2 is: put the prepared mold shell into a single crystal furnace, melt and refine the vacuum pressure <4Pa; the upper heater temperature is 1510 ℃; the lower heater temperature is 1530 ℃; DD419 alloy is 1555 After refining at ℃, pour it into the shell mold from the pouring cup of the pouring system, and the pulling rate is 3.5mm/min. After the completion, the vacuum is broken and then cooled.

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

Example 4

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

Comparative Example 1

For different alloys, the greater the number of recrystallizations found, the larger the diameter of the turbulent injector and the larger the radius of the fillet, the greater the recrystallization tendency of the turbulent column of this alloy.

For example, Example 1 and Example 2 are DD6 alloy and DD419 alloy respectively, and their typical process parameters are used. The larger the radius, the greater the recrystallization tendency of the spoiler column of this alloy.

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

For the DD419 alloy, the heat treatment temperatures of Examples 2 and 3 are different. If the number of recrystallizations at 1320°C is significantly greater than that at 1315°C, the heat treatment temperature must be lowered during the development of the blade 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 present invention is not limited to the details of the above-described exemplary embodiments, but that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments are to be regarded in all respects as illustrative and not restrictive, and the scope of the invention is to be defined by the appended claims rather than the foregoing description, which are therefore intended to fall within the scope of the claims. All changes within the meaning and range of the equivalents of , are included in the present invention.

In addition, it should be understood that although this specification is described in terms of embodiments, not each embodiment only includes an independent technical solution, and this description in the specification is only for the sake of clarity, and those skilled in the art should take the specification as a whole , the technical solutions in each embodiment can also be appropriately combined to form other implementations that can be understood by those skilled in the art.

Claims (10)

1. A method for evaluating the recrystallization formation tendency of a single crystal superalloy hollow blade spoiler column, characterized in that it comprises the following steps: Step 1, core preparation: use the designed ceramic core mold to press the ceramic core; Step 2, wax mold pressing: pressing into a wax mold in a shape mold, and combining the wax mold into a module; Step 3, shell preparation: coating and hanging refractory material on the module, drying and sintering to obtain a shell shape, the shell shape is a multi-layer structure, and the shell shape is dewaxed and sintered after coating and hanging; Step 4, directional solidification: using a single crystal furnace to pour different single crystal superalloys to prepare single crystal superalloy castings, and after cutting, shelling and core removal; Step 5, vacuum heat treatment: according to the heat treatment specifications of different alloys, the single crystal superalloy castings are subjected to vacuum heat treatment; Step 6: Recrystallization inspection: After dissecting the casting along the height direction of the spoiler column, macroscopic corrosion is performed, and recrystallization is visually inspected. 2 . The method for evaluating the recrystallization tendency of a single crystal superalloy hollow blade spoiler column according to claim 2 , wherein the ceramic core is a plate-like structure with a thickness of 2 mm, and 16 groups of through holes are evenly distributed. 3 . , used to form the spoiler column structure of the casting. 3. The method for evaluating the recrystallization tendency of a single crystal superalloy hollow blade spoiler column according to claim 2, wherein each of the 16 groups of through holes is composed of 5 through holes of the same diameter, and 5 The diameter of each through hole is the same, and the radius of the transition fillet is the same. 4. The method for evaluating the recrystallization tendency of a spoiler column of a single crystal superalloy hollow blade according to claim 3, wherein the specific arrangement rule of each group of holes is: a through hole in the center, and a through hole on the outer side. There are 4 through holes evenly distributed in the center of the center hole; the minimum distance between the outer 4 holes and the center hole is the diameter; there are 4 groups of through holes in the transverse direction, each group has different diameters, 1, 1.5, 2, 2.5mm, respectively, and the transition circle The corners are the same; 4 groups of longitudinal through holes have the same diameter, and the transition radius of each group of through holes is different, which are 0.1, 0.3, 0.5, and 0.7 mm, respectively. 5 . The method for evaluating the recrystallization tendency of a single crystal superalloy hollow blade spoiler column according to claim 1 , wherein in the second step, the wall thickness of the wax mold is 1-3 mm. 6 . 6. The method for evaluating the recrystallization tendency of a single crystal superalloy hollow blade spoiler column according to claim 1, wherein the specific process steps in the directional solidification of the step 4 are: Put the prepared mold shell into a single crystal furnace, melt and refine the vacuum pressure <4Pa; the upper heater temperature is 1500-1520 ℃; the lower heater temperature is 1520-1540 ℃; the alloy is refined at 1550-1560 ℃ from The pouring cup of the pouring system is poured into the shell mold, and the pulling rate is 3-4mm/min. After the completion, the vacuum is broken and then cooled. 7 . The method for evaluating the recrystallization tendency of single crystal superalloy hollow blade spoiler column recrystallization according to claim 1 , wherein the heat treatment system in the vacuum heat treatment in step 5 is: heating to 1315-1320° C., and keeping the temperature for 4 hours. 8 . , Cooling with argon gas, when it is cooled to 500 ℃ or below, the cooling rate of the casting is not less than 40 ℃/min. 8. The method for evaluating the recrystallization tendency of single crystal superalloy hollow blade spoiler column recrystallization according to claim 1, characterized in that, in the step 6, the macro-corrosion adopts a hydrochloric acid etchant or a ferric chloride etchant Macroscopic corrosion of castings. 9 . The method for evaluating the recrystallization tendency of a single crystal superalloy hollow blade spoiler column according to claim 1 , wherein: the shell-shaped multilayer structure is 6-8 layers; the alloy comprises DD6 alloy or DD419 alloy. 10. The method for evaluating the recrystallization tendency of a single crystal superalloy hollow blade spoiler column according to claim 1, wherein the refractory material is a mixture of white steel jade powder and silica sol, white corundum powder and silica sol The weight ratio is (2~3):1.

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