KR102203857B1 - Method of forming an environmental barrier layer - Google Patents

Abstract

In one embodiment of the present invention, forming a coating layer by coating a composition for forming an environmental barrier layer including silicate powder on a base material; And a post-treatment step of post-treating the coating layer to form the environmental barrier layer, wherein the post-treatment step includes a heating step of heating the coating layer to 1350°C to 1500°C and a cooling step of cooling to room temperature. Disclosed is a method for forming an environment-resistant barrier layer that is repeated 3000 to 5000 times.

Description

Method of forming an environmental barrier layer {Method of forming an environmental barrier layer}

Embodiments of the present invention relate to a method of forming an environment resistant barrier layer applicable to a surface of a component exposed to a high temperature environment.

Heat-resistant parts that are directly exposed to a high-temperature environment in a device operating at a high temperature, such as a gas turbine, need to maintain excellent heat resistance, excellent mechanical properties, and excellent durability even in a heat fatigue environment where heating and cooling are repeated. For example, since a silicon carbide (SiC)-based material has excellent thermal and mechanical properties, it can be used to form a heat-resistant component exposed to high temperatures. On the other hand, in order to improve the efficiency of gas turbines, etc., it is necessary to increase the operating temperature of the gas turbine, etc., and in this case, the operating temperature and atmosphere of the gas turbine may cause deterioration of the properties of the silicon carbide-based material forming the heat-resistant part. . Accordingly, in order to prevent deterioration of the heat-resistant part, a heat shielding layer may be formed on the surface of the heat-resistant part made of a material such as ceramic. However, when a rapid temperature change occurs as the operation and stop of the device are repeated, the heat shield layer may peel from the heat resistant component due to a difference in the coefficient of thermal expansion between the heat resistant component and the heat shield layer. To prevent this, by intentionally forming a vertical crack in the heat shield layer, it is possible to prevent the heat shield layer from peeling off from the heat-resistant part. However, the vertical cracks formed in the heat shield layer can become a penetration path through which oxygen or moisture reaches the heat-resistant part made of a silicon carbide-based material, whereby an oxide layer is formed by the reaction of silicon carbide and oxygen, or silicon carbide and moisture Part of the silicon carbide is vaporized by the reaction of, so that the durability of the heat-resistant part may be reduced.

10-1681195

Embodiments of the present invention provide a method of forming an environment-resistant barrier layer capable of preventing peeling from the surface of a component when applied to the surface of a component exposed to a high temperature environment and blocking the transmission of external moisture or oxygen do.

In one embodiment of the present invention, forming a coating layer by coating a composition for forming an environmental barrier layer including silicate powder on a base material; And a post-treatment step of post-treating the coating layer to form the environmental barrier layer, wherein the post-treatment step includes a heating step of heating the coating layer to 1350°C to 1500°C and a cooling step of cooling to room temperature. Disclosed is a method for forming an environment-resistant barrier layer that is repeated 3000 to 5000 times.

In the present embodiment, the post-treatment step may include a process in which a plurality of vertical cracks are formed in the environmental barrier layer, and at least some of the formed vertical cracks are healed.

In the present embodiment, a location where at least some of the plurality of vertical cracks are healed may have a greater crystalline content than the surrounding area.

In this embodiment, between the heating step and the cooling step, it may further include a holding step of maintaining the heated state of the coating layer.

In this embodiment, the silicate powder is yttrium oxide (Y ₂ O ₃ ) powder and silicon oxide (SiO ₂ ) powder, ytterbium oxide (Yb ₂ O ₃ ) powder and silicon oxide (SiO ₂ ) powder, or mullite (mullite) powder may be included.

In this embodiment, the base material may be formed of a silicon carbide sintered body or a silicon carbide-silicon carbide fiber reinforced composite material (SiC _f -SiC) using a silicon carbide fiber as a reinforcing material.

In this embodiment, the coating layer may be formed by a thermal spray coating method.

In this embodiment, the step of heat-treating the silicate powder may be further included.

In this embodiment, before the formation of the coating layer, it may further include forming an intermediate layer on the surface of the base material.

In this embodiment, the coefficient of thermal expansion of the intermediate layer may have a value between the coefficient of thermal expansion of the base material and the coefficient of thermal expansion of the environmental barrier layer.

Other aspects, features, and advantages other than those described above will become apparent from the following drawings, claims, and detailed description of the invention.

According to an embodiment of the present invention, the environmental barrier layer is formed through a step of healing after the formation of a plurality of vertical cracks, thereby maintaining structural stability in the presence of vertical cracks and allowing external oxygen or moisture to prevent environmental barriers. It can prevent penetration of the layer. Of course, the scope of the present invention is not limited by these effects.

1 is a cross-sectional view schematically illustrating an example of a device including a heat-resistant component to which an environment-resistant barrier layer is applied according to an embodiment of the present invention.
2 is a flow chart schematically showing a method of forming an environment-resistant barrier layer according to an embodiment of the present invention.
3 is a graph showing the density of vertical cracks generated in the environmental barrier layer during the process of forming the environmental barrier layer according to an embodiment of the present invention.
4 is a plan view showing a state in which vertical cracks have occurred in the environmental barrier layer during the process of forming the environmental barrier layer according to an embodiment of the present invention.
5 is a plan view illustrating a state in which the vertical crack of FIG. 4 is healed.
6 is a cross-sectional view showing a state in which the vertical crack of FIG. 4 is healed.
7 is a diagram showing the results of testing the stability of the environmental barrier layer according to whether or not the vertical cracks generated in the environmental barrier layer are healed.

Since the present invention can apply various transformations and have various embodiments, specific embodiments are illustrated in the drawings and will be described in detail in the detailed description. Effects and features of the present invention, and a method of achieving them will be apparent with reference to the embodiments described later in detail together with the drawings. However, the present invention is not limited to the embodiments disclosed below and may be implemented in various forms.

In the following embodiments, terms such as first and second are not used in a limiting meaning, but are used for the purpose of distinguishing one component from another component.

In the following examples, the singular expression includes the plural expression unless the context clearly indicates otherwise.

In the following embodiments, terms such as include or have means that the features or elements described in the specification are present, and do not preclude the possibility of adding one or more other features or elements in advance.

In the following embodiments, when a part such as a film, a region, or a component is on or on another part, not only the case directly above the other part, but also another film, region, component, etc. are interposed therebetween. This includes cases where there is.

In the drawings, components may be exaggerated or reduced in size for convenience of description. For example, the size and thickness of each component shown in the drawings are arbitrarily shown for convenience of description, and the present invention is not necessarily limited to what is shown.

When a certain embodiment can be implemented differently, a specific process order may be performed differently from the described order. For example, two processes described in succession may be performed substantially simultaneously, or may be performed in an order opposite to the described order.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, and when describing with reference to the drawings, the same or corresponding components will be given the same reference numerals.

1 is a cross-sectional view schematically showing an example of a device including a heat-resistant component to which an environment-resistant barrier layer is applied according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of an environment-resistant barrier layer according to an embodiment of the present invention. It is a flow chart schematically showing the formation method. Meanwhile, although FIG. 1 illustrates a gas turbine as an apparatus, the present invention is not limited thereto, and the environment-resistant barrier layer of the present invention can be applied to various fields such as engines, power plants, and aerospace parts of aircraft.

First, referring to FIG. 1, a gas turbine is a rotary heat engine that operates a turbine with high temperature and high pressure combustion gas, and may include an air compressor, a combustion chamber, and a turbine. The gas turbine compresses air with an air compressor, and the compressed air is supplied to the combustion chamber. In addition, fuel is supplied to the combustion chamber through a pump to combust with compressed air, and the turbine is rotated around the output shaft using the high-temperature and high-pressure gas generated at this time. Meanwhile, since the turbine gas temperature may be at a high temperature of 1,300° C. or higher, heat-resistant parts 1000 such as combustion chambers and turbines that are directly exposed to the turbine gas must have excellent heat resistance and durability.

For example, as illustrated in FIG. 1, the heat-resistant component 1000 may include a base material 10 and an environment-resistant barrier layer 100 formed on the base material 10. In addition, an intermediate layer 20 capable of reducing a difference in thermal expansion coefficient between the base material 10 and the environment-resistant barrier layer 100 may be further formed.

The base material 10 may be made of, for example, a silicon carbide sintered body or a silicon carbide fiber-reinforced composite material (SiC _f -SiC) using a silicon carbide fiber as a reinforcing material.

The silicon carbide-silicon carbide fiber-reinforced composite material may have a structure in which silicon carbide is dispersed in a matrix composed of silicon carbide fibers. Silicon Infiltration), Polymer Impregnation and Pyrolysis, etc. may penetrate into the voids in the matrix made of silicon carbide fibers.

The environment-resistant barrier layer 100 may include silicate. For example, the environment-resistant barrier layer 100 may include at least one of ytterbium silicate (Yb ₂ SiO ₅ ), yttrium silicate (Y ₂ SiO ₅ ), and mullite. The environment-resistant barrier layer 100 may prevent the base material 10 from being exposed to a high temperature environment.

In addition, the environment-resistant barrier layer 100 may include a region in which a crack formed in the vertical direction is healed. As will be described later, the region in which the crack is healed has a higher crystalline content than the other regions, whereby the environment-resistant barrier layer 100 can be prevented from being peeled off as in a state in which the crack is formed.

In addition, since the crack inside the environmental barrier layer 100 is in a healed state, that is, a filled state, external moisture or oxygen through the crack is prevented from passing through the environmental barrier layer 100, thereby preventing the silicon carbide sintered body. Alternatively, the base material 10 formed of the silicon carbide fiber as a reinforcing material may react with oxygen and/or moisture to prevent a decrease in the durability of the heat-resistant component 1000.

The intermediate layer 20 bonds the base material 10 and the environment-resistant barrier layer 100. The thermal expansion coefficient of the intermediate layer 20 may have a value between the thermal expansion coefficient of the base material 10 and the thermal expansion coefficient of the environmental barrier layer 100. The intermediate layer 20 may include silicon. For example, the intermediate layer 20 may be silicon, silicon nitride, silicon oxide, or the like. Accordingly, the intermediate layer 20 can prevent the environmental barrier layer 100 from being peeled off from the base material 10 by reducing a difference in thermal expansion between the base material 10 and the environment-resistant barrier layer 100. As an example, the intermediate layer 20 may be formed as a single layer.

The method of forming the environment-resistant barrier layer 100, as shown in FIG. 2, the step of forming the intermediate layer 20 on the base material 10 (S10), forming the environment-resistant barrier layer on the intermediate layer 20 It may include a step of forming a coating layer by coating the solvent composition (S20), a post-treatment step (S30) of forming an environment-resistant barrier layer by post-treating the coating layer.

As described above, the base material 10 is made of a silicon carbide sintered body or chemical vapor infiltration (CVI), liquid silicon infiltration (Liquid Silicon Infiltration), polymer impregnation and pyrolysis (Polymer Impregnation and Pyrolysis) It can be made of a silicon carbide-silicon carbide fiber-reinforced composite material (SiC _f -SiC) formed by a method such as

The intermediate layer 20 may be formed by a method such as plasma spraying, PVD, CVD, PECDV, or a sputtering method using a target containing silicon.

The composition for forming an environment-resistant barrier layer may include silicate powder. Specifically, the composition for forming an environment-resistant barrier layer is yttrium oxide (Y ₂ O ₃ ) powder and silicon oxide (SiO ₂ ) powder, ytterbium oxide (Yb ₂ O ₃ ) powder and silicon oxide (SiO ₂ ) powder, or mullite (mullite) powder may be included.

For example, yttrium oxide (Y ₂ O ₃ ) powder and silicon oxide (SiO ₂ ) powder, ytterbium oxide (Yb ₂ O ₃ ) powder and silicon oxide (SiO ₂ ) powder, or mullite powder at high temperature and high pressure It is charged in a plasma air stream to form a molten or semi-melted state, and then, it is mechanically coated on the intermediate layer 20 at high speed to form a coating layer. Meanwhile, ytterbium oxide (Yb ₂ O ₃ ) powder and silicon oxide (SiO ₂ ) powder are mixed to form ytterbium silicate (Yb ₂ SiO ₅ ), and yttrium oxide (Y ₂ O ₃ ) powder and silicon oxide (SiO ₂ ) ₂ ) The powder may be mixed to form yttrium silicate (Y ₂ SiO ₅ ).

As another example, the composition for forming an environment-resistant barrier layer further includes a binder, a dispersant, a defoamer, a release agent, etc., and may be coated on the intermediate layer 20 by thermal spray coating. have. When the composition for forming an environmental barrier layer is coated by thermal spray coating, the composition for forming an environmental barrier layer may include heat-treated powder.

For example, the heat treatment of the powder may be performed for 2 hours or more at a temperature of 1100°C to 1300°C. If the heat treatment temperature is lower than 1100℃, the powder cannot maintain proper strength, and the coating may be made uneven. On the other hand, if the heat treatment temperature is higher than 1300℃, the strength of the powder increases excessively and the powder does not melt during coating. A non-uniform coating layer may be formed.

In addition, during thermal spray coating, the feed rate of the powder, the size of the voltage/current of the plasma gun, the spray rate of the plasma gun, the distance between the plasma gun and the base material 100 (spray distance, spray distance), etc., the properties of the coating layer can be adjusted. For example, if the powder supply speed, the moving speed of the plasma gun is too small, or the spray distance is too large, the density of the coating layer decreases, and in the opposite case, a dense coating layer may be formed.

After coating the composition for forming an environment-resistant barrier layer on the intermediate layer 20, post-treatment thereof is performed to form the environment-resistant barrier layer 100.

In the post-treatment step, the heating step of heating the formed coating layer to 1350°C to 1500°C and the cooling step of cooling to room temperature are repeated a plurality of times. It repeats 3000 to 5000 times, preferably 4000 to 5000 times. Hereinafter, one heating step and one cooling step are referred to as one cycle. In each cycle, after heating the coating layer to 1350°C to 1500°C, a holding step of maintaining it for 30 to 60 minutes may be included.

The post-treatment step process includes a process in which a plurality of vertical cracks are formed in the environmental barrier layer 100 and at least some of the formed plurality of vertical cracks are healed.

Vertical cracks are formed in the environment-resistant barrier layer 100 from the early to the middle of the post-treatment step, for example, from 2000 cycles to 3000 cycles. When vertical cracks are formed in the environmental barrier layer 100, the environmental barrier layer 100 has a structurally stabilized state. Therefore, even if a sudden temperature change occurs in the environmental barrier layer 100, the thermal stress is compensated by vertical cracking, so that the environmental barrier layer 100 can be prevented from being peeled off or damaged from the base material 10. However, as described above, the vertical crack may be a penetration path of external moisture and/or oxygen.

In the middle of the post-treatment stage, for example after 3000 cycles to 4000 cycles, the vertical cracks that have formed can be healed. This is because vertical cracks are already formed and structurally stabilized environmental barrier layer 100 is repeatedly heated and cooled to a high temperature of 1350°C or higher, so that the environmental barrier layer 100 is prevented from forming additional vertical cracks. This is because the vertical cracks are partially melted and recrystallized to fill up the vertical cracks. At this time, a relatively large number of crystal phases are formed in the vertical cracks. That is, the area where the vertical crack is healed has a relatively higher content of crystal phase than the surrounding area.

For example, in the case of forming a coating layer using a composition for forming an environment-resistant barrier layer containing mullite powder and post-treating it, the area where the vertical crack is healed has an Al ₂ O ₃ crystalline content higher than the surrounding area. When the coating layer is formed and post-treated using a composition for forming an environmental barrier layer containing ytterbium oxide (Yb ₂ O ₃ ) powder and silicon oxide (SiO ₂ ) powder, the vertical crack is healed. The region may contain more crystalline phases of SiO ₂ than the periphery.

The crystalline phase has a higher coefficient of thermal expansion than the glass phase. Therefore, even if a sudden temperature change occurs in the environmental barrier layer 100, the region from which the vertical crack is healed serves as a buffer, so that the environmental barrier layer 100 has stress resistance and fatigue resistance, and the environmental barrier layer ( 100) structural stability can be maintained. Therefore, even if the vertical crack is filled, the environment-resistant barrier layer 100 is prevented from being peeled off or damaged from the base material 10 as in the state in which the crack is formed, and at the same time, the penetration path of moisture and/or oxygen is blocked, thereby preventing heat resistance. It is possible to prevent the durability of the component 1000 from decreasing.

Hereinafter, the present invention will be described in more detail through examples. However, the following examples are for explaining the present invention more specifically, and the scope of the present invention is not limited by the following examples. The following examples can be appropriately modified and changed by those skilled in the art within the scope of the present invention.

<Formation of environmental barrier layer>

Example 1: On a base material formed of a silicon carbide-silicon carbide fiber-reinforced composite material, silicon was deposited to form an intermediate layer, and an environment-resistant barrier layer including mullite was formed on the intermediate layer.

The environment-resistant barrier layer was formed by thermal spray coating a composition for forming an environment-resistant barrier layer including mullite powder to form a coating layer on the intermediate layer, and then performing a post-treatment process. The post-treatment process performed 5000 cycles of a heating step of raising to 1350°C at a rate of 5°C per minute and a cooling step of cooling to room temperature.

Example 2: On the base material formed of silicon carbide-silicon carbide fiber reinforced composite material, silicon was deposited to form an intermediate layer, and an environment-resistant barrier layer including ytterbium silicate (Yb ₂ SiO ₅ ) was formed on the intermediate layer. .

As the environmental barrier layer, a coating layer was formed on the intermediate layer by thermal spray coating using a composition for forming an environmental barrier layer containing ytterbium oxide (Yb ₂ O ₃ ) powder and silicon oxide (SiO ₂ ) powder, and then carried out. It was formed by performing the same post-treatment process as in Example 1.

<Density change of vertical crack during post-treatment process>

3A shows the change in the density of the vertical cracks generated in the environmental barrier layer during the post-treatment process of Example 1, and FIG. 3B shows the change in the environmental barrier layer during the post-treatment process of Example 2. It shows the change in the density of vertical cracks. In FIG. 3, the density of vertical cracks is the number of cracks over a straight line of unit length (1 mm) after photographing the surface in each cycle of the post-treatment step.

As can be seen from Fig. 3, in the case of A, the number of vertical cracks increases up to 3000 cycles, and then decreases, and in the case of B, the number of vertical cracks increases until 2000 cycles, and then decreases thereafter. I can. In addition, the result is shown only up to 5000 cycles in FIG. 3, because after 5000 cycles, both A and B maintain a state in which the number of vertical cracks is rapidly decreased. Therefore, it is preferable to repeat the heating step and the cooling step up to 5000 times in the post-treatment step in consideration of the manufacturing time of the environmental barrier layer.

The reason for the decrease in vertical cracks is that, as described above, by repeatedly heating and cooling the structurally stabilized environmental barrier layer at a high temperature of 1350°C or higher, rather than forming additional vertical cracks, the environmental barrier layer This is because the composition of is partially melted by eutectic reaction and fills up the vertical crack through the process of recrystallization.At this time, the region where the vertical crack is healed has a relatively higher content of crystalline phase than the surrounding region, so that the environmental barrier layer is structurally It can maintain a stable state.

4 is a plan view showing a state in which vertical cracks have occurred in the environmental barrier layer during the process of forming the environmental barrier layer according to an embodiment of the present invention, and FIG. 5 is a diagram illustrating a state in which the vertical crack of FIG. 4 is healed. It is a plan view, and FIG. 6 is a cross-sectional view showing a state in which the vertical crack of FIG. 4 is healed.

4 is a result of repeating the heating step and the cooling step 3,000 times during the manufacturing process of the environment-resistant barrier layer 100 formed according to the second embodiment, and it can be seen that the vertical crack C is formed. In addition, as a result of repeating the heating step and the cooling step 5000 times during the manufacturing process of the environment-resistant barrier layer 100 formed according to Example 2, it can be seen that the vertical crack C is healed. . That is, as shown in Figs. 4 to 6, it can be seen that the vertical crack C is formed through the post-treatment step and then healed. In addition, the area where the vertical crack C is healed has a higher crystalline content than the surrounding area. As shown in FIG. 6, it can be seen that the area healed by the vertical crack C is distinguished from the surrounding area.

7 is a diagram showing the results of testing the stability of the environmental barrier layer according to whether or not the vertical cracks generated in the environmental barrier layer are healed.

7 is a durability test result of a heat-resistant component including an environment-resistant barrier layer formed according to Example 2. FIG. 7A is an environment-resistant barrier formed by repeating the heating step and the cooling step 5000 times as in FIG. It is a result of exposing the heat-resistant part including the layer to a high-temperature steam atmosphere, and FIG. 7B shows a heat-resistant part including an environment-resistant barrier layer formed by repeating the heating step and the cooling step 3,000 times as in FIG. 4. It is the result of exposure to a high-temperature steam atmosphere.

7(A) shows that the environment-resistant barrier layer did not fall off and the substrate was not damaged, while FIG. 7(B) shows that the environment-resistant barrier layer did not come off, but the mass of the base material was reduced, resulting in damage. Represents. In the case of (B) of FIG. 7, this is because silicon hydroxide is formed by allowing moisture to penetrate into the substrate and react with the substrate through vertical cracks.

In other words, according to the present invention, since the environment-resistant barrier layer is formed through a post-treatment step, dropping of the environment-resistant barrier layer, etc. can be prevented, and moisture and the like can be blocked from penetrating the environment-resistant barrier layer. It can be seen that the reduction can be prevented.

10: base material
20: middle layer
100: environmental barrier layer

Claims (10)

Forming a coating layer by coating a composition for forming an environmental barrier layer including silicate powder on a base material; And
Including; a post-treatment step of forming the environmental barrier layer by post-treating the coating layer,
In the post-treatment step, a heating step of heating the coating layer to 1350°C to 1500°C and a cooling step of cooling to room temperature are repeated 3000 to 5000 times. The method of claim 1,
In the post-treatment step, a plurality of vertical cracks are formed in the environmental barrier layer in a thickness direction of the environmental barrier layer, and at least some of the formed vertical cracks are healed. Method of formation. The method of claim 2,
A method of forming an environment-resistant barrier layer at a location where at least some of the plurality of vertical cracks are healed has a larger crystalline content than the surrounding. The method of claim 1,
Between the heating step and the cooling step, the method of forming an environment-resistant barrier layer further comprising a maintaining step of maintaining the heated state of the coating layer. The method of claim 1,
The silicate powder is i) yttrium oxide (Y ₂ O ₃ ) powder and silicon oxide (SiO ₂ ) powder, ii) ytterbium oxide (Yb ₂ O ₃ ) powder and silicon oxide (SiO ₂ ) powder, or iii) mullite (mullite) A method of forming an environment-resistant barrier layer containing powder. The method of claim 1,
The base material is a method of forming an environment-resistant barrier layer formed of a silicon carbide sintered body or a silicon carbide fiber-reinforced composite material (SiC _f -SiC) using a silicon carbide fiber as a reinforcing material. The method of claim 1,
The coating layer is a method of forming an environment-resistant barrier layer formed by a thermal spray coating method. The method of claim 7,
Before the step of forming the coating layer, the method of forming an environment-resistant barrier layer further comprising the step of heat-treating the silicate powder. The method of claim 1,
Before the formation of the coating layer, the method of forming an environment-resistant barrier layer, further comprising forming an intermediate layer on the surface of the base material. The method of claim 9,
The thermal expansion coefficient of the intermediate layer is a method of forming an environmental barrier layer having a value between the coefficient of thermal expansion of the base material and the coefficient of thermal expansion of the environmental barrier layer.

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