JP2807465B2 - Ceramic heat-resistant composite parts - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a ceramic heat-resistant composite part in which a metal reinforcing member (core metal) is disposed in a ceramic-made covering member (shell), and particularly to a heat-resistant composite component. The present invention relates to a composite part capable of improving impact resistance. The present invention is applied to various heat-resistant parts such as gas turbines and jet engines, but is suitable for gas turbine blades. Therefore, the gas turbine blades will be described below as an example.

[Conventional technology]

Conventionally, in heat engines such as gas turbines, it has been known that the higher the combustion gas temperature, the higher the thermal efficiency.
At present, the combustion gas is used at a temperature of about 800 ° C. or less due to the limited heat resistance of components such as turbine blades. If it becomes possible to use ceramics for such turbine blades and the like, it is expected that the gas temperature can be increased to about 1400 ° C. and the thermal efficiency can be significantly improved. In order to realize this ceramic turbine blade, it is essential to ensure the reliability of the parts by optimizing the structural design and material selection of the blade.

By the way, although ceramics are excellent in heat resistance, they have a drawback that they are easily broken by large thermal strain, impact, or local contact due to low deformability. For this reason, when ceramics is used for a turbine blade member, there is a problem in that the ceramic blade is easily broken by thermal stress due to a temperature difference between components caused by rapid heating in a temperature rising process and rapid cooling in an emergency stop. Also,
Conventionally, mechanical fitting has been used to attach ceramic turbine blades to the rotor or stator.However, in this case, the problem that the ceramic portion is easily damaged by stress concentration at the contact portion is also a problem to be solved. is there.

As a method for solving these problems, instead of integrally forming a turbine blade having a complicated shape with ceramics, a ceramic component is contacted with a plurality of portions having a simple shape, for example, a blade portion in which combustion gas is in direct contact with a rotor, and the rotor is connected to a rotor. It is divided into a shroud part as an attachment part for attaching to etc., and these are mechanically assembled with metal parts to secure the necessary wing shape, so that thermal stress due to temperature difference is released. (See, for example, JP-A-61-66802).

[Problems to be solved by the invention]

However, the following problems remain unsolved in the above-described conventional turbine blade.

The cross section of the blade portion of the turbine blade becomes thinner toward the trailing edge, so that the trailing edge is cooled more rapidly than the leading edge during an emergency stop. Therefore, a considerable temperature difference occurs in the cross section. However, the method described in the above publication cannot reduce the thermal stress due to the temperature difference as long as the wing portions are integrated.

In the case of a split or assembled type, the structure is generally complicated, and the shape tends to have many stress concentration points, which is unreliable.

The present invention has been made to solve the above-described conventional problems, and can suppress the occurrence of thermal stress even during rapid cooling such as during an emergency stop, and has a simple structure with few stress concentration points, improving reliability. The purpose is to provide a ceramic heat-resistant composite part that can be made.

[Means for solving the problem]

In order to achieve the above object, the present inventors have studied thermal stress reduction measures at the time of quenching.In particular, in order to suppress the tensile stress generated at the trailing edge of the turbine blade, a compressive stress should be given in advance. We paid attention to good points. On the other hand, during a steady operation, since the thermal expansion coefficient of the reinforcing member made of a metal member is large, the above-mentioned initial compressive stress is eliminated as it is. In order to prevent this, the inventors conceived that the temperature of the reinforcing member should be lowered according to the difference in thermal expansion between the reinforcing member and the covering member. In addition, lowering the temperature of the reinforcing member in this way is also advantageous in compensating for the fact that the heat resistance of the member is lower than that of ceramics.

Accordingly, the present invention provides a component body in which a reinforcing member made of a heat-resistant metal having a larger coefficient of thermal expansion is inserted and placed in a ceramic covering member, and formed on both ends of the main body, and provided on a device support portion. In the ceramic heat-resistant composite part comprising a fixed mounting portion and used in a high-temperature atmosphere, a compression initial stress that suppresses a thermal stress generated due to a local temperature difference at the time of rapid cooling of the covering member is generated at room temperature. The covering member is compressed and held by the mounting portion,
A heat insulating layer is formed between the covering member and the reinforcing member in a steady state so that a temperature difference is generated between the two members, and the covering member is so formed that the compressive stress in the steady state is not more than the allowable compressive stress of the ceramics. In addition, a temperature difference, a thermal expansion coefficient difference, and a sectional area ratio between the reinforcing members are set.

Here, in the present invention, it is necessary to set the initial compressive stress to a magnitude that can cancel the thermal stress based on the temperature difference between the parts generated at the time of rapid cooling. As a method of applying the initial compressive stress to the covering member, For example, the following method can be adopted.

First, a coating portion made of ceramics is formed, and metal powder for a reinforcing member is filled into the coating portion and portions corresponding to the mounting portions located at both ends of the coating portion.
HIP) and cooled. Then, due to the difference in the amount of thermal shrinkage between the covering member and the reinforcing member, the covering member is compressed and held by the mounting portion, thereby generating an initial compressive stress. Of course, a tensile stress is generated in the reinforcing member.

Both mounting portions arranged on both ends of the covering member so as to sandwich the covering member are fastened with fastening bolts, thereby mechanically generating an initial compressive stress in the covering member.

Further, it is necessary to maintain the compressive stress to be generated in the covering member during the steady operation to be equal to or higher than the initial compression stress and equal to or less than the allowable compressive stress of the covering member. This is a covering member,
It is determined by the difference in thermal expansion coefficient of the reinforcing member, the temperature difference between the two, and the cross-sectional area ratio between the two. On the other hand, the temperature difference is generally determined from the heat-resistant temperature (for example, 600 ° C.) of the reinforcing member and the ambient temperature for use (for example, 1400 ° C.). The difference in the coefficient of thermal expansion and the ratio of the cross-sectional area are appropriately selected so as to obtain the stress. In addition, in order to generate a predetermined temperature difference between the covering member and the reinforcing member, in the present invention, a heat insulating layer is formed between both members, and the heat insulating layer is, for example, about 1 mm of ceramic wool. It can be realized by disposing a member molded to a thickness between both members.

[Action]

In the ceramic heat-resistant composite part according to the present invention, the compressive initial stress is generated in the ceramic covering member, and the heat insulating layer is formed so that a considerable temperature difference occurs between the covering member and the reinforcing member in a normal use state. As a result, in the normal use state, a compressive stress corresponding to the temperature difference, the thermal expansion coefficient difference, and the cross-sectional area ratio is generated in the covering member, which promotes the above-mentioned initial compressive stress. Therefore, when a rapid cooling state is established, such as an emergency stop of a gas turbine, a part to be locally cooled is generated depending on the cross-sectional shape of the component.
The thermal stress in this portion is offset by the above-described compressive stress in the steady state, and no tensile stress is generated by this local cooling, and as a result, the thermal shock resistance is greatly improved.

〔Example〕

 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

1 to 5 are views for explaining a stationary blade for a gas turbine according to an embodiment of the present invention. In FIGS. 1 and 2 showing the stationary blade, reference numeral 1 denotes a gas turbine stationary blade, which is a blade portion 2 and mounting portions 3 formed at both ends thereof.
It consists of three.

The wing portion 2 has a so-called wing shape in which the thickness is gradually reduced by being chipped from the leading edge 2a to the trailing edge 2b. The wing portion 2 serves as a reinforcing member with a heat insulating layer 5 interposed in a ceramic shell 4 as a covering member. The metal liner 6 is inserted and arranged. A plurality of air holes 6a are formed in the metal liner 6 to prevent abnormal temperature rise of the liner 6 due to the flow of air. A stepped pressing portion 6b is formed outwardly at the upper and lower ends of the metal liner 6, and the ceramic shell 6 has both pressing portions 6b, 6b at its upper and lower ends in the drawing.
At a predetermined compression initial stress.
This initial compressive stress is large enough to offset thermal stress (for example, tensile stress of 30 kg / mm ² ) due to the cooling of the trailing edge 2b of the wing portion 2 more rapidly than the leading edge 2a at the time of emergency stop, and therefore at least 30kg. / mm ² or more.

The ceramic shell 4 is formed by firing powder such as SIC or Si ₃ N ₄ , and the heat insulating layer 5 is formed by molding ceramic fibers such as SiC to a thickness of, for example, 1 mm. The metal liner 6 may be made of, for example, Ti alloy or
A composite material composed of long fibers such as SiC, Si ₃ N ₄ or Ni
A composite material in which long fibers such as SiC and Si ₃ N ₄ are composited with a base alloy is employed. This metal liner 6 and ceramic shell 4
Are selected so as to have a predetermined coefficient of thermal expansion difference. The difference in the coefficient of thermal expansion is determined by the temperature difference between the ceramic shell 4 and the metal liner 6 caused by the heat insulating layer 5 during the steady operation and the cross-sectional area ratio between the two. Set to occur. The compressive stress at the time of steady operation is set to a stress not less than the initial compressive stress (30 kg / mm ² ) and not more than the allowable compressive stress of the ceramics (for example, 90 kg / mm ² ).

The mounting part 3 is configured as follows. That is, a metal shroud portion 7 of the same material as the liner 6 is fitted to a pressing portion 6b integrally formed in a stepwise outward direction at the upper and lower ends of the metal liner 6 to join them together. The ceramic shroud 9 made of the same material as the shell 4 is inserted inside the shroud 7 via an insert member 8.
Are joined. On both sides of the metal shroud portion 7, fitting pieces 7a projecting outward from the metal shroud portion 7 are formed, and these are fitted and mounted on the support portion of the apparatus. The insert member 8 is made of a soft material or a material having a thermal expansion coefficient intermediate between that of the ceramic shroud portion 9 and the metal shroud portion 7, and the stress based on the difference in the amount of thermal expansion when the two are joined at a high temperature. The purpose of this is to suppress the occurrence of.

The step inner surface of the pressing portion 6b and the end surface 4a of the shell 4 are separated from each other without being joined by interposing a release agent such as BN therebetween, and the shell 4 and the ceramic shroud portion are separated. A slight gap 4b is provided between the gap 4b and the gap 7b.

Here, a method for manufacturing the turbine vane 1 will be described.

The ceramics shell 4 of the wing portion 2 is formed by sintering using a powder such as SiC or Si ₃ N ₄ .

The inside of the ceramic shell 4 and the portion corresponding to the pressing portion 6b of the liner 6 are filled with a Ti alloy or a Ni-based alloy powder, or a mixture of any of them and a long fiber such as SiC or Si ₃ N _4. I do. At this time, the heat insulating layer 5 made of long fiber such as SiC, Si ₃ N _{4 is} previously formed on the inner surface of the ceramics shell 4.
And the upper and lower end surfaces 4a of the shell 4
A release agent such as BN is applied beforehand.

The above are hot isostatic pressing (HIP)
For example, integral molding is performed at 1000 ° C. and 200 kg / cm ² .

The mounting part 3 prepared separately from the above and formed by joining the metal shroud part 7 and the ceramic shroud part 9 is mounted on the wing part 2, and this is also diffusion bonded by HIP.

In the manufacture of such a turbine vane 1, as described above, the metal liner 6, the thermal expansion coefficient difference and the temperature difference depend on the cross-sectional area ratio of the metal liner 6 and the ceramic shell 4 of the blade section 2.
The initial stress generated in the ceramic shell 4 and the stress during steady operation are determined.

FIG. 3 to FIG. 5 show the results of numerical analysis performed to find the optimum ranges of the above-mentioned difference in thermal expansion coefficient, cross-sectional area ratio, and the like.
First, FIG. 3, the ratio A _m / A _c of the cross-sectional area A _c of the cross-sectional area A _m and ceramic shell 4 of the metal liner 6 on compression initial stress generated during HIP molding described above, and respective thermal FIG. 4 shows the results of numerical analysis on the effect of the difference Δα = α _m −α _c between the expansion coefficients α _m and α _c . FIG. 4 also shows the ceramic shell 4 at 1400 ° C. and the metal liner 6 at 550 ° C. during steady operation. FIG. 3 shows the stress when the stress caused by this temperature difference is superimposed on the initial stress in FIG.

Regarding both the initial stress and the stress during steady operation, the ceramic shell 4 has a large sectional area ratio (the metal liner 6).
The larger the cross-sectional area is, the larger the difference in thermal expansion coefficient (the larger the thermal expansion coefficient of the metal liner 6).

For example, in the case of an emergency stop from the steady operation state, rapid cooling is performed from the thin portion of the wing portion 2, for example, from the trailing edge portion 2 b of the wing portion 2. The higher the compressive stress is, the greater the effect of canceling the thermal stress by local cooling is. Therefore, the above-mentioned cross-sectional area ratio and thermal expansion coefficient ratio should be selected so as to increase the compressive stress. However, if the compressive stress on the ceramics shell 4 side is too high, there is a possibility that destruction may occur due to local bending or the like. According to experiments by the present inventors, the critical compressive stress is about 90 kg / mm ² . On the other hand, the thermal stress due to the rapid cooling of the trailing edge 2b is approximately 30 kg.
Since / it mm ² or more is known, eventually during steady need minimum 30kg / mm ^2, compressive stress maximum 90 kg / mm ² is generated in the ceramic shell 4. It is also desirable that the compressive stress in the cooled state has an appropriate value. Further, as apparent from FIG. 4, when the cross-sectional area ratio becomes too small (the cross-sectional area of the metal liner is small), the tensile stress of the metal liner 6 becomes excessive. Therefore, it is necessary to select the cross-sectional area ratio so as not to exceed the tensile strength of the metal liner 6 at the maximum temperature of 550 to 600 ° C.

Considering the above constraints, the conditions to be satisfied in the cross-sectional area ratio and the difference in the coefficient of thermal expansion are determined as follows, and the range in which the conditions are satisfied is shown in FIG. It is necessary to set the area surrounded by the straight lines A, B, C in the figure, and more preferably, the straight lines B, C, D
The area surrounded by is good.

Line A is the limit for providing effective compression initial stress in ceramic shell 4, represented by A _m / A _c = 0.4.

The straight line B is a limit for preventing the ceramic shell 4 from compressive failure, and is represented by Δα × 10 ⁻⁶ ≦ 5.0−6.67 (A _m / A _c −1).

The straight line C is a limit for preventing the metal liner 6 from breaking in tension.
(Kg / mm ² ), Δα × 10 ⁻⁶ ≦ σ / 90 × A _m / A _c

In order to obtain the above-mentioned necessary compressive stress, it is necessary to satisfy the above three conditions. Curve D shows the limit for applying a more effective compressive force in a state where the initial stress and the thermal stress due to the temperature deviation are offset during rapid cooling, and is surrounded by this curve D and straight lines B and C. It is more desirable to set the range.

As a material for a reinforcing member that satisfies the above conditions, there is a Ti alloy or a Ti-based composite material in which a SiC long fiber is compounded with a Ti alloy to adjust the coefficient of thermal expansion and high-temperature strength. Ni-based alloys and stainless steels are excellent in heat resistance, but as they are, the difference in thermal expansion coefficient with ceramics becomes too large to satisfy the above conditions. However, this can be used if the thermal expansion coefficient is adjusted by compounding a low thermal expansion coefficient fiber such as SiC fiber with this.

 Next, the operation and effect of this embodiment will be described.

In the turbine vane 1 of this embodiment, both ends of the ceramic shell 4 are shortened and pinched by both pressing portions 6b of the liner 6, whereby the shell 4 has a compressive stress in a normal temperature state, that is, in an initial state. It has occurred. In a high-temperature steady operation state, the temperature of the ceramics shell 4 is about 1400 ° C., whereas the temperature of the metal liner 6 is about 600 ° C. due to the presence of the heat insulating layer 5 and the air holes 6a. A larger compressive stress acts on the ceramic shell 4. When an emergency shutdown of the gas turbine is performed in such a state, the trailing edge portion 2b of the blade portion 2 cools more rapidly than the leading edge portion 2a thereof, and a temperature difference occurs between the two portions. In this embodiment, however, the thermal stress based on this temperature difference is offset by the compressive stress acting on the ceramics shell 4 of the wing portion 2 in a steady state, and therefore, even during rapid cooling, the thermal stress becomes abnormal. Never rise,
As a result, the thermal shock resistance can be significantly improved.

By the way, in the case of a structure in which both ends of the ceramic shell 4 are pressed and held by the pressing portions 6b of the metal liner 6, if this pressing portion and the ceramic shell are joined in advance, when the metal liner 6 contracts during cooling, this pressing is performed. It has been found that the portion 6b may be warped upward and the ceramic shell 4 may be pulled. In order to prevent this, in the present embodiment, a mold release agent is interposed between the upper and lower ends 4a of the ceramic shell 4 and the pressing portion 6b to separate them. Therefore, even if the above-mentioned warpage occurs, the ceramics shell 4 is not damaged.

In addition, when the ceramics shell 4 and the ceramics shroud portion 9 were integrally formed, it was found that the entire body was thermally deformed at the time of rapid cooling, and that thermal stress was likely to concentrate on a cross-sectional change portion between the two. Therefore, in this embodiment, a gap 4b is formed between the ceramics shell 4 and the ceramic shroud portion 9 without integrating them, thereby preventing the occurrence of this problem. That is, a wing portion 2 in which the ceramics shell 4 and the metal liner 6 are integrated and a mounting portion 3 in which the metal shroud portion and the ceramic shroud portion are integrated are separately prepared, and the two are joined together. The structure was such that only the joints were used.

In addition, since the fitting portion 7a formed on the metal shroud portion 7 of the mounting portion 3 is fitted to the support portion of the device, the ceramic portion is made of another member. And the reliability of the mounting portion can be improved accordingly.

Next, the results of experiments performed to explain the effects of the present invention will be described.

In this experiment, a turbine vane having the shape shown in FIGS. 1 and 2 was manufactured using the various materials shown in Table 1 by the above-described manufacturing method, and the initial stage generated at the trailing edge 2b of the ceramic shell 4 was obtained. The stress was measured and the thermal shock resistance was evaluated. The evaluation results are shown in the same table, and in FIG. 5, the positions related to the appropriate range are indicated by crosses. Incidentally, in the table L is longitudinal length of the blade portion 2, L _t is a ceramic shell 4, a rear distance between the metal liner 6.

As is clear from this experiment, No. 4, 5, 7, and 7 having the most desirable cross-sectional area ratio and thermal expansion coefficient difference (in the region surrounded by straight lines B, C, and D in FIG. 5) In the cases of 9, 10, 12 and 14, the initial compressive stress in an appropriate range was obtained, and it was found that there was no breakage in the thermal shock test, and that the thermal shock resistance was secured.

On the other hand, in Nos. 1 to 3, the cross-sectional area ratio and the difference in thermal expansion coefficient are not within the appropriate ranges, and the ceramic shell 4 and the pressing portion 6b (pressing block) of the metal liner 6 are joined. Therefore, in No. 1, the compressive stress was excessive and breakage occurred during molding. In Nos. 2 and 3, the initial compressive stress could not be obtained, and cracks and breakage occurred.

In No. 6, the combination of the difference in thermal expansion coefficient and the cross-sectional area ratio was not in the most preferable range, and although no breakage occurred, sufficient initial compressive stress was not generated. Nos. 8 and 11 are examples in which the difference in thermal expansion coefficient with respect to the cross-sectional area ratio was too large and an excessive compressive force acted on the ceramic shell 4.

Although the gas turbine blades have been described in the above embodiments, the scope of the present invention is not limited to this. The gas turbine blades are used in a high-temperature atmosphere where rapid temperature changes occur, such as jet engine parts. It is effective if it is a part.

〔The invention's effect〕

As described above, according to the ceramic heat-resistant composite part according to the present invention, the cover member is given a compressive initial stress that suppresses thermal stress due to a local temperature difference, and a heat insulating layer is formed between the cover member and the reinforcing member. In the steady state, a compressive stress less than the allowable compressive stress of the ceramics was generated. Even if the occurrence occurs, there is an effect that the thermal stress can be suppressed and the thermal shock resistance can be greatly improved.

[Brief description of the drawings]

1 to 5 are views for explaining a gas turbine vane according to an embodiment of the present invention. FIG. 1 is a partially sectional perspective view of FIG. 1, FIG. FIG. 5 to FIG. 5 are characteristic diagrams for explaining an appropriate range of the cross-sectional area ratio-thermal expansion coefficient difference. In the figure, 1 is a turbine vane (ceramic heat-resistant composite part), 2 is a blade part (part body), 3 is a mounting part, 4 is a ceramic shell (coating member), 5 is a heat insulating layer, 6 is a metal liner (reinforcing member). Is).

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor, Kiminori Nakayama 2- 10-6 Kita-Aoki, Higashinada-ku, Kobe-shi, Hyogo (72) Inventor Ken-ichi Aota 3- 9-9, Soyama-cho, Kita-ku, Kobe, Hyogo (72) Inventor Yoichiro Yoneda 731-1-4 Tehiro, Kamakura City, Kanagawa Prefecture (56) References JP-A-62-41903 (JP, A) JP-A-61-89905 (JP, A) JP-A-62-605 (JP) , A)

Claims (1)

(57) [Claims] 1. A component body in which a reinforcing member made of a heat-resistant metal having a larger coefficient of thermal expansion than a coating member is inserted and placed in a coating member made of ceramics; In the ceramic heat-resistant composite part comprising a fixed mounting portion and used in a high-temperature atmosphere, a compression initial stress that suppresses a thermal stress generated due to a local temperature difference at the time of rapid cooling of the covering member is generated at room temperature. The covering member is compression-clamped by the mounting portion, and a heat insulating layer is formed between the covering member and the reinforcing member so that a temperature difference occurs between the covering member and the reinforcing member in a steady state. Wherein the temperature difference, the coefficient of thermal expansion difference, and the cross-sectional area ratio between the covering member and the reinforcing member are set to be equal to or less than the allowable compressive stress of the ceramics heat-resistant composite part.