JPH01285603A - Ceramics heat resistant composite part - Google Patents

Abstract

PURPOSE:To improve heat resistant impact by a method wherein a compression initial stress is exerted on a covering member made of ceramics, a heat insulating layer is formed between the covering member and a reinforcing member made of a metal disposed in the covering member, and a compression stress is generated even in a steady state. CONSTITUTION:When a part is applied for a vane part 2 and a stator blade 1 for a gas turbine formed with mounting parts 3 and 3 formed at both ends thereof, the blade part 2 is formed such that a metallic liner 6 serving as a reinforcing member is inserted and situated in a ceramic shell 4 serving as a covering member with a heat insulating layer 5 therebetween. In this case, the shell 4 is compressed and nipped by means of a mounting part 3 so that a compression initial stress is generated under a room temperature state at the shell 4. The heat insulating layer 5 is formed between the shell 4 and the liner 6 so that a temperature difference is produced under a steady using state between the shell 4 and the metallic liner 6. This constitution enables the com pression stress of the shell 4 to be held in a given range by means of a tempera ture difference, a difference in the coefficient of thermal expansion, and a sec tional area ratio between the shell 4 and the liner 6.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a ceramic heat-resistant composite component in which a metal reinforcing member (core metal) is disposed within a ceramic covering member (shell). In particular, the present invention, which relates to composite parts that can improve thermal shock resistance, is applied to various heat-resistant parts such as gas turbines and jet engines. will be explained using an example.

[Conventional technology]

It has long been known that the thermal efficiency of heat engines such as gas turbines improves as the combustion gas temperature increases, but currently there are limits to the heat resistance of components such as turbine blades, so the combustion gas It is used at temperatures below about 800°C. If it were possible to use ceramics for these turbine blades, etc., it would be possible to increase the gas temperature to about 1400° C., and it would be expected that thermal efficiency could be significantly improved.

In order to realize this ceramic turbine blade, it is essential to optimize the blade's structural design and material selection to ensure reliability as a component.

By the way, ceramics have excellent heat resistance, but on the other hand, because of their low deformability, they have the disadvantage that they are easily destroyed by large thermal distortions or impact or localized contact.

Therefore, when ceramics are used for turbine blade members, there is a problem in that they are easily damaged by thermal stress due to temperature differences between various parts due to rapid heating during the temperature rising process and rapid cooling during emergency shutdown. In addition, conventionally, mechanical fitting has been used to attach ceramic turbine legs to the rotor or stator, but in this case, the ceramic part is easily damaged due to stress concentration at the contact area, which should be resolved. That's a problem.

As a way to solve these problems, instead of integrally forming turbine blades with complex shapes from ceramics, ceramic parts are made into multiple parts with simple shapes, such as the blade part that comes into direct contact with the combustion gas, and the part that connects this part to the rotor. It is divided into a shroud part that serves as a mounting part for attaching to the air conditioner, etc., and is mechanically assembled with metal parts to secure the necessary blade shape, thereby releasing thermal stress caused by temperature differences. (For example, see Japanese Patent Laid-Open No. 61-66802).

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

■ When looking at the blade section of a turbine blade in cross section, the trailing edge is thinner, so during an emergency stop, the trailing edge is cooled more rapidly than the leading edge. Therefore, a considerable temperature difference will occur within the cross section, but in the method described in the above-mentioned partial axis, since the wing portion is integrated, it is not possible to reduce the thermal stress due to the above-mentioned temperature difference.

■ Split, &! In the case of an I-vertical type, the structure is generally complicated and tends to have a shape with many stress concentration points, resulting in a lack of reliability.

The present invention has been made to solve the above-mentioned conventional problems, and can suppress the generation of thermal stress even during rapid cooling such as during an emergency stop, has a stiff structure, has few stress concentration points, and is reliable. The aim is to provide ceramic heat-resistant composite parts that can improve the

[Means for solving problems]

In order to achieve the above object, the present inventors investigated measures to reduce thermal stress during rapid cooling, and in particular, in order to suppress the tensile stress generated at the trailing edge of the turbine blade, it is necessary to apply compressive stress in advance. I focused on the good points. On the other hand, during steady operation, the reinforcing member made of metal has a large coefficient of thermal expansion, so if left as is, the compressive initial stress will be eliminated.To prevent this, the difference in the coefficient of thermal expansion between the reinforcing member and the covering member is We have come up with the idea that the temperature of the reinforcing member can be lowered depending on the situation. Moreover, lowering the temperature of the reinforcing member in this manner is advantageous in the sense of compensating for the fact that the heat resistance of the reinforcing member is lower than that of ceramics.

Therefore, the present invention provides a component main body in which a reinforcing member made of a heat-resistant metal having a coefficient of thermal expansion larger than that of the covering member is inserted into a covering member made of ceramics, and a device supporting portion formed at both ends of the main body. In a ceramic heat-resistant composite component used in a high-temperature atmosphere, the covering member is compressed and clamped by both the mounting parts so that compressive initial stress is generated in the covering member at room temperature, and the covering member is compressed and held by the mounting parts. A heat insulating layer is formed between the member and the reinforcing member, and the compressive stress of the covering member is maintained within a predetermined range by the temperature difference that occurs between the two members under normal use, the difference in thermal expansion coefficient and the cross-sectional area ratio of the two members. It is characterized by being configured to do so.

Here, in the present invention, the compressive initial stress needs to be set to a size that can offset the thermal stress caused by the temperature difference between each part that occurs during rapid cooling, and the method of applying this compressive initial stress to the covering member is as follows: For example, the following method can be adopted.

■ First, a coating made of ceramics is formed, and metal powder for the reinforcing member is filled in the coating and a portion corresponding to the mounting part located at the 1ilf end of the coating, and then this is subjected to, for example, hot isostatic pressing (
(hereinafter referred to as HIP) and cooled. Then, due to the difference in the amount of thermal contraction between the covering member and the reinforcing member, the covering member is compressed and clamped by the attachment portion, thereby generating a compressive initial stress. Of course, tensile stress is generated in the reinforcing member. ■ Both mounting parts, which are placed at both ends of the covering member, are tightened with fastening bolts, thereby mechanically applying compressive initial stress to the covering member. generate.

Further, the compressive stress to be generated in the covering member during steady operation must be maintained at the above-mentioned initial compressive stress or higher and below the allowable compressive stress of the covering member.

This is determined by the thermal expansion coefficient difference 5 between the covering member and the reinforcing member, and the temperature difference between the two, and the cross-sectional area ratio between the two. -, the above-mentioned warm J
f Thatch is generally used to withstand the heat resistance temperature of reinforcing members (600℃ for 4N).
) and the operating atmosphere temperature (for example, G4 is 1400°C), so the thermal expansion coefficient difference and cross-sectional area ratio should be adjusted appropriately to obtain compressive stress within the above-mentioned allowable range depending on the temperature difference when maintained at this heat-resistant temperature. A selection will be made. 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 the two members, and this heat insulating layer is made of, for example, ceramic wool with about In This can be achieved by placing a molded product between the two members.

[Effect]

In the ceramic heat-resistant composite component according to the present invention, an initial compressive stress is generated in the ceramic covering member, and the insulation is insulated so that there is a considerable temperature difference between the covering member and the reinforcing member under normal use. Under steady use conditions, this temperature difference formed a layer.

A compressive stress corresponding to the difference in thermal expansion coefficient and the cross-sectional area ratio is generated in the covering member, and the above-mentioned initial compressive stress is promoted. Therefore, when a rapid cooling condition occurs, such as in the case of an emergency shutdown of a gas turbine, some parts are locally cooled depending on the cross-sectional shape of the part, but the thermal stress in these parts is equal to the above-mentioned compressive stress at steady state. This local cooling does not generate tensile stress, and as a result, thermal shock resistance is significantly improved.

〔Example〕

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

1 to 5 are diagrams for explaining a stator blade for a gas turbine according to an embodiment of the present invention.

In FIGS. 1 and 2 showing this stationary blade, 1 is a gas turbine stationary blade, which is composed of a blade section 2 and attachment sections 3.3 formed at both ends thereof.

The wing section 2 has a so-called wing shape in which the thickness gradually becomes thinner with chipping from the leading edge 2a to the trailing edge 2b, and the insulation 1) 15 is sandwiched between the ceramic shell 4 as a covering member and used as a reinforcing member. A metal liner 6 is inserted and arranged. A plurality of air holes 6a are formed in this metal liner 6, and these are for preventing abnormal temperature rise of the liner 6 due to air circulation. Further, step-shaped pressing portions 6b are formed outwardly at the upper and lower ends of the metal liner 6, and as shown in the figure, both lower ends of the ceramic shell 6 are compressed to a predetermined level by the pressing portions 6b, 6b. It is clamped so that the initial stress resides therein. This initial compressive stress is thermal stress (for example, tensile stress of 30 kg/n') caused by the trailing edge 2b of the wing section 2 being cooled more rapidly than the leading edge 2a during an emergency stop.
Therefore, it is set to a minimum of 3Qkg/w'' or more.

The ceramic shell 4 has S I C+ S i
It is made by firing powder such as s Na, and the above section p15
is made by molding ceramic fibers such as the above-mentioned SiC to a thickness of, for example, one inch. Further, the metal liner 6 may be made of, for example, a Ti alloy, a composite material made of Ti alloy and a composite material such as SiC + 5isNa, or a Ni-based alloy and Si
A composite material made of long fibers such as C+ 5itNs is used. The metal liner 6 and the ceramic shell 4 are selected to have a predetermined difference in thermal expansion coefficient. This thermal expansion coefficient difference is caused by the temperature difference between the ceramic shell 4 and the metal liner 6 caused by the heat insulating layer 5 during steady operation, and the cross-sectional area ratio of both, which causes compressive stress in the ceramic shell 4 within a predetermined range during steady operation. set to occur.

And this compressive stress during steady operation is equal to the above compressive initial stress <
The stress is set to be at least 30 kt/vaa'') and less than the allowable compressive stress for ceramics (for example, 90 kt/1)').

The mounting portion 3 is configured as follows.

That is, the metal shroud part 7 made of the same material as the liner 6 is fitted onto the pressing part 6b integrally formed in an outward step shape at the upper and lower end parts of the metal liner 6 to join them together. , a ceramic shroud part 9 made of the same material as the shell 4 is joined to the inside of the shroud part 7 via an insert member 8. The metal shell part 7
Fitting pieces 7a are formed on both sides of the device and project outward from the fitting pieces 7a, which are fitted and attached to the support portion of the device.

In addition, the insert material 8 is made of a soft material or a material having a coefficient of thermal expansion intermediate between the ceramic shroud part 9 and the metal shroud part 7, and the stress due to the difference in thermal expansion when the two are joined at high temperature. This is to suppress the occurrence of.

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

Here, a method for manufacturing the turbine static j[1 will be explained.

■ The ceramic shell 4 of the wing part 2 is made of SiC, Si3
Sinter and shape using powder such as N4.

■ Inside the ceramic shell 4 and in the portion corresponding to the pressing portion 6a of the liner 6, Ti alloy or Ni-based alloy powder, or any of these in addition to SiC, 5IzN
Fill with a mixture of long fibers such as a. At this time, S iC+ S r s is applied to the inner surface of the ceramic shell 4 in advance.
A heat insulating FJ5 made of long fibers such as N4 is inserted and arranged, and a release agent such as BN is applied to the upper and lower end surfaces 4a of the shell 4.

■ The above materials are integrally molded using hot isostatic pressing (HIP), for example, at 1000° C. and 200 kir/on.

(2) The attachment part 3, which is prepared separately from the above and made by joining the metal shroud part 7 and the ceramic shroud part 9, is attached to the wing part 2, and this is also diffusion-bonded by HIP.

In manufacturing such a turbine stationary blade 1, as described above, the metal liner 6 is affected by the cross-sectional area ratio, thermal expansion coefficient difference, and temperature difference between the metal liner 6 of the blade part 2 and the ceramic shell 4.
, the initial stress generated in the ceramic shell 4 and the stress during steady operation are determined.

Figures 3 to 5 show the results of numerical analysis conducted to find the optimal ranges of the thermal expansion coefficient difference, cross-sectional area ratio, etc. First, Figure 3 shows the compression generated during HIP molding as described above. Regarding the effect of the ratio A, /Ac between the cross-sectional area A1) of the metal liner 6 and the cross-sectional area Ac of the ceramic shell 4, and the difference Δα-α, -α6 between the respective thermal expansion coefficients α and α6 on the initial stress Figure 4 shows the stress generated by this temperature difference when the temperature of the ceramic shell 4 reaches 1400°C and the temperature of the metal liner 6 reaches 550°C during steady operation. This shows the stress when superimposed on

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

For example, if there is an emergency stop from a steady state of operation,
A thinner portion of the wing portion 2, for example, the trailing edge portion 2 of the wing portion 2
Since rapid cooling is performed from step b, the higher the compressive stress of the ceramic shell 4 that is the coating member, the greater the effect of offsetting the thermal stress due to local cooling. Therefore, the above-mentioned cross-sectional area ratio and thermal expansion coefficient ratio may be selected so as to increase this compressive stress. However, ceramic shell 4
If the compressive stress on the side is too high, there is a risk that destruction may occur due to local bending, etc.According to experiments by the inventor Hisashi, the critical compressive stress is approximately 90kg7m''.
On the other hand, it is known that the thermal stress due to rapid cooling of the trailing edge portion 2b is approximately 30 kg/tm" or more, so in steady state the minimum stress is 30 kg/tm, and the maximum is 90 kg/tm".
It is necessary that a compressive stress of "g/tm" is generated in the ceramic shell 4. It is also desirable that the compressive stress in the cooled state be at an appropriate value, and as is clear from Fig. 4. In addition, if the cross-sectional area ratio is too small (the cross-sectional area of the metal liner is small), the tensile stress of the metal liner 6 will become excessive.
It is necessary to select the cross-sectional area ratio so as not to exceed the tensile strength at ~600°C.

Considering the above constraints, the conditions to be satisfied in terms of cross-sectional area ratio and thermal expansion coefficient difference are determined as follows, and the range that satisfies this is surrounded by straight lines A, B, and C in Figure 5. It is necessary to set the range within a certain range, and more preferably straight line B,
The range surrounded by C and D is good.

■ Direct & lA is a ceramic shell 4 with the stress of growth and compression.
is the limit given to A, /Ac-0,4.

■ Straight line B is the limit to prevent the ceramic shell 4 from being compressed and destroyed, Δα×104≦5.0-6.67(A, /A, -1
).

■ Straight line C is the limit to prevent the metal liner 6 from tensile failure, and if its tensile strength at 600°C is σ (kg/n'), then Δα×101≦g/9
It is represented by 0 x A, / AC.

In order to obtain the above-mentioned necessary compressive stress, it is necessary to satisfy the above three conditions. In addition, the curve indicates the limit for applying a more effective compressive force when the initial stress and the thermal stress due to temperature deviation are canceled out during rapid cooling.
This curve and straight line B.

It is more desirable to set the range surrounded by C.

Examples of materials for reinforcing members that can satisfy the above conditions include Ti alloys and TiI & composite materials in which the Ti alloy is composited with SiC long fibers to adjust the coefficient of thermal expansion and high-temperature strength. In addition, Ni-based alloys and stainless steel have excellent heat resistance, but if they are used as they are, the difference in thermal expansion coefficient with ceramics becomes too large and the above conditions cannot be met. However, if they are combined with low thermal expansion coefficient fibers such as SiC fibers It can be used by adjusting the coefficient of thermal expansion.

Next, the effects of this embodiment will be explained.

In the turbine engine of this embodiment, both ends of the ceramic shell 4 are compressed and held between both pressing parts 6a of the liner 6, and as a result, compressive stress is generated in the shell 4 at room temperature, that is, in the initial state. are doing. In addition, in a high-temperature steady state of operation, the temperature of the ceramic 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. An even larger compressive stress will act on the ceramic shell 4. When an emergency stop of the gas turbine is performed in such a state, the trailing edge 2b of the blade section 2 cools more rapidly than the leading edge 2a, and a temperature difference occurs between the blade sections. However, in this example,
Thermal stress based on this temperature difference is offset by the compressive stress acting on the ceramic shell 4 of the wing section 2 during steady state, so that the thermal stress does not increase abnormally even during rapid cooling, and as a result, the heat resistance Impact resistance can be greatly improved.

By the way, in the case of a structure in which both ends of the ceramic shell 4 are pressed and held between the pressing parts 6a of the metal liner 6, if this pressing part and the ceramic shell are joined, this will be avoided when the metal liner 6 contracts during cooling. It has been found that the pressing portion 6a may warp upward, causing tension in the ceramic shell 4. In order to prevent this, in this embodiment, a mold release agent is interposed between the upper and lower end portions 4a of the ceramic shell 4 and the pressing portion 6a to separate them.

Therefore, even if the above-mentioned warpage occurs, the ceramic shell 4 will not be damaged.

In addition, the ceramic shell 4 and the ceramic shell part 9
It has also been found that when these are integrally formed, the entire structure is thermally deformed during rapid cooling, and thermal stress is likely to be concentrated in the cross-sectional area between the two. Therefore, in this embodiment, the ceramic shell 4 and the ceramic shroud portion 9 are not integrated, but a gap 4b is formed between them to prevent this problem from occurring. That is, the wing part 2 which is made by integrating the ceramic shell 4 and the metal liner 6, and the attachment part 3 which is made by integrating the metal shroud part and the ceramic shroud part are made separately, and both metal parts are attached to each other. The structure is such that it can be joined with chisels.

In addition, the turbine stationary blade l is attached to peripheral equipment by fitting the fitting part 7a formed on the metal shroud part 7 of the attachment part 3 into the supporting part of the equipment, so that the ceramic part is attached to other parts. The reliability of the mounting part can be improved accordingly.

Next, the results of experiments conducted to explain the present invention in detail will be explained.

This experiment was conducted using the various materials shown in Table 1.
A turbine stationary blade having the shape shown in FIGS. 2 and 2 was manufactured by the above manufacturing method, and the initial stress generated in the trailing edge portion 2b of the ceramic shell 4 was measured, and the thermal shock resistance was evaluated. The evaluation word i is shown in the same table, and its relative position with respect to its appropriate range is indicated by an X mark in FIG. In addition, the inside of the table is the front-to-back length of the wing section 2.

4. Ceramic shell. This is the distance between the rear ends of the metal liner 6.

As is clear from this experiment, the most desirable cross-sectional area ratio and thermal expansion coefficient difference exist (direction IB in Fig. 5).

(in the area surrounded by C and D)flh4,5゜7
．． In No. 9, 10.12 to 14, an initial compressive stress within an appropriate range was obtained, and no damage occurred in the thermal shock % test, indicating that thermal shock resistance was ensured.

On the other hand, -1 to 3 are because the cross-sectional area ratio and the difference in thermal expansion coefficient are not within the appropriate range, and the ceramic shell 4 and the pressing part 6b (pressing block) of the metal liner 6 are joined. , l! In ILI, compressive stress becomes excessive and damage occurs during molding, resulting in +! At 12°3, initial compressive stress could not be obtained and cracks occurred.

Damage has occurred.

Further, in the hermitage 6, the combination of the thermal expansion coefficient difference and the yfTWJ volume ratio is not in the most desirable range, and although no damage has occurred, sufficient initial compressive stress has not been generated.

Further, lb8.1) is an example in which the difference in thermal expansion coefficient was too large with respect to the cross-sectional area ratio, and an excessive compressive force was applied to the ceramic shell 4.

In the above embodiments, a gas turbine blade was described; however, the present invention is not limited to this, and may be applied to jet engine parts, etc., in an atmosphere where high temperatures and rapid temperature changes exist. It is valid if the parts are used in

〔Effect of the invention〕

As described above, according to the ceramic heat-resistant composite component according to the present invention, compressive initial stress is applied to the covering member, and a heat insulating layer is formed between the covering member and the reinforcing member, so that compressive stress is generated even in a steady state. As a result, even if local temperature deviation occurs due to rapid cooling, thermal stress can be suppressed and thermal shock resistance can be significantly improved.

[Brief explanation of the drawing]

1 to 5 are diagrams for explaining a gas turbine stationary blade according to an embodiment of the present invention, in which FIG. 1 is a partially sectional perspective view, FIG. 2 is a sectional plan view thereof, and FIG. 5 through 5 are characteristic diagrams for explaining the appropriate range of the cross-sectional area ratio-thermal expansion coefficient difference. In the figure, ■ is a turbine stationary blade (ceramic heat-resistant composite part), 2 is a blade part (component body), 3 is a mounting part, 4 is a ceramic shell (coating member), 5 is a heat insulation layer, and 6 is a metal liner (reinforcing member). ). Patent Applicant Kobe Steel Co., Ltd. Representative Patent Attorney Tsutomu Shimoichi Figure 1 Figure 2 Figure 5 XN0I X'°II JCixlO-' 0 0.2 0.4 0.6 0.8
1.0 1.2 1.4a-Am/Ac

Claims (1)

[Claims] (1) A component body formed by inserting a reinforcing member made of heat-resistant metal having a higher coefficient of thermal expansion than the covering member into a ceramic covering member, and a component body formed at both ends of the main body and fixed to the device support part. In a ceramic heat-resistant composite component used in a high-temperature atmosphere, the covering member is compressed and clamped by the mounting part so that an initial compressive stress is generated in the covering member at room temperature. A heat insulating layer is formed between the covering member and the reinforcing member so that a temperature difference is created between the two members, and the compressive stress of the covering member is reduced by the temperature difference, thermal expansion coefficient difference, and cross-sectional area ratio between the two members. A ceramic heat-resistant composite part characterized by being configured to maintain the temperature within a predetermined range.