JP3388949B2 - Heat resistant member and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat resistant member having a ceramic coating excellent in thermal shock resistance and thermal fatigue resistance and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, high temperature heat resistant members such as gas turbine blades and aircraft turbine blades have been made of iron-based alloys,
A structure in which a ceramic coating is formed as a thermal barrier coating layer on the surface of a metal base material made of a heat resistant alloy such as a nickel base alloy or a cobalt base alloy, or a metal bonding layer is interposed between the metal base material and the ceramic coating. Different structures are used. In such a heat-resistant member, the above-mentioned thermal barrier coating layer protects the metal base material from high temperatures exceeding the durability limit, which makes it possible to use it at high temperatures for a long period of time, so it can be used for various large industrial applications. Application to equipment is being studied.

As a material for forming the above-mentioned thermal barrier coating layer, zirconia, which has excellent mechanical properties such as high strength and high toughness, has a coefficient of thermal expansion close to that of a metal, and has a small thermal conductivity, is drawing attention. ing. As a method of forming the thermal barrier coating layer made of such a ceramic coating, a thermal spraying method, a PVD method, etc. are generally used.

By the way, when a high-temperature device using a heat-resistant member having a ceramic coating as described above is operated so as to cause a thermal cycle, or is frequently stopped suddenly, in particular, a metal base material and a ceramic coating are formed. Due to the thermal stress generated due to the difference in the thermal expansion coefficient of the ceramics, cracks are likely to occur in the ceramic coating of the heat-resistant member or at the interface between the ceramic coating and the metal substrate (or the metal bonding layer), and the ceramic coating may be peeled or chipped. There was a problem that it would occur.
It is considered that such peeling or breakage of the ceramic coating occurs especially when cracks propagate in a direction parallel to the coating surface (horizontal direction).

[0005]

As described above, the conventional heat-resistant member having the ceramic coating has cracks in the ceramic coating or at the interface between the ceramic coating and the metal base material (or metal bonding layer) due to thermal stress or the like. It is apt to occur, and there is a problem that the crack propagates in the horizontal direction, resulting in peeling or loss of the ceramic coating. The peeling and cracking of the ceramic coating have been a major cause of shortening the life of the heat resistant member.

From the above, cracks due to thermal stress and the like are prevented from propagating in the horizontal direction, and the ceramic coating as the thermal barrier coating layer is prevented from peeling or cracking, so that the heat resistance of the heat resistant member is improved. There is a strong demand for improvement in fatigue characteristics and thermal shock resistance.

The present invention has been made in order to solve such a problem, and a heat-resistant member and a heat-resistant member which are improved in thermal fatigue resistance and thermal shock resistance by preventing peeling or damage of the ceramic coating. It is intended to provide a manufacturing method.

[0008]

The heat-resistant member of the present invention is a heat-resistant member comprising a metal base material and a ceramic coating film formed on the metal base material. A plurality of fibrous particles composed of at least one selected from nitrides and metal oxides are dispersed , and 50% by volume or more of the fibrous particles are the fibers.
+30 to the direction in which the long direction is perpendicular to the surface of the metal substrate
It is characterized in that it is oriented in the range of degrees to -30 degrees .

Further, the method for producing a heat-resistant member of the present invention comprises a step of forming a ceramic coating on a metal substrate, in which at least one kind of particles selected from metal, metal carbide and metal boride is dispersed. The ceramic coating is heat-treated in an atmosphere containing at least nitrogen, and at least one kind of particles selected from the metal, metal carbide and metal boride is mixed with at least one kind of fiber selected from metal nitride and metal oxide. And a step of growing the ceramic coating in the thickness direction as particulates.

As described above, the ceramic coating in the heat resistant member of the present invention has at least one kind of fibrous particles selected from the metal nitride and the metal oxide dispersed in the thickness direction.

Here, as described above, the breakage of the ceramic coating on the conventional heat-resistant member due to peeling, cracking, etc. is caused by the horizontal movement in the ceramic coating or in the vicinity of the interface between the ceramic coating and the metal base material (or metal bonding layer). It is caused by the propagation of cracks in the direction (parallel to the ceramic coating surface).

On the other hand, in the present invention, since the fibrous particles made of metal nitride or metal oxide are dispersed, the propagation of the crack in the horizontal direction is prevented by the fibrous particles. That is, even if a crack is generated due to thermal stress or the like, it is possible to prevent the fibrous particles from changing the direction in which the crack progresses and propagating the crack in the horizontal direction. As a result, it is possible to prevent the ceramic coating from peeling off or being damaged, so that it is possible to improve the thermal fatigue resistance and thermal shock resistance of the heat resistant member. The fibrous particles are
It is necessary that the 50 vol% or more of the fiber length direction is distributed so as to be substantially the same direction as the thickness direction of the film.

The reason why the above-mentioned fibrous particles are made of metal nitride or metal oxide is that they are relatively stable even in a high temperature oxidizing atmosphere, and at the same time, they can be formed in a ceramic film by the production method of the present invention described in detail later. This is because dispersed fibrous particles can be easily obtained.

The fibrous particles may be composed of either metal nitride or metal oxide. For example, the ceramic coating having the metal nitride fibrous particles is heat treated in an oxidizing atmosphere to form a metal nitride. It is particularly preferable to form an oxide on the surface of the fibrous particles. in this way,
By forming an oxide on the surface of the metal nitride fibrous particles, microcracks can be formed at the interface between the ceramic coating and the fibrous particles. That is, since microcracks that effectively act to relieve thermal stress and suppress crack propagation can be formed in the ceramic film in the same direction as the film thickness direction (vertical direction), the life of the ceramic film is further improved. It is possible to improve.

The fibrous particles have an average diameter of 10 to 10
It is preferably 10000 nm, the average length is 0.1 to 50 μm, and the average aspect ratio is 1 to 3000. Further, the dispersion amount of the fibrous particles is preferably 1 to 30% by volume with respect to the ceramic coating. If the dispersion amount of the fibrous particles is less than 1% by volume with respect to the ceramic coating, the effect of suppressing crack propagation as described above may not be sufficiently obtained,
On the other hand, if it exceeds 30% by volume, it may become brittle due to volume expansion due to formation of fibrous particles or oxidation in a high temperature oxidizing atmosphere.

By arranging most of the fibrous particles in the direction perpendicular to the surface of the metal base material, a particularly large crack propagation suppressing effect can be obtained. Thus, at least 50 vol% or more of the fibrous particles shall be distributed in the range of +30 degrees to -30 degrees with respect to the direction perpendicular to the metal substrate.

The microcracks as described above have a length not less than the length of the fibrous particles and not more than the film thickness of the ceramic coating, and in order to effectively alleviate the thermal stress, 1/3 or more of the thickness of the ceramic coating is required. Is desirable.

The ceramic coating in the heat-resistant member of the present invention is preferably a zirconia coating from the viewpoints of strength, toughness, etc., but is not particularly limited to the type of ceramics, and alumina, calcium phosphate, rare earth oxide, calcium silicate, etc. may be used. It is also possible to apply. The ceramic coating may be directly formed on the metal substrate,
It is preferably formed on a metal substrate through a metal bonding layer made of an M-Cr-Al-Y alloy (M is at least one selected from Fe, Ni and Co) or the like. Furthermore, as the metal base material,
Examples include heat-resistant alloys containing at least one selected from Fe, Ni, and Co as main components, and various known heat-resistant alloys can be used depending on the application. Practically IN939,
Ni-based superalloys such as In738, Mar-M247, RENE80, FSX-414,
It is effective to use a Co-based superalloy such as Mar-M509.

Next, a method of manufacturing the heat resistant member of the present invention will be described.

First, a ceramic coating in which at least one kind of particles selected from metals, metal carbides and metal borides (hereinafter referred to as raw material particles) is dispersed is formed on a metal substrate. At this time, a metal bonding layer is preliminarily formed on the metal base material if necessary. The method for forming the ceramic coating is not particularly limited, and various coating forming methods such as a thermal spraying method, a PVD method, and a CVD method can be applied, but the coating forming cost is low and the thick coating is relatively easy. It is possible to apply the thermal spraying method because a relatively porous film that can easily diffuse reaction gases such as nitrogen and oxygen into the film in the process of forming fibrous particles described below is obtained. preferable. From this point of view, the porosity of the ceramic coating is preferably about 8 to 25%.

The raw material particles to be dispersed in the ceramic coating are grown into fibrous particles while being converted into at least metal nitride by the subsequent heat treatment. The reason why the raw material particles initially dispersed in the ceramic coating are made of metal, metal carbide or metal boride is that metal nitride can be easily produced by the subsequent heat treatment and that the stable coating is formed in the coating formed by the thermal spraying method or the like. This is because it can exist. Further, for the same reason as the specific type of the raw material particles, Zr, Ti, Ce, Al, B, Ta, Nb, Mg, etc. for metal particles, TiC, ZrC, HfC for metal carbide particles. , MnC ₂ , Ta ₂ C
, TiC, NbC, Al ₄ C ₃ , B ₄ C, etc., and in the case of metal boride particles, ZrB ₂ , TiB ₂ , TaB ₂ etc. are preferably used.

The raw material particles as described above are preferably present in the ceramic coating in an amount of 5 to 40% by volume. If the amount of raw material particles is less than 5% by volume, it may not be possible to generate sufficient amount of fibrous particles, while if it exceeds 40% by volume, the amount of generated fibrous particles exceeds 30% by volume. .

Next, the ceramic coating in which the raw material particles are dispersed and arranged is heat-treated in an atmosphere containing at least nitrogen. When the ceramic coating is heat-treated in a nitrogen-containing atmosphere and at least nitrogen gas permeates into the ceramic coating, raw material particles grow while converting into nitride in the permeating direction of the gas (that is, the coating thickness direction). A ceramic coating is obtained in which fibrous particles made of metal nitride are dispersed in the fiber length direction substantially in the same direction as the thickness direction of the ceramic coating. Thus, the raw material particles mainly grow while converting into metal nitride to become fibrous particles. Therefore, the heat treatment is performed in an atmosphere containing at least nitrogen.

The heat treatment atmosphere may be an atmosphere containing at least nitrogen as described above, for example, a nitrogen atmosphere,
A mixed atmosphere of nitrogen and an inert gas or oxygen can be used. The pressure of the atmosphere gas is preferably 1.0 × 10 ⁻³ Pa or more. When the pressure of the atmospheric gas is less than 1.0 × 10 ⁻³ Pa, the raw material particles made of metal, metal carbide, and metal boride are not sufficiently nitrided or oxidized. As described above, since the fibrous particles mainly grow due to the formation of nitrides, it is preferable to heat-treat the fibrous particles in a mixed gas of nitrogen containing 80% or more of nitrogen and an inert gas in the process of growing the fibrous particles. Furthermore, it is desirable to perform the treatment in an atmosphere of 100% nitrogen. The aspect ratio of the fibrous particles can be controlled by adjusting the amount of nitrogen in the heat treatment atmosphere.

The surface of the ceramic coating containing the produced fibrous particles can be oxidized by heat treatment in an atmosphere containing oxygen. It is not necessary to change all the dispersed particles to nitrides or oxides, but 90% or more of the raw material particles should be converted from nitrides or oxides in the portion where stress is likely to occur in a high temperature oxidizing atmosphere, for example, near the surface of the ceramic coating. It is preferable to change the fibrous particles to the following, and it is desirable that 80% or more of them be nitrides.

Further, in order to form a ceramic film having excellent thermal shock resistance, it is preferable to prolong the time for forming the above-mentioned nitride and then heat-treat it in an atmosphere gas containing 10% or more of oxygen. Furthermore, after the treatment, it is desirable to take it out of the furnace and perform a quenching treatment. By performing such a treatment, an oxide can be formed on the surface of the fibrous particles made of metal nitride, and microcracks can be formed perpendicularly to the thickness direction of the ceramic coating. As a result, as described above, it is possible to better suppress the crack growth in the horizontal direction, which causes the film peeling and the like. In particular, it is desirable to introduce microcracks in a portion where stress is concentrated so as to relax the stress.

The heat treatment described above is preferably performed at a temperature in the range of 873 to 1473K. If the heat treatment temperature is less than 873K, the conversion of the raw material particles to the nitride does not occur sufficiently and the formation of fibrous particles becomes insufficient, while if it exceeds 1473K, the metal base material may be deteriorated. Further, in order to avoid adverse effects on the metal member, it is desirable to perform heat treatment at a temperature of 1373K or less, and more desirably 1273K or less. Furthermore, it is more preferable to carry out at 1223K or less.

Although attempts have been made to increase the toughness value by dispersing silicon carbide fibers or the like in a sintered body such as silicon nitride, the conventional method is used as a composite material with a metal substrate. It is extremely difficult to apply it to the ceramic coatings used. That is, there is a process of firing powder in which fibrous particles are dispersed in advance in order to manufacture a ceramic member in which fibrous particles are dispersed, but it is suitable for a manufacturing process of a ceramic film such as a thermal barrier coating layer. Absent. In addition, even if ceramic fibers or the like are added to the thermal spray material, the ceramic fibers will be destroyed during the thermal spray or will not be melted to maintain the fiber shape.

On the other hand, as a method of dispersing / precipitating another substance in the ceramic layer, for example, a heat treatment method represented by crystallized glass particles or acicular mullite is known. It is also 1373 K or higher, and heat treatment at such a high temperature adversely affects the metal base material, so it was extremely difficult to apply it to heat-resistant members and the like. Therefore, it is not applied to a composite member with a metal substrate such as a ceramic coating. For these reasons, the prior art has not obtained a ceramic coating in which fibrous particles are dispersed and which has excellent thermal fatigue resistance and thermal shock resistance.

[0030]

EXAMPLES Examples of the present invention will be described below.

Example 1 and Comparative Example 1 First, as a metal base material, Ni-base superalloy IN738 (30 × 30 × 3 mm) was used.
On the surface of this Ni-based superalloy.
A -Cr-Al-Y alloy layer (Ni-23.8% Co-16.7% Cr-13% Ar-0.65% Y) was formed by coating. On this Ni-Co-Cr-Al-Y alloy layer, a mixture of zirconia powder with an average particle size of 1 μm and 10% by volume of aluminum powder with an average particle size of 40 μm was used as a spraying raw material, and a thickness of 250 μm was obtained. Plasma spraying was performed to form a zirconia coating. The porosity of the zirconia coating was about 12%.

Next, the metal base material on which the zirconia coating containing the aluminum particles is formed is subjected to 1273K in a mixed atmosphere of 90% nitrogen and 10% argon (atmospheric pressure: 1.0 × 10 ⁵ Pa).
After heat treatment for 20 hours, a heat resistant member of the present invention was obtained. When the inside of the zirconia coating after heat treatment was examined by SEM,
It was confirmed that about 20% by volume of fibrous particles having an average diameter of 100 nm, an average length of about 20 μm and an average aspect ratio of about 200 were dispersed. Further, the fibrous particles were mainly made of aluminum nitride, and some of the fibrous particles made of aluminum oxide were recognized. Furthermore, 90% by volume or more of fibrous particles are approximately +30 degrees to −30 with respect to the direction perpendicular to the metal substrate.
It was oriented in the range of degrees.

On the other hand, as Comparative Example 1 with the present invention, a single powder of zirconia was used as the thermal spraying raw material, and the heat treatment after forming the coating film was not carried out. A zirconia coating was formed via a Ni-Co-Cr-Al-Y alloy layer.

A thermal cycle test of 1273K × 1 hour + 293K × 1 hour was performed on each heat-resistant member according to Example 1 and Comparative Example 1 described above, and the heat-resistant member of Comparative Example 1 had the zirconia coating peeled 500 times. However, the heat-resistant member of Example 1
The zirconia coating did not peel off even after the application of heat cycles of 5000 times or more. From this, it was confirmed that the thermal shock resistance was improved by dispersing the fibrous particles made of aluminum nitride and aluminum oxide in the zirconia coating.

Example 2 and Comparative Example 2 As in Example 1, a Ni-based superalloy / IN738 (30 × 30 × 3 mm) Ni-Co-Cr-Al-Y alloy layer with a thickness of 150 μm was formed by coating on the surface. Above the zirconia powder with an average particle size of 60 μm, the average particle size is
Using a mixed powder prepared by mixing 35% by volume of 1 μm of aluminum carbide powder as a spraying raw material, plasma spraying was performed to a thickness of 250 μm to form a zirconia coating.
The porosity of the zirconia coating was about 15%.

Next, 90% nitrogen-1 was added to the metal substrate on which the zirconia coating containing the above aluminum carbide particles was formed.
Heat treatment was performed at 1273 K for 20 hours in a mixed atmosphere of 0% argon (atmospheric pressure: 1.0 × 10 ⁵ Pa) to obtain a heat resistant member of the present invention. When the inside of the zirconia coating after heat treatment was examined by SEM, it was confirmed that about 18% by volume of fibrous particles having an average diameter of 500 nm, an average length of about 38 μm and an average aspect ratio of about 100 were dispersed. Further, 90% by volume or more of the fibrous particles were made of aluminum nitride and were oriented in the range of approximately +30 to -30 degrees with respect to the direction perpendicular to the metal substrate.

On the other hand, as Comparative Example 2 with the present invention, N was formed on the Ni-base superalloy in the same manner as in Example 2 except that the heat treatment atmosphere after forming the zirconia film was 100% oxygen atmosphere.
A heat resistant member having a zirconia coating formed via an i-Co-Cr-Al-Y alloy layer was obtained. When the inside of the zirconia coating film of Comparative Example 2 was examined by SEM, the aluminum carbide particles had been converted to aluminum oxide but did not grow into fibrous form.

A heat cycle test of 1273K × 1 hour + 293K × 1 hour was performed on each heat-resistant member of Example 2 and Comparative Example 2 described above. As a result, the heat-resistant member of Comparative Example 2 had the zirconia coating peeled off 300 times. However, the heat-resistant member of Example 2
The zirconia coating did not peel off even after the application of 6000 heat cycles. From this, it was confirmed that the thermal shock resistance was improved by heat-treating the zirconia coating containing aluminum carbide particles in a nitrogen-argon atmosphere.

Example 3 As in Example 1, aluminum was formed on a Ni-Co-Cr-Al-Y alloy layer having a thickness of 150 μm and formed by coating the surface of a Ni-base superalloy / IN738 (30 × 30 × 3 mm). Composite powder in which the surface of carbide particles is covered with zirconia (volume ratio of aluminum carbide 10
%, Particle size: 10-88 μm) as a thermal spray material, thickness 2
Plasma spraying was performed to a thickness of 50 μm to form a zirconia coating. The porosity of the zirconia coating was about 18%. Next, the metal base material on which the zirconia coating composed of the above composite powder was formed was subjected to heat treatment at 1073 K for 24 hours in a mixed atmosphere of 90% nitrogen and 10% argon (atmospheric pressure: 1 × 10 ⁴ Pa). A heat resistant member of the present invention was obtained. When the inside of the zirconia coating after heat treatment was examined by SEM, the average diameter was 300
It was confirmed that about 8% by volume of fibrous particles having a size of nm, an average length of about 5 μm and an average aspect ratio of about 17 were dispersed.
Further, 90% by volume or more of the fibrous particles were made of aluminum nitride and were oriented in the range of approximately +30 to -30 degrees with respect to the direction perpendicular to the metal substrate.

The heat resistant member according to the third embodiment described above is
When a thermal cycle test of 3K x 1 hour + 293K x 1 hour was performed, the zirconia coating did not peel off even after applying 6500 thermal cycles.

Example 4 In the same manner as in Example 1, an average was formed on a Ni-Co-Cr-Al-Y alloy layer having a thickness of 150 μm and formed by coating the surface of a Ni-base superalloy / IN738 (30 × 30 × 3 mm). Zirconia powder with a particle size of 30 μm has an average particle size of
Using a mixed powder prepared by mixing 30% by volume of 1 μm of titanium carbide powder as a spraying raw material, plasma spraying was performed to a thickness of 250 μm to form a zirconia coating. In addition,
The porosity of the zirconia coating was about 14%.

Next, first, 90% nitrogen-10% was added to the metal base material on which the zirconia coating containing the titanium carbide particles was formed.
1 in a mixed atmosphere of argon (atmospheric pressure: 1 × 10 ⁵ Pa)
Heat treatment was performed at 273 K for 20 hours, and then 10% oxygen was introduced to further perform heat treatment for 3 hours. Then, it was taken out of the furnace and rapidly cooled. Inside the zirconia coating after quenching, S
When examined by EM, the average diameter is about 300 nm and the average length is about
It was confirmed that about 20% by volume of fibrous particles having a particle size of 10 μm and an average aspect ratio of about 35 were dispersed. The fibrous particles were composed of titanium nitride and titanium oxide, and were oriented in the range of approximately + 30 ° to −30 ° with respect to the direction perpendicular to the metal substrate. Furthermore, it was confirmed that microcracks were introduced into the zirconia coating approximately in the direction perpendicular to the metal substrate.

The heat-resistant member according to the fourth embodiment described above is
When a thermal cycle test of 3K x 1 hour + 293K x 1 hour was conducted, the zirconia coating did not peel off even after the application of 10,000 thermal cycles. From this, it was confirmed that the thermal shock resistance was further improved by introducing microcracks into the zirconia coating.

[0044]

As described above, according to the heat-resistant member of the present invention, fibrous particles are dispersed in the ceramic coating in the film thickness direction, so that crack propagation in the horizontal direction can be suppressed. This makes it possible to prevent the ceramic coating from peeling off or being damaged. Therefore, it is possible to provide a heat resistant member having excellent thermal fatigue resistance and thermal shock resistance. Further, according to the method for producing a heat-resistant member of the present invention, it becomes possible to stably and reproducibly produce the heat-resistant member having the above-mentioned thermal fatigue resistance and thermal shock resistance.

[0045]

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Tateishi 1 Komukai Toshiba Town, Komukai Toshiba Town, Kawasaki City, Kanagawa Prefecture Toshiba Research & Development Center (56) Reference JP-A-59-153876 (JP, A) ( 58) Fields investigated (Int.Cl. ⁷ , DB name) C23C 4/06 C23C 4/18 C23C 30/00

Claims (2)

(57) [Claims] And 1. A metal substrate, in heat resisting member, comprising a coating formed ceramic coating on the metal substrate, the ceramic in the coating, at least one selected from metal nitrides and metal oxides A plurality of fibrous particles are dispersed , and 50% by volume or more of the fibrous particles are
The fiber length direction is perpendicular to the surface of the metal substrate.
Then , the heat-resistant member is characterized by being oriented in the range of +30 to -30 degrees . 2. A step of coating and forming a ceramic coating on a metal substrate, wherein particles of at least one selected from a metal, a metal carbide and a metal boride are dispersed, and the ceramic coating contains at least nitrogen. Heat treatment in an atmosphere, the metal, at least one kind of particles selected from metal carbides and borides, the thickness of the ceramic coating as at least one kind of fibrous particles selected from metal nitrides and metal oxides And a step of growing the heat-resistant member in a direction.