JP7457633B2 - Thermal barrier coatings and heat-resistant components - Google Patents

Description

Embodiments of the present invention relate to thermal barrier coatings and heat resistant components having the thermal barrier coatings. In particular, the present invention relates to a thermal barrier coating suitable for high-temperature parts such as gas turbines and a heat-resistant member having this thermal barrier coating.

Among gas turbine parts, the combustor liner and transition piece, which are exposed to high temperatures due to combustion gas, as well as the moving and stationary blades that make up the turbine, are coated with thermal barrier coatings to provide strength and chemical protection for the metal base materials. (Thermal Barrier Coating) may be applied.

A thermal barrier coating (hereinafter sometimes referred to as TBC) is generally composed of a bonding layer made of a metal with higher oxidation resistance than the base material, and a layer made of a ceramic material with low thermal conductivity. It has the function of protecting the base material from high-temperature gases. Since the base material of many mechanical parts is made of metal, thermal barrier coatings are required to have bonding strength, heat shielding performance, and durability to the metal material base material.

JP 2012-172610 A JP 2011-140693 A

In recent years, high-temperature parts, such as combustor liners and transition pieces, are required to have a longer operating life, but the outer surfaces of high-temperature parts that have been operated for a long period of time show only mechanical wear and tear. Instead, it became clear that thinning occurs due to chemical factors caused by high-temperature oxidation. Since thinning due to high-temperature oxidation is a factor that determines the final lifespan of high-temperature parts, it is desirable to suppress thinning due to such oxidation. By increasing the thickness of the ceramic layer that makes up the thermal barrier coating and increasing the thermal resistance of the coating, it is possible to lower the base material temperature and suppress high-temperature oxidation. TBCs with a thickness greater than 1 mm may be used.

TBC is mainly formed by a thermal spraying method in which molten particles are sprayed onto a construction target, and generally, as the ceramic layer becomes thicker, the ceramic layer tends to peel off around the interface with the bonding layer. Particularly when the thickness of the ceramic layer exceeds 1 mm, peeling of the ceramic layer may occur over a wide area. Therefore, there has been a problem in that the metal portion of the high-temperature component is exposed to high-temperature gas at the peeled portion of the ceramic layer, resulting in mechanical or chemical deterioration of the high-temperature component.

In order to solve the above problems, embodiments of the present invention are designed to improve the peeling resistance of a thickly applied TBC and maintain good protection of the base material for a long period of time, taking into consideration the long-term use of high-temperature components. It provides a thermal coating.

According to the present invention, it is possible to improve the peeling resistance of a thickly applied TBC, maintain the protection of the base material, and provide a thermal barrier coating for high-temperature parts such as combustors and gas turbines. , high temperature components can be used for longer periods of time.

According to the present invention, it is possible to improve the peeling resistance of a TBC in which a thick ceramic layer is formed in high-temperature parts where the inspection period is prolonged and a longer operating life is required, and even when peeling occurs, it is possible to improve the peeling resistance of the TBC. Deterioration of parts can be suppressed without exposing metal parts to high-temperature gas over a wide range.

1 is a cross-sectional view showing an outline of a thermal barrier coating according to a first embodiment of the present invention. FIG. 3 is a cross-sectional view schematically showing a thermal barrier coating according to a second embodiment of the present invention. FIG. 3 is a cross-sectional view schematically showing a thermal barrier coating according to a third embodiment of the present invention.

The thermal barrier coating according to the embodiment of the present invention is a thermal barrier coating consisting of a bonding layer and a ceramic layer formed on the surface of a base material via the bonding layer,
The ceramic layer has a thickness of more than 1 mm, and has a porosity in the vicinity of the interface on the bonding layer side that is lower than that in the vicinity of the surface on the opposite side of the bonding layer. be.

A heat-resistant member according to an embodiment of the present invention is characterized by having the above-mentioned thermal barrier coating.
Here, the thermal barrier coating is a coating applied to suppress the temperature rise of the base material constituting the high-temperature member due to combustion gas, and is a coating applied to the surface of the base material constituting at least a part of the heat-resistant member. It includes a bonding layer and a ceramic layer covering the bonding layer.

<Embodiment>
Hereinafter, thermal barrier coatings and heat-resistant members according to embodiments of the present invention will be described with reference to the accompanying drawings.
1-3 illustrate thermal barrier coatings according to embodiments of the invention.
The thermal barrier coating 1 shown in each figure has a ceramic layer 4 with a thickness of more than 1 mm on the surface of a base material 2 with a bonding layer 3 interposed therebetween. A typical example of the base material 2 is a metal material, which corresponds to a metal material forming a heat-resistant member. For example, metal materials constituting high-temperature members such as steam turbine components, preferably Ni-based or Co-based superalloys that can withstand high temperature conditions during turbine operation, can be used.

The bonding layer 3 is interposed between the base material 2 and the ceramic layer 4 to improve the adhesion between the base material 2, the ceramic layer 4, and the base material 2, and to protect the surface of the base material 2 from high-temperature corrosion and oxidation. It has the ability to improve The bonding layer 3 is preferably made of a metal material with a high concentration of chromium or aluminum, particularly preferably an MCrAlY alloy having excellent corrosion resistance and oxidation resistance at high temperatures (here, M is at least one selected from Ni and Co). can be used. The thickness of the bonding layer 3 is not particularly limited, but can be appropriately determined in an optimal range depending on the temperature of the base material 2, the base material temperature expected during operation, and the thickness of the ceramic layer 4, but is preferably 0.1 to 1. The thickness is about 0.3 mm, and even if it is thick, it is about 0.5 mm.

The bonding layer 3 can be formed by, for example, depositing particles, clusters, or molecules of the above-mentioned MCrAlY alloy into a uniform film by a thermal spraying method, an electron beam evaporation method, or the like.

A ceramic layer 4 having a thickness of 1 mm or more is formed on this bonding layer 3. In conventional TBCs, the thickness of the ceramic layer 4 is usually about 0.5 to 0.6 mm, but the thickness of the ceramic layer 4 in the embodiment of the present invention is 1.0 mm or more, preferably 1.0 mm or more. The ceramic layer 4 has a thickness of 1 mm to 1.5 mm. The thicker ceramic layer improves the heat shielding properties of the ceramic layer in embodiments of the present invention.

The ceramic layer 4 has a lower porosity in the vicinity 4a of the bonding layer side interface than in the vicinity 4b of the opposite surface of the bonding layer. Here, the "vicinity 4a of the bonding layer side interface" refers to the region inside the ceramic layer 4 from the bonding layer 3 side interface (i.e., the interface between the bonding layer 3 and the ceramic layer 4) to 0.3 mm in the thickness direction of the ceramic layer 4. The "vicinity 4b of the opposite surface of the bonding layer" refers to the region inside the ceramic layer 4 from the opposite surface (i.e., the surface of the ceramic layer 4 opposite to the bonding layer 3) to 0.3 mm in the thickness direction of the ceramic layer 4. The porosity of the "vicinity 4a of the bonding layer side interface" refers to the porosity of the pores present in this vicinity 4a, and the porosity of the "vicinity 4b of the opposite surface of the bonding layer" refers to the porosity of the pores present in this vicinity 4b.

In the ceramic layer 4 according to the embodiment of the present invention, the porosity of the "portion 4a near the interface on the bonding layer side" is preferably 12 to 20%. If the porosity becomes too high, the adhesion to the bonding layer will decrease and peeling will occur easily. On the other hand, if the porosity is too low and the porosity becomes too dense, the toughness decreases and cracks tend to propagate near the interface on the bonding layer side, where thermal stress is strong, making it easier for the ceramic layer to peel off. tends to be widespread.

Further, in the ceramic layer 4, the porosity of the "near part 4b of the opposite surface" is preferably 13 to 30%. If the porosity is too low, the elastic modulus of the entire ceramic layer 4 cannot be reduced. On the other hand, if the porosity is too high, the strength of the ceramic layer surface may decrease, and the mechanical vibrations that occur during operation may decrease. may be unreliable for high-temperature gas flows. In addition, in the same ceramic layer 4, the porosity of the vicinity part 4a of the bonding layer side interface is lower than the porosity of the vicinity part 4b of the surface on the opposite side of the bonding layer.

Generally, in heat-resistant parts with TBC, the base material and ceramic layer are exposed to high temperatures during operation, so large thermal stress is generated at the interface between the ceramic layer and the bonding layer, which have significantly different mechanical properties at high temperatures. Occur. In particular, during long-term operation, one of the causes of delamination is the propagation of cracks in the vicinity of the bonding layer of the ceramic layer due to thermal stress caused by differences in thermophysical properties.

However, as described above, the thermal barrier coating 1 according to the embodiment of the present invention has the ceramic layer 4 with a thickness exceeding 1 mm, and this ceramic layer 4 has pores in the vicinity portion 4a of the bonding layer side interface. Since the porosity is lower than the porosity of the adjacent portion 4b on the opposite surface of the bonding layer, the adhesive strength with the bonding layer 2 is high, and peeling resistance can be improved.

The ceramic layer 4 is formed such that the porosity of the ceramic layer 4 is greater on the surface side (nearby portion 4b side) in contact with the high-temperature gas. A ceramic layer with high porosity is inferior in terms of adhesion, but since it has a relatively sparse structure, its elastic modulus is lower than that of a dense layer. Therefore, by lowering the porosity in areas other than the vicinity of the bonding layer 2, the thermal stress acting on the entire ceramic layer 4 can be reduced, and the peeling resistance of the film can be improved.

As the material for forming the ceramic layer 4, alumina, magnesia, zirconia, etc. can be preferably selected. Since the thermal conductivity of general Ni-based superalloys at room temperature is 10 W/(m/K) or less, it is preferable that the thermal conductivity at room temperature is 5 W/(m/K) or less, and zirconia A ceramic layer having a low thermal conductivity of usually about 0.5 to 1.2 W/(m/K) can be formed, so it is more suitable.

For example, in equipment that operates at high temperatures, such as steam turbines, zirconia contains stabilizing materials such as magnesia, calcia, and yttria to suppress the expansion associated with crystal phase transformation at high temperatures, which pure zirconium has. The reliability of the film can be improved. Zirconia forming the ceramic layer 4 may contain oxides made of rare earth elements such as hafnia, ceria, dysprosia, and gadolinia, and zirconia containing these oxides has lower thermal conductivity. , exhibiting desirable properties.

As a method for forming the ceramic layer 4 having the predetermined thickness and the predetermined porosity from the above-mentioned ceramic layer forming material, for example, a thermal spraying method, an electron beam evaporation method, etc. may be used to form ceramic material particles, clusters, etc. Alternatively, it can be formed by introducing molecules or the like and depositing them in a uniform film form. The porosity of the ceramic layer 4 can be adjusted by appropriately selecting the type of formation method such as thermal spraying or electron beam evaporation. For example, in the thermal spraying method, the temperature can be adjusted by appropriately selecting the thermal spraying temperature, the thermal spraying speed, the particle size of the powder used for thermal spraying, and the like. Further, the thickness can be adjusted as appropriate by changing the formation time by thermal spraying, electron beam evaporation, or the like.

The material on the surface side (nearby portion 4b side) of the ceramic layer 4 is exposed to high-temperature gas, and as combustion gas temperatures have risen in recent years, the effects of reduced thermal conductivity and peeling due to sintering of the porous structure have become more pronounced. For this reason, reliability can be improved by using high-purity materials with reduced impurities such as low-melting-point silica and alumina as the main components of the ceramic layer 4. Such materials can suppress deterioration of the coating structure due to sintering under high-temperature heating.

The thermal barrier coating of the present invention described above includes the following <<first embodiment>> to <<third embodiment>> as preferred embodiments.

<<First embodiment>>
FIG. 1 shows a first embodiment of the invention.
The thermal barrier coating according to the first embodiment of the invention shown in FIG.
A thermal barrier coating consisting of a bonding layer 3 and a ceramic layer 4 formed on the surface of a base material 2 via the bonding layer 3,
The ceramic layer 4 has a thickness of more than 1 mm, and a porosity of a portion 4a near the interface on the side of the bonding layer 3 is lower than a porosity of a portion 4b near the surface opposite to the bonding layer. , the ceramic layer 4 is composed of a ceramic layer 4 whose porosity sequentially and continuously changes in the thickness direction.

When forming the ceramic layer 4 on the bonding layer 3 by thermal spraying, when depositing and accumulating the material for forming the ceramic layer on the bonding layer 3 by thermal spraying, for example, the thermal spraying temperature, thermal spraying speed, particle size of the powder used for thermal spraying, etc. By continuously changing one or more of these conditions, it is possible to form a predetermined ceramic layer whose porosity changes sequentially and continuously.

<<Second embodiment>>
FIG. 2 shows a second embodiment of the invention.
The thermal barrier coating according to the second embodiment of the invention shown in FIG.
A thermal barrier coating consisting of a bonding layer 3 and a ceramic layer 4 formed on the surface of a base material 2 via the bonding layer 3,
The ceramic layer 4 has a thickness of more than 1 mm, and a porosity of a portion 4a near the interface on the side of the bonding layer 3 is lower than a porosity of a portion 4b near the surface opposite to the bonding layer. , the ceramic layer 4 is composed of a plurality of ceramic layers whose porosity differs stepwise in the thickness direction.

The ceramic layer 4 of the thermal barrier coating shown in FIG. 2 consists of a ceramic layer 41 with a porosity of 12 to 20% on the bonding layer side, and a ceramic layer 42 with a porosity of 13 to 30% on the opposite side.

Note that the ceramic layer 4 specifically shown in FIG. 2 is composed of two ceramic layers, a ceramic layer 41 and a ceramic layer 42, but between these ceramic layers 41 and 42, there are Another ceramic layer (not shown) having a porosity higher than ceramic layer 41 and lower than ceramic layer 42 may be provided.

When forming the ceramic layer 4 on the bonding layer 3 by thermal spraying, the ceramic layer 41 is first formed while maintaining predetermined thermal spraying conditions when depositing and accumulating the material for forming the ceramic layer on the bonding layer 3 by thermal spraying, Thereafter, by stepwise changing one or more of the conditions such as thermal spraying temperature, thermal spraying speed, and particle size of the powder used for thermal spraying, a plurality of ceramic layers having the above-mentioned porosity different in a stepwise manner are formed. be able to.

<<Third embodiment>>
FIG. 3 shows a third embodiment of the invention.
The thermal barrier coating according to the third embodiment of the invention shown in FIG.
A thermal barrier coating consisting of a bonding layer 3 and a ceramic layer 4 formed on the surface of a base material 2 via the bonding layer 3,
The ceramic layer 4 has a thickness of more than 1 mm, and a porosity of a portion 4a near the interface on the side of the bonding layer 3 is lower than a porosity of a portion 4b near the surface opposite to the bonding layer. , the ceramic layer 4 has an intermediate ceramic layer 44 having a higher porosity than the ceramic materials 43 and 45 adjacent in the thickness direction in the intermediate portion in the thickness direction.

In conventional TBCs, cracks that occur near the bonding layer of the ceramic layer due to thermal stress acting between the substrate and the ceramic layer during operation may progress to the surface of the ceramic layer, resulting in the ceramic layer peeling off and exposing the substrate. However, the thermal barrier coating according to the third embodiment of the present invention has an intermediate ceramic layer 44 in the middle of the ceramic layer 4 in the thickness direction, which has a higher porosity than the ceramic materials 43 and 45 adjacent in the thickness direction, and this intermediate ceramic layer 44 functions as a crack propagation suppression layer. Therefore, in the thermal barrier coating according to the third embodiment of the present invention, even if a crack occurs near the bonding layer 3 of the ceramic material 43 and the crack propagates, the crack is prevented or suppressed from propagating into the interior or surface of the ceramic material 45, even if it propagates into the intermediate ceramic layer 44.

For the intermediate ceramic layer 44, the same material as the film forming the ceramic layer 4 in the first embodiment can be used, but it is preferable to use the same material as the ceramic layer 43. The porosity of the intermediate ceramic layer 44 is preferably about 15 to 30%. If it is too low, it becomes difficult for cracks to propagate in the intermediate ceramic layer 44, and the cracks also propagate to the ceramic material 45 side, resulting in a damage form in which the entire ceramic layer 4 peels off. If the porosity of the intermediate ceramic layer 44 is too high, the mechanical strength will be too low and peeling will easily occur.

The position at which the intermediate ceramic layer 44 is formed can be adjusted as appropriate depending on the thermal stress acting on the TBC during operation, but is approximately 0.05 to 0.5 mm from the bonding layer 3, more preferably approximately 0.1 to 0.4 mm. It is. If the intermediate ceramic layer 44 is too close to the bonding layer 3, the entire ceramic layer 4 is likely to peel off, and if it is too far from the bonding layer 3, cracks will not propagate through the intermediate ceramic layer 44, making it impossible to obtain the desired effect. .

The porosity of the intermediate ceramic layer 44 can be adjusted by the conditions at the time of formation, and in the case of thermal spraying, the thermal spraying temperature, thermal spraying speed, particle size of the powder used for thermal spraying, etc. can be selected appropriately for the layer concerned. You can adjust it by doing this.

The porosity of the intermediate ceramic layer 44 may change continuously in the film thickness direction as shown in FIG. 3, or it may change in stages so that it is formed of three ceramic layers each with a different porosity as shown in FIG. 2.

<<Heat-resistant member>>
A heat-resistant member according to an embodiment of the present invention is characterized by having the above-described thermal barrier coating.
Heat-resistant members according to embodiments of the present invention are suitable for use in high-temperature components such as, for example, gas turbines, and in particular, preferably, those exposed to high-temperature gases during operation, such as combustor liners and transition pieces, moving and stationary blades, and shroud segments. Applied to the surface of the part.

In recent years, these parts have tended to be used for longer periods of time in order to extend their operational life, and there is a need for thermal barrier coatings with high thermal resistance that can further reduce the substrate temperature. The thermal barrier coating according to the present invention having a ceramic layer exceeding 1 mm has higher thermal resistance and reliability than conventional coatings, and therefore can further extend the life of the component. Moreover, even if peeling occurs, the deterioration of the component can be suppressed by the thermal barrier coating that maintains a constant thermal resistance without causing the entire ceramic layer to peel off.

1: Thermal barrier coating, 2: Base material, 3: Bonding layer, 4: Ceramic layer, 41, 43: Ceramic layer (low porosity), 42, 45: Ceramic layer (high porosity), 44: Intermediate ceramic layer , 4a: Near the bonding layer side (low porosity), 4b: Near the surface side (high porosity)

Claims (3)

A thermal barrier coating consisting of a bonding layer and a ceramic layer formed on the surface of a base material via the bonding layer,
The ceramic layer has a thickness of more than 1 mm, and has a porosity in the vicinity of the interface on the bonding layer side that is lower than that in the vicinity of the opposite surface of the bonding layer,
The ceramic layer has an intermediate ceramic layer having a higher porosity than the ceramic material adjacent in the thickness direction at an intermediate portion in the thickness direction,
The ceramic layer has a porosity of 12 to 20% in the vicinity of the interface on the bonding layer side, and a porosity of 13 to 30% in the vicinity of the surface on the opposite side of the bonding layer,
A thermal barrier coating , wherein the intermediate ceramic layer has a porosity of 15 to 30% . The thermal barrier coating of claim 1 , wherein the ceramic layer is comprised of zirconium dioxide containing a stabilizing material. A heat-resistant member comprising the thermal barrier coating according to claim 1 or 2 .

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