Patent Application
20180030584
The present invention relates to a thermal barrier coating, a turbine member, a gas turbine, and a manufacturing method for a thermal barrier coating.
Priority is claimed on Japanese Patent Application No. 2015-025194, filed on Feb. 12, 2015, the content of which is incorporated herein by reference.
In a gas turbine, a temperature of combustion gas to be used is set high in order to improve efficiency of the gas turbine. A thermal barrier coating (TBC) is applied to surfaces of turbine blade members such as blades and vanes subjected to the combustion gas having a high temperature. The thermal barrier coating is a coating of a thermal spraying material having low thermal conductivity (for example, a ceramics-based material having low thermal conductivity) applied by thermal spraying to a surface of a turbine member which is an object to be thermally sprayed. Heat-shielding properties and durability of the turbine member are improved by the thermal barrier coating.
For example, as described in PTL 1, a thermal barrier coating includes a metal bonding layer which is an undercoat layer and a ceramic layer which is a top coat layer formed on the metal bonding layer, on a surface of a heat-resistant substrate serving as a base material. The ceramic layer is formed by thermally spraying a powder mixture of ceramic powder and resin powder onto the undercoat layer. The ceramic layer described in PTL 1 is so configured that vertical cracks which are cracks extending in a thickness direction and pores are dispersed in a surface direction.
[PTL 1] Japanese Unexamined Patent Application, First Publication No. 2013-181192
A dense coating having the vertical cracks described in PTL 1 is referred to as a DVC (Dense Vertically Crack) coating. Since the DVC coating is a dense structure having a vertically cracked structure, durability is improved. However, since the structure is dense in the DVC coating, porosity decreases, and heat-shielding properties are likely to decrease.
The present invention provides a thermal barrier coating in which heat-shielding properties can be improved while sufficient durability is secured, a turbine member, a gas turbine, and a manufacturing method for a thermal barrier coating.
In order to achieve the above-described object, the present invention suggests the following means.
According to a first aspect of the present invention, there is provided a thermal barrier coating, including: a heat-resistant alloy substrate which is used in a turbine member; and a ceramic layer which is formed on the heat-resistant alloy substrate, vertical cracks extending in a thickness direction being dispersed in a surface direction, a plurality of pores being included inside the ceramic layer, wherein thermal spray particles composed of YbSZ having a particle-size distribution in which a 50% particle diameter in a cumulative particle-size distribution is 40 μm to 100 μm are thermally sprayed to form the ceramic layer.
According to this configuration, since the thermal spray particles composed of YbSZ in which the 50% particle diameter in the cumulative particle-size distribution is 40 μm to 100 μm are used, when the thermal spray particles are thermally sprayed on the heat-resistant alloy substrate to form the ceramic layer, surfaces of the thermal spray particles are melted while cores thereof remain so as not to be melted. Accordingly, in the ceramic layer, a porous structure is formed by the remaining cores of the thermal spray particles while a dense structure is formed by the melted surfaces of the thermal spray particles. Accordingly, it is possible to obtain the ceramic layer having a porous structure including an amount of pores required for securing heat-shielding properties while having a dense structure including vertical cracks required for securing sufficient durability.
In the thermal barrier coating, in the ceramic layer, the vertical cracks may be dispersed at a pitch of 0.5 cracks/mm to 40 cracks/mm in the surface direction, and the porosity may be 4% to 15%.
In the thermal barrier coating, in the ceramic layer, the vertical cracks may be dispersed at a pitch of 1 crack/mm to 6 cracks/mm in the surface direction, and the porosity may be 9% to 15%.
In the thermal barrier coating, in the ceramic layer, the vertical cracks may be dispersed at a pitch of 1 crack/mm to 2 cracks/mm in the surface direction, and the porosity may be 9% to 10%.
According to these configurations, it is possible to obtain, with high accuracy, the ceramic layer having improved heat-shielding properties while securing sufficient durability.
According to a second aspect of the present invention, there is provided a turbine member on which the thermal barrier coating is formed.
According to a third aspect of the present invention, there is provided a gas turbine including the turbine member.
According to these configurations, it is possible to prevent the turbine member from being damaged due to exposure to a high temperature for a long period of time. Since intervals between maintenance periods can be extended, it is possible to decrease a frequency of stopping an operation of the gas turbine.
According to a fourth aspect of the present invention, there is provided a manufacturing method for a thermal barrier coating, including a ceramic layer forming process of forming a ceramic layer on a heat-resistant alloy substrate used in a turbine member by thermally spraying thermal spray particles composed of YbSZ having a particle-size distribution in which a 50% particle diameter in a cumulative particle-size distribution is 40 μm to 100 μm, wherein in the ceramic layer, vertical cracks extending in a thickness direction are dispersed in a surface direction and a plurality of pores are included inside the ceramic layer.
According to this configuration, since the thermal spray particles composed of YbSZ in which the 50% particle diameter in the cumulative particle-size distribution is 40 μm to 100 μm are used, when the thermal spray particles are thermally sprayed on the heat-resistant alloy substrate to form the ceramic layer, the surfaces of the thermal spray particles are melted while the cores thereof remain so as not to be melted. Accordingly, in the ceramic layer, a porous structure is formed by the remaining cores of the thermal spray particles while a dense structure is formed by the melted surfaces of the thermal spray particles. Accordingly, it is possible to obtain the ceramic layer having a porous structure including an amount of pores required for securing heat-shielding properties while having a dense structure including vertical cracks required for securing sufficient durability.
In the manufacturing method for a thermal barrier coating, in the ceramic layer forming process, the ceramic layer may be formed such that the vertical cracks are dispersed at a pitch of 0.5 cracks/mm to 40 cracks/mm in the surface direction, and that the porosity is 4% to 15%.
In the manufacturing method for a thermal barrier coating, in the ceramic layer forming process, the ceramic layer may be formed such that the vertical cracks are dispersed at a pitch of 1 crack/mm to 6 cracks/mm in the surface direction, and that the porosity is 9% to 15%.
In the manufacturing method for a thermal barrier coating, in the ceramic layer forming process, the ceramic layer may be formed such that the vertical cracks are dispersed at a pitch of 1 crack/mm to 2 cracks/mm in the surface direction, and that the porosity is 9% to 10%.
According to these configurations, it is possible to obtain, with high accuracy, the ceramic layer having improved heat-shielding properties while securing sufficient durability.
According to the present invention, since the thermal spray particles composed of YbSZ having the particle-size distribution in which the 50% particle diameter in the cumulative particle-size distribution is 40 μm to 100 μm are used, it is possible to improve heat-shielding properties while securing sufficient durability.
Hereinafter, an embodiment of the present invention will be described with reference to
As shown in
The compressor 2 takes in a large amount of air and compresses the air.
The combustor 3 mixes compressed air A compressed by the compressor 2 with a fuel and combusts the mixture.
The turbine body 4 converts thermal energy of a combustion gas G introduced from the combustor 3 into rotation energy. In the turbine body 4, the thermal energy of the combustion gas G is converted into mechanical rotation energy by blowing the combustion gas G to blades (turbine members) 7 provided in the rotor 5, and power is generated. In the turbine body 4, other than the plurality of blades 7 provided on the rotor 5 side, a plurality of vanes (turbine members) 8 are provided on a casing 6 of the turbine body 4. In the turbine body 4, the blades 7 and the vanes 8 are alternately arranged in an axial direction of the rotor 5.
The rotor 5 transmits a portion of rotating power of the turbine body 4 to the compressor 2 so as to rotate the compressor 2.
Hereinafter, in this embodiment, the blade 7 of the turbine body 4 will be described as an example of the turbine member of the present invention.
As shown in
As shown in
The metal bonding layer 200 prevents the ceramic layer 300 from being peeled and is formed as a bonding coat layer having excellent corrosion resistance and oxidation resistance. For example, the metal bonding layer 200 is formed by thermally spraying metal thermal spray powder of an MCrAlY alloy which is thermal spray particles on the surface of the blade 7. Here, “M” of the MCrAlY alloy composing the metal bonding layer 200 indicates a metal element, and for example, indicates a single metal element such as NiCo, Ni, or Co, or a combination of two or more of them. The metal bonding layer 200 of the present embodiment is integrally laminated to cover each of the surface of the blade body portion 71 and the surface of the platform portion 72 on the side connected to the blade body portion 71. The metal bonding layer 200 of the present embodiment is formed to have a film thickness of approximately 0.05 mm to 0.2 mm.
The ceramic layer 300 is a top coat layer which is formed by thermally spraying the thermal spray particles toward the surface of the blade 7 on which the metal bonding layer 200 is formed. The ceramic layer 300 is a dense DVC (Dense Vertically Crack) coating in which vertical cracks C extending in a thickness direction of the ceramic layer 300 are dispersed in a surface direction in which a surface spreads, and a plurality of pores P are included inside the ceramic layer 300. In the ceramic layer 300 of the present embodiment, the vertical cracks C are dispersed such that the vertical cracks C per 1 mm is distributed at a pitch of 0.5 cracks/mm to 40 cracks/mm, and the ceramic layer 300 is formed such that the porosity is within a range of 4% to 15%. The ceramic layer 300 is formed to have a film thickness of approximately 0.2 mm to 1 mm.
Preferably, in the ceramic layer 300, the vertical cracks C are dispersed such that the vertical cracks C per 1 mm are distributed at a pitch of 1 crack/mm to 6 cracks/mm, and the ceramic layer 300 is formed such that the porosity is within a range of 9% to 15%. Particularly, more preferably, in the ceramic layer 300, the vertical cracks C are dispersed such that the vertical cracks C per 1 mm is distributed at a pitch of 1 crack/mm to 2 cracks/mm, and the ceramic layer 300 is formed such that the porosity is within a range of 9% to 10%.
The porosity in the present embodiment is not an occupancy ratio of only the pores P per unit volume, and the porosity is an occupancy ratio of the vertical cracks C and the pores P combined. Accordingly, if the range of 9% to 10% in the porosity of the above-described ceramic layer 300 is expressed as the occupancy ratio of only the pores P per unit volume, preferably, the ceramic layer 300 of the present embodiment is formed such that the porosity of the ceramic layer 300 is within a range of 5% to 7%.
The thermal spray particles forming the ceramic layer 300 are composed of YbS (ytterbia stabilized zirconia) which is ZrO2 partially stabilized by Yb2O3. The thermal spray particles of the present embodiment are YbSZ having a particle-size distribution in which a 50% particle diameter in a cumulative particle-size distribution is 40 μm to 100 μm.
As shown in
The reason why the 50% particle diameter in the cumulative particle-size distribution is set to 40 μm or more is because if the particle diameters are too small and below the 50% particle diameter in the cumulative particle-size distribution of 40 μm, the ceramic layer 300 becomes too dense, and porosity decreases. As a result, as shown in
In the present embodiment, the cumulative particle-size distribution is a value which indicates the size of particles as powder, that is, as an aggregate. The cumulative particle-size distribution represents a plurality of measurement results by a distribution of an abundance ratio for each particle diameter. The 50% particle diameter in the cumulative particle-size distribution is also referred to as a median diameter. The 50% particle diameter in the cumulative particle-size distribution is a particle diameter at which the amount of particles having larger diameters becomes equal to the amount of particles having smaller diameters when the powder is divided into two at that particle diameter.
For example, the distribution of the abundance ratio for each particle diameter of the thermal spray particles can be measured using a laser scattering diffraction type particle-size distribution measuring device or the like.
In the ceramic layer 300 composed of YbSZ, when an addition amount of Yb2O3 which is a stabilizer is increased to 2 wt % or more as an addition ratio of Yb2O3, an improvement in the thermal cycle durability starts. This effect works well until immediately before the addition amount reaches 35 wt %. For the thermal cycle durability, for example, a thermal cycle test is performed using a device shown in FIG. 7 or 8 of Japanese Patent No. 4388466. From the viewpoint of the thermal cycle durability, an effective addition amount of Yb2O3 is 4 wt % to 30 wt %. If the range of the addition amount of Yb2O3 is set to 8 wt % to 27 wt %, the thermal barrier coating 100 of the present embodiment can exert superior thermal cycle durability. In a case where the addition amount of Yb2O3 exceeds the above range, the thermal cycle durability decreases. This is because the amount of monoclinic phases (m phases) remaining in the ceramic layer 300 increases and thereby the durability decreases in a case where the addition amount is less than 8 wt %, and the ceramic layer 300 easily becomes a tetragonal crystal and a ratio of t′ phases having excellent durability decreases and thereby the durability of the ceramic layer 300 decreases in a case where the addition amount exceeds 25 wt %.
More preferably, the addition amount of Yb2O3 is 10 wt % to 25 wt %, and most preferably, the addition amount of Yb2O3 is 12 wt % to 20 wt %. By setting the addition amount to these ranges, the thermal barrier coating 100 can have superior thermal cycle durability.
Next, a manufacturing method for a thermal barrier coating of laminating the thermal barrier coating 100 on the surface of the blade 7 will be described.
As shown in
In the metal bonding layer forming process, the metal bonding layer 200 is formed by thermally spraying metal thermal spray powder to the surface of the blade 7 installed on the jig 91. The metal bonding layer forming process of the present embodiment is performed on the surface of the blade body portion 71 of the blade 7 and the surface of the platform portion 72 on the side to which the blade body portion 71 is connected. For example, in the metal bonding layer forming process, the metal bonding layer 200 is formed by thermally spraying metal thermal spray powder of an MCrAlY alloy to the surface of the blade 7 using the thermal spray gun 92 by an atmospheric plasma thermal spraying method.
In the ceramic layer forming process, the ceramic layer 300 is formed by thermally spraying thermal spray particles composed of YbSZ from above the metal bonding layer 200 formed in the metal bonding layer forming process toward the surface of the blade 7. In the ceramic layer forming process of the present embodiment, the ceramic layer 300 is formed by thermally spraying thermal spray particles composed of YbSZ having the particle-size distribution, in which the 50% particle diameter in the cumulative particle-size distribution is 40 μm to 100 μm, to the metal bonding layer 200 formed on the surface of the blade 7, by an atmospheric plasma thermal spraying method. For example, preferably, the ceramic layer forming process is performed with the output of the thermal spray gun 92 set to a current of 500 A to 800 A and a voltage of 55V to 70V. In order to obtain the ceramic layer 300 having a porous structure including the amount of pores P required for securing heat-shielding properties while having a dense structure including vertical cracks C required for securing sufficient durability, preferably, a thermal spray distance which is a distance between an outlet of the thermal spray gun 92 and a surface to which the thermal spray particles are thermally sprayed is set to a range from a minimum distance required for the thermal spray to 80 mm or less, and more preferably, is set to 70 mm or less. For example, in the ceramic layer forming process of the present embodiment, the thermal spray distance is set to 70 mm.
The thermal spray particles composed of YbSZ used in the present embodiment can be manufactured by the following procedure.
As shown in
According to the above-described thermal barrier coating 100 or the above-described manufacturing method for a thermal barrier coating, the ceramic layer 300 is formed by the thermal spray particles composed of YbSZ in which the 50% particle diameter in the cumulative particle-size distribution is 40 μm to 100 μm. When the thermal spray particles are thermally sprayed to the blade 7 to form the ceramic layer 300, the surfaces of the thermal spray particles are melted while the cores thereof remain so as not to be melted. Accordingly, in the ceramic layer 300, porous structures are partially formed by the remaining cores of the thermal spray particles while dense structures are formed by the melted surfaces of the thermal spray particles.
Specifically, as shown in Example of the following Table 1 or an enlarged photograph of
In Comparative Example 1 of Table 1, even when YbSZ is the same as that of Example, in the ceramic layer which is formed by thermally spraying the thermal spray particles composed of YbSZ in which the 50% particle diameter in the cumulative particle-size distribution is 30 μm, the vertical cracks C are dispersed at a pitch of 2 cracks/mm to 40 cracks/mm in the surface direction and the porosity which is an occupancy ratio per unit volume of the vertical cracks C and the pores P combined is approximately 8%. That is, in the case of the thermal spray particles composed of YbSZ in which the 50% particle diameter in the cumulative particle-size distribution is 40 μm or less, it is difficult to obtain the ceramic layer 300 having the structure in which the vertical cracks C are dispersed at a pitch of 1 crack/mm to 2 cracks/mm in the surface direction and of which the porosity is approximately 9% to 10%.
As shown in Example of Table 1, as for the characteristics of the ceramic layer 300 which is formed by the thermal spray particles composed of YbSZ in which the 50% particle diameter in the cumulative particle-size distribution is 70 μm, a ratio of thermal conductivity (with respect to Comparative Example 3) is 1.2 to 1.5, and a ratio of thermal cycle durability (with respect to Comparative Example 3) is approximately 1.5. As is apparent from a comparison between Example and Comparative Example 1 of Table 1, the above-described characteristics are superior to characteristics of the ceramic layer which is formed by the thermal spray particles composed of YbSZ in which the 50% particle diameter in the cumulative particle-size distribution is 30 μm. That is, it is understood that the thermal conductivity of the ceramic layer 300 of Example is lower than 1.6 to 1.8 which is the ratio of the thermal conductivity of the ceramic layer 300 of Comparative Example 1, and thus the heat-shielding properties of the ceramic layer 300 of Example are superior. It is understood that the thermal cycle durability of the ceramic layer 300 of Comparative Example 1 is the same as 1.5 which is the ratio of the thermal cycle durability of the ceramic layer 300 of Example and thus, the ceramic layer 300 of Example secures sufficient durability.
Accordingly, by forming the ceramic layer 300 using the thermal spray particles composed of YbSZ in which the 50% particle diameter in the cumulative particle-size distribution is 40 μm to 100 μm, it is possible to obtain the ceramic layer 300 having a porous structure including the amount of pores P required for securing heat-shielding properties while having a dense structure including the vertical cracks C required for securing sufficient durability. Accordingly, in the thermal barrier coating 100 of the present embodiment, it is possible to improve heat-shielding properties while securing sufficient durability.
If the ceramic layer 300 is formed such that the vertical cracks C are dispersed at a pitch of 0.5 cracks/mm to 40 cracks/mm in the surface direction and the porosity is approximately 4% to 15%, it is possible to obtain, with high accuracy, the ceramic layer 300 having improved heat-shielding properties while securing sufficient durability. If the ceramic layer 300 is formed such that the vertical cracks C are dispersed at a pitch of 1 crack/mm to 6 cracks/mm in the surface direction and the porosity is approximately 9% to 15%, it is possible to obtain higher performance. Particularly, if the ceramic layer 300 is formed such that the vertical cracks C are dispersed at a pitch of 1 crack/mm to 2 cracks/mm in the surface direction and the porosity is approximately 9% to 10%, it is possible to obtain, with higher accuracy, the ceramic layer 300 having improved heat-shielding properties while securing sufficient durability. Particularly, it is possible to obtain the ceramic layer 300 having higher performance by forming the ceramic layer 300 by thermal spray particles composed of YbSZ.
Specifically, as in Comparative Example 2 of Table 1, even when the vertical cracks C are dispersed at a pitch of 1 crack/mm to 2 cracks/mm in the surface direction by the thermal spray particles which are composed of YSZ instead of YbSZ, it is not possible to obtain sufficient heat-shielding properties. For example, it is understood that the thermal conductivity of the ceramic layer 300 of Example is lower than the thermal conductivity of the ceramic layer 300 of Comparative Example 2, and thus the ceramic layer 300 of Comparative Example 1 cannot obtain the heat-shielding properties which are equivalent to those of the ceramic layer 300 of Example.
As in Comparative Example 3 of Table 1, if the thermal cycle durability in a case where the porosity of approximately 10% is realized by the porous structure which does not have the vertical cracks C is set as 1 (base), it is understood that the thermal cycle durability of Comparative Example 3 is lower than 1.3 which is the ratio of the thermal cycle durability of Comparative Example 2 having the same YSZ as the thermal spray particles. It is understood that the thermal cycle durability of Comparative Example 3 is lower than 1.5 which is the ratio of the thermal cycle durability of Example which has YbSZ as the thermal spray particles and includes the vertical cracks C, and is lower than 1.5 which is the ratio of the thermal cycle durability of Comparative Example 1 which has YbSZ as the thermal spray particles and includes the vertical cracks C.
Accordingly, compared to the ceramic layer 300 which is formed by the thermal spray particles composed of YSZ having the structure in which only the vertical cracks C are dispersed at the pitch of 1 crack/mm to 2 cracks/mm in the surface direction and the structure in which only the porosity is approximately 10%, in the ceramic layer 300 of the present embodiment, it is possible to obtain higher performance.
As is apparent from the comparisons between Example and Comparative Examples 1 to 3, it is understood that high-temperature erosion characteristics indicating friction characteristics under a high temperature environment at TBC surface temperature of 1100° C. indicate high performance. Accordingly, it is also possible to secure erosion resistance.
It is possible to form the ceramic layer 300 by thermal spray particles composed of only YbSZ which hardly includes impurities such as a polyester resin and an acrylic resin. Accordingly, it is possible to include the amount of pores P required for improving the heat-shielding properties inside a dense structure having the vertical cracks C without performing a heat treatment or the like after the thermal spray. Therefore, it is possible to obtain the thermal barrier coating 100 having improved heat-shielding properties while securing sufficient durability using a small number of processes.
According to the blade 7 which is the turbine member of the above-described embodiment, it is possible to prevent the blade 7 from being damaged due to exposure to a high temperature for a long period of time. Since intervals between maintenance periods can be extended, it is possible to decrease a frequency of stopping an operation of the gas turbine 1.
Hereinbefore, the embodiment of the present invention is described in detail with reference to the drawings. However, configurations and combinations thereof in the embodiment are merely examples, and addition, omission, replacement, and other modifications of the configurations can be made within a scope which does not depart from the gist of the present invention. In addition, the present invention is not limited to the embodiment and is limited by only the claims.
In addition, the metal bonding layer 200 or the ceramic layer 300 may be formed by a method other than that of the present embodiment. For example, low pressure plasma spraying which is electrical thermal spraying other than atmospheric pressure plasma spraying may be used, or a flame thermal spraying method and high-speed flame thermal spraying which are gas type thermal spraying may be used. The metal bonding layer 200 or the ceramic layer 300 may be formed by a method other than the thermal spraying method and, for example, an electron beam physical vapor deposition method may be used.
In the present embodiment, the metal bonding layer 200 and the ceramic layer 300 are each formed to have the same film thickness over the entire region. However, the present invention is not limited to this and the film thickness may be appropriately set according to conditions such as an environment in which these layers are to be used.
In the present embodiment, the blade 7 is described as an example of the turbine member. The present invention is not limited to this. For example, the turbine member may be the vane 8.
In the ceramic layer forming process of the present embodiment, the output of the thermal spray gun 92 is set to a current of 500 A to 800 A and a voltage of 55V to 70V, and the thermal spray distance is set to 70 mm. However, the present invention is not limited to these conditions. Accordingly, in the ceramic layer forming process, the conditions such as the output or the thermal spray speed may be changed as long as the ceramic layer 300 can be formed such that the vertical cracks C are dispersed in the surface direction at the pitch of 0.5 cracks/mm to 40 cracks/mm and the porosity is 9% to 15%.
According to the above-described thermal barrier coating 100 and the manufacturing method for a thermal barrier coating, since the thermal spray particles composed of YbSZ having the particle-size distribution in which the 50% particle diameter in the cumulative particle-size distribution is 40 μm to 100 μm are used, it is possible to improve heat-shielding properties while securing sufficient durability.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2015-025194 | Feb 2015 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2016/053506 | 2/5/2016 | WO | 00 |
