Stock material or miscellaneous articles – All metal or with adjacent metals – Composite; i.e. – plural – adjacent – spatially distinct metal...
Reexamination Certificate
2002-12-11
2004-06-29
McNeil, Jennifer (Department: 1775)
Stock material or miscellaneous articles
All metal or with adjacent metals
Composite; i.e., plural, adjacent, spatially distinct metal...
C428S680000, C428S697000, C428S699000, C428S701000, C428S702000, C428S621000, C420S442000, C420S445000, C420S447000, C420S455000, C420S460000, C420S588000, C416S24100B
Reexamination Certificate
active
06756131
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a high temperature corrosion resistant alloy, and a thermal barrier coating material, a turbine member, and a gas turbine using the high temperature corrosion resistant alloy. In particular, the present invention relates to a composition of a high temperature corrosion resistant alloy having an excellent oxidation resistance and ductility which is suitable for use in a metal bonding layer of a thermal barrier coating material.
2. Description of Related Art
Recently, as one of the energy saving countermeasures, improvements in thermal efficiency in thermal power generation has been studied. In order to improve the power generation efficiency of a gas turbine used for generating power, it is effective to increase a gas inlet temperature of a turbine, and the inlet temperature is often increased to 1,500° C. In order to realize such a high temperature of a power generation device, it is necessary to use a heat resisting material for a stationary vane and a rotor vane of a gas turbine, or for a wall of a combustor. However, even if a turbine vane is made using a heat resisting metal, it cannot withstand such a high temperature by itself. Accordingly, as shown in
FIG. 7
, it is generally carried out that a metal bonding layer
102
is formed on a base material
101
made of a heat resisting metal, and a ceramic layer
103
made of an oxide ceramics is laminated on the metal bonding layer
102
using a film forming method, such as thermal spraying, to form a thermal barrier coating (TBC) in order to be protected from a high temperature. As a metal bonding layer
102
, a MCrAlY alloy (where M is Co, Ni, or a combination thereof) is known, and as a ceramic layer
103
, a ZrO
2
type material, especially, a yttria stabilized zirconia (YSZ), which is a ZrO
2
partially stabilized or completely stabilized by Y
2
O
3
, is often used due to its relatively low thermal conductivity and relatively high thermal expansion rate.
It is possible to improve the heat resistance of a base material using the thermal barrier coating mentioned above. However, due to the use of a high temperature in a gas turbine in these days, it is expected that the inlet temperature of the turbine exceeds 1,500° C. depending on a kind of the gas turbine, and the inlet temperature of a recently developed ultra high temperature gas turbine, which is developed as one of the environmental countermeasures, may reach 1,700° C. Also, it is considered that the temperature at the surface of the thermal barrier coating of a turbine vane reaches about 1,300° C. Accordingly, thermal stress due to difference in linear expansion coefficient of a high temperature part, such as a turbine vane, becomes large since the difference in temperature of a heat cycle associated with the actuation of the turbine becomes large. For this reason, cracks may be generated in the metal bonding layer
102
during the operation of the turbine, and there is a danger that the cracks reach the base material
101
or the ceramic layer
103
may be separated from the bonding layer
102
.
Accordingly, it is required to improve the ductility of the metal bonding layer
102
in order to prevent the generation of cracks in the metal bonding layer
102
. Also, it is required to improve the corrosion resistance and oxidation resistance of the metal bonding layer
102
since it is expected that the corrosion or the oxidation of a turbine vane, etc., will significantly increase along with increases in the gas temperature due to corrosive components contained in the fuel or salinity of the air flow.
SUMMARY OF THE INVENTION
The present invention takes into consideration the above-mentioned circumstances, and has as an object of providing a high temperature corrosion resistant alloy having excellent oxidation and corrosion resistance, and ductility
Also, another object of the present invention is to provide a thermal barrier coating material with excellent exfoliation resistance including a metal bonding layer which is formed by the above-mentioned alloy.
Moreover, yet another object of the present invention is to provide a turbine member which is coated with the above-mentioned thermal barrier coating, and to provide a gas turbine including the turbine member.
The inventors of the present invention, in order to achieve the above objects, have carried out diligent studies on the composition of a MCrAlY alloy which forms a metal bonding layer, and have found that a metal bonding layer having excellent ductility and oxidation resistance can be formed by using a high temperature corrosion resistant alloy having the following composition, and completed the present invention.
That is, the high temperature corrosion resistant alloy according to an embodiment of the present invention includes 0.1-12% by weight of Co, 10-30% by weight of Cr, 4-15% by weight of Al, 0.1-5% by weight of Y, and 0.5-10% by weight of Re, and the rest is substantially formed by Ni.
A thermal barrier coating material including a metal bonding layer having excellent ductility and oxidation resistance may be made by forming the metal bonding layer on a base material using a high temperature corrosion resistant alloy having the above composition, and laminating a ceramic layer on the metal bonding layer. That is, stress applied to the ceramic layer laminated on the metal bonding layer can be reduced by the excellent ductility of the metal bonding layer, and hence, it becomes possible to prevent the ceramic layer from being separated from the metal bonding layer. Also, it becomes possible to prevent oxidation and corrosion of the base material at high temperatures due to the excellent oxidation resistance of the metal bonding layer, and a long-life thermal barrier coating material can be realized. Moreover, the metal bonding layer formed by using the high temperature corrosion resistant alloy having the above-mentioned composition has excellent affinity with stabilized zirconia which is often used for a ceramic layer, and hence, the ceramic layer may be firmly bonded so that it does not readily separate from the metal bonding layer.
Hereinafter, the function and appropriate weight range of each element contained in the high temperature corrosion resistant alloy according to an embodiment of the present invention will be explained.
Co (0.1-12% by weight):
The greater the amount of Co added, the more it increases the ductility of the high temperature corrosion resistant alloy. If the amount of Co is less than 0.1% by weight, a sufficient effect cannot be obtained. If the amount of Co is increased to exceed 12% by weight, the effect obtained will not change.
Cr (10-30% by weight):
The greater the amount of Cr added, the more it increases the oxidation resistance of the high temperature corrosion resistant alloy. If the amount of Cr is less than 10% by weight, a sufficient oxidation resistance cannot be obtained. However, if the amount of Cr is increased to exceed 30% by weight, the hardness of the resultant alloy is increased, and the ductility thereof is decreased. In addition to that, dense formation of Al
2
O
3
is inhibited. Accordingly, it is more preferable that the added amount of Cr be in the range of 15-25% by weight from the viewpoint of a balance between the oxidation resistance and the ductility.
Al (4-15% by weight):
When the high temperature corrosion resistant alloy is used for the metal bonding layer of the thermal barrier coating, Al has the effects of densely forming Al
2
O
3
on the surface thereof to improve the oxidation resistance of the metal bonding layer, and improving the oxidation resistance of the thermal barrier coating, for instance. If the amount of Al is less than 4% by weight, dense formation of Al
2
O
3
will not be occur due to the generation of (Ni, Co)(Cr, Al)
2
O
4
spinel composite oxide, and the effect of improving the oxidation resistance cannot be obtained. Also, if the amount of Al is increased to exceed 15% by weight, an intermetallic compound (Ni, Co—Al) phase formed by the
Oguma Hidetaka
Okada Ikuo
Takahashi Kouji
Torigoe Taiji
McNeil Jennifer
Mitsubishi Heavy Industries Ltd.
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