MXPA06003588A

MXPA06003588A - Layer system

Info

Publication number: MXPA06003588A
Application number: MXPA/A/2006/003588A
Authority: MX
Inventors: Subramanian Ramesh; Kaiser Axel; Schumann Eckart
Original assignee: Siemens Aktiengesellschaft
Priority date: 2005-04-01
Filing date: 2006-03-30
Publication date: 2006-12-13

Abstract

Thermal barrier coating layer systems, in addition to good thermal barrier properties, also have to have a long service life of the thermal barrier coating. The layer system (1) according to the invention comprises a specially adapted layer sequence of metallic bonding layer (7), inner ceramic layer (10) and outer ceramic layer (13).

Description

LAYER SYSTEM FIELD OF THE INVENTION The invention relates to a layer system. A layer system of this type has a substrate with a metallic alloy based on nickel, cobalt or iron. Products of this type serve above all as a component of a gas turbine, especially as gas turbine blades or thermal shields. The components are subjected to a hot gas flow of aggressive combustion gases. Therefore, they must be able to withstand high thermal loads. For the rest, it is necessary that these components are resistant to oxidation and corrosion. In addition, mechanical requirements have to be established especially in the mobile components, for example, the gas turbine blades, but also in the static parts. The performance and efficiency of a gas turbine, in which components that can be subjected to a charge by hot gas, are increased with an increasing operating temperature. In order to achieve high efficiency and high efficiency, the components of the gas turbine which are specially subjected to high temperature loading with a ceramic material are coated. This acts as a heat-insulating layer between the flow of hot gas and the metal substrate. The metallic base body is protected from the aggressive hot gas flow by means of coatings. In this respect, the modern components mostly have several coatings, which in each case satisfy specific tasks. There is thus a multilayer system. Since the performance and efficiency of gas turbines increase with an increasing operating temperature, it has been tried again and again to achieve greater productivity of gas turbines by improving the coating system.

BACKGROUND OF THE INVENTION EP 0 944 746 Bl discloses the use of pyrochlores as a heat-insulating layer. However, for the use of a material as a heat-insulating layer, not only good heat-insulating properties are needed, but also a good bond with the substrate. EP 0 992 603 Al discloses a system of heat-insulating layers of gadolinium oxide and zirconium oxide, which must not have any pyrochlore structure.

SUMMARY OF THE INVENTION It is, therefore, an object of the invention to show a layer system having good heat-insulating properties as well as a good bond with the substrate and with it a long lifetime of the entire layer system. The invention is based on the knowledge that the complete system must be considered as a unit and not as individual layers, or that layers can be considered and optimized. isolated from each other, to achieve a long lifespan.

BRIEF DESCRIPTION OF THE FIGURES Figure 1 shows a system 1 of layers according to the invention. Figure 2 shows a turbine blade. . Figure 3 shows a gas turbine.

DETAILED DESCRIPTION OF THE INVENTION The layer system (1) consists of a metallic substrate (4), consisting of a nickel or cobalt-based superalloy, especially for components at elevated temperatures.

Directly on the substrate (4) there is a metallic clamping layer (7), which consists either of 11-13% by weight of cobalt, 20-22% by weight of chromium, 10.5-11.5% by weight of aluminum, 0.3-0.5% by weight of yttrium, 1.5-2.5% by weight of rhenium and the rest of nickel or in 24% -26% by weight of cobalt, 16-18% by weight of chromium, 9.5 - 11% by weight of aluminum, 0.3 - 0.5% by weight of yttrium, 0.5 - 2% by weight of rhenium and the rest of nickel. On this metallic bonding layer (7), either before the application of additional ceramic layers, an aluminum oxide layer is formed or, during operation, an aluminum oxide layer of this type is formed.

On the metal bonding layer (7) or on the aluminum oxide layer (not shown) there is a fully or partially stabilized zirconium oxide layer as an internal ceramic layer. Preferably, zirconium oxide stabilized with yttrium is used. In the same way, calcium oxide, cerium oxide or hafnium oxide can be used for the stabilization of zirconium oxide. Preferably, zirconium oxide is applied as an injected layer of plasma, however; It can also be applied as a structure in the form of a column by means of electron beam evaporation. On the stabilized zirconium oxide layer (10) an outer ceramic layer (13) is applied, consisting mostly of a pyrochlore phase, that is, having at least 80% by weight of the pyrochlore phase and consists of either Gd2Hf207 or Gd2Zr07. Preferably, the outer layer (13) consists of 100% by weight of one of the two pyrochlore phases. In this respect, amorphous phases have been dispensed with pure Gd0 or pure Zr02 or pure Hf02. The mixing phases from Gd02 and Zr? 2 or Hf02, which do not have a pyrochlore phase, are not desired and must be minimized. The essence of the invention is the knowledge that not only is the interaction between the outer ceramic layer (13) and an internal ceramic layer (10) optimized, but the metal bond layer (7) also exerts an essential influence on the shelf life and function of the external ceramic layer (13) of this two-layer ceramic structure. Figure 2 shows in a perspective view an impeller blade (120) or a blade (130) directing a turbomachine, which extends along a longitudinal axis (121). The turbomachine can be a gas turbine of an aircraft or a power plant for the generation of electricity, a steam turbine or a compressor. The flange (120), (130) has along the longitudinal axis (121) a fastening area (400), a platform (403) of the blade bordering it, as well as a blade (406) of the blade. As the director blade (130), the labe (130) can present an additional platform at its tip (415) of the blade (not shown). In the fastening area (400), a foot (183) of the blade is formed, which serves for fastening the impeller blades (120), (130) to a shaft or disc (not shown). The leg (183) of the blade is configured, for example, as a hammer head. Other conformations such as foot in fishbone or dovetail are possible. The blade (120), (130) has an inlet ridge (409) and an outlet ridge (412), for a medium flowing through the blade (406). In conventional blades (120), (130) are used in all zones (400), (403), (406) of the blade (120), (130), by example, solid metallic materials, especially superalloys. Superalloys of this type are known, for example, from EP 1 204 776 Bl, EP 1 306 454, EP 1 319 729 Al, WO 99/67435 or WO 00/44949; These documents are in regard to the chemical composition of the alloy part of the description. In this case, the blade (120), (130) can be manufactured by a casting process, also by means of directed solidification, by a forging process, by a milling method or combinations thereof. Workpieces with structure or monocrystalline structures (s) are used as machine components, which are subjected to high mechanical, thermal and / or chemical loads. The production of monocrystalline workpieces of this type takes place, for example, by solidification directed from the melt. This relates to casting processes, in which the liquid metal alloy is solidified to give the monocrystalline structure, ie to give the monocrystalline workpiece, or in a directed manner. In this respect, dendritic crystals are aligned along the heat flow and form either a granular structure in the form of a crystalline stem (in the form of a column, that is, grains, running along the total length of the workpiece and here, according to the use of the general language, they are called as solidified in a directed way) or. a monocrystalline structure, ie the complete workpiece consists of a single crystal. In these processes, the transition to solidification in globulites (polycrystalline) must be avoided, since transverse and longitudinal granular boundaries are necessarily formed by non-directed growth, which destroy the positive properties of the solidified component in a directed or monocrystalline manner. In general, we speak of structures that are solidified in a directed manner, thus referring to both monocrystals, which do not have granular limits or much granular limits of small angle, such as crystalline stem-like structures, which do present granular limits. that run longitudinally, but no transverse granular limit. For these crystalline structures mentioned in the second place, we also refer to structures that are solidified in a directed manner. Such methods are known from US Pat. Nos. 6,024,792 and EP 0 892 090 Al; These documents are part of the description. Likewise, the blades (120), (130) can present coatings against corrosion or oxidation, for example (MCrAlX; M is at least one element of the group iron (Fe), cobalt (Co), nickel (Ni), X is an active element and represents yttrium (Y) and / or silicon and / or at least one element of the rare earths, or hafnium (Hf)). Such alloys are known from EP 0 486 489 Bl, EP 0 786 017 Bl, EP 0 412 397 Bl or EP 1 306 454 Al, which as regards the chemical composition of the alloy should be part of this description. On the MCrAlX there may still be a heat-insulating layer and consists for example of Zr02, Y204-Zr03, ie it is not partially or completely stabilized by yttrium oxide and / or calcium oxide and / or magnesium oxide. By means of suitable coating processes such as electron beam evaporation (EB-PVD), stem-shaped grains are generated in the heat-insulating layer. Renewal means that, if necessary, components (120), (130) must be released from the protective layers after use (for example by sandblasting). Then a removal of the corrosion and / or oxidation layers or products takes place. If necessary, cracks in the component (120), (130) are also repaired. Then a new coating of the component (120), (130) and a new use of the component (120), (130) takes place. The blade (120), (130) can be made hollow or solid. When the blade (120), (130) is to be cooled, it is hollow and, if necessary, still has film cooling holes (418) (indicated by stripes). Figure 3 shows by way of example a gas turbine (100) in a partial longitudinal section. The gas turbine (100) has inside a rotor 103 rotatably placed around a shaft (102) of rotation with a shaft (101), which is also called the rotor of the turbine. Along the rotor (103) follow in succession a suction housing 104, a condenser (105), a combustion chamber (110) for example of the torus type, especially an annular combustion chamber, with several burners (107) arranged coaxially, a turbine (108) and the housing (109) Exhaust gas. The annular combustion chamber (110) communicates with a hot gas channel (111), for example annular. There, for example, four stages (112) of the connected turbine form one behind the other the turbine (108). Each stage (112) of the turbine is formed, for example, from two rings of the blade. Seen in the direction of flow of a working medium (113), in the channel (11) of hot gas to the row (115) of guide vanes follows a row (125) formed from vanes (120) of impeller. In this regard, the director blades (130) are fixed to an internal housing (138) of a stator (143), while the blades (120) of a single-row impeller (125), for example, by means of a disc (133) of the turbine are placed in the rotor (103). A generator or an operating machine (not shown) is coupled to the rotor (103). During operation of the gas turbine (100), the condenser (105) sucks and condenses air (135) through the suction casing (104). The condensed air provided at the end on the turbine side of the condenser (105) is conducted to the burners (107) and is mixed there with a combustion agent. Then, the mixture is burned under -? - formation of the working medium (113) in the combustion chamber 110. From there flows the working medium (113) along the hot gas channel (111) passing the guide vanes (130) and the vanes (120) of the impeller. In the impeller blades (120), the working medium (113) is decompressed by transmitting the pulses, so that the impeller blades (120) drive the rotor (103) and the latter the operating machine coupled to it. The components exposed to the hot working medium (113) are subjected during operation of the turbine (100) of gas to thermal loads. The blades (130) directors and the blades (120) of the impeller of the first stage (112) of the turbine seen in the direction of the flow of the working medium (113), together with the elements of the thermal shield that line the chamber ( 110) of annular combustion, are the most subjected to thermal loads. To resist the temperatures that prevail there, they can be cooled by means of a cooling agent. In the same way, the substrates of the components can present a directed structure, that is they are monocrystalline (structure SX) or present only grains directed longitudinally (structure DS). As a material for the components, especially for the turbine blade (120), (130) and the components of the combustion chamber (110), for example, iron, nickel or cobalt-based superalloys are used.

Superalloys of this type are known, for example, from EP 1 204 776 Bl, EP 1 306 454, EP 1 319 729 Al, WO 99/67435 or WO 00/44949; These documents are in regards to the chemical composition of the alloys part of the description. Likewise, the blades (120), (130) may present coatings against corrosion (MCrAlX; M is at least one element of the iron (Fe), cobalt (Co), nickel (Ni) group, X is an active element and represents yttrium (Y) and / or silicon and / or at least one element of the rare earths or hafnium). Such alloys are known from EP 0 486 489 Bl, EP 0 786 017 Bl, EP 0 412 397 Bl or EP 1 306 454 Al, which as regards the chemical composition should be part of this description. On the MCrAlX there may also be a heat-insulating layer, and it consists for example of Zr02, Y203-Zr02, ie it is not partially or completely stabilized by yttrium oxide and / or calcium oxide and / or magnesium oxide. By means of suitable coating methods such as, for example, electron beam evaporation (EB-PVD), stem-shaped grains are generated in the heat-insulating layer. The director blade (130) presents a foot of the director blade directed to the internal casing 138 of the turbine (108) (not shown here) and a head of the head blade which is disposed facing the foot of the head blade. The head of the director blade is directed towards the rotor (103) and is fixed to a stator mounting ring (140) (143).

Claims

NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and, therefore, the content of the following is claimed as property CLAIMS: 1. Layer system consisting of a substrate (4), a metal bonding layer (7), consisting of: 24-26% by weight of cobalt, 16-18% by weight of chromium, 9.5-11% by weight of aluminum, 0.3 - 0.5% by weight of yttrium, 0.5 - 2% by weight of rhenium and the rest of nickel, a layer of stabilized zirconium oxide, especially a layer of zirconium oxide stabilized with yttrium, as a ceramic layer (10) internal layer on the metal bonding layer (7), on which (10) an outer ceramic layer (13) is present, consisting at least 80% by weight, especially 100% of the pyrochlorite Gd2Zr207. Layer system according to claim 1, characterized in that the Gd2Zr207 is replaced by Gd2Hf207. Layer system according to claim 1, characterized in that the metallic bonding layer is replaced by a metal bonding layer (7) with the composition: 11-13% by weight of cobalt, 20-22% by weight of chromium, 10. 5 - 11.5% by weight of aluminum, 0.3 - 0.5% by weight of yttrium, 1.5 - 2.5% by weight of rhenium and the rest of nickel.