FR2902691A1 - Laminate for gas turbine blades or thermal shield, comprises a substrate, an attachment layer, a zirconium oxide layer stabilized by yttrium, an inner ceramic layer on the metallic attachment layer, and an outer ceramic layer - Google Patents

Abstract

The laminate (1) for gas turbine blades or thermal shield, comprises a substrate (4), an attachment layer (7), a zirconium oxide layer stabilized by yttrium, an inner ceramic layer (10) on the metallic attachment layer, and an outer ceramic layer (13) having 100 wt.% of pyrochlore.

Description

LAMINATE SYSTEM HAVING A CERAMIC PYROCHLORE LAYER

  relates to a laminate. Such a laminate has a substrate having a metal alloy based on nickel, cobalt or iron. Products of this type are used primarily as components of a gas turbine, including gas turbine blades or heat shields. The constituent elements are subjected to a hot stream of aggressive combustion gas. They must therefore withstand high thermal stresses. It is also necessary for these constituent elements to resist oxidation and corrosion. It is imposed, moreover, especially on mobile components, for example gas turbine blades, but also on static constitutive elements, with high mechanical requirements. The power and efficiency of a gas turbine, in which constituents that can be exposed to hot gas, are used increases as the operating temperature rises. To obtain a good yield and a high power, the elements of the gas turbines particularly stressed by high temperatures of a ceramic material are coated. This serves as a heat insulating layer between the hot gas stream and the metal substrate. The base metal part is protected from the aggressive hot gas stream by coatings. In this respect, the modern constitutive elements most often have several coatings which fulfill, respectively, specific tasks. We are in the presence of a laminate.

  As power and efficiency of gas turbines increase as the operating temperature rises, it is constantly sought to obtain by an improvement of the coating system a greater power of gas turbines. EP 0 944 746 B1 describes the use of pyrochlore as a heat insulating layer. But for the use of a material as a heat-insulating layer, it is necessary not only good heat-insulating properties, but also good adhesion to the substrate. EP 0 992 603 A1 discloses a thermal insulation laminate of gadolinium oxide and zirconium oxide which should not have a pyrochlore structure.

  The present invention therefore relates to a laminate which has good heat-insulating properties and good adhesion to the substrate and which thus has a long life. The invention is based on the consideration that the entire laminate should be considered as a unit and that individual layers should not be considered in isolation from one another and should be optimized for long life. The invention relates to a laminate characterized in that it comprises a substrate, a bonding layer consisting (in% by weight) of 11% to 13% of cobalt, in particular 12% of cobalt, from 20% to 22% chromium, especially 21% chromium, 10.5% to 11.5% aluminum, in particular 11% aluminum, 0.3% to 0.5% yttrium, especially 0.4% yttrium, 1.5% to 2.5% rhenium, in particular 2.0% rhenium, and the remainder being nickel, a stabilized layer of zirconium oxide, in particular a layer of zirconium oxide stabilized with yttrium, as an inner ceramic layer on the metal bonding layer, on which layer there is a ceramic outer layer, which is constituted for at least 80%, especially for 100% by weight pyrochlore Gd2Zr2O7. According to other embodiments: - Gd2Zr2O7 is replaced by Gd2Hf2O7 In the accompanying drawings given solely by way of example: Figure 1 shows a laminate according to the invention; Figure 2 shows a turbine blade; Figure 3 shows a gas turbine. Figure 1 shows a laminate 1 according to the invention. The laminate 1 consists of a metal substrate 4 which is intended in particular for constituent elements for high temperatures in a superalloy based on nickel or cobalt. There is directly on the substrate 4 a metallic layer 7 which is constituted in% by weight of 11% to 13% of cobalt, in particular 12% of cobalt, 20% to 22% of chromium, especially of 21% chromium, 10.5% to 11.5% aluminum, especially 11% aluminum, 0.3% to 0.5% yttrium, in particular 0.4% yttrium, from 1.5% to 2.5% rhenium, especially 2.0% rhenium, and the remainder being nickel, on this layer 7 metal hooking is created before the deposition of other layers in ceramic a layer of aluminum oxide or a layer of aluminum oxide of this kind is created during operation. On the metal bonding layer 7 or on the aluminum oxide layer (not shown), there is a layer of zirconium oxide stabilized wholly or partially as an inner ceramic layer. Zirconium oxide stabilized with yttrium is preferably used. Calcium oxide, cerium oxide or hafnium oxide can also be used to stabilize zirconium oxide. The zirconium oxide is preferably deposited in the form of a plasma spray layer, but it can also be deposited in the form of a columnar structure by means of electron beam vapor deposition. . On the layer 10 of stabilized zirconium oxide, a ceramic outer layer 13 is deposited which consists for the most part of a pyrochlore phase, therefore at least 80% by weight of the pyrochlore phase and either of Gd2Hf2O7 either of Gd2Zr2O7. The outer layer 13 is preferably made up of 100% by weight of one of the two pyrochlore phases. Amorphous phases or pure GdO2 or pure ZrO2 or pure HfO2 are therefore out of consideration. Mixed phases of GdO2 and ZrO2 or HfO2, which do not exhibit the pyrochlore phase, are desirable and must be present at a minimum. The essence of the invention lies in the fact that one must optimize no. only the interaction of the ceramic outer layer 13 and a ceramic inner layer 10 with one another, but that the metal hooking layer 7 also has an essential influence on the longevity and the function of the ceramic outer layer 13; of this ceramic structure with two layers.

  Figure 2 is a perspective view of a blade 120 mobile or a blade 130 director of a turbomachine which extends along a longitudinal axis 121.

  The turbomachine may be a gas turbine of an aircraft or an electricity generating plant, a steam turbine or a compressor. The blades 120, 130 have, following one another along the longitudinal axis 121, a fixing portion 400, a blade platform 403 which is adjacent thereto and a blade 406 blade. As director blade 130, blade 130 may have another platform on its blade tip 415 (not shown).

  In the attachment portion 400 is formed a blade root 183 which serves to attach the blades 120, 130 movable on a shaft or on a disk (this is not shown). The blade root 183 is shaped, for example, at the head of the hammer. Other embodiments in fir or dovetail rooting are possible. The blades 120, 130 have a leading edge 409 and a trailing edge 412 of a fluid which passes in front of the blade blade 406.

  In blades 120, 130 which are usual, all parts 400, 403, 406 of blades 120, 130 are used, for example, solid metal materials, especially superalloys. Superalloys of this kind are known, for example, from EP 1 204 776 B1, EP 1 306 454, EP 1 319 729 A1, WO 99/67435 or WO 00/44949. Blades 120, 130 may be manufactured by a casting process also by means of directed solidification by a forging process, by a milling process or by one of their combinations. Parts with monocrystalline structure are used as constituent elements of machines which are subjected in operation to great mechanical, thermal and / or chemical stresses. The manufacture of single crystal pieces of this kind is effected for example by directed solidification in the melt. These are casting processes in which the liquid metal alloy is solidified into a monocrystalline structure, i.e. in a monocrystalline part or in a directed manner. Thus, dendritic crystals appear along the heat flow and a prismatic crystal grain structure is formed (in column, that is to say grains that extend over the entire length of the piece and are designated here in general use as directed solidification) or a monocrystalline structure, i.e. the whole piece is made of a single crystal. In these processes, it is necessary to prevent the transition to solidification in globules (polycrystalline) because it is created by a non-directed growth necessarily transversal and longitudinal grain boundaries that negate the good properties of the solidified constitutive element of directed or monocrystalline way. When, in general, it is a question of structures that are solidified in a directed manner, we mean both single crystals that have no grain boundaries or that have at most small angle grain boundaries that prismatic crystalline structures that have grain boundaries extending well in the horizontal direction but not transverse grain boundaries. In these crystalline structures mentioned second, we also speak of directionally solidified structures. Methods of this kind are known from US Patent 6,024,792 and EP 0 892 090 Al.

  The blades 120, 130 may also have protective coatings with respect to corrosion or oxidation, for example (in MCrAlX; M is at least one member of the iron (Fe) group, cobalt (Co) ), nickel (Ni), X is an active element and represents yttrium (Y) and / or silicon and / or at least one rare earth element or hafnium (Hf)). Alloys of this type are known from EP 0 486 489 B1, from EP 0 786 017 B1, from EP 0 412 397 B1 or from EP 1 306 454 A1. On the MCrAlX may be present still a heat-insulating layer constituted for example ZrO 2, Y 2 O 4 -ZrO 3 r, that is to say that it is not stabilized partly or completely by yttrium oxide and / or by calcium oxide and / or by magnesium oxide. By suitable coating processes, such as electron beam vapor deposition (EB-PVD), prismatic grains are produced in the heat insulating layer. Refurbishment means that constitutive elements 120, 130 must be discarded after their use, if necessary, of protective layers (for example by sandblasting). It is then carried out an elimination of the layers or products of corrosion and / or oxidation. If necessary, cracks are also repaired in the constituent element 120, 130. The constituent element 120, 130 is then again coated and the constituent element 120, 130 is reused. The vanes 120, 130 may be hollow or solid. When the blade 120, 130 is to be cooled, it is hollow and, if necessary, still has film cooling holes 418 (shown in dashed lines). Figure 3 shows by way of example a gas turbine 100 according to a longitudinal sectional view. The gas turbine 100 has inside a rotor 103 rotatably mounted relative to an axis 102 of rotation and having a shaft 101 which is also designated as being the rotor of the turbine. Along the rotor 103 follow a suction box 104, a compressor 105, a combustion chamber 110, for example toroidal, in particular an annular combustion chamber, having several burners 107 arranged coaxially, a turbine 108 and the box 109 of lost gas.

  The annular combustion chamber 110 communicates with an annular channel 111, for example, for hot gas. For example, four turbine stages 112 mounted one behind the other form the turbine 108. Each turbine stage 112 is formed, for example, two blade crowns. In the direction of the flow of a working fluid 113, in the hot gas channel 111, a row 115 of guide vanes and a row 125 formed of moving vanes 120 follow each other. The guide vanes 130 are fixed to a casing 138 inside a stator 143, while the blades 120 mobile of a row 125 are mounted on the rotor 103 for example by means of a turbine disc 133. A generator or machine providing work (not shown) is coupled to the rotor 103. During the operation of the gas turbine 100, air 135 is drawn from the compressor 105 through the box 104. suction and is compressed.

  Compressed air is provided at the end on the turbine side of the compressor 105 and is fed to the burner 107 and mixed therein with a fuel fluid. The mixture is then burned with formation of the working fluid 113 in the combustion chamber 110. From there, the working fluid 113 passes along the channel 111 for hot gas in front of the guide vanes 130 and the moving blades 120. The working fluid 113 expands on the moving blades 120 by transmitting a pulse, so that the moving blades 120 drive the rotor 103 and that the latter drives the machine providing work coupled thereto. The constituent elements exposed to the hot working fluid 113 undergo, during the operation of the gas turbine 100, thermal stresses. The guide vanes 130 and the moving blades 120 of the first turbine stage 112 in the direction of the flow of the working fluid 113 are most thermally stressed in addition to the heat shield elements lining the annular combustion chamber 110. To resist the temperatures that prevail, they can be cooled by means of a cooling fluid. Substrates of the constituent elements may also have a directed structure, i.e., be monocrystalline (SX structure) or have only longitudinally directed grains (DS structure). As materials for the constituent elements, in particular for the turbine blades 120, 130 and the components of the combustion chamber 110, use is made, for example, of superalloys based on iron, nickel or cobalt. Superalloys of this kind are known, for example, from EP 1 204 776 B1, EP 1 306 454, EP 1 319 729 A1, WO 99/67435 or WO 00/44949. Similarly, the vanes 120, 130 may have coatings against corrosion (MCrAlX; M is at least one member of the group of iron (Fe), cobalt (Co), nickel (Ni), X is an active element which represents yttrium (Y) and / or silicon and / or at least one rare earth element or hafnium). Alloys of this type are known from EP 0 486 489 B1, from EP 0 786 017 B1, from EP 0 412 397 B1 or from EP 1 306 454 A1. On MCrAlX, there may still be one layer heat-insulating material consisting for example of ZrO 2, Y 2 O 3 -ZrO 2, that is to say that it is not stabilized in whole or in part by yttrium oxide and / or by calcium oxide and / or with magnesium oxide. By suitable coating methods, such as electron beam vapor deposition (EB-PVD), prismatic grains are produced in the heat insulating layer. The guide vanes have a vane root facing the inner casing 138 of the turbine 108 (not shown) and an opposing vane head to the vane root. The guide blade head is turned towards the rotor 103 and is fixed to a ring 140 for fixing the stator 143.

  LISTING OF REFERENCE SIGNS 1 Laminate 4 Substrate 7 Layer 10 Inner ceramic layer 13 Outer layer of ceramic 100 Gas turbine 102 Rotor shaft 103 Rotor 104 Suction box 105 Compressor 106 Annular combustion chamber 107 Burner 108 Turbine 109 Gas box 110 Combustion chamber 111 Hot gas channel 112 Impeller stage 113 Working fluid 115 Guide vane array 120 Moving vane 121 Longitudinal axis 125 Row 130 Guide vane 133 Impeller crown 135 Air 138 Inner housing 140 Fixing ring 143 Stator 153 Combustion chamber wall 155 Heat shield element 183 Vane root 400 Fixing part 403 Blade platform 406 Blade blade 409 Leading edge 412 Leakage edge 415 Dawn tip 418 Pairs of cooling film

Claims (1)

  1. Laminate, characterized in that it comprises a substrate (4), a layer (7) of attachment consisting of 11% to 13% cobalt, in particular 12% cobalt, 20% to 22% chromium , in particular 21% chromium, 10.5% to 11.5% aluminum, in particular 11% aluminum, 0.3% to 0.5% yttrium, in particular 0.4% yttrium, from 1.5% to 2.5% of rhenium, in particular 2.0% of rhenium, and the balance being nickel, a stabilized layer of zirconium oxide, in particular a layer of zirconium oxide stabilized with yttrium, as an inner ceramic layer (10) on the layer (7), a layer (10) on which there is a ceramic outer layer (13), which is formed for at least 80%, in particular for 100%, by weight of pyrochlore Gd2Zr2O7 or Gd2Hf2O7. 20