Abradable coating system with good abradability and method to produce it

Abstract

An abradable coating system for a turbine blade comprises a substrate 4, preferably a nickel-based superalloy, a metallic bond coat 7, preferably base on NiCoCrAlY, optionally an oxide layer grown on

Description

The invention relates to an abradable coating system with good abradability of turbine blades. Abradable coatings with high temperature capability are used in gas turbines to reduce the gap between a stator, e.g. ring-segment or vane platform and a rotor, e.g. blades. These must have appropriated thermo-mechanical capabilities which should fulfill the wear behavior, while remain stable and attached to the underlying TBC at the operating temperatures . One example is given in EP 3 592 953 Al. Nowadays high concentration of stabilizers and the use of a polymer mixture to achieve the specified high porosity level are used for Zirconia. But it has been observed that the rub and erosion-resistance behavior of this coating are nor suitable for this task. Example is given in US 6,930,066 Bl. However, feedback shows the failure of these coatings by some delamination of the coating during rubbing, which in some cases reaches the interface of the bond coat. By this, turbine component is exposed to extreme high temperatures, which directly affects their capability to fulfill their design lifetime. It is therefore aim of the invention of to overcome the problem of the state of the art. The problem is solved by abradable coating system according to claim 1 and a method according to claim 8. In the dependent claims further features are listed which lead in arbitrarily combinations to further advantages. The description and the figure only show embodiments of the invention. The figure shows a layer system 1. The layer system 1 for turbines comprises a metallic substrate 4. The metallic substrate 4 comprises preferably a nickel or cobalt base superalloy, like CMSX, IN759 or Alloy247. On the metallic substrate 4 there is a metallic bond coat 7. The metallic bond coat 7 comprises preferably a MCrAlY alloy, such as NiCoCrAlY, NiCoCrAlYRe, NiCoCrAlYSi, NiCoCrAlYTa or NiCoCrAlYTaSi. The metallic bond coat 7 forms during application of a TBC or during use a thermal grown oxide layer (TGO) based on oxide of aluminum (Al). Onto this a TBC (thermal barrier coating) system 8 is formed. The new TBC system 8 is composed by an inner thermal barrier coating layer 10 with high fracture toughness, based on partially stabilized Zirconia, but with a porosity of 14vol%-22vol% . The stabilizer are Yttria (8YSZ) or Yttria / Ytterbia, with 3,5wt% to 6,5wt% Y2O3 and l,0wt% to 8,0wt% Yb2Oa. Preferably these 2 elements are used for stabilization, optionally Hafniumoxid is added. Preferably this TBC layer 10 is produced using APS, HVOF, but not by suspension plasma spraying (SPS). Preferably there is no intermediate layer. The outermost abradable layer 13 is made of fully stabilized Zirconia ceramic like, especially 20YSZ, 48YSZ or 33YBZO or even of a partially stabilized Zirconia, especially 8YSZ. But the outermost layer (13) is produced via Suspension Plasma Spray (SPS), which forms preferably a columnar structure . The outermost SPS columnar abradable layer will improve the erosion resistance compared with high porosity abradable systems and enhance the rubbing behavior of this layer, as well as the full coating system compliance working under thermos-cyclic conditions. This layer system is applied on top of the tip of a blade. The airfoil of a turbine blade comprises a different layer system, especially no SPS manufactured outermost coating. This layer system is applied on stator parts, like ring segments or an platform of a vane. The use of the APS TBC / SPS Abradable coating system would enhance both: (a) the capability of the TBC system to avoid spallation due to the shear loads induced into the base layer during rubbing, (b) retain the good abradability of the wearing ceramic material with low fracture toughness, and (c) reduce erosion damage by the application of the columnar tough top layer. The columnar structure of the SPS abradable would improve the sensibility towards erosion, especially induced by small particles flying inclined to the surface of the coating. Patent claims 1. Abradable coating system (8) for a turbine blade, comprising a substrate (4 ) , especially a Nickel-based superalloy a metallic bond coat (7), especially based on NiCoCrAlY, optionally an oxide layer made out of the bond coat (7), an inner partially stabilized Zirconia based layer (10) with 14%-22% porosity, and an outermost abradable layer (13) made by Suspension Plasma Spray. 2. System according to claim 1, wherein the outermost layer (13) comprises a fully stabilized Zirconia, which comprises, especially consists of, 20YSZ, 48YSZ or 33YBZO. 3. System according to claim 1, wherein the outermost layer (13) comprises a partially stabilized Zirconia, which comprises, especially consists of 8YSZ, 4. System according to claim 1, 2 or 3, wherein the inner partially stabilized Zirconia based layer (10) comprises 8YSZ or Zirconia partially stabilized by Y / Yb, especially with 3,5wt% to 6,5wt% Y2O3 and l,0wt% to 8,0wt% Yb2O3. 5. System according to claim 1, 2, 3 or 4, wherein the coating system is applied on top of the tip of a blade. 6. System according to any of the previous claims, wherein an airfoil of a turbine blade comprises a different coating system, especially no SPS manufactured outermost coating. 7. System according to any of the previous claims, wherein this coating system (8) is applied on stator parts, like ring segments or an platform of a vane. 8. Method to produce a abradable coating system (8), especially according to any of the previous claims, providing a substrate (4), coating with a bond coat (7), using plasma spraying or HVOF to apply the inner layer (10) of Zirconia, using Suspension Plasma Spray to apply the fully or partially stabilized outermost Zirconia layer (13) onto the inner layer (10). Intellectual Property Office Application GB2501299.8 Search report under Section 17 of the Patents Act 1977 Date search completed: 11 July 2025 Claims searched: 1 - 8 International classification Subclass and subgroup Valid from C23C28 / 00 01 / 01 / 2006 C23C4 / 129 01 / 01 / 2016 C23C4 / 134 01 / 01 / 2016 F01D5 / 28 01 / 01 / 2006 Field of search Worldwide search of patent documents classified in the following areas of the IPC: C23C, F01D Databases used in the preparation of this search report: SEARCH-PATENT Documents considered to be relevant Patent literature Category Relevant Document of relevance

Claims

Intellectual Property Office is an operating name of the Patent Officewww.gov.uk / lpoX 1, 3 - 8 DE 102014222686A1 (SIEMENS AG), See paragraphs 12 - 18 and figure 1. X 1,4 - 7 CN 118910534 A (UNIV INNER MONGOLIA TECHNOLOGY), See WPI Abstract Accession No. 2024-C0237U and figures. X 1, 2, 4 - 7 US 2013 / 0260132 A1 (HAZEL et al.), See paragraphs 8 - 12 &17 and figure 1. X 1, 3 - 8 JP 2018003103 A (MITSUBISHI HEAVY IND LTD), See WPI Abstract Accession No. 2018-032062 and figure 7. X 1, 3 - 8 CN 119101861 A (DONGFANG TURBINE CO LTD DONGFANG ELECTRIC CORP), See WPI Abstract Accession No. 2024-D2324J and figure 1. X 1,4 - 7 US 2018 / 0251881 A1 (UNITED TECHNOLOGIES CORP), See paragraphs 32 - 36 and figure 1. Non-patent literature Category Relevant claims Document of relevanceCategoriesLetter or DescriptionsymbolDocument indicating lack of novelty or inventive step.Letter or symbol Description Y Document indicating lack of inventive step, if combined with another document of the same category. & Member of the same patent family. A Document indicating technological background. P Document published on or after the priority date but before the fling date of the present application. E Earlier application published on or after the filing date of the present application.

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