JP5878629B2 - Method for applying a protective layer - Google Patents

Description

  The present invention provides a method for applying a protective layer to a metal substrate having the characteristics described in the preamble of claim 1 and a construction coated with such a protective layer for use in the high temperature region of a gas turbine. Parts and a gas turbine provided with this kind of component.

  Such a method is known, for example, from European Patent Application No. 1637622.

  In current gas turbines, the surface in the hot gas region is provided with a coating almost entirely. In some cases, rear turbine row blades may be excluded. The thermal barrier coating (TBC) used for this purpose serves to lower the material temperature of the cooled component. In this way, component life can be extended, cooling air can be saved, or the gas turbine can be operated at high input temperatures.

  The thermal barrier coating system is always formed by a metal bonding layer diffusion bonded to a substrate (metal substrate) and a ceramic layer on the bonding layer. This ceramic layer has low thermal conductivity, provides an actual barrier to heat flow, and protects the metal substrate from high temperature degradation due to corrosion and erosion. A commonly accepted ceramic material for thermal barrier coatings is zirconium oxide partially stabilized with about 7% by weight yttrium oxide (the international acronym for zirconia partially stabilized with yttria is YPSZ).

  Thermal barrier coatings can be classified into two different categories, depending on how they are used.

  The first category consists of thermal barrier coatings vapor deposited by electron beam physical vapor deposition (EB-PVD). When specific deposition conditions are maintained, these thermal barrier coatings have a columnar, strain-resistant structure that results in particularly good resistance to thermal cycle fatigue (TCF). In the accompanying method of applying the thermal barrier coating, the thermal barrier coating is a pure alumina layer (thermally grown oxide) formed by the tie layer during its formation and subsequent feeding through the formation of the alumina-zirconia mixture. , TGO). On the one hand, this method imposes specific requirements on oxide growth on the tie layer, while on the other hand it guarantees a particularly strong bond.

  The second category includes thermal barrier coatings (usually by atmospheric plasma spraying (APS)). These thermal barrier coatings have a porosity of between about 10% and 25% by volume, depending on the desired layer thickness and stress distribution. In this case, due to the fact that the ceramic layer is mechanically bonded to the bonding layer, the bonding layer is intentionally rough during spraying in order to maximize the interface and consequently the adhesion. . A specific chemical bond is provided by TGO formation only after long-term feeding. This application method is relatively simple, so that the cost of the coating is relatively favorable.

European Patent Application No. 1637622

  The present invention further develops the method described in the preamble of claim 1 so that a good resistance to thermal fatigue is achieved in the protective layer while still allowing the method to be carried out easily. With the goal. This object is achieved through the features described in the characterizing part of claim 1.

  A further object of the present invention is to provide a component for use in the hot gas region of a gas turbine, the component being coated with a protective layer that is resistant to high temperature degradation due to corrosion and erosion, and this kind of configuration. It is to provide a gas turbine having a part, the protective layer can be produced on the component in a simple manner and has a good resistance to thermal fatigue. This object is achieved by a component as claimed in claim 7 and by a gas turbine as claimed in claim 8.

  Further developments of the invention are defined in the respective dependent claims.

  For the tie layer (preferably in the stationary gas turbine), a primer layer based on sprayed MCrAlY (M = Ni, Co) is used. The MCrAlY layer comprises intermetallic β-phase NiCoAl when the aluminum is retained in a NiCoCr (“Y”) matrix. However, since this also has the effect of embrittlement, the Al content that can actually be realized in the MCrAlY layer is 12 wt% or less.

  To further increase resistance to oxidation, the MCrAlY coating is overaluminized with an Al diffusion layer. Due to the risk of embrittlement, this is greatly limited to low aluminum (Al ≦ 8%) starting layers.

  The structure of the over-aluminized MCrAlY layer is the inner, substantially unchanged, mixed Y, β phase, i.e. the diffusion region, in which the Al content is increased to about 20% and the outer And a β-NiAl phase having an Al ratio of about 30%. This outer β-NiAl phase presents certain drawbacks with regard to brittleness and sensitivity to crack formation in the layer system. Accordingly, the overaluminized coating is ablated so that the outer β-NiAl phase is removed until it reaches the diffusion region. This has a favorable effect on the activity of aluminum, and as a result, improves TGO formation performance.

  In doing so, good bonding of the ceramic layers can be achieved without the need for the presence of a rough bonding layer, especially using low pressure plasma spraying (LPPS) or spraying such as, for example, high-speed flame spraying (HVOF) or vacuum plasma spraying. It makes it possible to apply a MCrAlY layer. High velocity flame spraying is more economical and tends to produce a smooth surface.

  According to a first aspect of the present invention, there is provided a method for applying a protective layer resistant to high temperature degradation due to corrosion and erosion on a metal substrate, wherein the bonding layer comprising MCrAlY as a main component is a metal substrate. The tie layer is coated by being overaluminized with an Al diffusion layer, the Al diffusion layer is subjected to ablation treatment, and the outer layer is removed from the Al diffusion layer, and the yttria partially stabilized zirconia A ceramic thermal barrier coating is applied to the remaining Al diffusion layer. The method according to the invention is characterized in that a ceramic thermal barrier coating is applied to the remaining Al diffusion layer by atmospheric plasma spraying.

  According to an embodiment of the method according to the invention, the applied tie layer is subjected to a polishing treatment before being overaluminised. By the polishing treatment, a surface roughness Ra of 2 μm or less is generated in the bonding layer.

  According to another embodiment of the method according to the invention, the bonding layer is applied to the metal substrate by spraying, such as, for example, high-speed flame spraying (HVOF) or vacuum plasma spraying or deposition from the gas phase.

  According to a further embodiment of the method of the present invention, the Al diffusion layer is subjected to a polishing process after the ablation process, and a surface roughness Ra of 2 μm or less is generated in the remaining Al diffusion layer.

  According to yet another embodiment of the method of the invention, a heat treatment is performed to affect the mechanical properties of the metal substrate after the over-aluminization of the tie layer and before the ablation treatment of the Al diffusion layer. The

  According to yet another embodiment of the method of the present invention, during overaluminization, an internal diffusion region having an Al content of about 20% by weight is formed in the Al diffusion layer, and the Al content is about 30% by weight. A layer superposed on the outside of the Al diffusion layer is formed on the diffusion region, and the layer superposed on the outside of the Al diffusion layer has an Al content of the remaining Al diffusion layer surface of greater than 18 wt% and less than 30 wt% Until it is removed by ablation.

  According to a second aspect of the present invention, a component for use in the hot gas region of a gas turbine is provided, the component being one of the above-described embodiments of the present invention in conceivable combinations, or two. It has a surface that is at least partially provided with a protective layer that is resistant to high temperature degradation due to corrosion and erosion, applied in one or more or all ways.

  According to a third aspect of the present invention, there is provided a gas turbine comprising a component according to the second aspect of the present invention having a hot gas region and disposed therein.

  By using the method according to the invention for forming a protective layer on a component, the protective layer has good resistance to thermal fatigue and can nevertheless be formed in a simple manner.

  Finally, the present invention provides the idea of a thermal barrier coating that combines the advantages of chemically bonding between the bond layer and the ceramic layer with the preferred cost of the APS process. In this way, the TCF behavior can be improved relative to the behavior of the conventional APS layer. Therefore, a thermal barrier coating with improved resistance to thermal fatigue can be produced by a simple method, and as a result, the cost is low compared to the EB-PVD method.

  Obviously, the invention extends to embodiments not given by a combination of features by explicitly referring to the claims, and the disclosed features of the invention are not Can also be combined with others.

  In the following, the present invention will be described with reference to preferred embodiments and with reference to the accompanying drawings.

1 shows a cross-sectional view of a region of a gas turbine component according to an embodiment of the invention. The component is disposed in the hot gas region and includes a protective layer.

  FIG. 1 is a cross-sectional view illustrating a region of a component 10 of a gas turbine 1 according to an embodiment of the present invention, where the component 10 is disposed in a hot gas region and includes a protective layer 12-14.

  In order to protect against high temperature degradation due to corrosion and erosion, components 10, for example, turbine blades or other components of gas turbine 1 that contact hot gas, are resistant to high temperature corrosion and erosion in whole or in part. A metal substrate 11 (substrate) having a surface with a ceramic thermal barrier coating. The ceramic thermal barrier coating 13 is formed of zirconium oxide partially stabilized with about 7 wt% yttrium oxide (the international acronym for zirconia partially stabilized with yttria is YPSZ).

  In order to improve the adhesion of the thermal barrier coating 13 to the metal substrate 11, an undercoat or tie layer 12 is first applied to the metal substrate 11 (its surface). The tie layer 12 comprises a special alloy based on MCrAlY (eg LCO 22). Here, the letter M represents Ni or Co or a combination thereof. The tie layer 12 can be applied by low pressure plasma spray (LPPS) or high velocity flame spray (HVOF), which is preferred in this case.

  The applied tie layer 12 is then subjected to a polishing process (eg, precision finishing), thereby forming a surface roughness of 2 μm or less on the tie layer 12.

In order to increase the Al content of the bonding layer 12, this bonding layer 12 is then coated by overaluminizing with an Al diffusion layer 14. Overaluminization is a process in which a reactive Al-containing gas (sometimes Al halide (AlX ₂ )) causes diffusion into the interior of Al and at the same time to the exterior of Ni, such as chemical vapor deposition at high temperatures ( CVD).

  Overaluminization produces an internal diffusion region 14.1 having an Al content of about 20% by weight within the Al diffusion layer 14 on the bonding layer 12 with almost no change, on which an Al content of about 30% is formed. This results in an overlying layer 4.2 containing 1% brittle β-NiAl phase.

  After overaluminization of the tie layer 12, a heat treatment may be performed to affect or adjust the mechanical properties of the metal substrate 11.

  Subsequently, the overlying layer 14.2 is ablated such as by blasting with hard particles (eg corundum, silicon carbide, cut metal wire, etc.) or with other known grinding or polishing media. By the treatment, the Al diffusion layer 14 is removed until reaching the inner diffusion region 14.1. The ablation process is performed until the surface of the remaining Al diffusion layer 14 (diffusion region 14.1) has an Al content greater than about 18% by weight and less than about 30% by weight.

  After the abrasion, the Al diffusion layer 14 is subjected to a polishing process (for example, precision finishing) so that the surface roughness of the remaining Al diffusion layer 14 (diffusion region 14.1) is Ra ≦ 2 μm.

  A ceramic thermal barrier coating (YPSZ ceramic layer) 13 is then applied to the surface of the remaining Al diffusion layer 14 produced as described above by atmospheric plasma spraying (APS). The same parameters as the APS method for conventional tie layers can be used.

DESCRIPTION OF SYMBOLS 1 Gas turbine 10 Component part 11 Metal base material 12 Bonding layer 13 Thermal barrier coating 14 Al diffusion layer 14.1 Internal diffusion area 14.2 Layer overlaid outside

Claims (4)

A bonding layer (12) containing MCrAlY as a main component is attached to the metal substrate (11), and the bonding layer (12) is covered by being overaluminized with the Al diffusion layer (14), and the Al diffusion layer (14 ) Was ablated and the outer layer (14.2) was removed from the Al diffusion layer (14) and the yttria partially stabilized zirconia ceramic thermal barrier coating (13) was applied to the remaining Al diffusion layer. Where the ceramic thermal barrier coating (13) is applied to the remaining Al diffusion layer (14) by atmospheric plasma spraying to provide a protective layer resistant to high temperature degradation due to corrosion and erosion of the metal substrate (11). The method of
The attached tie layer (12) is subjected to a polishing treatment prior to overaluminization, and the tie layer (12) has a surface roughness Ra ≦ 2 μm,
A method characterized in that the Al diffusion layer (14) is subjected to a polishing process after the ablation process, and the surface roughness of the remaining Al diffusion layer (14) is Ra ≦ 2 μm.   2. Method according to claim 1, characterized in that the tie layer (12) is applied to the metal substrate (11) by thermal spraying.   In order to influence the mechanical properties of the metal substrate (11), a heat treatment is performed after the over-aluminization of the bonding layer (12) and before the wear of the Al diffusion layer (14). The method according to claim 1 or 2.   During overaluminization, an internal diffusion region (14.1) having an Al content of about 20% by weight is formed inside the Al diffusion layer (14), and Al content is contained on the internal diffusion region (14.1). An outer overlying layer (14.2) having an amount of about 30% by weight is formed, and the outer layer (14.2) overlying the Al diffusion layer (14) is on the diffusion region (14.1). The layer (14.2) formed on the outer side of the Al diffusion layer (14) has an Al content on the surface of the remaining Al diffusion layer (14) greater than 18% by weight and 30% by weight. 4. A method according to any one of claims 1 to 3, characterized in that it is removed by an ablation process until an amount of less than.

Images