EP1970461A1 - Turbine part with heat insulation layer - Google Patents

Abstract

Iron-based alloy contains (in wt.%) 15-30 chromium, 1.5-5 aluminum, less than 0.2 silicon, 0.1-0.7 yttrium, 0.1-0.5 cerium, 0.1-0.5 hafnium, : Independent claims are also included for the following: (1) Protective layer containing the iron-based alloy for protecting a component against corrosion and/or oxidation; and (2) Method for producing an iron-based alloy.

Description

The invention relates to an iron-based alloy according to claim 1, a protective layer according to claim 10, a layer system according to claim 11 and a method for producing the iron-based layer according to claim 16.

Protective layers for metallic components intended to increase their corrosion resistance and / or oxidation resistance are known in the art in large numbers. Most of these protective layers are known under the collective name MCrAlY, where M stands for at least one of the elements from the group consisting of iron, cobalt and nickel and further components chromium, aluminum and yttrium.

Thermal barrier coatings that are applied to turbine components, for example, in the EP 1 541 810 A1 described. The effort to increase the inlet temperatures of the live steam in steam turbines is of great importance, because to achieve optimum thermal efficiency, the inlet temperature of the live steam is an important determinant. Due to the use of specially developed ferritic base materials for thermally highly stressed turbine components, steam temperatures of approx. 620 ° C can currently be achieved. Through the use of thermal barrier coatings on these base materials, a fresh steam inlet temperature should be increased or the use of cost-effective materials should be made possible at the same steam temperature.

In order to achieve sufficient resistance to oxidation and corrosion of the ferritic base materials, protective coatings must be used. In addition to the sufficient chemical resistance of a protective layer, a protective layer must also be resistant to good mechanical properties Properties, not least in view of the mechanical interaction between the protective layer and the base material, have. In particular, the protective layer must be sufficiently ductile in order to be able to follow any deformations of the base material and not to break, since in this way points of attack for oxidation and corrosion would be created.

It is advantageous to arrange an adhesive layer between the base material and the thermal barrier coating when using thermal barrier coatings on steam turbine components. On the one hand, the adhesive layer ensures good adhesion of the thermal barrier coating to the base material and, on the other hand, protection of the base material against oxidation and corrosion.

In order to protect the thermal barrier coating against erosion and corrosion, a further protective layer can be arranged on the thermal barrier coating, which is referred to as top-coating. Adhesive layers and / or top coatings made of Ni-Cr 80/20 and / or MCrAlY are particularly suitable for the base materials used in steam turbine construction. In particular, these abovementioned adhesive layers are suitable for base materials such as, for example, Ni-base alloys, where suitability above 700 ° C. appears possible.

A disadvantage of the use of these adhesive layers and / or top coatings is that their thermal expansion coefficient compared to the base materials or thermal barrier coatings is relatively high, which means that stresses and / or strains can lead to undesirable cracking.

The object of the invention is therefore to provide a suitable material for the adhesive layer and / or top coatings.

This object is achieved by an alloy according to claim 1, a protective layer according to claim 13 and a layer system according to claim 14.

The object is also achieved by a method for producing a layer according to claim 16 and / or 19.

The measures listed in the dependent claims can be combined in any advantageous manner with each other.

The invention is based inter alia on the finding that the proportion of chromium content on the chemical and physical properties of the adhesive layer and / or the topcoat depends substantially on the chromium content, wherein the aluminum content plays an essential role. By the solutions described in the claims accordingly adhesive layer types and / or top coatings are given, which meet both the required properties in terms of oxidation and corrosion resistance due to their chemical composition, as well as have a suitable coefficient of thermal expansion.

In essence, the invention is characterized in that the thermal spraying a spray powder is used with a chromium content of 25 wt .-% to 35 wt .-% chromium, whereby a chromium content of 15 wt .-% - 30 wt. % is achieved in the iron-based layer after the manufacturing process. It has been determined by experiments that the chromium content of the spray powder falls by up to 10% by weight during the manufacturing process.

In order to reduce the tendency of this iron-based alloy to embrittlement by sigma phase formation, an aluminum content of 1% by weight to 5% by weight of aluminum can be added to the sprayed powder. To further reduce sigma phase formation, the lowest possible silicon content <0.2% by weight is used.

To improve the oxidation resistance, for example, the elements Ce, Y and / or Hf can be used.

The invention will be explained in more detail below.

Figur 1, 2, 3, 4

Anordnungsmöglichkeiten einer Wärmdämmschicht eines Bauteils.

Show it:

Figure 1, 2, 3, 4

Arrangement possibilities of a thermal insulation layer of a component.

FIG. 1 shows a first embodiment of an inventively designed component. 1
The component 1 could, for example, be an inflow region of a turbine, in particular a steam turbine, and has a base material 4 and a thermal insulation layer 7 applied thereto. The thermal insulation layer 7 may be formed from a ceramic material. Thus, for example, the thermal barrier coating 7 may be formed as a ceramic thermal barrier coating of zirconium oxide, wherein the zirconium oxide is unstabilized, partially stabilized or fully stabilized by yttrium oxide and / or magnesium oxide. In an alternative embodiment, the ceramic thermal barrier coating may be titanium oxide, the thickness being between 0.1 mm and 2 mm.

Various coating methods can be used to produce the ceramic thermal barrier coating 7. For example, the ceramic thermal barrier coating 7 by thermal spraying such as atmospheric plasma spraying (APS) and by chemical or physical coating methods such. As CVD or PVD can be used.

The FIG. 2 shows a further embodiment of the inventively constructed component 1. The difference between the FIG. 1 and the FIG. 2 is that between the base material 4 and the thermal barrier coating 7 at least one adhesive layer 10, comprising an iron-based alloy is formed.

The adhesive layer 10 serves firstly to protect against corrosion and / or oxidation of the base material and secondly to better bond the ceramic thermal barrier coating 7 to the base material 4. This is particularly the case when the ceramic thermal barrier coating and the base material consist of a metal. The iron-based adhesive layer in this case comprises 15 wt .-% to 30 wt .-% chromium. Furthermore, the iron-based alloy comprises 1.5 wt% to 2.5 wt% aluminum and less than 0.2 wt% silicon.
Furthermore, the iron-based adhesive layer may comprise the element Y, the element hafnium and the element Cer with the following proportions by weight:
0.1 wt.% To 0.7 wt.% Y
0.1% by weight to 0.5% by weight of cerium
0.1 wt .-% to 0.5 wt .-% hafnium have.

• Ausführungsform I:
  • 15 Gew.-% bis 30 Gew.-% Chrom.
• Ausführungsform II:
  • 13 Gew.-% bis 15 Gew.-% und 1,5 Gew.-% bis 5 Gew.-% Aluminium.
• Ausführungsform III:
  • 15 Gew.-% bis 30 Gew.-% Chrom und 1,5 Gew.-% bis 3 Gew.-% Aluminium und Silizium mit weniger als 0,2 Gew.-%.

The adhesive layer 10 for protecting the base material 4 against oxidation and corrosion and erosion at a high temperature consists, for example, essentially of the following elements:

• Embodiment I:
  • 15 wt .-% to 30 wt .-% chromium.
• Embodiment II:
  • 13 wt .-% to 15 wt .-% and 1.5 wt .-% to 5 wt .-% aluminum.
• Embodiment III:
  • 15% by weight to 30% by weight of chromium and 1.5% by weight to 3% by weight of aluminum and silicon with less than 0.2% by weight.

The thermal expansion coefficients of the base material 4 and the adhesive layer 10 are thereby very well matched or even equal, so that there is no or only low thermal stresses between the base material 4 and the adhesive layer 10, the chipping and / or cracking the adhesive layer 10 or could cause the thermal barrier coating. This is particularly important because in ferritic materials often no heat treatment for diffusion bonding is performed, but the thermal barrier coating 7 largely or only by adhesion to the base material adheres. The base material 4 may be a ferritic base alloy, a steel, in particular a 1% CrMoV steel or a 9% -13% chromium steel. Further advantageous ferritic substrates 4 of the component 1 consist of a 1% - 2% chromium steel for waves: such. 30CrMoNiV5-11 or 23CrMoNiWV8-8,
1% - 2% chrome steel for housing:
G17CrMoV5-10 or G17CrMo9-10,
10% chrome steel for shafts:
X12CrMoWVvNbN10-1-1,
10% Cr-steel for housing:
GX12CrMoWVNbN10-1-1 or GX12CrMoVNbN9-1.

In particular, the component 1 is manufactured by thermal spraying, using iron-based powder comprising 25% by weight to 35% by weight of chromium. In such a production process, oxygen uptake during the injection process leads to a more or less pronounced formation of Cr oxide, which in turn results in a strong localized Cr depletion up to a fraction below 12%. The use of the iron-based powder according to the invention ensures that the iron-based alloy has a proportion of 15% by weight to 30% by weight of chromium after the production process.

The manufacturing process is improved in that aluminum is added to the powder with 1 wt% to 5 wt% aluminum. After thermal spraying, an aluminum content of 1.5 wt.% To 3 wt.% Aluminum in the iron-based alloy remains.

In an alternative embodiment, the process uses a powder comprising 28% to 30% by weight of chromium, aluminum being added to the powder with 2.5 wt .-% to 3.5 wt .-% aluminum. The powder in this case has less than 0.2 wt .-% silicon.

The method of producing the iron-based layer using thermal spraying can be improved so that the iron-based powder consists of 25 wt% to 35 wt% of chromium.

Alternatively, the powder may consist of 25 wt% to 35 wt% chromium and 1 wt% to 5 wt% aluminum.

Alternatively, the iron-based powder may consist of 28% to 30%, 2.5% to 3.5%, by weight, aluminum and silicon less than 0.2% by weight.

The FIG. 3 shows a further embodiment of the inventively designed component. 1

On the ceramic thermal barrier coating 7 now forms an erosion protection layer 13, the outer surface. The erosion protection layer 13 can also be referred to as a top coating. It consists in particular of a metal or a metal alloy and protects the component from erosion and / or wear, as is the case in particular in steam turbine power plants which have a scaling in the superheated steam region, where average flow velocities of about 50 m / sec and pressures of up to 350 bar occur.

The erosion protection layer 13 may have substantially the same chemical elements as the adhesion layer 10. This achieves the advantage that the thermal stresses between a thermal barrier coating and the erosion control layer 13 are minimal.

Likewise, in comparison to an embodiment according to FIG. 3 still an adhesive layer 10 may be present.

Claims (23)

Iron-based alloy (10),
full
15% by weight to 30% by weight Cr. Iron-based alloy (10),
full
1.5% by weight to 5% by weight Al. Iron-based alloy (10) according to claim 1,
comprising Si with less than 0.2 wt% Si. Iron-based alloy (10) according to one of the preceding claims,
comprising the element Y, in particular comprising
0.1% by weight to 0.7% by weight of Y. Iron-based alloy (10) according to one of the preceding claims,
comprising the element Ce, in particular comprising
0.1% by weight to 0.5% by weight of Ce. Iron-based alloy (10) according to one of the preceding claims,
comprising-the element Hf, in particular comprising
0.1% by weight to 0.5% by weight Hf. Iron-based alloy (10) according to claim 1 consisting of 15 wt .-% to 30 wt .-% Cr Iron-based alloy (10) according to claim 2 consisting of 15 wt .-% to 30 wt .-% Cr and
1.5% to 5% by weight A1. Iron-based alloy (10) according to claim 3 consisting of 15 wt .-% to 30 wt .-% Cr and
1.5 wt .-% to 5 wt .-% Al and
Si with less than 0.2 wt .-%. Protective layer for protection of a component (1) against corrosion and / or oxidation,
especially at high temperatures,
which has the composition of the alloy according to any one of claims 1 to 9. Layer system,
comprising a protective layer according to claim 10. Layer system according to claim 11,
wherein the thermal barrier coating (7) comprises zirconium oxide (ZrO ₂ ). Layer system according to claim 11,
wherein the thermal barrier coating (7) comprises titanium oxide (TiO ₂ ). Layer system according to one of claims 7 to 9,
wherein the substrate (4) is formed of an iron-based alloy. Layer system according to one of claims 10 to 14, for a component (1) of a steam turbine,
for protection against corrosion, erosion and oxidation at high temperatures. A process for producing an iron-based layer according to claim 10,
the layer being applied by thermal spraying and
an iron-based powder is used, which comprises 25 wt .-% to 35 wt .-% Cr. Method according to claim 16,
the powder
1 wt .-% to 5 parts by weight A1. Method according to claim 16,
the powder
28 wt .-% to 30 wt .-% Cr. Method according to claim 18,
the powder
2.5 wt .-% to 3.5 wt .-% A1. Method according to claim 19,
the powder
has less than 0.2 wt .-% Si. A process for producing an iron-based layer according to any one of claims 1 to 10,
the layer being applied by thermal spraying and
an iron-based powder is used, which consists of 25 wt .-% to 35 wt .-% Cr. Method according to claim 21,
wherein the powder consists of 25 wt .-% to 35 wt .-% Cr and 1 wt .-% to 5 wt-A1. Method according to claim 21,
wherein an iron-based powder is used, which consists of 28 wt .-% to 30 wt .-% Cr, 2.5 wt .-% to 3.5 wt-Al and Si with less than 0.2 wt .-% consists ,

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