EP1029114A1

EP1029114A1 - Product designed to be subjected to the effects of hot gas and method for producing a coating for this product

Info

Publication number: EP1029114A1
Application number: EP98961039A
Authority: EP
Inventors: Wolfram Beele
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1997-11-03
Filing date: 1998-10-21
Publication date: 2000-08-23
Anticipated expiration: 2018-10-21
Also published as: DE59802578D1; EP1029114B1; JP2001521992A; WO1999023277A1; US6517959B1

Abstract

The invention relates to a product (1) which is designed to be subjected to the effects of hot gas. Said product has a coating (3) into which chromium nitride (6) has been incorporated in the form of a diffusion barrier to improve the long-term resistance of the coating (3). The invention also relates to a method for producing a coating (3) for a product (1) designed to be subjected to the effects of hot gas.

Description

description

PRODUCT DESIGNED FOR HOT GAS APPLICATION AND METHOD FOR PRODUCING A COATING FOR ONE FOR THIS PRODUCT

The invention relates to a product designed for hot gas application with a coating, in particular a gas turbine blade. The invention further relates to a method for producing a coating for a product designed for the application of hot gas.

In the article "Diffusion barrier coatings with active bonding, designed for gas turbine blades", by 0. Knotek, E. Lugscheider, F. Löffler, W. Beele, in the "Proceedings of the 21 ^sC International Conference on Metallurgical Coatings and Thin Films ", San Diego, CA, USA, April 25-29, 1994, describes a diffusion barrier coating for a gas turbine blade. A gas turbine blade often has an oxidation or corrosion protection coating on a base material, usually a superalloy. Diffusion processes can lead to the formation of brittle phases in the coating, which affects the service life of the gas turbine blade. The aim of the research is to develop a diffusion barrier between the base material and the coating, which at the same time guarantees a good connection of the coating to the base material. This is achieved using a chrome-aluminum-oxide-nitride system (Cr-AL-0-N).

The object of the invention is to provide a product designed for hot gas application, in which a coating is provided which is improved with regard to its long-term resistance. Another object of the invention is to provide a method for producing a coating for a product designed for the application of hot gas. According to the invention, the object aimed at specifying a product is achieved by a product made of a base material on which a coating is applied and which is designed for hot gas application, comprising:

a) a protective layer made of MCrAlY, which contains at least one metal from the group (iron, cobalt,

Nickel), abbreviated to M;

Chromium (Cr) with a content of at least 15 wt%, in particular at least 20 wt%;

Aluminum (AI) and

Yttrium (Y) and / or hafnium and / or a metal from the

Rare earth group, especially scandium,

Contains lanthanum or cerium; b) an oxide layer, in particular with aluminum oxide and / or chromium oxide; c) Chromium nitride.

A product which can be subjected to hot gas is often provided with a protective layer of the type just mentioned. Such

Protective layer serves to protect against oxidation and corrosion. Upon contact with oxygen, an oxide layer is formed on such a protective layer, which essentially consists of aluminum oxide and / or chromium oxide. The oxide layer can also be formed by oxidation from a thin layer of an oxide former, such as aluminum or chromium, applied to the protective layer. In the course of time, the protective layer of aluminum and chromium becomes poorer because aluminum and / or chromium diffuse into the oxide layer and oxidize there. As a result, the oxide layer grows. This is usually the life-limiting aging process for the coating and affects the mechanical properties of the growing oxide layer. In order to counteract the diffusion of aluminum and / or chromium to oxygen or vice versa, chromium nitride is built into the coating. The invention is based on the surprising finding that chromium nitride is present in sufficient amounts in the protective layer can be formed if the concentration of chromium is above 15 wt%, preferably above 20 wt%. The chromium nitride acts as a particularly efficient diffusion barrier for the diffusion of aluminum and / or chromium to oxygen. This significantly improves the long-term durability of the coating.

The protective layer preferably contains rhenium, in particular with a proportion between 1 wt% and 15 wt%. Here and below, wt% means percent by weight and at% atomic percent.

The chromium nitride is preferably contained in the oxide layer. The chromium nitride is more preferably present in a concentration between 10 at% and 60 at%, in particular about 50 at%. The chromium nitride is preferably present between the protective layer and the oxide layer, preferably in a transition region or also anchoring region between the oxide layer and the protective layer.

Surprisingly, it is possible to form chromium nitride in the form of a lattice. The chromium nitride preferably forms such a lattice, in particular an approximately rectangular lattice with a side length between 0.1 μm and 10 μm. The formation of such a lattice represents a particularly efficient diffusion barrier. In addition, the lattice structure reduces the susceptibility of the coating to cracking, which additionally improves the long-term durability of the coating.

The product is preferably designed as a turbine blade, in particular as a gas turbine blade. Today, gas turbine showings are mostly exposed to particularly high thermal loads and an intensive attack by oxidation or corrosion. The service life of the coating of a gas turbine blade usually determines the inspection interval of the entire blade. The product is preferably designed as a heat shield of a thermal machine, in particular for a combustion chamber. A ceramic thermal barrier coating is preferably applied to the oxide layer, in particular a zircon-based thermal barrier coating. A ceramic thermal barrier coating serves to protect the turbine blade from very high temperatures. The ceramic thermal barrier coating is coupled to the protective layer via the oxide layer. An increase in the oxide layer leads to an increasing brittleness of the oxide layer. The increasing brittleness of the oxide layer has a reducing effect on the long-term durability of the coating due to an increased susceptibility to detachment of the thermal insulation layer. Because the diffusion-inhibiting effect of the chromium nitride slows down the growth of the oxide layer, the long-term stability of the coating is improved at a particularly vulnerable point, namely the boundary layer between the thermal insulation layer and the protective layer.

According to the invention, the object aimed at specifying a method is achieved by a method for producing a coating for a product designed for the application of hot gas, whereby

a) a protective layer of MCrAlY, the

At least one metal from the group (iron, cobalt, Nikkei), abbreviated with M, • chromium (Cr) with a content of at least 15 at%, in particular at least 20 at%,

• Aluminum (AI) and

• Yttrium (Y) and / or hafnium and / or a metal from the group of rare earths, in particular scandium, lanthanum or cerium, is applied to the product, b) an oxide layer, in particular with aluminum oxide and / or chromium oxide, is formed on the protective layer and c) chromium nitride is generated via a nitrogen supply in the coating. The nitrogen is preferably supplied from a nitrogen plasma source via a nitrogen plasma treatment. A nitrogen plasma, which additionally contains hydrogen as an oxygen getter, is more preferably supplied to the coating. The provision of hydrogen in a non-molecular form enables oxygen to be extracted from the chromium oxide. This allows nitrogen to attach to the chromium, which leads to the formation of chromium nitride. A DC voltage (BIAS) is more preferably applied between the product and the nitrogen plasma source. This enables faster production of chromium nitride because the nitrogen penetrates the product more efficiently. A DC voltage of 50 V to 600 V, in particular 100 V to 300 V, is preferably applied.

The invention is explained in more detail in an exemplary embodiment with reference to the drawing. Show it:

Fig. 1 shows a longitudinal section through a coating of a hot gas product and

Fig. 2 is an enlarged, schematic representation of a chromium nitride lattice in an oxide layer.

The same reference numerals have the same meaning in the figures.

1 shows a section of a longitudinal section through a gas turbine blade which represents the product 1 which can be subjected to hot gas. The gas turbine blade 1 consists of a

Base material 2, e.g. made of a nickel-based superalloy. The gas turbine blade 1 has a surface 1A. A protective layer of MCrAlY is applied to the surface 1A, preferably with the following concentrations: Cr = chromium between 15 wt% and 30 wt%,

AI = aluminum between 6 wt and 15 wt% y = yttrium and / or hafnium and / or a rare earth metal, in particular scandium, lanthanum or cerium between 0.01 wt% and 2 wt%, M = nickel and / or cobalt and / or iron as the rest.

Rhenium or other additives may also be present.

An oxide layer 5 adjoins the protective layer 4. This is shown greatly enlarged. A ceramic thermal barrier layer 7, e.g. made of yttrium-stabilized zirconium oxide. Chromium nitride 6 is built into the oxide layer 5. The chromium nitride 6 reduces the diffusion of aluminum or chromium from the protective layer 4 into the oxide layer 5. This slows down the increase in the thickness of the oxide layer 5. Since a thick oxide layer 5 leads to an increased risk of the thermal insulation layer 7 becoming detached, the slowing down takes place the growth of the oxide layer 5 increases the long-term durability of the coating 3.

2 shows an enlarged longitudinal section through an oxide layer 5. A grid 8 made of chromium nitride 6 is shown schematically, which grid is made up of grid cells 7A. The interior of the grid cells 7A consists of aluminum oxide and / or chromium oxide. The grid 8 is not geometrically perfect, so it has e.g. Interruptions, changing thicknesses and changing area sizes of the grid cells 7A. On average, however, an approximate average side length A of a grid cell 7A can be specified, which is preferably between 0.1 μm and 5 μm. This average side length A depends in particular on the material of the protective layer and / or the oxide layer or also on process parameters in the formation of the chromium nitride. Such a lattice of the chromium nitride 6 particularly efficiently prevents diffusion of aluminum or chromium.

Claims

1. A product (1) made of a base material (2) on which a coating (3) is applied, which is designed for hot gas application, comprising: a) a protective layer (4) made of MCrAlY, the

At least one metal from the group (iron, cobalt, Nikkei), abbreviated to M,

Chromium (Cr) with a content of at least 15 wt%, in particular at least 20 wt%,

• Aluminum (AI) and

• contains yttrium (Y) and / or hafnium and / or a metal from the group of rare earths, in particular scandium, lanthanum or cerium; b) an oxide layer (5), in particular with aluminum oxide and / or chromium oxide; c) Chromium nitride (6).

2. Product (1) according to claim 1, wherein the protective layer (4) contains rhenium, in particular with a proportion of 1 wt% to 15 wt%.

3. Product (1) according to claim 1 or 2, wherein the chromium nitride (6) is contained in the oxide layer (5).

4. Product (1) according to one of the preceding claims, in which the chromium nitride (6) is present between the protective layer (4) and the oxide layer (5).

5. Product (1) according to one of the preceding claims, in which the chromium nitride (6) is contained in a concentration between 10 at% and 60 at%, in particular about 50 at%.

6. Product (1) according to one of the preceding claims, in which the chromium nitride (6) forms a grid (8), in particular an approximately rectangular or square grid (8) with a side length (A) between 0.1 μm. and 5 μm.

7. Product (1) according to one of the preceding claims, which is designed as a turbine blade, in particular as a gas turbine ^¬ blade.

8. Product (1) according to one of the preceding claims, which is designed as a heat shield element of a thermal machine, in particular for a combustion chamber.

9. Product (1) according to one of the preceding claims, in which on the oxide layer (5) a ceramic thermal barrier coating

(7) is applied, in particular a heat insulation layer (7) based on zirconium oxide.

10. A method for producing a coating (3) for a hot gas-resistant product (1), wherein a) a protective layer (4) made of MCrAlY, which • at least one metal from the group (iron, cobalt, Nik ^¬ kei), abbreviated with M ,

• chromium (Cr) WT provided with a content of at least 15%, in particular at least 20 wt% ^¬ sondere,

• aluminum (Al) and • yttrium (Y) and / or hafnium and / or a metal from the group of rare earths, in particular scandium, lanthanum or cerium, applied to the product, b) an oxide layer (5), in particular with Aluminum oxide and / or chromium oxide are formed on the protective layer (4) and c) chromium nitride (6) is produced via a nitrogen ^{supply in the} coating (3).

11. The method of claim 10, wherein the nitrogen supply is carried out via a nitrogen plasma treatment.

12. The method of claim 10, wherein from a nitrogen plasma source ^¬ a nitrogen plasma of the coating (3) applied ^¬ leads, is additionally water ^¬ material contains as oxygen getters.

13. The method according to claim 10 or 11, in which a direct voltage (BIAS), in particular between 50 V and 600 V, is applied to the product relative to the nitrogen ^plasma source.