DE102009049018A1 - Component for a high-temperature steam turbine and high-temperature steam turbine - Google Patents

Abstract

A component for a high-temperature steam turbine, which operates at temperatures above 600 ° C, in particular above 700 ° C, consists of a nickel-based alloy. The negative influence of oxidation of the component caused by superheated steam is prevented by the fact that the alloy used has the following composition [in% by weight]: C: <= 0.2 Si: <= 1.0 Mn: <= 1, 0 Cr: 22.0-25.0 Co: 15.0-25.0 Mo: <= 3.0 Nb: <= 2.0 Al: 1.0-3.0 Ti: 2.0-4, 0 Fe: <= 2.0 Zr: <= 0.2 B: <= 0.05 Ni: remainder.

Description

TECHNICAL AREA

The The present invention relates to the field of steam turbines. It relates to a component for a high-temperature steam turbine according to the preamble of claim 1, as well as a high-temperature steam turbine.

STATE OF THE ART

modern Steam turbines work at very high temperatures to increase their efficiency to improve. At temperatures above 600 ° C, and in particular Above 700 ° C, many components of such a high-temperature steam turbine made of nickel-based alloys to the required high-temperature strength (Creep, fatigue, etc.) to achieve.

• – ein Verlust an belastbarer Fläche die betriebsbedingte Belastung erhöht;
• – die Oxidation entlang der Korngrenzen „Mikrokerbungen” erzeugt, welche die Gefahr einer Ermüdungsrissbildung erhöhen;
• – eine Oberflächenrauigkeit aufgrund der Bildung von irregulären Oxidschichten entsteht und ein Abplatzen von Oxiden von der Oberfläche erfolgt (welche beiden Effekte zu einem Aufrauen der Oberfläche führen, das die aerodynamische Effektivität der Turbine verringert).

At high operating temperatures, the materials used (as well as the nickel-based alloys) oxidize when exposed to hot steam. This is the case in particular in the case of the turbine blades, in which the oxidation leads to

• - a loss of loadable area increases the operational burden;
• - the oxidation along the grain boundaries produces "micro-notches" which increase the risk of fatigue cracking;
• - surface roughness due to the formation of irregular oxide layers is generated and surface chipping of oxides occurs (both of which cause roughening of the surface which reduces the aerodynamic efficiency of the turbine).

From the US 62-7,238,005 is a steam turbine power plant with operating temperatures of over 650 ° C is known, which is characterized by the use of selected nickel-based alloys instead of austenitic heat-resistant steels for certain components of turbines such as housings or blades to reduce the thermal stresses during load changes. The eligible alloys have different proportions of Cr, Co and Mo, either a Cr content of ≤ 21 wt .-%, z. B. 11.0 to 20.0 or 17.0 to 21.0 wt .-%, or a Cr content of 19.0 to 24.0 wt .-%, but a Co content of ≤ 15 wt % or Cr content of 19.0 to 25.0% by weight, but no Co content and Mo content of ≦ 2.0% by weight.

The question of grain boundary oxidation and the associated fatigue cracking, as well as questions of the oxidation - related surface roughness play in the solution of the US B2-7,238,005 not matter.

PRESENTATION OF THE INVENTION

It is therefore an object of the invention, which exposed the hot steam heavy-duty components of a hot steam turbine in terms of the possible oxidation and its harmful consequences to improve, and specify a corresponding hot steam turbine.

The The object is achieved by the entirety of the features of claim 1 and of claim 4 solved. An essential feature of the invention is that the component is made of a special alloy which is the high strength at high operating temperatures of nickel-based alloys with high resistance against grain boundary oxidation, against the oxidation of the surface in general and against the spalling of surface oxides, due to the choice of alloying elements, especially the chromium component combined.

According to the invention, the alloy used has the following composition [in% by weight]:
C: ≤ 0.2
Si: ≤ 1.0
Mn: ≤ 1.0
Cr: 22.0-25.0
Co: 15.0-25.0
Mo: ≤ 3.0
Nb: ≤ 2.0
Al: 1.0-3.0
Ti: 2.0-4.0
Fe: ≤ 2.0
Zr: ≤ 0.2
B: ≤ 0.05
Ni: rest.

According to an embodiment of the invention, the proportion of Cr on the Range limited between 23.0 and 25.0 [wt .-%].

Prefers the component is a blade of the steam turbine.

The high-temperature steam turbine according to the invention is characterized in that the component consists of a nickel-based alloy which has the following composition [in% by weight]:
C: ≤ 0.2
Si: ≤ 1.0
Mn: ≤ 1.0
Cr: 22.0-25.0
Co: 15.0-25.0
Mo: ≤ 3.0
Nb: ≤ 2.0
Al: 1.0-3.0
Ti: 2.0-4.0
Fe: ≤ 2.0
Zr: ≤ 0.2
B: ≤ 0.05
Ni: rest.

According to One embodiment is the proportion of Cr in the area between 23.0 and 25.0 [wt%]. Especially the component is a blade of the high-temperature steam turbine.

SHORT EXPLANATION THE FIGURES

The Invention is intended below in conjunction with the drawings be explained. Show it

1 a graph of the average creep rupture strength after 1000 hours above the temperature of a commercially available alloy according to the invention (Nimonic 101 ^® ) compared to a previously used commercially available alloy (Waspaloy ^® ) and

2 a plot of average tensile strength versus temperature of both alloys 1 compared.

WAYS TO EXECUTE THE INVENTION

According to the invention, for the high-temperature steam of 600 ° C and more loaded components, in particular blades (blades and vanes), a high-temperature steam turbine, a nickel-based alloy is used, which is characterized by a relatively high content of Cr and Co, and the has the following composition [in% by weight]:
C: ≤ 0.2
Si: ≤ 1.0
Mn: ≤ l, 0
Cr: 22.0-25.0
Co: 15.0-25.0
Mo: ≤ 3.0
Nb: ≤ 2.0
Al: 1.0-3.0
Ti: 2.0-4.0
Fe: ≤ 2.0
Zr: ≤ 0.2
B: ≤ 0.05
Ni: rest.

hereby are realized components, which are characterized by a high strength characterized by the operating temperatures and a large resistance against oxidation at the grain boundaries as well as the surfaces in general, and not for chipping off oxide layers tilt from the surfaces.

Instead of a Cr content of 22.0-25.0 wt .-% can with advantage a limited range of 23.0-25.0% by weight come into use.

A commercially available, lying in the inventive composition range of nickel-based alloy is known under the brand name Nimonic 101 ^®. This known nickel-based alloy contains 24.2% by weight Cr, 19.7% by weight Co, 1.5% by weight Mo, 3.0% by weight Ti, 1.4% by weight Al, 1, 0 wt .-% Nb and 48.0 wt .-% Ni and has not yet been used for steam turbine components.

By a comparison with another commercially available nickel-based alloy, the Waspaloy ^®, which only contains 18.0 to 21.0 wt .-% Cr and 12.0 to 15.0 weight .-% of Co, it is clear that especially in the high temperatures above 600 ° C for the inventive alloys significant advantages.

So shows 1 That the mean creep rupture strength at 1000 h (Rm, 1000 h) of Nimonic ^® 101 (rectangles) is up to 16% higher in the temperature range of interest above 600-650 ° C than the corresponding value for Waspaloy ^® (diamonds).

Likewise, according to 2 the mean tensile strength (Rm) of Nimonic 101 ^® (rectangles) above 650 ° C slightly higher than that of Waspaloy ^® (diamonds).

• – Ein mechanisches Versagen der Schaufeln wird ausgeschlossen (lange Lebensdauer);
• – Ein Verlust an aerodynamischer Effizienz aufgrund erhöhter Oberflächenrauigkeit wird vermieden.

Overall, the invention provides the following advantages:

• - Mechanical failure of the blades is excluded (long life);
• - A loss of aerodynamic efficiency due to increased surface roughness is avoided.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - US 62-7238005 [0004]
• US 7238005 B2 [0005]

Claims (6)

Component for a high-temperature steam turbine, which operates at temperatures above 600 ° C, in particular above 700 ° C, which component consists of a nickel-based alloy, characterized in that the alloy used has the following composition [in wt .-%]: C: ≤ 0.2 Si: ≤ 1.0 Mn: ≤ 1.0 Cr: 22.0-25.0 Co: 15.0-25.0 Mo: ≤ 3.0 Nb: ≤ 2.0 Al: 1.0 -3.0 Ti: 2.0-4.0 Fe: ≤ 2.0 Zr: ≤ 0.2 B: ≤ 0.05 Ni: balance. Component according to claim 1, characterized that the proportion of Cr in the range between 23.0 and 25.0 wt .-% is limited. Component according to claim 1 or 2, characterized the component is a blade of the high temperature steam turbine. High-temperature steam turbine for operation at Temperatures above 600 ° C, especially above 700 ° C, which high-temperature steam turbine exposed to the hot steam Component comprises, characterized in that the component of a Nickel-based alloy consisting of the following composition [in% by weight] has: C: ≤ 0.2 Si: ≤ 1.0 Mn: ≤ 1.0 Cr: 22.0 to 25.0 Co: 15.0-25.0 Mo: ≤ 3.0 Nb: ≤ 2.0 al: 1.0-3.0 Ti: 2.0-4.0 Fe: ≤ 2.0 Zr: ≤ 0.2 B: ≤ 0.05 Ni: Rest. High-temperature steam turbine according to claim 4, characterized characterized in that the proportion of Cr in the range between 23.0 and 25.0 wt.% Is limited. High temperature steam turbine according to claim 4 or 5, characterized in that the component is a blade of the high-temperature steam turbine is.