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Research Papers

Development of a New High-Strength Steel for Low Pressure Steam Turbine End-Stage Blades

[+] Author and Article Information
Hannes Teuber

Siemens AG, Power and Gas,
Rheinstrasse 100,
Muelheim an der Ruhr 45478, Germany
e-mail: hannes.teuber@siemens.com

Jochen Barnikel

Siemens AG, Power and Gas,
Rheinstrasse 100,
Muelheim an der Ruhr 45478, Germany
e-mail: jochen.barnikel@siemens.com

Michael Dankert

Siemens AG, Power and Gas,
Rheinstrasse 100,
Muelheim an der Ruhr 45478, Germany
e-mail: michael.dankert@siemens.com

Walter David

Siemens AG, Power and Gas,
Rheinstrasse 100,
Muelheim an der Ruhr 45478, Germany
e-mail: walter.david@gmx.com

Andrei Ghicov

Siemens AG, Power and Gas,
Rheinstrasse 100,
Muelheim an der Ruhr 45478, Germany
e-mail: andrei.ghicov@siemens.com

Simon Voss

Siemens AG, Power and Gas,
Rheinstrasse 100,
Muelheim an der Ruhr 45478, Germany
e-mail: voss.simon@siemens.com

1Corresponding author.

Manuscript received June 22, 2018; final manuscript received July 4, 2018; published online September 18, 2018. Editor: Jerzy T. Sawicki.

J. Eng. Gas Turbines Power 141(1), 011021 (Sep 18, 2018) (7 pages) Paper No: GTP-18-1297; doi: 10.1115/1.4040849 History: Received June 22, 2018; Revised July 04, 2018

Influenced by the growing share of Renewable Energies, higher flexibility and increased efficiency of fossil power plants as well as improved cost efficiency in production of turbine components are evident market trends. Daily cycling in turbine operations leads to advanced requirements for robust design especially of rotating parts. Low pressure (LP) steam turbine end-stage blades with larger exhaust areas are one lever to increase the efficiency of the turbine by reduction of exhaust losses and also to realize cost-efficient single flow exhaust applications. Consequently, blade steels with improved mechanical properties are required. The results of the development of a new high-strength precipitation-hardening (PH) steel for LP end-stage blade application with significantly enhanced material properties are reported. The paper covers the testing strategy applied and information on crucial material parameters like improved low cycle and high cycle fatigue (HCF) behavior while keeping good stress corrosion cracking (SCC) resistance and corrosion fatigue (CF) properties. Furthermore, first manufacturing experiences and validation results from a full-scale component test rig are presented.

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References

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Figures

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Fig. 1

Comparison of absorbed impact energies

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Fig. 2

Surface condition of the blade steels after salt spray test

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Fig. 3

Time to fracture due to SCC in 3.5% NaCl solution

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Fig. 4

SEM picture of the crack growth specimens showing no SCC

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Fig. 5

Stress–cycle curve for fully reversed stress

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Fig. 6

Average Haigh diagram and air

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Fig. 7

Average Haigh diagram, air, and water

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Fig. 8

Stress–cycle curve for fully reversed stress for bar material and standard specimens from forged blades

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Fig. 9

Residual stresses from shot-peening

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Fig. 10

Hardness depth profiles from laser treatment

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Fig. 11

HCF component test facility for full-scale LP blades

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Fig. 12

Comparison of HCF component strength with HCF material strength

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