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Title: Metallurgical evaluation of keyway cracking in low-pressure turbine disks. Final report

Abstract

A metallurgical evaluation of keyway cracking in the rotor discs of large LP steam turbines was performed. Three particular cases of the development of major keyway cracks in LP turbine discs at two nuclear steam electric generating stations were investigated. The overall objectives of the investigation were to characterize the disc material, establish the nature and extent of the keyway cracks and identify the cracking mechanism. Metallographic and fractographic examinations established that the cracking was predominantly intergranular and that significant corrosive attack had occurred within the keyways. It was also determined that the composition, mechanical properties and microstructure were normal for quenched and tempered NiCrMoV alloy steels and that the cracking was not associated with any inherent materials defect or abnormality. The identified the cracking mechanism as intergranular stress corrosion cracking (IGSCC). It is concluded that the keyway cracks developed as the result of the combined effects of the inherent IGSCC susceptibility of NiCrMoV alloy steels, the operating stresses, and environmental conditions encountered within large LP steam turbines.

Authors:
Publication Date:
Research Org.:
Southwest Research Inst., San Antonio, TX (USA)
OSTI Identifier:
5228120
Report Number(s):
EPRI-NP-3341
ON: DE84920241
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
20 FOSSIL-FUELED POWER PLANTS; 21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS; NUCLEAR POWER PLANTS; STEAM TURBINES; CRACKS; CRACK PROPAGATION; FRACTOGRAPHY; INSPECTION; INTERGRANULAR CORROSION; METALLOGRAPHY; ROTORS; STEELS; STRESS CORROSION; ALLOYS; CHEMICAL REACTIONS; CORROSION; IRON ALLOYS; IRON BASE ALLOYS; MACHINERY; NUCLEAR FACILITIES; POWER PLANTS; THERMAL POWER PLANTS; TURBINES; TURBOMACHINERY; 200100* - Fossil-Fueled Power Plants- Power Plants & Power Generation; 210200 - Power Reactors, Nonbreeding, Light-Water Moderated, Nonboiling Water Cooled

Citation Formats

Burghard, Jr, H C. Metallurgical evaluation of keyway cracking in low-pressure turbine disks. Final report. United States: N. p., 1984. Web.
Burghard, Jr, H C. Metallurgical evaluation of keyway cracking in low-pressure turbine disks. Final report. United States.
Burghard, Jr, H C. Sun . "Metallurgical evaluation of keyway cracking in low-pressure turbine disks. Final report". United States.
@article{osti_5228120,
title = {Metallurgical evaluation of keyway cracking in low-pressure turbine disks. Final report},
author = {Burghard, Jr, H C},
abstractNote = {A metallurgical evaluation of keyway cracking in the rotor discs of large LP steam turbines was performed. Three particular cases of the development of major keyway cracks in LP turbine discs at two nuclear steam electric generating stations were investigated. The overall objectives of the investigation were to characterize the disc material, establish the nature and extent of the keyway cracks and identify the cracking mechanism. Metallographic and fractographic examinations established that the cracking was predominantly intergranular and that significant corrosive attack had occurred within the keyways. It was also determined that the composition, mechanical properties and microstructure were normal for quenched and tempered NiCrMoV alloy steels and that the cracking was not associated with any inherent materials defect or abnormality. The identified the cracking mechanism as intergranular stress corrosion cracking (IGSCC). It is concluded that the keyway cracks developed as the result of the combined effects of the inherent IGSCC susceptibility of NiCrMoV alloy steels, the operating stresses, and environmental conditions encountered within large LP steam turbines.},
doi = {},
url = {https://www.osti.gov/biblio/5228120}, journal = {},
number = ,
volume = ,
place = {United States},
year = {1984},
month = {1}
}

Technical Report:
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