Journal Published Online: 01 May 1990
Volume 18, Issue 3

Nondestructive Evaluation of In-Service Toughness Degradation for Cr-Mo-V Steam Turbine Rotor Steel

CODEN: JTEVAB

Abstract

Embrittlement was investigated for five retired and three laboratory-aged steam turbine rotors by sampling Charpy V-notch test coupons and testing them. A nondestructive evaluation method of toughness degradation was discussed.

The investigation has revealed that Cr-Mo-V rotor steel becomes embrittled by phosphorus segregation at the grain boundaries over a long period of use at high temperatures. The phosphorus-enhanced toughness degradation can be nondestructively detected by the electrochemical polarization (ECP) test.

An approximate formula to evaluate the degraded fracture appearance transition temperature (FATT) of a specific Cr-Mo-V rotor was established that included the nondestructive information of the ECP minimum current density, grain size, and data given from the fabrication record. The nondestructive estimation procedure for the ductile fibrosity percentage versus the temperature curve for the specific rotor is also presented.

Author Information

Kimura, K
Heavy Apparatus Engineering Laboratory, Toshiba Corporation, Yokohama, Japan
Inukai, T
Heavy Apparatus Engineering Laboratory, Toshiba Corporation, Yokohama, Japan
Saito, K
Heavy Apparatus Engineering Laboratory, Toshiba Corporation, Yokohama, Japan
Kashiwaya, H
Heavy Apparatus Engineering Laboratory, Toshiba Corporation, Yokohama, Japan
Pages: 10
Price: $25.00
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Stock #: JTE12470J
ISSN: 0090-3973
DOI: 10.1520/JTE12470J