A new evaluation procedure for detecting the material degradation of a CrMoV turbine rotor steel.

1 January 1987

journal article
Published by Japan Society of Mechanical Engineers in TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series A

Vol. 53 (492) , 1550-1557
https://doi.org/10.1299/kikaia.53.1550

Abstract

A CrMoV turbine rotor retired after long service operation (22 years at 500°C) was investigated to characterize the material degradation due to temper embrittlement by use of three different kinds of techniques ; the electrochemical polarization curve (EPC) method, the electrochemical noise analysis (ENA) and the small punch (SP) test. Grain boundary embrittlement due to phosphorous segregation can be detected as a change in repassivation behavior in the EPC method ; a significant difference in corrosion potential fluctuation in ENA ; and a shift of SP transition temperature. Diagrams for evaluating the temper embrittlement of a CrMoV turbine rotor were also proposed. Furthermore, a realistic and rational procedure for evaluating material degradation during service operation has been also discussed by combined EPC, ENA and SP methods.

Keywords

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