電気化学的手法によるステンレス鋼の材質劣化現位置評価技術の開発

概要

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The change in electrochemical properties caused by microstructural changes was utilized for the nondestructive detection of material degradation. S/H tubes of fossil boilers were studied where carbide, Laves and sigma phase formation were detected by the anodic current peak I_P in an anodic polarization measurement of 316H stainless steel in lM KOH electrolytes. For practical uses, a small and light-weight electrochemical probe and a portable anodic polarization measuring system were developed; their effectiveness was shown through on-site measurements in many actual plants. Using measured I_P, the equivalent operational temperature of tubes after long-term service operation was estimated with reference to the I_P-t exp (-Q/RT) curve of aged materials. It is suggested that their metallographic changes can be evaluated by a parameter of I_P/I_<PC>, where Ipc is estimated as to be the threshold value of I_P. It is also indicated that their mechanical damage markedly increases by nucleation and growth of Laves phases at I_P/I_<PC> value over 0.7.
社団法人日本機械学会の論文
1991-06-25