Corrosion Resistance of Power Plant Components Exploited for Long Terms at 600, 650, and 800°C

Three austenitic steels (18Cr-8Ni, 18Cr-10Ni, and. 21 Cr-30Ni) exploited for long periods of time at temperatures between 600 degrees C and 800 degrees C Were investigated. In the investigation, electrochemical potentiokinetic reactivation-double loop (EPR-Dl,) and oxalic acid etch corrosion tests, metallography, scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, and energy-dispersive x-ray spectroscopy were used. In the severe sensitized 18Cr-8Ni steel, small, densely arranged intergranular particles, mostly of M(23)C(6). were found. The 18Cr-10Ni steel was classified as less-sensitized compared to the 18Cr-8Ni steel as a result of the presence of larger, discrete grain boundary particles in addition to small, densely arranged particles. In the unsensitized 21 Cr-30Ni steel, huge, discrete clusters often exceeding. 10 mu m were observed at the grain boundaries. The clusters were found to consist of large Cr-rich M(23)C(6) and small Ti-rich MC particles.