Failure analysis of casing of draft tube of turbine used in hydropower plant

Abstract Corrosion of massive components used in hydropower plants causes considerable technical problems and economic losses. Due to the corrosive environment and strong dynamic loading, such components must meet high demands. Quality of the components is essentially influenced by quality of material—chemical composition, correct metallurgical processes and also good practice of subsequent forming and welding technology. Aim of the analysis was to determine the failure cause of the massive casing of draft tube from turbine used in hydropower plant. The main part of this study was focused on detailed analysis of chemical composition and microstructural analysis of the failed component. Light microscopy and scanning electron microscopy techniques together with energy dispersive spectroscopy were used for assessment and detailed evaluation of present phases. Detailed analysis determined corrosion attack to be intergranular corrosion. Furthermore influence of deviations in chemical composition and presence of a typical titanium nitrides on corrosion resistance of material were identified.