Fatigue failure of a boiler feed pump rotor shaft

This paper deals with a detailed failure investigation of a rotor shaft in a boiler feed pump of a thermal power plant. The investigation mainly included chemical analysis, microscopy, fractography, hardness measurement and residual stress measurement. Analysis revealed that the metallization processes was primarily responsible for the failure. There were a large number of defects at the interface where the metallization process was terminated near the fillet. The crack had initiated from one or more such defect areas and then further propagated by fatigue. The mode of fracture was fatigue and the presence of oxides at the base of the cavities at the interface regions indicated that surface preparation was not made properly prior to metallization.