Two compressor rotors of similar design and construction were severely damaged during operation. In one rotor, all the blades in the third and fourth stages had been sheared off and some had lifted from the dovetail portion of the drum. The damage in the other rotor was more extensive. Most of the blades in the first four stages had sheared off and many lifted from the dovetail region, particularly in the first two stages where several mounting dovetails had also fractured. Based on visual examination and the results of SEM fractography, metallography, and chemical analysis, investigators concluded that the...