Analysis and Prevention of Premature Corrosion Failure of Blower Impeller for Salt and Chemical Industry

On the basis of microstructure and crack morphology observation, the reason for premature corrosion cracking failure of a blower impeller for salt and chemical industry was analyzed. The results show that the failure of the impeller was due to stress corrosion cracking, which was promoted by chloride ions. The microstructure near the fusion line of the impeller body changed significantly by the weld thermal cycle after welding spoilers on the impeller body. The precipitation of secondary phases led to the degradation of corrosion resistance of the impeller body directly, and then the stress corrosion cracking occurred in the combination of working stresses and welding residual stresses. The working stresses on the impeller body distributed unevenly, that is, the closer to the impeller heart, the greater the work stresses were, and the more easily the stress corrosion cracking happened. A prevention method of removing the 4 spoilers near the impeller heart was proposed. It was verified by on-site application that this method can prevent the premature stress corrosion cracking of the impeller effectively.