Failure analysis of the impeller of slurry pump used in zinc hydrometallurgy process

The failure of the trial impeller of slurry pump used in zinc hydrometallurgy process occurred only after a service of about a month, the expected service life was more than 3 months. The failure impeller was subjected to serious corrosive wear. This paper deals with failure analysis of the impeller (mainly including composition analysis of the slurry, corrosive wear surface characteristics by visual inspection and optical microscopes as well as scanning electron microscope (SEM), composition analysis of the impeller material by spectrum analyser and SEM–EDX, microstructure analysis by optical microscopes) and an improved method. Failure analysis revealed that an improper austenite/ferrite ratio of duplex stainless steel (DSS) material resulting from a too high nitrogen content was primarily responsible for the rapid failure of the impeller. In addition, a melting test in a vacuum furnace verified again that nitrogen content had a significant effect on austenite/ferrite ratio of duplex stainless steel, a comparing corrosive wear test revealed further that DSS consisting of equal austenite/ferrite volume showed better corrosive wear resistance.