Failure analysis of counter shafts of a centrifugal pump

An analysis of the premature failure of two counter shafts used in centrifugal pumps for lifting slurry has been carried out. Chemical analysis, microstructural characterisation, fractography, hardness measurement, tensile and Charpy impact tests were used for the analysis. The chemical compositions for the shafts were as per recommendation. The microstructure of one of the shafts was ferritic–pearlitic and its mechanical properties were inferior to the recommended values. For the other shaft the microstructure was tempered bainite; although the impact energy satisfied the specification, the other properties (hardness, UTS) were inferior. It was concluded that the improper heat treatment was the prime cause for the premature failure of the shafts.