Failure analysis and mechanism study of submersible electric pump made of high nickel austenitic cast iron

Submersible electric pump plays a key role in the oil extraction, however, the failure of the impeller and guide vane often causes accidents, resulting in lower deliverability. In this study, the failure mechanism of high nickel alloy submersible electric pumps in the production wells of an oilfield in Bohai Sea was analyzed from the perspective of micro-materials science by carrying out tests such as macro-morphological analysis, optical microscope (OM), metallographic analysis, scanning electron microscope (SEM) and energy spectrum analysis (EDS), chemical composition analysis, and combining with the hydrodynamics and on-site working conditions. The results show that the spoon-like perforation of the guide vane is in horizontal alignment with the spoon-like perforation of casing. And plough-like microstructure is observed in the perforation position. Besides, a large number of white ceramic balls is discovered in the pump. Therefore, it is inferred that the failure mode of the pump is that the fluid carrying particles wear the guide vane and casing, resulting in perforation. The C-type graphite in the matrix of the guide vane is the essential reason of the erosion wear, which has a negative impact on the erosion resistance. The proportion of pearlite in the microstructure of the pump casing is relatively high, resulting in a decrease in the wear resistance of the matrix.