Fracture analysis of a centrifugal ore slurry pump shaft: a study using fatigue tests, microstructural analysis and finite element simulation

Failures in centrifugal pump shafts used in ore slurry applications can cause significant downtime in mining operations. However, limited studies focus on the comprehensive analysis of such failures, particularly in terms of fatigue behavior, microstructure, and stress distribution. This study investigates the fracture failure of an AISI 4140 steel shaft from a centrifugal ore slurry pump used by a large mining company in Brazil. The research includes chemical and microstructural analyses, as well as mechanical tests (tensile, hardness, impact, and fatigue), with numerical simulations conducted under defined boundary conditions: torque of 3885 Nm and shaft support through two rolling bearings. Results revealed that fatigue nucleation occurred at multiple stress concentration points in the threaded region, leading to final fracture. The maximum equivalent stress was quantified as 203.57 MPa, consistent with the simulation results. The shaft's coarse bainitic microstructure reduced impact toughness, with a measured impact energy of 9 +/- 2 J, while the fatigue limit was determined to be approximately 350 MPa.