Abstract
Cavitation erosion is a common phenomenon that occurs in hydraulic turbine blades and result in mass loss. Welding is the most common technique used to recover the geometrical profile of these cavitation eroded turbine blades, however it is known that tensile residual stress can develop. The development of manufacture process that could reduce or eliminate the residual stress level will contribute for a longer service life of this component. It is aimed in this study evaluate cavitation erosion mechanism of Fe- Mn-Cr-Si-Ni arc thermally sprayed coating. Coatings were analyzed by optical and scanning electronic microscopy, microhardness, cavitation tests (ASTMG32-92) and the analysis of eroded surface areas after ultrasonic cavitation tests with DRX and SEM. The results showed that lamellae morphology, oxide volume fraction and porosity modified by changings in parameters deposition, modified cavitation mass loss mechanisms. After ultrasonic cavitation tests, it was verified that mass loss occurred by interlamellae oxide removal and splats surface deformation in initial stages, followed by rupture and finally detachment of the lamellae. Splashing droplets promote greater mass loss in some localized areas because they lower intersplat cohesion.
