Abnormal erosion–slurry velocity relationship of high chromium cast iron with high carbon concentrations

It is usually expected that the damage to materials by sand-containing water slurry erosion is enhanced as the slurry velocity increases. However, a recent study on high chromium cast iron (HCCI) showed abnormal decreases in erosion of hypereutectic HCCIs having high carbon concentrations (e.g., 6 wt.%C) as the velocity of water–sand slurry increased from 2.5 m/s to 5 m/s. For HCCIs having lower carbon concentrations (hypoeutectic), the trend was reversed. In order to explain the abnormal erosion behavior of the hypereutectic HCCIs, microstructure, erosion–corrosion resistance, mechanical and electrochemical properties of the HCCIs under study were characterized and evaluated. It was demonstrated that the observed abnormal erosion–slurry velocity relationship was attributed to the competition between mechanical attack (erosion) and electrochemical attack (corrosion). At low slurry velocities, corrosion played an important role in erosion–corrosion, while at higher slurry velocities the mechanical attack/erosion became dominant.