Effect of Flow Velocity and Impact Angle on Erosion-Corrosion Behavior of Chromium Carbide Coating

In this study, the effect of flow velocity (4-7.5 m s(-1)) and impact angle (30-90 deg) on erosion-corrosion behavior of chromium carbide coating was investigated under impingement by silica containing NaCl solution. Chromium carbide coating was deposited on low carbon steel by thermal reactive deposition/diffusion method at 1050 degrees C for 12 h in a molten salt bath. Mass loss measurement and potentiodynamic polarization tests were employed in order to determine coating performance under impingement. Polarization curves showed that the coated samples had less corrosion current density and high chemical stability. High mass loss at low impact angle indicated ductile behavior for the uncoated sample, while the mass loss for the coated sample changes less than 30% with impact angle up to 60 deg. Furthermore, the erosion-corrosion behavior of the coated sample was slightly dependent on flow velocity. Scanning electron micrographs showed that at lower impact angle, the Cr7C3 coating eroded with flake fragmentation mechanism, while at high impact angle, fatigue fracture is the main degradation mechanism.