Corrosion resistance of 91W-6Ni-3Fe refractory metal, TiAl compound and iron based alloys in molten aluminum

The corrosion behaviors of 91W-6Ni-3Fe (91W) refractory alloy, TiAl intermetallic compound and two types of iron based alloys (QT700 and H13 tool steel) in a liquid aluminum were investigated. Corrosion experiments or static immersion-tests were carried out in pure molten aluminum at 750 degrees C. The surface micro-topographies, corrosion interfaces and phase compositions of the immersed samples were investigated by 3D optical microscopy, SEM, EDS and XRD. The results show that 91W exhibits the best corrosion resistance, followed by QT700, H13 and TiAl alloy, consequently. The corrosion mass loss of the four metallic materials adheres to parabolic criterion, and the corrosion rate trends to be stable after initial acceleration. The diffusion-reaction mechanism is proposed for the dissolution of materials in molten aluminum, and the diffusion process is the rate-determining step during the dissolution of 91W in molten aluminum, while the low activation energy for the reaction between TiAl-(TiAl3)-Al couple results in poor corrosion resistance of TiAl alloy in molten aluminum.