A corrosion mechanism of titanium diboride in KF - AlF3 - Al2O3 melt

TiB2 samples were exposed to molten KF - AlF3 - Al2O2: 54.8-42.1-3.1 mol% salt, at 680 degrees C for 50, 100 and 200 h. The corroded samples of TiB2 were investigated by SEM-EDX, EBSD, XRD, FT-IR and MAS NMR analysis. Corrosion was noted to occur predominantly as pitting attacks on the surface of the investigated materials. An inter-crystal and trans-crystal corrosion were identified on the cross-sections of the samples. A perturbation of Ti-B bonds was detected (SEM-EDX and NMR analysis), at which a formation of orthorhombic TiO2 was also identified (EBSD analysis). The subsequent NMR, XRD and FT-IR analysis of the behaviour of TiB2 powder in molten KF - AlF3 - Al2O3 supports the statement about the formation of orthorhombic TiO2 and mullite type of aluminium borates.