Oxidation behavior of Si₃N₄ -TiN composites at 1400 deg C

In this paper, the oxidation behavior of silicon nitride with different contents of TiN was evaluated at 1400 deg C for 64 hours in air. The oxidized samples were characterized by X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy. Weight gain measurements have shown that the oxidation followed a multiple-law model with linear, parabolic, and logarithmic contributions. The samples presented high weight gain at the beginning of the process followed by the formation of an amorphous silica surface layer containing Y₂Ti₂O₇ and rutile crystals. Cracks and holes were detected on the oxide layer. The oxidation resistance of the composites was strongly influenced by the initial content of TiN. (author)