High-temperature SO2-gas corrosion of TiN–Ti5Si3 composites prepared by polymer pyrolysis

By pyrolyzing a mixture of Si-containing pre-ceramic polymers and TiH2 powders in a N2 atmosphere, a TiN–Ti5Si3 composite was synthesized. The composite was then corroded between 700 °C and 1000 °C for 20 h in an Ar–0.2% SO2 atmosphere. TiN was mainly oxidized to rutile TiO2. Ti5Si3 was oxidized to TiO2 supersaturated with Si ions, and sulfidized to Ti2S supersaturated with Si ions. At initial stage of corrosion, oxidation dominated sulfidation. As corrosion proceeded, sulfidation progressively occurred underneath the oxide scale based on the decreased oxygen potential and increased sulfur potential near the scale/matrix interface.

Research highlights
► The TiN–Ti5Si3 ceramic composites were fabricated from our new starting material system via polymer pyrolysis, and corroded in an Ar–SO2 gas atmosphere at high temperatures for the first time.
► Their oxidation and sulphidation characteristics were studied between 700 °C and 1000 °C for 20 h in an Ar-0.2% SO2 atmosphere.
► TiN was mainly oxidized to rutile TiO2.
► Ti5Si3 was oxidized to TiO2 supersaturated with Si ions, and sulfidized to Ti2S supersaturated with Si ions.