TiC, TiN, TiCN, TiCNO, CVDコーティング膜の水熱酸化腐食

抄録

Wet corrosion by high temperature-high pressure water has been studied on CVD coated Ti base ceramic films (thickness ca. 10μm, TiC, TiN, TiC_0.3N_0.7, TiC_0.3N_0.7O_0.1) at 300-680°C under 100MPa for 2h. The order of corrosion resistance was obtained as TiN>TiCN>TiCNO>TiC from the X-ray diffraction analysis of scale layers and the reaction ratio calculated from the weight gain. The order was discussed on the volume ratio φ defined by Pilling-Bedworth, the internal stress within the coated films, and the dissolution behavior of gaseous species at the interface of ceramic film-oxide scale. The oxide scale crystallized as anatase in TiC and transformed into rutile at higher temperatures. On the other hand, rutile deposited directly in other samples having a higher corrosion resistance.