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Studies on the oxidation resistance of silicon nitride with TiN have shown the important role of porosity, the composition of oxide sintering aids and microstructure on the rate of oxidation. Oxidation of TiN to TiO(2) dominates below 1000 C and the large increase in volume associated with this reaction results in intermittent cracking and spalling of the surface scale which leads to paralinear kinetics. Oxidation of Si(3)N(4) is more important above 1000 C, and above 1200 C parabolic kinetics reflect a reaction in which the cations of the sintering aids participate. The hot salt corrosion behaviour of the electroconductive, particulate composite Si(3)N(4)-30 vol% TiN in a simulated combustion atmosphere has been studied using a low velocity burner rig. Tests were carried out for 50 hours in the temperature range 1000 C to 1300 C. An activation energy of 189 kJ/mol was calculated from the parabolic weight change data and rationalised in terms of the composition and morphology of the corrosion products formed. The corrosion scale and the cross-sections were investigated by means of X-ray diffraction, scanning electron microscopy and microanalysis.

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Authors: GRAZIANI T, JRC Petten (NL);BAXTER D J, JRC Petten (NL);BELLOSI A, CNR-IRTEC, National Research Council, Research Institute for Ceramics Technology, Faenza (IT)
Bibliographic Reference: Article: Key Engineering Materials (1995)
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