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A commercially produced monolithic silicon nitride was corrosion tested in a low-velocity burner rig in the temperature range 800 C to 1100 C at ambient pressure. A marine-type gas turbine environment was created by burning a high-sulphur fuel in air contaminated with sea salt. At temperatures less than 1000 C deposition of sodium sulphate on the surfaces of the ceramic occurred following reaction of sodium chloride with SO(2)/SO(3). Above the dew point of Na(2)SO(4) (approximately 950 C) the main sodium-containing species was NaOH vapour. In the 50 hour tests, a predominantly SiO(2) surface layer formed which provided protection to the underlying ceramic. Both Na from the salt contaminant and Y, present as a sintering agent in the Si(3)N(4), contributed to the corrosion process. The mechanism of corrosion is discussed and a preliminary assessment of the effect of corrosion on the flexural strength of the material is presented.

Additional information

Authors: BAXTER D J, JRC Petten (NL);MORETTO P, JRC Petten (NL);BURKE A, JRC Petten (NL);NORTON J F, JRC Petten (NL)
Bibliographic Reference: Paper presented: 2nd International Conference on Microscopy of Oxidation, Cambridge (GB), March 29-31, 1993
Availability: Available from (1) as Paper EN 37539 ORA
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