Hot corrosion of α silicon carbide and β silicon nitride

Abstract

AbstractThe effect of hot salt corrosion on the room temperature fracture strength of reaction sintered α silicon carbide and β silicon nitride is investigated. Exposure is carried out using both spray and immersion tests in the temperature range 900–1100°C. The results show a significant reduction in fracture strength following exposure to sodium sulphate and sodium sulphate/chloride environments. Statistical analysis of the results using both cumulative probability and Weibull statistics gives improved data presentation to bar charts and student t tests.Fractographic examination of silicon nitride samples after exposure to sodium sulphate show the preferential attack of the binder phase between the lenticular grains. The mechanism of molten salt attack and methods of data presentation for safe load prediction are discussed. It is suggested that these ceramics be used to replace metals at current operating temperatures in contaminant conditions where they show superior corrosion resistance rather than to use them to increase operating temperatures.