Oxidation and burner rig corrosion of liquid phase sintered SiC

Liquid phase sintering permits lower temperatures to be used to produce SiC with a consequent saving in terms of cost, while maintaining mechanical properties. For application at elevated temperatures, corrosion resistance must also be maintained. Oxidation in air at 1000 and 1300°C of a SiC sintered with additions of Al2O3+Y2O3 resulted in protective oxidation kinetics with rates approximately an order of magnitude greater than generally available low-additive SiC. The contaminants present in combustion atmospheres, particularly S and Na, have a marked influence on the rate of material degradation depending on the partial pressure of SO3 and thus the sulphur content of the fuel. Burner rig tests at 1000°C resulted in high rates of attack due to the formation of a low viscosity Na-silicate surface layer in a low sulphur fuel combustion gas (Jet A1 kerosene). With a low-sulphur fuel (1% S marine diesel) the high SO3 partial pressure resulted in a low Na2O activity and limited acid (SiO2) base (Na2O) reaction. At 1300°C, similar rates of material degradation were observed. Details of the oxidation kinetics and oxidation product morphologies are given.