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 degrees C of a SiC sintered with additions of Al(2)O(3) + Y(2)O(3) 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 SO(3) and thus the sulphur content of the fuel. Burner rig tests at 1000 degrees 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 Al kerosene). With a low-sulphur fuel (1% S marine diesel) the high SO(3) partial pressure resulted in a low Na(2)O activity and limited acid (SiO(2)) base (Na(2)O) reaction. At 1300 degrees C, similar rates of material degradation were observed. Details of the oxidation kinetics and oxidation product morphologies are given. (C) 2000 Elsevier Science Ltd. All rights reserved.