Paralinear Oxidation of Cr-Si-C-Coated C/SiC at 1300°C in Wet and Dry Air Environments

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The oxidation kinetics of a Cr3Si-Cr7C3/SiC/SiC-coated C/SiC were comparatively investigated in dry and wet air at 1300°C under 1 atm. After oxidation for 10 h, Cr2O3 and SiO2 were produced in both oxidations. However, a larger amount of SiO2 formed during the wet air oxidation. After the dry air oxidation, the surface of Cr3Si-Cr7C3/SiC/SiC coating became relatively loose with many pores. After the wet air oxidation, the surface of Cr3Si-Cr7C3/SiC/SiC coating became undulating and loose with notable damage at the position of bulges. The Cr3Si-Cr7C3/SiC/SiC-coated C/SiC showed paralinear weight gains in both oxidation environments. Although the initial weight gains within the first 1 h in the wet air oxidation condition were higher, the gradual weight gains thereafter were lower. The parabolic rate constant for oxide formation and the linear rate constant for oxide volatilization in the wet air oxidation condition were higher than those in the dry air oxidation condition.