Dense and uniform Iridium (Ir) coating was deposited on the surface of the graphite substrate by double glow plasma. The phase identification and the morphology of the coating were examined by X-ray diffraction and scanning electron microscopy, respectively. The coating was composed of uniformly distributed regularly conical aggregates which were composed of the columnar crystals with a preferential (220) orientation. The preferential orientation was regardless of different deposition parameters and substrate properties. The analytic equation of the generatrix of the conical aggregate was determined by measuring its external dimensions. The deposition rate of the coating was up to 20 mm h 21 . The gap appeared within the fracture surface of the coating could result from the shadow effect of the conical aggregate. Because of the poor wetting between Ir element and C element, Ir coating grew according to the Stranski-Krastanov model.
Herein, a chemo-mechanical coupled constitutive and failure model is proposed to predict the tensile behavior of SiC/SiC composites under oxidizing environments. The diffusion of O 2 through the oxide scale and the oxidation reaction of SiC/O 2 are modeled and implemented in finite element software, through a user-defined element. Numerical validation studies and tests are conducted on a domestic SiC fiber. An orthotropic constitutive model for reinforcements, which considers modulus reduction due to oxidation damage, and a continuum damage model associated with O 2 diffusion along the micro-cracks in the SiC matrix are subsequently presented. The developed framework is used to simulate the mechanical behavior and oxidation process of a single fiber SiC/SiC composite.
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