Boria effects on the oxidation mechanisms of SiC/BN/SiC CMCs

Conference Dates

November 5-9, 2017


Ceramic matrix composites comprised of silicon carbide fibers, a boron nitride interphase, and a silicon carbide matrix (SiC/BN/SiC) will be used in service in high temperature oxidizing environments. The SiC constituents oxidize to form silica and the BN interphase oxidizes to form boria which in turn react to form borosilicate glasses. However, the effects of the borosilicate glass properties on CMC oxidation are not well understood. In this work, we present a number of studies that elucidate the effects of boria on the CMC oxidation including: i) the experimentally determined composition of thermally grown borosilicate glasses; ii) the change in composition of the borosilicate glass due to boria vaporization as a function of temperature; iii) the spatial variation of the thermally grown borosilicate glass on the surface and within the composite; iv) the effects of boria on oxygen transport and oxidation kinetics of SiC; v) the viscosity of borosilicate glasses; and vi) the fluxing of SiC by boria. The results of these studies will be discussed in terms of impact on development of CMC thermochemical life prediction models.

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