  Silicon carbide (SiC) represents a promising but largely untested
plasma-facing material (PFM) for next-step fusion devices. In this work, an
analytic mixed-material erosion model is developed by calculating the physical
(via SDTrimSP) and chemical (via empirical scalings) sputtering yield from SiC,
Si, and C. The Si content in the near-surface SiC layer is predicted to
increase during D plasma bombardment due to more efficient physical and
chemical sputtering of C relative to Si. Silicon erosion from SiC thereby
occurs primarily from sputtering of the enriched Si layer, rather than directly
from the SiC itself. SiC coatings on ATJ graphite, manufactured via chemical
vapor deposition, were exposed to repeated H-mode plasma discharges in the
DIII-D tokamak to test this model. The qualitative trends from analytic
modeling are reproduced by the experimental measurements, obtained via
spectroscopic inference using the S/XB method. Quantitatively the model
slightly under-predicts measured erosion rates, which is attributed to
uncertainties in the ion impact angle distribution, as well as the effect of
edge-localized modes. After exposure, minimal changes to the macroscopic or
microscopic surface morphology of the SiC coatings were observed. Compositional
analysis reveals Si enrichment of about 10%, in line with expectations from the
erosion model. Extrapolating to a DEMO-type device, an order-of-magnitude
decrease in impurity sourcing, and up to a factor of 2 decrease in impurity
radiation, is expected with SiC walls, relative to graphite, if low C plasma
impurity content can be achieved. These favorable erosion properties motivate
further investigations of SiC as a low-Z, non-metallic PFM.
