B(sub 4)C-SiC reaction-sintered coatings on graphite plasma facing components

摘要

Boron carbide plus silicon carbide (B(sub 4)C-SiC) reaction-sintered coatings for use on graphite plasma-facing components were developed. Such coatings are of interest in TEXTOR tokamak limiter-plasma interactions as a means of reducing carbon erosion, of providing a preferred release of boron for oxygen gettering, and of investigating silicon's effect on radiative edge phenomena. Specimens evaluated had (a) either Ringsdorfwerke EK 98 graphite or Le Carbon Lorraine felt-type AEROLOR A05 CFC substrates; (b) multiphase coatings, comprised of B(sub 4)C, Sic, and graphite; (c) nominal coating compositions of 69 wt.-% B(sub 4)C + 31 wt.-% SiC; and (d) nominal coating thicknesses between 250 and 775 (mu)m. Coated coupons were evaluated by high heat flux experiments in the JUDITH (electron beam) test facility at KFA. Simulated disruptions, with energy densities up to 10 MJm(sup (minus)2), and normal operation simulations, with power densities up to 12 MWm(sup (minus)2), were conducted. The coatings remained adherent; at the highest levels tested, minor changes occurred, including localized remelting, modification of the crystallographic phases, occasional microcracking, and erosion.