EROSION BEHAVIOR OF BORON-CARBIDE UNDER HIGH-POWER PULSED FLUXES OF HYDROGEN PLASMA

The erosion values of hot-pressed in vacuum boron carbide were measure d under conditions of irradiation by 1 mu s pulses of hydrogen plasma with an energy flux density on the target of about 5.5 J cm(-2). At va riations of angles of plasma flux incidence from 0 to 85 degrees the n et erosion values changed from 6 x 10(-5) to 4 x 10(-4) g cm(-2) pulse . For B4C balls the erosion values were identical to those for flat ta rgets at angular incidence or 45 degrees. No dependence of the erosion values on the density (1.99-2.46 g cm(-3)) and the :number of pulses (2-50) was observed. As optical examination of surface morphology or i rradiated samples has shown a new kind of erosion mechanism takes plac e during irradiation, where erosion processes are determined not only by the interaction between the plasma and the bare B4C-surface but als o by plasma interaction with the scale (shelling layer) and flakes whi ch have coated the target surface after a few first plasma pulses. Pos sible physical mechanisms of this erosion behaviour and their implicat ions for the solid target boronization procedure in plasma devices; an d for other technological applications of boron carbide are also discu ssed here. (C) 1998 Elsevier Science S.A. All rights reserved.