Erosion behaviour of boron carbide under high-power pulsed fluxes of hydrogen plasma

The erosion values of hot-pressed in vacuum boron carbide were measured 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 variations of angles of plasma flux incidence from 0 to 85 degrees the net erosion values changed from 6 x 10(-5) to 4 x 10(-4) g cm(-2) pulse. For B(4)C balls the erosion values were identical to those for flat targets 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 irradiated samples has shown a new kind of erosion mechanism takes place during irradiation, where erosion processes are determined not only by the interaction between the plasma and the bare B(4)C-surface but also by plasma interaction with the scale (shelling layer) and flakes which have coated the target surface after a few first plasma pulses. Possible physical mechanisms of this erosion behaviour and their implications for the solid target boronization procedure in plasma devices; and for other technological applications of boron carbide are also discussed here. (C) 1998 Elsevier Science S.A. All rights reserved.