Sintering of Boron Carbide Heat‐Treated with Hydrogen

Abstract

Hydrogen gas (H 2 ) was used to extract B 2 O 3 coatings from boron carbide (B 4 C) particles, permitting a lower temperature onset of sintering and restricting coarsening via solution and precipitation of B 4 C in B 2 O 3 liquid. Remnant H 2 had to be removed from the furnace before specimens were heated through temperature ranges in which evaporation‐condensation coarsening competed with sintering (2010°–2140°C), because the presence of H 2 increased the B 4 C vapor pressure. Heat treatment of B 4 C compacts in a 50:50 H 2 ‐He mixture at 1350°C, followed by a purge of the H 2 gas and then rapid heating to 2230°C, resulted in a percentage of theoretical density of 94.7%. This is higher than the value of 92.8%, which was the highest achieved without the use of H 2 .