The Effect of Stoichiometry on Mechanical Properties of Boron Carbide

Abstract

The mechanical properties of chemically vapor‐deposited boron carbides (B 4 C) with varied B/C ratios were investigated as a function of composition. The maximum hardness, H, and fracture toughness, K 1c , were observed at an almost stoichiometric composition. For nonstoichiometric B 4 C (B/C>4), H and K 1c decreased with increasing B content, suggesting that excess B diminishes the bond strength in the B 4 C structure. The decrease in H and K 1C at B /C <4 was attributed to free C in the microstructure.