Mechanical properties of room-temperature injection molded, pressurelessly sintered boron carbide

Abstract

Boron carbide (B4C) is of interest in the armor community due to its combination of extreme hardness and low density. However, it is difficult to utilize these properties in many applications due to the challenges associated with forming near-net shapes of B4C, combined with its low inherent sinterability without the application of external pressure. In this study, highly loaded (51 vol. %) aqueous B4C suspensions were developed and injection molded at room temperature followed by pressureless sintering up to 2075 °C. Three different sintering aids (Y2O3, Al, and Al2O3) were used to aid the densification process. B4C parts were sintered to high density (up to 97.7% relative density) and high hardness values (up to 3200 Vickers). The flexural strength of the samples was limited by grain pullout during polishing of the tensile surface; the strength was correlated to the maximum grain pullout flaw measured at the intersection of the tensile surface and the fracture surface (R2 > 0.98). The robust performance of the B4C suspensions and their resulting densities and hardness demonstrate the room-temperature injection molding process as a viable alternative for low-cost near-net shaping of B4C components.