Micro powder injection molding of boron carbide components with SiC-Al₂O₃-Y₂O₃ sintering additives

Sintering additives and micro-powder injection molding offer an effective method to densify boron carbide (B₄C) and make B₄C components with complex shapes. By adjusting the proportion of three kinds of powders (SiC, Al₂O₃ and Y₂O₃), four kinds of sintering additives were prepared. The feedstock uniformity, debinding behavior, phase composition and microstructure of micro injection molded B₄C components with different sintering additives were studied. The results showed that the defects such as lattice distortion and vacancy were introduced into ball milling, which increase the surface energy and benefit subsequent sintering densification. The feedstock had good uniformity and rheology that met the requirements of micro powder injection molding. After debinding, B₄C components had enough strength and showed certain sintering characteristics. The addition of sintering additives was beneficial to densification and sintering temperature reduction. The addition of sintering additives formed a second phase in the B₄C crystal and at the grain boundary of B₄C crystal, which changed the fracture mode from transgranular fracture to mixed fracture mechanism with transgranular fracture.