Silicon carbide fiber-shaped microtools by extrusion and sintering SiC with and without carbon powder sintering additive

Silicon carbide powder was mixed with a thermoplastic polymer binder system consisting of a wax and a polyethylene. Thermal gravimetric analysis under argon showed that a carbon residue remains in the powder after binder decomposition. Because of the possibility of utilizing this residue as a sintering aid, two different feedstock series were tested: one series with and one without an additional carbon black sintering additive. Strength measurements on sintered fibers showed that the residue from the binder cannot be used as a sintering additive. Fibers made from the feedstock series without additional carbon black powder were characterized by a lower sinterability and a bigger grain size in the sintered fiber microstructure. Bigger grain size is caused by the absence of free carbon during the heating ramp up to the sintering temperature. To achieve dense silicon carbide fibers, a SiC content above 52 vol% in the feedstock is a prerequisite.