Effect of iron silicon addition in the sintering behavior of silicon nitride

Different percentages of iron silicon were added to silicon nitride powder containing a fixed amount of sintering aids. The mixtures were pressed at 60 MPa and sintered at 1675 °C and 1700 °C in a graphite furnace under 0.2 MPa nitrogen pressure. For each sintering condition, all the compositions tested were evaluated with respect to the degree of sinterability, microstructure and fracture toughness. It was observed that, as the amount of iron silicon increases, the average length and thickness of β-grains seem to decrease. All samples with iron silicon also presented a greater value of fracture toughness (K1C) when compared with no iron silicon containing samples.