Effect of Processing Parameters and Additives on Partially Sintering of Si3N4-MoSi2 Composite

Addition of MoSi2 to Si3N4 matrix leads to an improvement in the mechanical properties and oxidation resistance as well as an increase in the electrical conductivity of the produced composite, thus allowing for machining via Electrical Discharge Machining (EDM) or its potential applications as pieces of tinder (igniter) in diesel engines or aerospace devises. In this study, Si3N4 powder was mixed with MoSi2 (synthesized in the previous work through SHS) and additives such as MgO, CeO2, and Y2O3 in varying percentages. Some of the mixed powders were milled using a SPEX 8000. All material powders were then formed into pellets using a uniaxial press. The pellets were then sintered in an atmosphere-controlled tube furnace in argon at a maximum temperature of 1500 °C with a soaking time of 2 or 3 hours through Pressureless Sintering (PLS) process. The sintered samples were analyzed at different stages: density measurements, phase and microstructure studies using XRD and SEM, and HV microhardness measurements. The results demonstrated that Si3N4-MoSi2 structural porous composites were successfully prepared and optimized by controlled parameters such as pressing pressure, milling process, type and percentage of additives, and soaking times.