MATERIAL AND PROCESS DESIGN FOR SILICON NITRIDE PIM FOR THE FABRICATION OF ENGINE COMPONENTS

摘要

A silicon nitride feedstock system was developed for fabricating the combustion engine of an unmanned aerial vehicle (UAV). The feedstock consisted of nanoscale silicon nitride particles. Magnesia and yttria were used as sintering additives. The powders were mixed with a paraffin wax-polypropylene binder system. The feedstock was analyzed for physical properties and molding attributes. Simulations of the injection molding process stage were conducted to assess the feasibility of manufacturing a ceramic engine and determine its optimal process parameters. The model building required for the simulation was based on flow and solidification behavior data compiled for the binder-powder mixture. The simulations were performed using the Moldflow software package. The Box-Behnken method was used to gain an understanding of critical process parameters as well as identifying a feasible process window. The influence of several quality criteria was subsequently analyzed in order to determine their dependence on several process parameters. Subsequently an optimization was performed using a non-linear programming (NLP) model to identify the best combination of process parameters. The study resulted in the successful development of design parameters that will enable fabrication of silicon nitride UAV engine components by powder injection molding.