The gas pressure sintering (GPS) process is one of the most promising sintering techniques for the fabrication of high performance silicon nitride ceramics. Through his process, a almost pore-free dense compact is obtained. They present high strength with high reliability and good heat resistance. These properties make them one of the best candidate materials for heat engine components as well as other industrial fields application. The primary applications are long tubes such as thermocouple protection tubes and heat riser tubes, both used in the aluminum and non-ferrous alloy industries. This material has excellent temperature response, is unaffected by corrosion, and is gas tight.