Si3N4 ceramics are excellent metal cutting materials. The cutting behavior can be improved by hard particle dispersion phase hardening and heat treatment so as to reduce glass phase in the grain boundaries. Compared with cemented carbide tools, the cutting life of the composite Si3N4 cutting tool is about 10-100 times longer, and the optimum cutting speed is about 3-10 times faster. It performs well in cutting hardened tools, nickel based alloys, and other hard materials and can sustain shock loads in operations such as milling, planing and other types of interrupted cutting. Applications in various fields show that machining efficiency can be increased by 3-10 times resulting in savings of time, electricity, and machining of 30-70% or even more.