Performance of silicon nitride cutting tool inserts prepared by gas pressure sintering

Abstract

Hot-pressed silicon nitride inserts have been used for several years in order to obtain the best results in machining cast iron. Nevertheless, extensive research is directed towards the development of new, less expensive preparation methods of silicon nitride base materials. One of the most promising new methods for the preparation of ceramic materials of high performance is gas pressure sintering, by which inserts with complicated shapes can be prepared. Cold-pressed and gas pressure sintered cutting tool inserts were prepared from silicon nitride and additives. The effects of composition, oxide content, structure and sintering parameters on the mechanical properties of gas pressure sintered silicon nitride materials were examined. Cutting tool inserts prepared either by hot pressing, pressureless or gas pressure sintering were tested in the turning and milling of gray cast iron. The performance of gas pressure sintered inserts was comparable with that of hot pressed inserts.