Ceramic cutting tool formed from Si3N4-Y2O3-SiO2 and method of making

摘要

A method is disclosed comprising placing in a hot pressing environment a controlled mixture of a first powder of Si3N4 containing a controlled amount of SiO2 (with or without a limited amount of milling media) with a second powder consisting essentially of Y2O3, hot pressing the controlled mixture, and cooling the resultant unitary object. A novel silicon nitride comprising a unitary object is disclosed which can be shaped to form a novel cutting tool useful for machining metal such as cast iron. The object has selected crystalline phases formed beta Si3N4 and beta prime Si3N4 and has intergranular crystalline secondary phases consisting essentially of YSiO2N, Y10Si17N4O23 and Y2Si2O7 with the YSiO2N phase representing at least a 25% volume fraction of the secondary phases and comprising essentially all of the yittria-silicon oxide.