Patent ID: 6610113
Filing Date: 2003-08-26
Classification: B23B,C04B,Y10T

Abstract:
A heat treated ground ceramic cutting insert formed in the presence of a reaction source, the cutting insert comprising:a substrate having a surface which defines a rake face and a flank face wherein there is a cutting edge at the intersection of the rake face and the flank face; the substrate presenting a microstructure wherein there being a surface region extending inwardly from the surface of the substrate, and there being a bulk region inwardly of the surface region; the bulk region having a bulk composition; the surface region having a surface composition resulting from a reaction at a temperature between about 1300 degrees Centigrade and about 2200 degrees Centigrade with the reaction source wherein the surface composition being different from the composition of the bulk region; wherein the surface region has a first microstructure and a first hardness; and the bulk region having a second microstructure and a second hardness; the first microstructure of the surface region being different from the second microstructure of the bulk region; and the first hardness of the surface region being greater than the second hardness of the bulk region; and wherein the substrate comprising a silicon nitride-based composition, and the first microstructure of the surface region comprising &bgr;-silicon nitride phase and Y2Si3O3N4 phase, and the second microstructure of the bulk region comprising &bgr;-silicon nitride.