CERAMIC CUTTING TOOL COMPOSITION, METHOD OF ITS MANUFACTURE AND ITS USE IN MACHINING CAST IRON

摘要

A ceramic material suitable for use in cutting tools comprises a hot pressed composition containing Si3N4 and at least one of the oxides Y2 O3, ZrO2 and MgO. Ternary systems based on Si3N4, SiO2 and 4 to 12 wt% Y2 O3 are preferred in which Y2 O3: SiO2 is from 1.2 to 3.0 Hot pressing at 1700 to 1750 DEG C and 5000 to 6,500 psi for 3 to 8.5 hours produces a material with a thermal shock parameter of at least 26 x 104 BUT - lbs/hr (in3) at 1200 DEG C which can be used for making cast iron.