POLYCRYSTALLINE CUBIC BORON NITRIDE CUTTING TOOL

摘要

A polycrystalline cubic boron nitride cutting tool is from 50 to 85 % by weight cubic boron nitride crystals bonded together as a polycrystalline mass. A supporting phase commingled with the polycrystalline cubic boron nitride is made from 15 to 40 % by weight of a refractory material which is preferably titanium carbonitride or titanium aluminum carbonitride. The starting composition also comprises from 4 to 10 % by weight of Co2Al9. Mixed powders of these ingredients are treated in ammonia at a temperature in the range of from 1100 to 1250 ~C, which significantly increases the nitrogen content and reduces carbon content of titanium carbonitride or titanium aluminum carbonitride. Instead of mixed powders of the starting materials, coated particles may be used such as cubic boron nitride coated with titanium carbonitride, or titanium carbonitride coated with cobalt, aluminum or cobalt aluminide. Hexagonal boron nitride may be substituted as a starting material for a portion of the cubic boron nitride.