method of making cemented carbide tool

A method of making a coated cemented car bide cutting insert comprising the steps of:

• blending starting powders to form a starting powder mixture wherein the powders contain the following components:
• a binder selected from one or more of cobalt, nickel, iron and their alloys, tungsten, carbon, and one or more of the following:
• titanium, tantalum, niobium, hafnium, zirconium, and vanadium;
• pressing the starting powder mixture to form a green cutting insert blank;
• dewaxing the green cutting insert blank to form a dewaxed cutting insert blank;
• sinter heating the dewaxed cutting insert blank from about the maximum dewaxing temperature to at least a pore closure temperature in an atmosphere having a first nitrogen partial pressure for substantially the entire sinter heating step so as to form a pre-sintered cutting insert blank;
• sinter holding the pre-sintered cutting insert blank at a sinter hold temperature in an atmosphere having a second nitrogen partial pressure for substantially the entire sinter holding step to form a sintered cutting insert blank wherein the second nitrogen partial pressure is greater than the first nitrogen partial pressure;
• cooling the sintered cutting insert blank from the sintering temperature to a target temperature below the eutectic temperature so as to form an as-sintered cutting insert substrate having a peripheral surface with a zone of non-stratified binder enrichment beginning adjacent to and extending inwardly toward a bulk region of the substrate;
• and
• coating the as-sintered cutting insert substrate with a coating comprising one or more layers including a base layer on the surface of the substrate, and the base layer comprising a material containing nitrogen.

A method of selectively making either as as-sintered substrate that exhibits a surface zone of binder enrichment or an as-sintered substrate that does not exhibit a surface zone of binder enrichment, the method comprising the steps of:

• blending starting powders with an effective amount of nitrogen being absent and containing a binder alloy selected from one or more of cobalt, nickel, iron and their alloys, tungsten, carbon, and one or more of the following:
• titanium, tantalum, niobium, hafnium, zirconium, and vanadium;
• pressing the starting powder mixture to form a green cutting insert blank;
• dewaxing the green cutting insert blank to form a dewaxed cutting insert blank;
• sinter heating the dewaxed cutting insert blank from the maximum dewaxing temperature to at least a pore closure temperature in an atmosphere having a first nitrogen partial pressure for substantially all of the entire sinter heating step so as to form a pre-sintered cutting insert blank;
• sinter holding the pre-sintered cutting insert blank at a sinter hold temperature in an atmosphere having a second nitrogen partial pressure for substantially the entire sinter holding step as to form a sintered cutting insert blank and wherein the second nitrogen partial pressure may selectively be either greater than equal to or less than the first nitrogen partial pressure;
• cooling the sintered cutting insert blank from the sintering temperature to a target temperature below the eutectic temperature so as to form an as-sintered cutting insert substrate wherein when the second nitrogen partial pressure is greater then the first nitrogen partial pressure the as-sintered cutting insert substrate does not exhibit a surface zone of binder enrichment and when second nitrogen partial pressure is equal to or less than the first nitrogen partial pressure the as-sintered cutting insert substrate exhibits a surface zone of binder enrichment;
• and
• coating the as-sintered cutting insert substrate with a coating comprising one or more layers.