Patent ID: 6866921

Claim:
A coated cutting insert comprising: a rake face and a flank face, a cutting edge at the juncture of the rake face and the flank face; the cutting insert having a hard refractory coating and a substrate wherein the coating is adherently bonded to the substrate; the substrate comprising a tungsten carbide-based material comprising a bulk composition of at least about 70 weight percent tungsten and carbon, between about 3 weight percent and about 12 weight percent cobalt, and greater than 0.1 weight percent chromium wherein the ratio of the weight percent of the chromium to the cobalt ranges between about 0.03 and about 0.15; the cobalt and essentially all of the chromium and some of the tungsten forming a binder alloy and wherein the binder alloy consisting essentially of cobalt and chromium and tungsten; and wherein the binder alloy content being enriched in a surface zone of binder alloy enrichment beginning near and extending inwardly from a peripheral surface of the substrate.