Patent ID: 7678327

Claim:
A method of making a cemented carbide body with a wear resistant surface zone, the method comprising: providing a compact of cemented carbide from a single powder mixture; optionally presintering the compact and grinding the compact to a desired shape and size; placing a powder of a grain refiner containing carbon and/or nitrogen on at least one portion of an exposed surface of the compact, the grain refiner containing C and/or N; sintering the compact and grain refiner powder to diffuse the grain refiner toward the center of the compact to form a surface portion in the sintered compact and to form an interior portion in the sintered compact; adding an isostatic gas pressure during a final stage of sintering; optionally post-HIP-ing at a temperature lower than a sintering temperature and at a pressure of 1 to 100 MPa; optionally grinding to a final shape; and optionally removing undesired carbides and/or graphite from a surface, wherein the surface portion has a smaller WC grain size than the interior portion and wherein the surface portion has a lower cobalt content than the interior portion, wherein a maximum in Co-content occurs at a location in the cemented carbide body between an outermost surface of the surface portion and an outermost region of the interior portion, and wherein the Co-content in a region inward of the location of the maximum in Co-content is lower than the maximum.