Patent ID: 7708936

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 Cr on at least one portion of an exposed surface of the compact; sintering the compact and grain refiner powder so as 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; optionally 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 final shape; and optionally depositing a wear resistant coating on 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, and wherein the surface portion contains Cr in an amount of greater than zero to less than about 0.7 wt-%.