Matrix drill bits and method of manufacture

A drill bit having a composite matrix bit body comprising:

• a plurality of cutting elements disposed at select locations on exterior portions of the bit body;
• the composite matrix bit body having at least a first zone and a second zone disposed adjacent to each other;
• the first zone formed at least in part by hard particles comprising cemented carbides and at least one binder material selected from the group consisting of cobalt, nickel, iron or alloys of these elements;
• and
• the second zone formed at least in part from hard particles selected from the group consisting of macrocrystalline tungsten carbides and cast carbides;
• and
• the second zone formed by the same binder material as the first zone.

A method of making a matrix drill bit comprising:

• placing at least a first layer of a first matrix material selected from the group consisting of cemented carbides and spherical carbides in a matrix bit body mold;
• placing a hollow metal blank in the mold;
• placing at least a second layer of a second matrix material selected from the group consisting of macrocrystalline tungsten carbide and cast carbide in the mold;
• placing a binder material in the mold with the binder material proximate the second layer of matrix material and the hollow metal blank;
• heating the mold and the materials disposed therein in a furnace to a selected temperature to allow the binder material to melt and to infiltrate the second matrix material and the first matrix material with hot, liquid binder material;
• starting solidification of the hot, liquid binder material with the first matrix material before the hot, liquid binder material solidifies with the second matrix material;
• and
• cooling the mold and materials disposed therein to form a coherent composite matrix bit body securely engaged with the hollow metal blank.