Highly wear resistant diamond insert with improved transition structure

An insert for a drill bit comprising:

• a metallic carbide body;
• an outer layer of polycrystalline diamond material on the outermost end of the insert, the polycrystalline diamond material comprising a plurality of interconnected first diamond grains and a first binder material in interstitial regions between the interconnected first diamond grains;
• and
• at least one transition layer between the metallic carbide body and the outer layer, the at least one transition layer comprising a composite of second diamond grains, first metal carbide particles, and a second binder material,
• wherein the second diamond grains have a smaller grain size than the first diamond grains.

An insert for a drill bit comprising:

• a metallic carbide body;
• an outer layer of polycrystalline diamond material on the outermost end of the insert, the polycrystalline diamond material comprising a plurality of interconnected first diamond grains and a first binder material in interstitial regions between the interconnected first diamond grains, the plurality of first diamond grains occupying more than 91.5 volume percent of the outer layer;
• and
• at least one transition layers between the metallic carbide body and the outer layer, the at least one transition layers comprising a composite of second diamond grains, first metal carbide or carbonitride particles, and a second binder material;
• and
• wherein the second diamond grains have a larger grain size than the first diamond grains.

An insert for a drill bit comprising:

• a metallic carbide body;
• an outer layer of polycrystalline diamond material on the outermost end of the insert, the polycrystalline diamond material comprising a plurality of interconnected first diamond grains and a first binder material and first metal carbide particles in interstitial regions between the interconnected first diamond grains;
• and
• at least one transition layer between the metallic carbide body and the outer layer, the at least one transition layer comprising a composite of second diamond grains, second metal carbide particles, and a second binder material,
• wherein the second diamond grains have a larger grain size than the first diamond grains, and
• wherein the first metal carbide particles have an average tungsten carbide grain size of less than about 1 micron.