An insert for a drill bit may include 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 larger grain size than the first diamond grains.