Patent ID: 7883775

Claim:
A diamond coated tool comprising: a substrate; and a polycrystalline diamond coating formed on a surface of the substrate, wherein said substrate is made of a cemented carbide or a cermet, said polycrystalline diamond coating is an aggregate of secondary diamond grains, each of which includes an aggregate of primary diamond fine grains, the primary diamond fine grains having a first crystal structure and the secondary diamond grains having a second crystal structure different from the first crystal structure, said secondary diamond grains constituting a growth surface of said polycrystalline diamond coating has an average grain size of about 1.5 micrometers or below, grain boundaries are formed between each of said secondary diamond grains, said primary diamond fine grains are elongated in a growth direction of said polycrystalline diamond coating, said primary diamond fine grains have a major axis diameter ranging from 0.01 micrometer to 1 micrometer, said polycrystalline diamond coating has a thickness ranging from about 0.1 micrometer to 20 micrometers, and said polycrystalline diamond coating has an average surface roughness Ra ranging from about 0.01 micrometer to 0.2 micrometer.