To provide a surface coated cemented carbide cutting drill exerting excellent wear resistance by high speed cutting.
This surface coated cemented carbide cutting drill is made a sintered body of green compact having a composition made of Co: 8 to 10%, composite carbide of W and Ti: 20 to 30% having a composition formula: (W1-YTiY) C (Y shows 0.3 to 0.6 at an atomic ratio), niobium carbide: 5 to 10% and tungsten carbide: remnants, in mass %. In the sintered body, a dispersed phase constituted of a tungsten carbide phase, a core part constituted of composite carbide of W and Ti and a surrounding part composite carbide of Ti and Nb form a cored structure composite carbide phase, and a combined phase is constituted by forming a composite nitride layer of Ti and Al of average layer thickness: 0.5 to 6 μm having a composition formula: (Ti1-XAlX) N (X shows 0.1 to 0.6 at the atomic ratio) as a hard coating layer on the surface of a tungsten carbide group cemented carbide base body having a structure made of Co-W alloy, by a structural observation by a scanning type electronic microscope.
TAKAHASHI SATOSHI
OKADA KAZUKI
YANAI TOSHIYUKI
