CEMENTED CARBIDE INSERT FOR WEAR RESISTANCE DEMANDING SHORT HOLE DRILLING OPERATIONS

摘要

The present invention relates to a coated cemented carbide insert particularly useful for short hole drilling in steel at high speed and moderate feed. The insert has a binder phase enriched and essentially cubic carbide free surface zone A of a thickness of <20 µm and along a line C, essentially bisecting the edge, in the direction from the edge to the centre of the insert, a binder phase content increases essentially monotonously until it reaches the bulk composition. The binder phase content at the edge in vol-% is 0.65-0.75 times the binder phase content of the bulk and the depth of the binder phase depletion is 100-300 µm.The insert is coated with - a first, innermost, layer of TiCxNyO2 with equiaxed or columnar grains. with size <0.5 µm - a next layer of TiCxNyOz with columnar grains and with a diameter of about <5 µm - a next layer of TiCxNyO2, with equiaxed or needlelike grains with size =0.5 µm, and - an outer layer of a smooth, textured, fine-grained, CX-AI2O3 layer with a surface roughness (Ra) of less than 0.3 mm over a measured length of 0.25 mm.