PVD/CVD TECHNOLOGY FOR COATING CEMENTED CARBIDES

The results of examinations of an intermediate layer between the TiN coating obtained by physical vapor deposition (PVD) and the cemented-carbide substrate show the presence of the TiC coating and the decarbonized eta-phase underlayer after carrying out bombardment of the substrate with Ti ions. A new PVD technology, which allows elimination of the decarbonization or damage of the cemented carbide substrate, is used for depositing a special barrier underlayer before deposition of the conventional coating by chemical vapor deposition (CVD). The PVD-CVD coating produced by use of the technology does not lead to a decrease in the transverse rupture strength and toughness of the coated cemented carbides and allows a high level of wear resistance of the conventionally CVD coated cemented carbides to be achieved. The PVD-CVD coated cutting inserts have a longer tool lifetime in milling and approximately the same tool lifetime in turning compared with the conventionally CVD coated inserts.