Tribological properties of the PVD and CVD coatings deposited onto the nitride tool ceramics

The tribological properties of the multi-layer PVD and CVD coatings deposited onto the Si₃N₄ nitride tool ceramics are compared in the paper in relation to the fundamental mechanical properties like hardness, adhesion. The inserts made from Si₃N₄ were multilayer coated in the PVD process with the TiN + multiTiAlSiN + TiN, TiN + TiAlSiN + TiN, and TiN + TiAlSiN + AlSiTiN coatings and in the CVD process with the TiC, Ti(C, N), Al₂O₃ and TiN. Additional investigations were carried out to compare coatings obtained in this way on inserts from various manufacturers offering the nitride tool ceramics with the CVD coatings based on the Al₂O₃ and TiN layers. Basing on the tribological test made with the "pin-on-disk" method in respect to the hardness and adhesion investigations the correlation was revealed between these two properties. Machining tests results and roughness tests results for the machined grey cast iron surface are also presented. The CVD coatings demonstrate high abrasion resistance in comparison with the PVD ones, whose adhesion to the nitride ceramics is low.