Structure and properties of the wear resistant coatings obtained in the PVD and CVD processes on tool ceramics

The paper presents investigation results of structure and functional properties of the hard wear resistant coatings obtained in the PVD and CVD processes on the Si3N4 nitride tool ceramics. Examinations of coatings structures were made using the transmission (TEM) and scanning (SEM) electron microscopes, microhardness tests, coating adhesion to the substrate with the,scratch test", and the coatings abrasive resistance ,,pin-on-disc" test. Machining tests results and roughness tests results for the machined grey cast iron surface are also presented. The research carried out proved that depositing the hard, anti wear, multilayer coatings based on the Al2O3 and TiN layers onto the Si3N4 nitride tool ceramics with the PVD method results in obtaining better functional properties like extension of the cutting tool life, than in case of the uncoated nitride ceramics or coated with the PVD coatings and some CVD ones.