PVD and CVD gradient coatings on sintered carbides and sialon tool ceramics
L. A. Dobrzanski; M. Staszuk
Journal of Achievements in Materials and Manufacturing Engineering
Abstract
Purpose: The main objective of the work is to investigate the structure and properties of multilayer gradient coatings produced in PVD and CVD processes on sintered carbides and on sialon ceramics, and to define the influence of the properties of the coatings such as microhardness, adhesion, thickness and size of grains on the applicable properties of cutting edges covered by such coatings. Design/methodology/approach: The investigation studies pertaining to the following have been carried out: ...Morethe structures of the substrates and coatings with the application of transmission electron microscopy; the structure and topography of coating surfaces with the use of electron scanning microscopy; chemical composition of the coatings using the GDOES and EDS methods; phase composition of the coatings using X-ray diffraction and grazing incident X-ray diffraction technique (GIXRD); grain size of the investigated coatings using Scherrer's method; properties of the coatings including thickness, microhardness, adhesion and roughness; properties of the operating coatings in cutting trials. The models of artificial neural networks have been worked out which involve the dependencies between the durability of the cutting edge and properties of the coatings. Findings: Good adhesion of the coatings to the substrate from sintered carbides is connected with the diffusive mixing of the components of the coating and substrate. In the case of PVD coatings obtained on sialon ceramics, the highest adhesion to the substrate (Lc=53-112 N) has been demonstrated by the coatings containing the AlN phase of the hexagonal lattice having the same type of atomic (covalence) bond in the coating as in the ceramic substrate. The damage mechanism of the investigated coatings depends to a high degree on their adhesion to the substrate. The durability of cutting edges covered by the investigated coatings depends principally on the adhesion of the coatings to the substrate, and to a lesser degree on the other properties. Practical implications: While selecting a proper coating material on ceramic cutting edges, it is advisable to remember that the coatings having the same type of atomic bond as the ceramic substrate have higher adhesion to the substrate. Another relevant aspect of the research presented in the paper is the fact that the adhesion of the coatings contributes significantly to the durability of the cutting edge, whereas the microhardness of the coatings, their thickness and grain size have a slightly lower influence on the durability of the tool being coated. Originality/value: The paper presents the research involving the PVD and CVD coatings obtained on an unconventional substrate such as sialon ceramics. Furthermore, to define the influence of coating properties on the durability of cutting edges, artificial neural networks have been applied.
keywords:Working properties of materials and products, Mechanical properties, PVD and CVD coatings
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