STRUCTURE AND PROPERTIES OF PVD COATINGS DEPOSITED BY ARC AND LARC TECHNOLOGY
Abstract
The paper presents methods for assessment of structure and properties of thin hard coatings. The coatings were TiAlN a nc-(Ti1-xAlx)N/a-Si3N4 (nACo) were deposited on the steel substrate by ARC and LARC coating technology, which belong to PVD (Physical Vapour Deposition) technologies. The development of TiAlN coatings did not stop at the level of simple systems. Currently the advantages of multilayer arrangement of TiAlN coating or its combination with other thin coatings have been used extensively and the utilization of high hard nanocomposite coatings is successfully. Tools and machine parts protected deposited PVD coatings have to show sufficient quality during their application in practice. Before deposited process of coating by a coating machine the substrate must be adjusted to appropriate hardness by suitable heat treatment. Then the substrate surface is further prepared by polishing and acetone cleaning. Additional cleaning, preheating and activation of substrate surface are accomplished directly by the coating machine. A methods is available for determination of properties of the coated system that consider the fact that they have to deal with thin hard coatings only several micrometers thick. Electron microscopy was used in our study to investigate the structure of coatings. For determination of coating properties was used hardness measurement by nanoindentor. Nanoindentation method allowed us to measure hardness and modulus of elasticity of thin coatings also at low loads (in mN). Thickness measurements were carried out with Calotest. This method enables the configuration of particular layers in multilayer coating. The wear resistant of coated materials was tested by Rockwell test. This test is based on forcing the Rockwell indenter into a surface of the specimen using a constant load. The indentation test results in formation and increase of cracks. Resistance to increase of these cracks along the interface is adhesion criterion of coating to the substrate. HF scale used for evaluation of coatings quality. The result of this test was estimate of adhesive – cohesive behaviour coatings. Wear tracks after several tests was evaluated by microscopy.
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