Stress analysis and microstructure of PVD monolayer TiN and multilayer TiN/(Ti,Al)N coatings

Abstract

Two PVD titanium nitride based coatings; monolayer TiN and multilayer resulting from the stacking of TiN and (Ti,Al)N layers were evaluated with respect to their stress state and microstructure. The TiN was deposited by triode evaporation ion plating, whereas the TiNy(Ti,Al)N was deposited using a reactive hybrid deposition process consisting of a combination of electron beam evaporation of Ti and DC magnetron sputtering of a Ti-Al alloy. The structural and mechanical state characterisations of the as-deposited coatings on steel substrates were performed using X-ray diffraction methods. The Bragg-Brentano geometry was used to study the texture and the sin c method was applied to obtain the stress-free lattice parameter, the Poisson's ratio 2 and the residual stresses. The monolayer exhibited a preferred orientation with (1 1 1) parallel to the surface. However, the TiN and (Ti,Al)N layers from the multilayer revealed a slightly (3 1 1) preferred orientation. All coatings were in a state of compressive stress ranging from 10.1 to 2.7 GPa, depending logically on the substrate material, layer thickness and deposition processes. The microstructure and composition of the coatings were investigated using a combination of scanning electron microscopy, plan-view and cross-sectional transmission electron microscopy, energy-dispersive spectroscopy and electron energyloss spectroscopy. The TiN exhibited a fibrous microstructure where only a few columns extended through the whole coating thickness. The TiNy(Ti,Al)N multilayer revealed a more pronounced columnar microstructure with the columns extending throughout the film thickness. Micrometer-sized macroparticles were present in the multilayer at various distances from the substrate, but never at the substrate surface. The results showed that they were incorporated in the growing film in the solid state and consisted of a core structure with equiaxed grains having the a-Ti phase and an outer layer of TiN. Evidence was found of nitrogen diffusion, presumably from both the working gas into the solidifying Ti droplet during migration to the film and through the TiN outer layer. ᮊ

Improvement of Wear Performance of Nano-Multilayer PVD Coatings under Dry Hard End Milling Conditions Based on Their Architectural Development

“…The monolayer TiAlCrN coating has a nano-crystalline structure [20] and the lowest Table 2 shows that the residual stress is highly compressive for all the coatings studied. This range of residual stress is normal for the multilayer PVD coatings deposited under conditions specified in the experimental section [22]. This is beneficial considering the heavy loaded conditions associated with the experiments performed and prevents excessive chipping of the cutting edge under operation.…”

Microstructure and mechanical properties of Ti/AlTiN/Ti-diamondlike carbon composite coatings on steel

“…Coatings' stresses depend on the layer thickness, substrate materials, and deposition temperature. De Hosson 25,26 showed that the stress in TiN and AlTiN layers is related to the coating thickness, substrate roughness, and grain size. In our experiments, the deposition parameters of the Ti and AlTiN layer are the same for different samples, therefore the stress levels in the AlTiN layer are the same.…”

Application of dilatometry with modulated temperature for thermomechanical analysis of anti-wear coating/substrate systems

“…The core is identical as in the case of the type 1 system. The physical and mathematical model that makes it possible to determine the internal thermal stresses was developed based on the [18][19][20][21][22][23][24] and classical theory of elastic-plastic materials [25]. The details of the design of the computer model used based on an FEM analysis are contained in the studies [13,26] and in the documentation of the Comsol package, with the aid of which the calculations were made.…”

“…For the purpose of computer designing and testing of the properties of coatings, simulation packages are used. They are based on the finite element method (FEM), and they make it possible to determine the state of internal stresses and strains in substrate/coating systems, which occur as a result of external thermomechanical loads [18][19][20][21][22][23][24][25]. This offers a possibility to conduct virtual in-service tests that support the selection of the optimal physico-chemical parameters and the geometry of anti-wear coatings [26][27][28].…”