S.V. Fortuna

Microstructural features of wear-resistant titanium nitride coatings deposited by different methods☆

Titanium nitride, TiN, is used as wear protective and decorative coatings in various applications. These coatings are deposited by standard industrial methods such as chemical and physical vapor deposition (CVD and PVD, respectively), including magnetron sputtering or its modifications [e.g. the plasma-enhanced magnetron sputtered deposition (PMD) method]. The coatings have different microstructures (size and morphology of grains, orientation, dislocation structure, residual stress, etc.) depending on the method used and the deposition regime. The results of comparative transmission electron microscopy (TEM) investigations of the microstructure of thin TiN coatings deposited by classical CVD and PVD, including PMD, are presented. The microstructure was studied in sections perpendicular and parallel to the coating surface. The grain size was estimated from dark field images and the residual stress was determined using the bend extinction contours in the bright field images. It was found that the coatings deposited by PVD and CVD methods have different grain microstructures and residual stresses. The CVD coatings have an equiaxed microcrystalline structure with very low levels of the local residual stress. The mean grain size is 0.4–0.6 μm. The PVD coatings (Balzers and Metaplas) have a non-equilibrium submicron grain structure with a high level of the local residual stress equal to 0.06–0.08E, where E is Youngs modulus, and a mean grain size of 0.1–0.2 μm in the section parallel to the coating surface. The PMD coating structure is highly non-equilibrium nanocrystalline, with a very high level of residual stress equal to 0.13E and a much finer grain size of 0.06 μm.

Formation of intermetallic layers at high intensity ion implantation

The experimental results are presented on a study of intermetallic phase formation in the surface zone of metal target at high intensity ion implantation. High intensity ion implantation allow to obtain the surface-alloyed layers of a much greater thickness in comparison with ‘ordinary’ ion implantation. Pure polycrystalline nickel was chosen as the target. The nickel samples were irradiated with the aluminum ions using the vacuum-arc ion beam and plasma flow source ‘Raduga-5’. The RBS and TEM were used for the investigations presented. It was established that the fine dispersed intermetallic precipitates are formed in the surface alloyed nickel layer. The alloyed layer thickness is equal to 150 nm and more, while the ion projected range that is equal to 70 nm. Compositions of these intermetallic precipitates are close to Ni3Al and NiAl phases. The solid solution of aluminum in nickel is also formed. The depth dependence of the formation of intermetallic phases can be deduced from the Ni–Al phase diagram.

A transmission electron microscope study of the long-range effect in titanium nitride after metal ion implantation

Abstract The improvement in the properties of tools and components after ion implantation is the result of specific structural-phase states developed both in the implanted zone (IZ) and beyond into the implantation-affected zone (IAZ). The formation of defect structures beyond the implanted zone is called the long-range effect and occurs both in metals having high plasticity and low yield strength and in high-strength materials. In the present work, the microstructure of TiN coatings deposited by PVD and CVD methods is studied by transmission electron microscopy. Before dual implantation with Ni and Ti ions the PVD coating has a highly non-equilibrium submicron crystal structure with a high level of local residual stress, whereas the CVD TiN coating has a microcrystalline structure with low internal residual stress. Implantation into PVD TiN causes a relaxation of the local stress in the IZ and beyond. In contrast, in CVD TiN ion implantation leads to the development of subgrains, both within the IZ and immediately below it, in the IAZ of the coating. No additional phases are formed in either case. A possible mechanism for explaining the formation of the defect structure beyond the IZ is introduced. This is based on the emission of a dislocation flux from stress maxima developed at the IZ–IAZ interface in the form of mezo-bands.

High-intensity ion implantation: A technique to form finely dispersed intermetallic compounds in surface layers of metals

The results of experimental investigations of microstructure and phase composition of surface ion-alloyed layers of nickel, titanium, and iron formed under the conditions of high-intensity aluminum-ion implantation are presented. It is established that aluminum-ion implantation under high-intensity modes makes it possible to form finely-dispersed intermetallic phases of Me3Al (Me = Ni, Ti, Fe) and MeAl (Ni, Ti), as well as solid solutions of a composition variable with respect to depth in the surface layers measuring up to 2000 nm. It is shown that the average grain-size of intermetallic phases formed in ion-alloyed layers is 20–80 nm. Regions of localization of the phases thus formed over the implanted layer depth are determined.

Producing titanium-niobium alloy by high energy beam

The research is involved in producing a Ti-Nb alloy surface layer on titanium substrate by high energy beam method, as well as in examining their structures and mechanical properties. Applying electron-beam cladding it was possible to produce a Ti-Nb alloy surface layer of several millimeters, where the niobium concentration was up to 40% at. and the structure itself could be related to martensite quenching structure. At the same time, a significant microhardness increase of 3200-3400 MPa was observed, which, in its turn, is connected with the formation of martensite structure. Cladding material of Ti-Nb composition could be the source in producing alloys of homogeneous microhardness and desired concentration of alloying niobium element.

STRUCTURAL AND PHASE TRANSFORMATIONS IN Ni3Fe DURING HIGH-DOSE ION IMPLANTATION

The results are given for experimental studies of the structural-phase state formed in the surface and nearsurface layers of a disordered polycrystalline Ni3Fe alloy during high-dose ion implantation. The studies used Auger electron spectroscopy, transmission electron microscopy, x-ray structural analysis, and microhardness measurements. The ion implantation was done using the “Raduga” vacuum arc source with a multicomponent cathode of composition Zr (89.5 wt. %)+C+N+O with an acceleration voltage of 50 kV. The implanted ion dose was varied in the range (6.0·1016–6.0·1017) ions/cm2. It was established that in the surface layer which is alloyed during ion implantation there is amorphization with simulataneous formation of finely dispersed ZrO2 particles whose dimensions increase with increasing implanted ion dose; this is accompanied by an increased internal mechanical stress. Beyond the ion-implanted layer a sublayer about 10 μm thick with a high dislocation density is formed (the “long-range action” effect). The results of microhardness measurements correlate with the data from structural studies.