Development of modifying compounds for multilayer nano-structured coatings for cutting tools

The subject of this study was to research and develop modified multilayer nanostructured wear-resistant coatings (NWC) for cutting tools. NWC are formed through the innovation process of filtered cathodic vacuum-arc deposition (FCVAD). The processes of FCVAD allow forming NWCs by filtering vapour-ion flow of macro/micro particles in the plasma torch of vacuum arc, using the plasma duct of special structure isolated from the station chamber, when the angle of rotation of the plasma stream is 120°. This work presents the configuration of the system, alongside with the influence of process parameters on the output. The topology of the coatings is presented together with the hardness and a comparison between standard physical vapour deposition (arc PVD) and FCVAD coating technologies. Machining tests were undertaken in turning of standard HB200 steel and heat resistant nickel alloy. The results are presented in terms of tool flank wear. It is shown that the application of the NWC secured 2-6 fold extended tool lif

Development of wear-resistant coatings compounds for high-speed steel tool using a combined cathodic vacuum arc deposition

This article presents the work on wear-resistance coatings (WRC), formed on the working surfaces of HSS tools, in order to increase their efficiency. The wear-resistant complex includes nitride layer, which increases the plastic strength of the HSS tool cutting wedge and cutting tool wear resistance, as well as a three-layer nano-structured composite coating that increases tool life. The equipment for the processes of ion nitriding in the gas plasma and the formation of nano-structured multi-layer composite coatings in the filtered metal-gas plasma cathode vacuum arc discharge has been developed. Particular attention was paid to the regularities in the formation of the nitride layer and optimization of its parameters and structure, together with the study of the properties and structure of functional coating layers, depending on the parameters of the deposition process. The parameters of the combined cathodic vacuum arc processing (CCVAP), provides minimum intensity of tool wear during the cutting tests. Sample of coated tools were used to conduct a certification of the developed WRC. This allowed determining the optimal parameters WRC that provided the maximum increase in tool life for a variety of cutting conditions. The outcomes are compared with uncoated HSS tool and standard commercial coatings

The Optimization of Port Charge Rates on Inland Waterways

Inland waterways play an important role in the transport system of the country because of their ability to provide large volumes of traffic at low cost. The port charges are an important source of financial resources for the infrastructure development of inland waterways and river ports. The most optimal port charge rate can be determined only by appropriate economic and mathematical models. Such models are built and investigated first in general form, then the necessary condition of port charge rate optimality is found. This optimal rate is a fixed point of continuous mapping, which translates non-empty compact convex set in itself. The optimization of port charge rates by the criterion of maximum profit at different costs and competitors rates is shown on corresponding visual charts of dependencies. The models of port charge rates optimization on internal waterways under three various possible principal kinds of dependence of ship calls from these rates (linear, convex up, convex down) are also built. The relevant optimal values of port charge rates and the related amounts of ship calls and financial results are analytically determined. It makes possible to choose the adequate for real data type of dependence and determine its parameters by methods of mathematical statistics, then substitute these values into the appro­priate formulas to obtain optimal values of port charges. This approach can be used to facilitate the development of inland waterways.&nbsp

Wear Mechanism and Failure of Carbide Cutting Tools with Nanostructured Multilayered Composite Coatings

The aim of this work is to study physical and chemical properties of nanostructured multi-layered composite coating based on three-layered architecture, deposited to a carbide substrate, as well as to study the mechanism of wear and failure of coated carbide tools under the conditions of stationary cutting. The coating were obtained by the method of filtered cathodic vacuum arc deposition (FCVAD). Here, the microstructure of coating as well as its hardness, strength of the adhesive bond to the substrate, chemical composition and phase composition were investigated on a transverse cross-section of experimental samples. The studies of cutting properties of the carbide inserts with developed coatings was conducted on a lathe in longitudinal turning of steel C45 (HB 200). The analysis of mechanisms of wear and failure of coated tool was carried out, including the processes of diffusion and oxidation in the surface layers of the coated substrate. Tools with harder and less ductile coatings showed less steady kinetics of wear, characterized by sharp intensification of wear and failure in transition from “steady” to drastic wear, i.e., at the end of the tool life. The X-ray microanalysis showed a considerable increase in oxygen content in the transverse cracks in the coating

Оценка эффективности копаксона у больных с ремиттирующим типом течения рассеянного склероза

We investigated the effectiveness of Copaxone in patients with relapsing-remitting multiple sclerosis for 3 and 5 years. Significant improvement found the decrease of the frequency of clinical exacerbations and delay the accumulation of physical disability during treatment period.Проанализированы результаты наблюдения за больными ремиттирующим рассеянным склерозом, получающими непрерывное лечение копаксоном в течение 3 и 5 лет. Обнаружено статистически значимое снижение частоты обострений в обеих группах больных и отсутствие нарастания инвалидизации в течение всего периода лечения

Effect of adhesion and tribological properties of modified composite nano-structured multi-layer nitride coatings on WC-Co tools life

The paper presents the results of the comparative tests of carbide samples with multilayered nano-structured coatings based on titanium nitrides (Ti-TiN-(Ti,Cr,Al,Si)N) and zirconium nitrides (Zr-ZrN-(Nb,Zr,Cr,Al)N and Zr-ZrN-(Zr,Al,Si)N). The phase composition and microstructure of these coatings were studied. The scratch test method was applied to study the adhesion bond strength to the substrate and the coating fracture patterns. The tribological parameters of the coated samples were studied at temperatures of 450°C-900 °C. The cutting properties of the tools with the coatings under study were investigated in turning AISI 321 steel. Various coating parameter effects on the cutting tool life were studied

Comparison of the Mechanical Properties and Corrosion Resistance of the Cr-CrN, Ti-TiN, Zr-ZrN, and Mo-MoN Coatings

In this work, the mechanical properties and corrosion resistance of Cr-CrN, Ti-TiN, Zr-ZrN, and Mo-MoN coatings deposited by the physical vapor deposition (PVD) method on Ti-6Al-4V alloy were compared. The phase composition of the coatings, their hardness and fracture resistance in scratch tests were determined, and their structural characteristics were also studied using a scanning electron microscope (SEM) and a transmission electron microscope (TEM). The diffraction spectra were made using an automatic X-ray diffractometer. The value of the adhesive component of the friction coefficient f adh of the pair “coated and uncoated Ti-6Al-4V alloy” was investigated in the temperature range of 20–900°C. The lowest value of f adh was detected for the Zr-ZrN coating at temperatures below 400°C, while for the Mo-MoN coating it was observed at temperatures above 700°C. The polarization curves of the coated and uncoated samples were performed in a 3% aqueous NaCl solution. The level of corrosion of the Ti-6Al-4V alloy samples with Cr-CrN, Ti-TiN, Zr-ZrN, and Mo-MoN coatings was evaluated using the Tafel extrapolation method, the iteration method, and the polarization resistance method. The results obtained with these methods indicate that the Zr-ZrN coated sample has the best corrosion resistance in the 3 wt.% NaCl solution, with a corrosion current density of 0.123 µA/cm 2

Multilayer composition coatings for cutting tools: formation and performance properties

The paper considers the concept of a multi-layer architecture of the coating in which each layer has a predetermined functionality. Latest generation of coatings with multi-layered architecture for cutting tools secure a dual nature of the coating, in which coatings should not only improve the mechanical and physical characteristics of the cutting tool material, but also reduce the thermo-mechanical effect on the cutting tool determining wear intensity. Here are presented the results of the development of combined methods of forming multi-layer coatings with improved properties. Combined method of forming coatings using a pulsed laser allowed reducing excessively high levels of compressive residual stress and increasing micro hardness of the multilayered coatings. The results in testing coated HSS tools showed that the use of additional pulse of laser processing increases tool life up to 3 times. Using filtered cathodic vacuum arc deposition for the generation of multilayer coatings based on TiAlN compound has increased the wear-resistance of carbide tools by 2 fold compared with tool life of cutting tool with commercial TiN coatings. The aim of this study was to develop an innovative methodological approach to the deposition of multilayer coatings for cutting tools with functional architectural selection, properties and parameters of the coating based on sound knowledge of coating failure in machining process

Effectiveness of Copaxone in patients with relapsing-remitting multiple sclerosis

We investigated the effectiveness of Copaxone in patients with relapsing-remitting multiple sclerosis for 3 and 5 years. Significant improvement found the decrease of the frequency of clinical exacerbations and delay the accumulation of physical disability during treatment period