Key Engineering Materials Vol. 674

Abstract: The research reported in this article has considered the frictional characteristics of three kinds of AMS nickel-chromium alloys that are commonly used in aerospace industry. These are alloys with additions of titanium and aluminum AMS5542, nickel-chromium alloy AMS5596, and non-magnetic, corrosion and oxidation resistant, nickel-chromium alloy AMS5599. To determine the friction coefficient two tribological tests, a strip drawing test and a pin-on-disc tribometer have been conducted. Three different friction conditions were considered, dry friction, lubrication conditions using two grades of oils used in sheet metal forming of AMS alloys. The experimental results have ascertained several relationships showing the effect of sheet metal surface roughness, lubricant conditions and sheet orientation on the value of friction coefficient in sheet metal forming processes. Different levels of normal pressure were also used in friction tests. The results further showed that the surface topography and sample orientation in the rolling direction of the sheet are significant factors that influence the friction coefficient. It has been observed that the tested AMS alloys, selected from aerospace industry applications, exhibit anisotropic resistance to the friction corresponding to the measured orientation in relation to the rolling direction of the sheet.

Abstract: Increase of energy efficiency, reliability and durability of technical systems in combination with resource conservation using environmentally friendly water-based lubricants would be an overarching goal in all tribological applications. According to this aim the objective of this work is to investigate and identify new water-based lubricants containing ionic liquids (ILs) to reduce friction and wear. Therefore the tribological behavior of different water-based ionic liquid mixtures, compared with a standard water based cooling lubricant emulsion, was studied using a ball-on-disk test. A three electrode setup was used to analyze the influence of different electric potentials. The results show that friction and wear can be improved by using ionic liquid. In addition, the tribological behavior can be strongly influenced by electric potentials. As tribological mechanism the attraction of cations and the formation of a triboactive layer is assumed, due to charging of the surface.

Abstract: T This paper examines the abrasive and erosive wear of duplex multilayer TiN/TiCN and TiN/TiBN coatings deposited on quenched and tempered hot work tool steel grade X37CrMoV5-1. The coatings were produced by duplex method composed of a plasma nitriding and pulsed direct current (DC) plasma-assisted chemical-vapor deposition (PACVD). Measurements of the thickness of the deposited coatings were determined by calotest. Adhesion of the layers were determined by the Rockwell-C indentation test and the microhardness profile in a diffusion zone beneath the surface was determined by Vickers method (HV 0.05). Tests of abrasive wear resistance were carried out using "Dry Sand-Rubber Wheel” method. Test of erosion resistance of the base material and of duplex layers was carried out by exposing test samples to impact erosion of fine sand particles and determining the loss of mass after 60 minutes of wear. Worn surface were analysed by stereomicroscopy. The results show increasing wear resistance of duplex multilayer coatings of TiN/TiCN and TiN/TiBN in relation to plasma nitrided and uncoated steel (in the quenched in tempered condition).

Abstract: Tribological tests were conducted using a pin-on-disc tester. In the experiment, a steel disc of hardness 40 HRC was put in contact with a steel ball of hardness 62 HRC. Disc samples were prepared in order to obtain very similar values of the Sa parameter, smaller than 0.5 μm. Different methods of preparing smooth surfaces were used. Dry tests using similar contact conditions were carried out. During tests, the friction force was monitored as a function of time. Wear of discs and balls was measured after the test using white light interferometer. In order to decrease variation of the experimental results, during tests the wear debris was continuously removed from the disc surface. It was shown that type of treatment play a role on tribological behavior of sliding pairs.

Abstract: This article deals with the machining of Inconel 718 alloy. In the research, several carbide milling tools with different carbide grades and coatings were used. The main aim is compare all cutting tools in terms of their cutting tool life during machining super alloy Inconel 718. This material is used for highly stressed components in the nuclear industry, such as combustion turbine. Due to its rapid hardening and high heat generation, it is very problematic to machining. The right choice of appropriate carbide grade is necessary to achieve high-quality cutting wedge, which is important for good adhesion of the coating. The results of this work will be used for further research and development of cutting tools for machining Inconel 718.

Abstract: Unsaturated polyester resins (UPRs) are most commonly used coating materials on steel among thermosetting polymers because of their low cost, easy application and good performance properties. However, UPRs show insufficient fire-resistance in respect of relatively high flammability accompanied by smoke production upon burning due to aromatic groups in the structure. Consequently, improving the fire retardancy of UPRs for extending their application becomes pivotal. Fire retardants (FRs) are widely used in polymers because they prolong the time to ignition, slow down the rate of flame spread, and generate less heat and smoke or toxic fume compared with the unmodified polymers. It has been a challenge to develop a cost effective, environmentally friendly fire retardant system which minimizes the negative effect on performance properties of the polymers [1 - 4].

Abstract: The main objective of this paper is to offer ion-plasma technology for production of Ti (titanium) and titanium nitride (TiN) erosion-resistant nanocoatings for the machine building products, which ensures the coatings with optimum and stable properties. As a result of experiments and processing experimental data the optimum composition of ion-plasma titanium and titanium nitride nanocoatings was obtained and offered.The approbation of the developed technology on the existing machine building products (compressor blade of the helicopter gas turbine; base material: Incoloy 800) was carried out. The comparative study on the influence of the coating on the surface quality, coefficient of friction, adhesion strength and erosion resistance was done. For evaluation of the obtained nanocoating surface’s quality 2D and 3D surface description approaches were applied. Achieved results prove the effectiveness of offered ion-plasma technology for production of titanium and titanium nitride erosion-resistant nanocoatings with appropriate and stable properties.

Abstract: The wear properties of steel dental curettes coated with wear resistant Diamond Like Carbon (DLC) and metal nitride coatings deposited by Physical Vapor Deposition (PVD) were studied by using a customized mechanical device simulating motion and load of dental curettes against human teeth. The wear surfaces were studied by optical microscopy, Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and Nanoindentation. Rockwell indentation testing was used to evaluate the coating adhesion. With the optimized combination of substrate steel and wear resistant coating reduction of 80% in the wear of instruments could be achieved.

Abstract: The present study aimed to investigate the exploitation of Concentrated Solar Power (CSP) for the in-situ production of anti-wear TiC-based surface layers onto steel substrates. For this purpose, “solar” experiments were carried out at the installations of Plataforma Solar de Almería (Spain). TiC powder was pre-deposited onto carbon steel substrates that have been subsequently exposed to concentrated solar irradiation for various dwell time values. The temperature field developed at the specimens’ surface during solar exposure was recorded in real-time by the aid of an optical pyrometer. Microscopic observations revealed the characteristic microstructure features of the hardfacing surface layers obtained and preliminary dry sliding tests performed in a pin-on-disc apparatus, allowed to estimate their machinability using conventional cutting tools.

Abstract: GaN epitaxial layers were successfully grown by hydride vapour phase epitaxy (HVPE) on β-Ga₂O₃ substrates produced by cleaving. The initial stages of GaN epitaxial growth on β-Ga₂O₃ were studied by scanning electron microscopy (SEM) and x-ray diffraction analysis (XRD). The nucleation and the transition from the nucleation layer to a continuous GaN film were studied. It was found that the growth starts with formation of small crystallites on the substrate surface. As the growth continues, crystallites transform into pyramidal islands which increase in size and merge together. It was found that the structural quality of the GaN layers rapidly improves with increasing thickness. The full width at half maximum of x-ray ω rocking curves for (0002) peak decreased from 1370 to 540 arcsec as the deposition time was increased from 30 to 120 sec. This corresponds to the variation of the nominal layer thickness from 250 nm to 1000 nm.