Mechanism of adaptability for the nano-structured TiAlCrSiYN-based hard physical vapor deposition coatings under extreme frictional conditions (original) (raw)
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An extensive study of surface/interface phenomena during wear of an adaptive TiAlCrSiYN/TiAlCrN nano-multilayer coating deposited using physical vapor deposition was undertaken under increasingly severe tribological conditions associated with dry end milling of H13 hardened tool steel. The results of FEM modeling on the temperature/stress distribution at different cutting speeds outline actual cutting conditions on the both rake and flank frictional surfaces of the coated tool. Studies of the surface/interface phenomena were made by means of SEM/high-resolution transmission electron microscopy/XPS analyses. Results demonstrate that intensifying tribological conditions facilitates improved wear performance of the adaptive coating layer. In extreme tribological conditions of ultra-performance machining (cutting speed of 500 m/min), the self-organization process establishes entirely through the formation of a nano-scale layer of dynamically regenerating tribo-ceramic films. The formation of these surface nano-films results in exceptionally efficient protection of the underlying coating layers. In response to the extreme external environment, the coating layer remained almost undamaged during a long run, demonstrating the capacity to efficiently replenish necessary tribo-ceramic films. In this way, interconnection of various surface and undersurface processes is established in the hierarchically structured tribo-films/coating layer. This integral performance is responsible for exceptional wear resistance under intensifying and extreme tribological conditions.
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This study was performed with the aim of evaluating the relative tribological behaviour at high temperature of (Ti 1−x Al x )N coatings commercially deposited on WC inserts. The (Ti 1−x Al x )N multilayered, nanostructured and single-layer coatings, which contained different Ti/Al atomic ratios varying from 7/3 to 2/3 respectively, were deposited by employing a commercial PVD cathodic arc process. The absolute hardness value for each coating is also reported and has been calculated from the Vickers microhardness measurements by using one of the models published in the literature. Standard ball-on-disc testing was conducted in order to determine friction coefficients and wear rates for these systems against a 6 mm alumina ball. These tests have been carried out in conditions that are not common in industrial use, e.g. metal cutting tools inasmuch as alumina is not a representative workpiece material. The sliding tests were performed out at 25, 500 and 700 • C with 5 N normal loads. At 25 • C, a wear volume, V , of approximately 10 −2 mm 3 was obtained for all the tested coatings. When the test temperature increased to 500 • C, the singlelayered coatings showed a wear volume of the same order of magnitude as those tested at room temperature. The multilayered coated samples decreased their wear volume by one order of magnitude, whereas the nanostructured samples showed almost no wear. At 700 • C, the wear volume values reported for all samples were similar and of the same order of magnitude as those tested at room temperature. The wear mechanism is discussed together with the morphological and compositional characteristics, determined by SEM coupled with EDX analysis.
Journal of the Korean Physical Society, 2017
With a view to improving the mechanical properties of coatings applied in the field of cutting tools and machine parts, the TiAlBN coatings were deposited by using direction-current (dc) magnetron sputtering with the various contents of nitrogen gas in an argon-nitrogen gas mixture. The structural characteristics of the coatings were determined by using X-ray diffraction, the friction coefficient, and the hardness and elastic modulus of the coatings were investigated by using a tribometer and nano-indentation. The surface morphologies and the roughnesses of the coatings were analyzed by using field emission scaning electron microscopy (FESEM) and atomic force microscopy (AFM). Additionally, the effects of nitrogen gas flow on the properties of the TiAlBN coatings were investigated. The structural characterization results revealed a typical face-centered cubic TiN structure with (111), (220), and (222) diffraction peaks. The strongest intensity in the (111) orientation was obtained for the coating prepared at a nitrogen gas flow of 4 sccm. For this kind of samples were obtained the highest values of the hardness and the stability, a low friction coefficient, and a smooth surface.
Entropy
Experimental investigations of nano-scale spatio-temporal effects that occur on the friction surface under extreme tribological stimuli, in combination with thermodynamic modeling of the self-organization process, are presented in this paper. The study was performed on adaptive PVD (physical vapor deposited) coatings represented by the TiAlCrSiYN/TiAlCrN nano-multilayer PVD coating. A detailed analysis of the worn surface was conducted using scanning electron microscopy and energy dispersive spectroscopy (SEM/EDS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy (AES) methods. It was demonstrated that the coating studied exhibits a very fast adaptive response to the extreme external stimuli through the formation of an increased amount of protective surface tribo-films at the very beginning of the running-in stage of wear. Analysis performed on the friction surface indicates that all of the tribo-film formation processes...
Tribological properties of TiBx and WC/C coatings
Ceramics– …, 2011
Tribological properties of TiB x and WC/C coatings have been studied using the ball-on-disc method at room and elevated temperatures in air to investigate their behavior under conditions approaching high performance dry cutting. The average room temperature coefficients of friction (COF) of both nanocomposite DC magnetron sputtered TiB x coatings and PECVD WC/C coatings were in the range 0.2-0.6. The lowest value of TiB x coatings of 0.16 was achieved in case of prefferentially oriented stuctures deposited at the highest negative bias. The lowest COF of WC/C was around 0.11. The increase of testing temperature to 450°C caused the increase of COF up to approximately 0.7-0.8. The experiments at elevated temperatures suggest the existence of the oxide transfer film with higher COF than that of the sliding contact without the film. Although both coating systems have relatively high COF values at elevated temperatures, they exhibit elements of some adaptive behavior.