Papers by Keyword: PVD Coating

Abstract: Material transfer is a critical tribological issue in aluminum forming processes, particularly at high temperatures. Although applying PVD or CVD coatings on the forming tool surface could be a solution to alleviate the material transfer issue, selecting an appropriate coating with sufficient tribological performance is still a challenging task. This paper aims to evaluate the tribological performance of AlCrN and TiAlN coatings against 6082-T6 aluminum alloy under dry contact conditions at 400°C by using a process centered approach. The methodological approach implies: 1. pre-processing to assess the contact conditions to be simulated and prepare the experimental samples, 2. processing where the friction tests are performed, and 3. post-processing in which test results are analyzed in terms of coating performance. The warm and hot upsetting sliding test (WHUST) is used as a tribometer in the processing step. A scaled-down version of the existing WHUST is developed to integrate into the heating chamber of Bruker UMT TriboLab for precise control of the specimen and contactor temperatures. Numerical simulation is applied to identify the WHUST parameters in the pre-processing step to reproduce severe contact conditions from the industrial forming processes. The post-processing step includes the identification of Coulomb’s coefficient of friction (COF) and the surface analysis with quantitative and qualitative techniques.

Abstract: The tool steel materials are expensive this is the reason why the lifetime increase is a goal of the production technology. The tool life is determined by the various complex mechanical, thermal, chemical, and tribological properties. Tools properties depend on the chemical composition and their microstructure. The microstructure depends on the chemical composition, the production process, the heat treatment and surface treatment technologies. The goal of this research was to increase the service lifetime of the casting mould tool. It was prepared and investigated four kinds of test specimens. The first kind of specimen was made from conventional steel (W302). It was made an austenitization (1020°C) and was cooled with 9 bar nitrogen gas to 40°C and kept for 6 minutes. The quenching was followed with three times tempering processes (570°C, 580°C, 560°C) in 2 bar N₂ gas. The second kind of test specimen was made from Unimax electro-slag remelted steel (ESR). It was made an austenitization (1020°C) and was cooled with 9 bar nitrogen gas to 40°C and kept for 6 minutes. After quenching the process continues with three times tempering (610°C, 620°C, 600°C). The third kind of test specimen Unimax a electro-slag remelted steel (ESR), to which firstly an austenitization (1020°C) was made, quenched in nitrogen gas with 9bar and then cooled in liquid nitrogen till minus 150°C. After cryogenic treatment, the process continues with three times tempering (610°C, 620°C, 600°C). The fourth kind of specimen was made by the same process as the second and after it a PVD coating process was made to coat the surface by a TiBN layer. It investigated the hardness and wear resistance of all heat-treated and surface-coated steel specimens. The comparative wear resistance testing was investigated by a ball cratering tester. The rank of the tested specimen was the next: the lowest wear resistance measured in the case of the heat-treated W302, the middle in the case of cryogenic heat-treated Unimax and the highest wear resistance earned in the case of the PVD-coated Unimax. The results of the investigations proved that the Unimax tool steel service lifetime can increase better than the conventional tool steel by heat treatment and surface treatment. The practice certified that the surface-treated Unimax tools' service lifetime is much longer than the conventional ones.

Abstract: An attempt is made in this work to improve the performance and tool life of the tungsten carbide (WC) coated aluminium chromium nitride (AlCrN) via physical vapor deposition (PVD) method. Various deposition temperatures ranging from 250, 350, 400, and 450 oC were investigated to evaluate the characteristic of coated carbide. Prior to the deposition process, WC surfaces were treated in Murakami’s solution for 15 minutes followed by Caro’s solution for 10 seconds to improve the coating adhesion on WC by the dissolution of cobalt (C); roughened the carbide surface. The thickness of the coated AlCrN increases proportional with higher deposition temperatures (from 1.14 μm to 2.18 μm) and homogenously coated. While XRD analysis observed the presence of AlN and CrN phases attributed to AlCrN coating. The hardness of the coated carbide was highest at 450 oC deposition temperature (1325 HV). The qualitative scratch test following ASTM D 3363 indicated that higher temperature (400 oC and above) provides good adhesion characteristics between AlCrN coating and WC.

Abstract: Hard coatings applied by the Physical Vapor Deposition method often provide very good mechanical properties, especially when applied to metal parts that are mentioned to withstand certain level of wear. In this study, TiN coating combined with deep rolling were applied to the investigated steel samples, prepared by powder metallurgy and subjected to contact-fatigue stress. Computational analysis of stress states in samples by the finite element method helped to reveal the behavior and formation of fatigue failures when loading samples. The results, processed in the form of fatigue curves, probabilistic Weibull curves using metallography and electron microscopy, showed a positive effect of the used coatings and their combination with other surface treatments on the contact-fatigue strength of the examined samples. Microscopic study also showed the different mechanisms of crack formation and of crack propagation rate due to contact loading of material with a laser hardened surface, which has an obvious impact on material lifetime.

Abstract: In manufacturing technology, sensors are important elements for monitoring process parameters and for recording data in the Industrie 4.0. Thin sensors manufactured by means of physical vapor deposition (PVD) offer a way to combine wear and corrosion protection on the one hand and the integration of a temperature sensor function on the other hand. For the analysis of the performance of PVD sensor coatings based on the thermoelectric effect, no standardized methods and procedures are state of the art. In this paper a measuring setup is presented, which allows reference measurements using a calibrated thermocouple and a thermographic camera besides the potential difference measurement of the sensor coating. Two measuring modes, which allow a continuous and a discontinuous measurement, are presented. The measuring methodology was evaluated using the PVD sensor coating Al₂O₃+Ni+NiCr+Al₂O₃. This multilayer sensor coating was deposited using an industrial coating unit and was tested with regard to the sensor properties. The deposition technology used for the sensor coating results in an interface without defects between the two sensor layers with a smooth transition. This provides a suitable electrical contact and a promising compound adhesion. The results show a suitable and detailed measurement of temperature and potential differences by means of calibrated measurement methods and the sensor coating. The measured results are reproducible and show a linear relationship between the potential difference and the surface temperature.

Abstract: Four hard thin coatings (TiSiN, TiN-CrN multi, AlTiN a WC) were deposited on the WC+Co substrate by cathodic arc deposition. Adhesion test of PVD coatings was evaluated by comparison failure of coating surfaces. The surface features after the Rockwell indentation test were examined by light microscopy. The results showed that the AlTiN and WC coatings exhibited acceptable failure and are appropriate for usage in practice. Unlike them, had TiSiN and TiN-CrN coatings poor adhesion, which resulted in unacceptable failure after Rockwell C test.

Abstract: Physical Vapour Deposited (PVD) coatings are used in wide range of industrial applications where requirements differ. For example, in cutting applications adhesive-abrasive wear along with high contact stresses prevail and PVD coating with thickness of ~2 μm are used. In forming applications adhesive wear usually dominates and relatively thick PVD coatings (~5 μm) are preferred. For both the applications coatings are subjected to cyclic stress and therefore it is a point of interest to learn the behaviour of PVD coatings with different thickness under cyclic loading. Cracking resistance and fatigue properties of gradient TiCN on hard metal substrate was evaluated by means of the cyclic Vickers indentation method. Hard metal was chosen as a substrate material to avoid pile-up effect and support the hard coating during indentation. The results of the single indentation Vickers test show that secondary radial and circumferential cracks appear in tested coatings already after the first indent. With increasing cycles the cracks grow up to a critical crack length after which the crack length doesn’t increase further. The tested coating thickness has no significant effect on cracking behaviour.

Abstract: For better selection of coated cutting tools, TiAlN (Ti₅₀Al₅₀N) and CrAlN (Cr₅₀Al₅₀N) coatings were deposited onto ball-nose and square end mills using arc evaporation, and their cutting performances were evaluated using steel workpieces of various hardnesses. In particular, cutting tests were performed on three types of workpieces, made from S50C, SKD61, and SKD11 steels, having Brinell hardness numbers of HB220, HRC40, and HRC60, respectively. The results of the cutting experiments were elucidated and discussed in terms of the mechanical properties and anti-oxidation resistances of the different coatings. The results revealed that TiAlN-coated square end mills at high cutting speeds (V = 200 m/min ) had superior performance when used on steels with high hardness (SKD11), whereas CrAlN-coated ball-nose end mills were superior when used on low hardness steel (S50C). Therefore, CrAlN-coated ball-nose end mills are concluded to be suitable for the machining of low hardness steels, whereas TiAlN-coated square end mills are preferable for the machining of high hardness steels (SKD11).

Abstract: The aim of the study was to validate non-destructive diagnostics of surface of tools and metal sheets after steel grit blasting. We used replicas produced by fy Struers, known under commercial name RepliSet-F5. The replicas were extracted from surfaces of thirty specimens with PVD coatings (CrN, TiCN) and from flat specimens after steel grit blasting. Qualitative and quantitative parameters characteristic of surface morphology were determined by means of an optical profilometer, and confocal microscope was used for surface contactless metrology measurements. We observed a qualitative coincidence of morphological images of original surfaces and replicas. The values of the quantitative parameter Sa (Arithmetic mean height according to ISO 25178) of surfaces and replicas extracted from them differed at the second decimal place. Replicas document well the surface morphology and allow one to obtain information about the state of surface in difficult-to-access sites of the tools or constructions.

Abstract: The requirements on tools used in the production of coins include high quality and reliability, dependent on the materials from which they are made, on manufacturing technology, heat treatment and final operations achieving functional area modification. Properties of the material of coins vary during their production and there is the so-called operational degradation that can be caused by an inappropriate technology of manufacturing. The quality of coining dies is expressed as their service life which ranges from approximately one hundred thousand to one million pieces of coins produced. Therefore, it is necessary to pay enough attention to the service life of coining dies. Surface treatment in the form of the application of hard PVD coatings is one of the ways of increasing the durability of coining die.In the present study, we analysed and tested three types of coatings deposited onto coining dies made of tool steel.