@misc{NaveedObrosovWeiss, author = {Naveed, Muhammad and Obrosov, Aleksei and Weiß, Sabine}, title = {Investigation of the wear resistance properties of Cr/CrN multilayer coatings against sand erosion}, series = {Conference Papers in Science}, volume = {2015}, journal = {Conference Papers in Science}, doi = {10.1155/2015/873543}, pages = {1 -- 10}, abstract = {The wear of metallic components used in gas and steam turbines due to erosive sand particles lead to a tremendous decrease in their lifetime. This wear can be reduced by the use of suitable erosion resistant coatings resulting in lower maintenance costs. In this context, multilayer Cr/CrN PVD coatings using an industrial coater was designed and applied on Inconel 718, a material which finds its application in gas turbines. A variation in the bimodal period has been induced in order to achieve an optimal coating architecture providing optimum properties needed for the erosion resistant coatings. The coating was deposited using a single Cr- target with an induction of N2 during the nitriding phase at a temperature of 480-500 °C and the coating thickness of 24-26 µm was kept constant throughout. The erosion tests were conducted at angles of 30°, 60° and 90°. The sand used for the test is an irregular shaped SiO2. The erosion tests were followed by a detailed microscopic examination of the eroded coating structure in combination with nanoindentation and scratch tests.}, language = {en} } @misc{NaveedObrosovZaketal., author = {Naveed, Muhammad and Obrosov, Aleksei and Zak, Andrzej and Dudzinski, Wlodzimierz and Volinsky, Alex A. and Weiß, Sabine}, title = {Sputtering Power Effects on Growth and Mechanical Properties of Cr2AlC MAX Phase Coatings}, series = {Metals}, volume = {6}, journal = {Metals}, number = {11}, issn = {2075-4701}, doi = {10.3390/met6110265}, pages = {265}, abstract = {Coating growth and mechanical properties of nanolamellar Cr2AlC coatings at various sputtering power were investigated in the present study. Cr2AlC coating was deposited on the IN 718 superalloy and (100) Si wafers by DC magnetron sputtering at different sputtering powers. The structure and properties were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nanoindentation. It was found that coatings had columnar structure with nanocrystalline substructure. Deposition rate increased with the sputtering power. XRD results showed the presence of the Cr2AlC MAX phase, intermetallic AlCr2 and Cr7C3 carbide phases, along with the change in preferential coating growth orientation. TEM observations confirmed the occurrence of these phases, and the SAED patterns demonstrated significant texture of the coatings. Hardness values were measured in the range between 11-14 GPa, showing a slight increase with the sputtering power.}, language = {en} } @misc{ObrosovNaveedVolinskyetal., author = {Obrosov, Aleksei and Naveed, Muhammad and Volinsky, Alex A. and Weiß, Sabine}, title = {Substrate Frequency Effects on CrxN Coatings Deposited by DC Magnetron Sputtering}, series = {Journal of Materials Engineering and Performance}, volume = {26}, journal = {Journal of Materials Engineering and Performance}, number = {1}, issn = {1544-1024}, doi = {10.1007/s11665-016-2426-4}, pages = {366 -- 373}, abstract = {Controlled ion bombardment is a popular method to fabricate desirable coating structures and modify their properties. Substrate biasing at high frequencies is a possible technique, which allows higher ion density at the substrate compared with DC current bias. Moreover, high ion energy along with controlled adatom mobility would lead to improved coating growth. This paper focuses on a similar type of study, where effects of coating growth and properties of DC magnetron-sputtered chromium nitride (CrxN) coatings at various substrate bias frequencies are discussed. CrxN coatings were deposited by pulsed DC magnetron sputtering on Inconel 718 and (100) silicon substrates at 110, 160 and 280 kHz frequency at low duty cycle. Coating microstructure and morphology were studied by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), scratch adhesion testing and nanoindentation. Results indicate a transformation of columnar into glassy structure of CrxN coatings with the substrate bias frequency increase. This transformation is attributed to preferential formation of the Cr2N phase at high frequencies compared with CrN at low frequencies. Increase in frequency leads to an increase in deposition rate, which is believed to be due to increase in plasma ion density and energy of the incident adatoms. An increase in coating hardness along with decrease in elastic modulus was observed at high frequencies. Scratch tests show a slight increase in coating adhesion, whereas no clear increase in coating roughness can be found with the substrate bias frequency.}, language = {en} } @misc{ObrosovGulyaevZaketal., author = {Obrosov, Aleksei and Gulyaev, Roman and Zak, Andrzej and Ratzke, Markus and Naveed, Muhammad and Dudzinski, Wlodzimierz and Weiß, Sabine}, title = {Chemical and Morphological Characterization of Magnetron Sputtered at Different Bias Voltages Cr-Al-C Coatings}, series = {Materials}, volume = {10}, journal = {Materials}, number = {2}, issn = {1996-1944}, doi = {10.3390/ma10020156}, pages = {156}, abstract = {MAX phases (M = transition metal, A = A-group element, and X = C/N) are of special interest because they possess a unique combination of the advantages of both metals and ceramics. Most attention is attracted to the ternary carbide Cr2AlC because of its excellent high-temperature oxidation, as well as hot corrosion resistance. Despite lots of publications, up to now the influence of bias voltage on the chemical bonding structure, surface morphology, and mechanical properties of the film is still not well understood. In the current study, Cr-Al-C films were deposited on silicon wafers (100) and Inconel 718 super alloy by dc magnetron sputtering with different substrate bias voltages and investigated using Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD), Atomic Force Microscopy (AFM), and nanoindentation. Transmission Electron Microscopy (TEM) was used to analyze the correlation between the growth of the films and the coating microstructure. The XPS results confirm the presence of Cr2AlC MAX phase due to a negative shift of 0.6-0.9 eV of the Al2p to pure aluminum carbide peak. The XRD results reveal the presence of Cr2AlC MAX Phase and carbide phases, as well as intermetallic AlCr2. The film thickness decreases from 8.95 to 6.98 µm with increasing bias voltage. The coatings deposited at 90 V exhibit the lowest roughness (33 nm) and granular size (76 nm) combined with the highest hardness (15.9 GPa). The ratio of Al carbide to carbide-like carbon state changes from 0.12 to 0.22 and correlates with the mechanical properties of the coatings. TEM confirms the columnar structure, with a nanocrystalline substructure, of the films.}, language = {en} } @misc{ObrosovGulyaevRatzkeetal., author = {Obrosov, Aleksei and Gulyaev, Roman and Ratzke, Markus and Volinsky, Alex A. and Bolz, Sebastian and Naveed, Muhammad and Weiß, Sabine}, title = {XPS and AFM Investigations of Ti-Al-N Coatings Fabricated Using DC Magnetron Sputtering at Various Nitrogen Flow Rates and Deposition Temperatures}, series = {Metals}, volume = {7}, journal = {Metals}, number = {2}, issn = {2075-4701}, doi = {10.3390/met7020052}, pages = {52}, abstract = {Ti-Al-N coatings were deposited by direct current magnetron sputtering (DCMS) onto IN 718 at different nitrogen flow rates and deposition temperatures. The coatings' properties were characterized using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) as well as nanoindentation. It was found that higher deposition temperature leads to higher surface roughness and nitrogen flux influences the shape of grains. According to XPS, the bonding structure of all coatings exhibited the (Ti,Al)N phase. Mechanical properties depend on the Al content within the films. The coating with the best mechanical properties (deposited at 500 °C and 20 standard cubic centimeters per minute (sccm)) was further deposited onto tungsten carbide (WC) cutting tools for cylindrical turning experiments. A quasi-constant flank wear was observed until a machining volume of 23,500 mm³.}, language = {en} } @misc{ObrosovSutyginaVolinskyetal., author = {Obrosov, Aleksei and Sutygina, Alina and Volinsky, Alex A. and Manakhov, Anton and Weiß, Sabine and Kashkarov, Egor B.}, title = {Effect of Hydrogen Exposure on Mechanical and Tribological Behavior of CrₓN Coatings Deposited at Different Pressures on IN718}, series = {Materials}, volume = {10}, journal = {Materials}, number = {5}, issn = {1996-1944}, doi = {10.3390/ma10050563}, pages = {563}, abstract = {In the current study, the properties of the CrₓN coatings deposited on the Inconel 718 superalloy using direct current reactive magnetron sputtering are investigated. The influence of working pressure on the microstructure, mechanical, and tribological properties of the CrₓN coatings before and after high-temperature hydrogen exposure is studied. The cross-sectional scanning electron micrographs indicate the columnar structure of the coatings, which changes from dense and compact columns to large columns with increasing working pressure. The Cr/N ratio increases from 1.4 to 1.9 with increasing working pressure from 300 to 900 mPa, respectively. X-ray diffraction analysis reveals a change from mixed hcp-Cr₂N and fcc-CrN structure to approximately stoichiometric Cr₂N phase. After gas-phase hydrogenation, the coating deposited at 300 mPa exhibits the lowest hydrogen absorption at 600 °C of all investigated coatings. The results indicate that the dense mixed cubic and hexagonal structure is preferential for hydrogen permeation resistance due to the presence of cubic phase with higher packing density in comparison to the hexagonal structure. After hydrogenation, no changes in phase composition were observed; however, a small amount of hydrogen is accumulated in the coatings. An increase of coating hardness and elastic modulus was observed after hydrogen exposure. Tribological tests reveal that hydrogenation leads to a decrease of the friction coefficient up to 20\%-30\%. The best value of 0.25 was reached for hydrogen exposed CrₓN coating deposited at 300 mPa.}, language = {en} } @inproceedings{ObrosovKashkarovWeissetal., author = {Obrosov, Aleksei and Kashkarov, Egor B. and Weiß, Sabine and Volinsky, Alex A.}, title = {Mechanical and tribological behaviour of hydrogenated CrxN coatings deposited at different pressure and voltages on IN718}, series = {American Advanced Materials Congress 2016}, booktitle = {American Advanced Materials Congress 2016}, editor = {Tiwari, Ashutosh}, publisher = {VBRI Press}, address = {Link{\"o}ping}, isbn = {978-91-88252-03-6}, abstract = {Hydrogen degradation is a serious problem in industrial applications like power plants (boilers, turbines), marine structures, car and aircraft components, as it leads to failures as well as to deterioration of properties. Inconel 718 is one of the most commonly used materials for these applications. Different metal nitrides like TiN coatings have been deposited in past to prevent hydrogen degradation, which are also known for their high hardness and good wear resistance [1, 2]. However, reports on hydrogen degradation of CrN coatings, which shows better oxidation and corrosion resistance, higher temperature stability and lower friction coefficient than TiN [3, 4] has not been reported till now. Despite a lot of publications about CrN films, up to now the effect of hydrogenation on mechanical and tribological properties of CrN coatings is still not completely understood. In the current work CrxN coatings were deposited by Direct Current Magnetron Sputtering (dcMS) on Inconel 718 substrate at different chamber pressures and substrate voltages. Substrate voltage is one of the most important process parameters which determines the structure of the coating and the adhesion between substrate and coating. Simultaneously a study of the chamber pressure is also needed to understand the deposited structure and growth rate because at higher pressures the high number of argon atoms reduce the number of ionized ions available for the deposition leading to low deposition rates [5]. Gas-phase hydrogenation of the samples was performed at a temperature of 600° C and hydrogen pressure of 2 atm. It was found that CrxN coatings are resistant against hydrogen exposure as compared to uncoated surfaces. The results of changes in the mechanical, tribological properties and phase composition of the coatings after hydrogenation are discussed. Coating microstructure was studied by scanning electron microscopy (SEM). The mechanical properties of the coatings were characterized by means of nanoindentation and scratch test.}, language = {en} } @misc{ObrosovNaveedKruppetal., author = {Obrosov, Aleksei and Naveed, Muhammad and Krupp, Ulrich and Solovev, Mikhail and Weiß, Sabine}, title = {Investigation of TiAlN HiPIMS coating deposited on the newly developed Ni-based superalloy AD730}, abstract = {The development of new alloys for gas turbine engines has been focused on withstanding against increasing service temperatures. AD730™ is a recently developed nickel-based superalloy for turbine disk applications with superior properties at 700°C, which is higher than the common service temperature for IN718. Use of coatings to enhance the properties of materials, such as wear resistance is widely known in various applications. This research presents an experimental study of TiAlN coatings, deposited onto AD730 superalloy using High Power Impulse Magnetron Sputtering (HiPIMS). Phase structure and chemical composition of the TiAlN films were characterized by X-ray diffractometry. Transmission electron microscopy as well as scanning electron microscopy were used to analyze the microstructure of the coating. Mechanical properties, including hardness, Young's modulus, and adhesion strength were measured using nanoindentation und scratch test.}, language = {en} } @misc{ObrosovNaveedWeiss, author = {Obrosov, Aleksei and Naveed, Muhammad and Weiß, Sabine}, title = {Effect of pulse time on structure and mechanical properties of HPPMS deposited AlTiN coatings}, abstract = {The use of PVD AlTiN as a protective coating on cutting tools is well known. With the introduction of pulsed deposition techniques like High Power Pulsed Sputtering (HPPMS), a possibility is provided to the coating developers to design their coatings by the variation in pulse parameters. To analyze the effect of pulse time HPPMS AlTiN coatings were deposited on Si (100) as well as 100Cr6 steel plates at a temperature of 500°C in a reactive gas environment. Oscilloscope measurements depicted a change in current-voltage characteristics with variation in pulse time. This influence the coating structure, deposition rates and phase formations as well. Nanoindentation results show a variation in the mechanical properties of the coatings with the change in pulse time. This study focuses on the potential of HPPMS technology for enhancement of mechanical and structural properties of AlTiN coating.}, language = {en} } @misc{KashkarovNikitenkovSutyginaetal., author = {Kashkarov, Egor B. and Nikitenkov, Nikolay and Sutygina, Alina and Laptev, Roman and Bordulev, Yuriy and Obrosov, Aleksei and Liedke, Maciej O. and Zak, Andrzej and Weiß, Sabine}, title = {Microstructure, defect structure and hydrogen trapping in zirconium alloy Zr-1Nb treated by plasma immersion Ti ion implantation and deposition}, series = {Journal of Alloys and Compounds}, volume = {732}, journal = {Journal of Alloys and Compounds}, issn = {0925-8388}, doi = {10.1016/j.jallcom.2017.10.151}, pages = {80 -- 87}, abstract = {The effect of low energy plasma immersion ion implantation and deposition of titanium on microstructure, defect structure and hydrogen trapping in zirconium alloy Zr-1Nb was studied. Defect structure and distribution were analyzed by Doppler broadening using slow positron beam. The surface microstructure after modification is represented by nanostructured Ti grains with random orientation. The gradient distribution of titanium as well as vacancy type defects were analyzed. The concentration of vacancy type defects is rising with increasing bias voltage. Gas-phase hydrogenation of the Ti-modified Zr-1Nb alloy was performed at 400 °C for 60 min. The strong interaction of hydrogen with vacancy type defects was demonstrated. Two different changes in the defect structure after hydrogenation were observed: when a titanium film is formed on the surface (after deposition at 500 V) hydrogen trapping occurs with the formation of titanium hydride phases, while in the implanted layer (deposition at 1000 and 1500 V) hydrogen is trapped due to interaction with vacancy type defects. The physical basis of Ti diffusion and its influence on the evolution of defect structure after surface modification and hydrogenation were discussed.}, language = {en} }