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Effect of Hydrogen Exposure on Mechanical and Tribological Behavior of CrxN Coatings Deposited at Different Pressures on IN718

1
Chair of Physical Metallurgy and Materials Technology, Brandenburg Technical University, Cottbus 03046, Germany
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Department of General Physics, National Research Tomsk Polytechnic University, Tomsk 634050, Russia
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Department of Mechanical Engineering, University of South Florida, Tampa, FL 33620, USA
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Laboratory of Inorganic Nanomaterials, National University of Science and Technology “MISiS”, Moscow 119049, Russia
*
Author to whom correspondence should be addressed.
Academic Editor: Silvia Gross
Materials 2017, 10(5), 563; https://doi.org/10.3390/ma10050563
Received: 28 March 2017 / Revised: 5 May 2017 / Accepted: 12 May 2017 / Published: 20 May 2017
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. View Full-Text
Keywords: CrxN coatings; PVD; hydrogenation; tribology; mechanical properties; GDOES CrxN coatings; PVD; hydrogenation; tribology; mechanical properties; GDOES
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Obrosov, A.; Sutygina, A.N.; Volinsky, A.A.; Manakhov, A.; Weiß, S.; Kashkarov, E.B. Effect of Hydrogen Exposure on Mechanical and Tribological Behavior of CrxN Coatings Deposited at Different Pressures on IN718. Materials 2017, 10, 563.

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