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Nanoscale multilayer coatings (NMCs) with different crystal structures are considered as capable of self-healing after radiation damage due to the recombination of vacancies and interstitials. This work is focused on a defect distribution study of NMCs based on Zr/Nb layers (25/25 nm and 100/100 nm) after proton irradiation. Coatings with a total thickness of 1.05 ± 0.05 µm were irradiated by 900-keV protons using a pelletron-type electrostatic accelerator with an ion current of 2 µA for durations of 60 min to 120 min. The influence of the irradiation effect was studied by X-ray diffraction analysis (XRD), glow discharge optical emission spectrometry (GD–OES), and Doppler broadening spectroscopy using a variable energy positron beam. The results obtained by these methods are compatible and indicate that defect concentration of Zr/Nb NMCs remains unchanged or slightly decreases with increasing irradiation time.

Abstract: The corrosion and tribocorrosion behaviour of thermally sprayed coatings and thermally sprayed/nanoscale multilayer CrN/NbN coatings deposited on steel specimens has been studied in 3.5% NaCl solutions. The thermally sprayed coatings are bulk HVOF deposits with nominal composition WC–12Co and Cr3C2–37WC–18Me, while the nanoscale multilayer deposit, topping the thermally sprayed ones, is a CrN/NbN coating, obtained by PVD magnetron sputtering technique. Combined wear–corrosion conditions have been achieved by sliding an alumina antagonist on the lateral surface of coated steel cylinders, during their exposure to the aggressive solution. Polarization curves recorded after 1h of immersion and polarization resistance values monitored during 3days exposures showed that under free corrosion conditions Cr3C2–37WC–18Me always exhibits low corrosion rates and efficiently protects the underlying steel substrate from corrosion. Even on WC–12Co-coated specimens, low corrosion rates are measured at long immersion times. Both cermet coatings suffer severe corrosion attack under tribocorrosion conditions. On the contrary, the duplex nanoscale multilayer CrN/NbN/WC–12Co deposit affords very good corrosion resistance both in the absence and in the presence of wear, within the studied exposure period. SEM observations and EDS analyses have also been carried out to characterize the original powder and coating microstructures and to assess the damage extent at the end of the corrosion and tribocorrosion tests. [Copyright &y& Elsevier]

The Stationary Shoulder Friction Stir Welding (SS-FSW) technique benefits from reduced heat input, improved mechanical properties and surface finish of the weld, avoiding the need for post weld processing. Coatings on the tool probe and the shoulder for welding of aggressive Aluminium alloys have rarely been successful. Such coatings must be well adherent and inert. In this study, coated tools were used for SS-FSW of AA6082-T6 alloy. Performance of a nanoscale multilayer TiAlN/VN coating deposited by High Power Impulse Magnetron Sputtering (HIPIMS) technology was compared with amorphous Diamond Like Carbon (a-C:H) by Plasma Assisted Chemical Vapour Deposition (PACVD), AlTiN deposited by arc evaporation and TiBCN along with TiB2 produced by Chemical Vapour Deposition (CVD) methods. The TiAlN/VN coating was found to have low affinity to aluminium, acceptable coefficient of friction and provided excellent weld quality by inhibiting intermixing between the tool and workpiece materials resulting in a significant reduction in tool wear. [ABSTRACT FROM AUTHOR]

Nanoscale multilayer coatings (NMCs) with different crystal structures are considered as capable of self-healing after radiation damage due to the recombination of vacancies and interstitials. This work is focused on a defect distribution study of NMCs based on Zr/Nb layers (25/25 nm and 100/100 nm) after proton irradiation. Coatings with a total thickness of 1.05 ± 0.05 µm were irradiated by 900-keV protons using a pelletron-type electrostatic accelerator with an ion current of 2 µA for durations of 60 min to 120 min. The influence of the irradiation effect was studied by X-ray diffraction analysis (XRD), glow discharge optical emission spectrometry (GD–OES), and Doppler broadening spectroscopy using a variable energy positron beam. The results obtained by these methods are compatible and indicate that defect concentration of Zr/Nb NMCs remains unchanged or slightly decreases with increasing irradiation time. [ABSTRACT FROM AUTHOR]