@inproceedings{KashkarovSutyginaNikitenkovetal., author = {Kashkarov, Egor B. and Sutygina, Alina and Nikitenkov, Nikolay and Syrtanov, Maxim S. and Obrosov, Aleksei}, title = {Microstructure changes and hydrogenation behaviour of Zr-1Nb alloy after plasma immersion titanium implantation at different time of exposure}, 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 = {Zirconium alloys are the main construction materials of water-cooled nuclear reactors. Zirconium is used in the core of nuclear reactors as fuel element claddings due to low thermal-neutron capture cross section. Hydrogen is released in the process of water radiolysis or high-temperature oxidation of fuel claddings under loss of coolant accident (LOCA) conditions. The penetration and accumulation of hydrogen in zirconium alloys lead to degradation of their physical and mechanical properties caused by hydrogen embrittlement and delayed hydride cracking [1, 2]. Plasma immersion ion implantation (PIII) is widely used to improve the mechanical properties, corrosion and erosion resistance as well as to decrease hydrogen absorption rate of zirconium [3, 4]. During PIII, a plasma ions are accelerated by high voltage pulsed bias applied to the target. The accelerated ions penetrate in the bulk of the target and modify the deeper layers of materials. Previous studies shown that PIII of titanium improves the protection properties of Zr-2.5Nb alloy from hydrogenation [5]. Moreover, the microdroplets and ion energy have significant impact on hydrogen absorption of the alloys. However, it is necessary to understand the mechanism of hydrogen interaction with the modified layers depending on the time of implantation. In this study, titanium ions were implanted into Zr-1Nb alloy target using filtered vacuum arc source and high frequency short pulser. Coaxial plasma filter was used to reduce the number and size of microdroplets evaporated from the cathode spots. The implantation parameters are: 70 A arc current, 0.15 Pa argon pressure, 1500 V pulsed bias, 100 kHz repetition frequency, 5 μs pulse length and 5-30 min implantation time. Gas-phase hydrogenation was performed at 623 K and 2 atm. hydrogen pressure for 60 min. Surface morphology, phase composition and depth distribution of elements were investigated using scanning electron and atomic force microscopies (SEM and AFM), X-ray diffraction and glow-discharge optical emission spectroscopy (GDOES). It was revealed that the microdroplets and craters with the size of several microns are formed after titanium implantation. The number and size of craters are increased with implantation time from 5 to 30 minutes. It is assumed that the presence of craters on the surface caused by bombardment of an accelerated ion clusters, which is formed due to incorporation (condensation) and ionization of evaporated atoms near the cathode region. Furthermore, the surface becomes rougher and the microstructure changes to fine-grained with an average grain size of 50-100 nm with increase of implantation time. Hydrogenation behaviour depends on the implantation time and differs from the non-treated Zr-1Nb alloy. Hydrogen absorption rate decreases by two times with increase in implantation time from 5 to 30 min. Furthermore, hydrogen preferably accumulates in the modified layer at higher implantation time. The distribution of hydrogen tends to decrease in the depth of implanted layer. The phase state of the alloy has not changed after implantation, however, the extensive distortions of the crystal lattice are observed after hydrogenation of the non-treated and implanted for 5 min Zr-1Nb alloys.}, 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} }