TY - CHAP A1 - Kashkarov, Egor B. A1 - Sutygina, Alina A1 - Nikitenkov, Nikolay A1 - Syrtanov, Maxim S. A1 - Obrosov, Aleksei ED - Tiwari, Ashutosh T1 - Microstructure changes and hydrogenation behaviour of Zr-1Nb alloy after plasma immersion titanium implantation at different time of exposure T2 - American Advanced Materials Congress 2016 N2 - 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. KW - implantation KW - titanium KW - zirconium KW - hydrogenation KW - microstructure Y1 - 2016 SN - 978-91-88252-03-6 PB - VBRI Press CY - Linköping ER -