Influence of grain boundaries on the radiation-induced defects and hydrogen in nanostructured and coarse-grained tungsten

Abstract We have studied the influence of grain boundaries (GBs) on the radiation-induced defect evolution and on H retention at 300 K, both experimentally and by computer simulations. For this purpose, coarse-grained tungsten (CGW) and nanostructured tungsten (NW) samples were implanted with H and C ions at energies of 170 keV and 665 keV respectively. Three different sets of experiments were carried out: (i) H single implantation, (ii) C and H co-implantation and (iii) C and H sequential implantation. Computer simulations were performed by using the Object Kinetic Monte Carlo (OKMC) methodology, which was parameterized by new and pre-existing Density Functional Theory (DFT) data. The three sets of experiments were simulated in monocrystalline tungsten (MW) and NW, resulting that (i) GBs have a clear influence on the amount and distribution of vacancies, being the vacancy concentration larger in NW than in MW samples, (ii) H retention is highly influenced by both the GBs themselves and the vacancy concentration, (iii) the size of H n V m clusters is slightly influenced by the presence of GBs and (iv) it can be inferred, from the comparison between experimental and computational results, that GBs act as preferential paths for H diffusion.