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

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 HnVm 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.