Surface roughening and grain orientation dependence of the erosion of polycrystalline stainless steel by hydrogen irradiation

Surface roughening of polycrystalline stainless steel mirrors due to hydrogen bombardment was studied as a function of ion fluence and energy (1-4.3 x 1024 H/m2, 300-1500 eV/H). A strong micro-relief (100 nm scale) on single grains and a strong variation of the erosion depth between different grains were observed by scanning electron microscopy (SEM). A broad variation of the in-grain micro-relief was found to be independent of impact energy. The sputtering yield (Y) depends on the grain orientation, varying by a factor of about 2 for all impact energies. The correlation between surface morphology and orientation of the single grains was investigated using electron back-scattering diffraction (EBSD). Grains with nearly (1 1 1) surface orientation do not show any significant in-grain micro-relief, although they have nearly the highest Y. For other orientations close to low indexed surfaces, e.g., (3 1 1), no correlation was found between Y and roughness