Influence of high flux hydrogen-plasma exposure on the thermal shock induced crack formation in tungsten

The influence of high flux hydrogen-plasma on the thermal shock behaviour of tungsten was investigated in a combined experiment using the linear plasma device Pilot-PSI and the electron beam facility JUDITH 1. Tungsten targets were exposed to high flux hydrogen plasma, cyclic thermal shock tests and a combination of both loading conditions. The induced thermal shock crack networks and surface modifications were investigated and characterised using scanning electron microscopy (SEM), optical microscopy and laser profilometry. Comparisons of the results showed that the combination of hydrogen plasma and thermal shock loading has a significant influence on the crack pattern in terms of crack distance, width and depth. Furthermore the sequence of the different loading types is of importance. Due to the prior loading with hydrogen plasma the thermal shock cracks were not limited to the electron beam loaded area but propagated through the just plasma loaded area and even through the unexposed area at the edges of the tungsten target.

► W samples were exposed to H-plasma and cyclic thermal shock events successively.
► Preloading with H-plasma changes the thermal shock behaviour of W significantly.
► Crack parameters of H-preloaded W samples like distance, width and depth decrease.
► The damaged area increases after a preloading with H-plasma.
► H-embrittlement and super-saturation of stresses reduce the crack resistance of W.