Hydrogen embrittlement of tungsten using deuterium plasma charging and microscale fracture experiments

Hydrogen embrittlement (HE) is the cause of widespread failure of engineering structures. In this work we report fracture toughness and indentation experiments to study the HE of tungsten. Micro-cantilevers with pre-notches were cut using a Focus Ion Beam into single large grains that were selected by using Electron Backscatter Diffraction. The samples with micro-cantilevers were charged with deuterium plasma (max ion flux 5.0E+21 m-2s-1) and were mechanically investigated. Micro-cantilever fracture experiments at different times (i.e. 5h, 24h, 72h) after plasma charging were carried out and compared to those of uncharged micro-cantilevers. Load-displacement curves and post-mortem scanning electron microscopy showed that both charged and uncharged cantilevers exhibit plastic deformation and a blunted crack tip with a trace of crack tip sharpening. We will discuss these findings, the evolution of the unloading-reloading stiffness and correlate them to the nanoindentation results to shed more light on the hydrogen effect on the mechanical properties of tungsten.