An SEM compatible plasma cell for in situ studies of hydrogen-material interaction

Abstract

An in-situ hydrogen (H) plasma charging and in-situ observation method was developed to continuously charge materials while tensile testing them inside a scanning electron microscope (SEM). The present work will introduce and validate the setup and showcase an application allowing high-resolution observation of H-material interactions in a Ni-based alloy, the alloy 718. The effect of charging time and pre-straining was investigated.Fracture surface observation showed the expected ductile microvoid coalescence behaviour in the uncharged samples, while the charged ones displayed brittle intergranular and quasi-cleavage failure. With the in-situ images, it was possible to monitor the sample deformation and correlate the different crack propagation rates with the load-elongation curves. H-charging reduced the material ductility, while increasing pre-strain decreased hydrogen embrittlement susceptibility due to the suppression of mechanical twinning during the tensile test and, therefore, a reduction of H concentration at grain and twin boundaries. All the presented results demonstrated the validity of the method and the possibility of in-situ continuously charging of materials with H without presenting any technical risk for the SEM.

Addressing H-Material Interaction in Fast Diffusion Materials—A Feasibility Study on a Complex Phase Steel

“…The Monte-Carlo program STrim.SP 6.0D gave a r mean =1.15 nm and that 41% of the particles are implanted. From Langmuir Probe measurements [ 40 ], the ion flux was calculated to be 10 20 m −2 s −1 . Table 3 shows the recombination coefficients that were calculated according to refs.…”

“… where C max is the maximum lattice H concentration, η the ion flux, and k f the recombination coefficient. The ion flux was calculated from Langmuir Probe measurements and it is described in detail in [ 40 ]. A Monte-Carlo program, SDTrim.SP 6.0 [ 44 ] was used for estimating the implanted fraction/particle reflection yield and the mean implantation range.…”

“…Even though the effect on mechanical properties can be determined, details on crack dynamics cannot be investigated without an in-situ approach. In order to overcome these limitations, several studies have already been made with in-situ charging [ 36 , 37 , 38 , 39 , 40 ] and, in the present work, the interaction between H and a CP steel was investigated by implementing an in-situ method, which allows for in-situ H charging during a tensile test inside a scanning electron microscope (SEM).…”

Current Challenges and Opportunities Toward Understanding Hydrogen Embrittlement Mechanisms in Advanced High-Strength Steels: A Review

“…The latter was also reported to affect the activity of dislocations [76]. Recently, some novel setups combining in situ H charging (performed using H plasma [77] or electrochemically [78]) and SEM observation have been developed, which opens new possibilities of studying the H effect in a more comprehensive manner. For example, Depover and Wan et al [74,79] have shown that the H plasma charging provides the possibility to in situ charge ferritic or dual-phase materials without causing significant damages on the sample surface.…”

The role of hydrogen diffusion, trapping and desorption in dual phase steels

“…Critical hydrogen sources are present during materials processing as well as during service [12,13]. Hydrogen can be absorbed at the surface, resulting in an inhomogenous hydrogen distribution [14][15][16][17] in the steels, which is strongly influenced by plastic deformation [18], residual stresses and edge conditions [19][20][21][22]. Hydrogen desorption at room temperature is a crucial problem during testing of hydrogen embrittlement [23], which makes determining the hydrogen embrittlement threshold for a given hydrogen content difficult.…”