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Hydrogen generally causes lattice distortions and phase transformations when introduced into a metallic crystal lattice. For the investigations reported in this contribution, hydrogen thermal desorption analysis has been carried out to observe the influence of hydrogen desorption on the lattice of super martensitic stainless steel during continuous heating. The lattice expansion parameter and the phase transformations have been monitored during the thermal desorption process, and the influence of hydrogen on such characteristics has been evaluated. It was found that hydrogen has a significant influence on both the lattice parameter and on the thermal expansion. However, hydrogen has no influence on phase transformation during thermal desorption. The hydrogen's desorption behavior in this process was also observed and it turned out that hydrogen desorbs in two stages, i.e., firstly diffusible hydrogen and trapped hydrogen afterward.
Revealing hydrogen embrittlement mechanisms in steels is of great interest to scientists and engineers. Neutron radiography makes it possible to measure in-situ hydrogen diffusion with high spatial and temporal resolution at concentrations as low as 20 ppm. We compare hydrogen-charged specimens with hydrogen-free reference specimens and use calibration standards to normalize the hydrogen concentrations. This allows quantitative tracking of the hydrogen concentration evolution as a function of time, space and temperature. Furthermore, a view into the material with 'neutron eyes' facilitates the detection of cavities that contain molecular hydrogen.
Quantification of hydrogen diffusion Coefficients and Effusion Behaviour in Duplex Steel Weld Metals
(2012)
The object of this research project related to investigations into the qualification of flux-cored wire electrodes for the laser-GMA hybrid welding of high-alloyed steels. Because of its annular metal shell and the powdery filling, this type of wire electrode permits stable, low-spatter metal transfer comparable with that in the spray arc, particularly in the upper range of the attainable deposition rates. In contrast with this, controlled metal transfer during the deposition of solid wire electrodes is achieved using pulsed arc technology. When these filler materials are welded, the properties specific to the material and to the process have a significant influence on the weld metallurgy as well as on the process stability. Tests were carried out on the AISI 403L (X2CrNi1911) high-alloyed base material in order to investigate the transferability of the attainable material properties from GMA welding to laser-GMA hybrid welding. Four wire electrodes were used according to DIN EN 12072 and DIN EN ISO 17633: a T 19 9 L P M 1 rutile fluxcored wire designed specifically for welding in position, a T 19 9 L R M (C) 3 rutile flux-cored wire suitable for welding in the flat position, a T 19 9 L M M 1 metal-powder flux-cored wire as well as a G 19 9 L Si solid wire.