The sensitivity to hydrogen induced cracking (HIC) for a carbide-rich high strength steel, that has been widely utilized to fabricate hydrogen reactors working in high temperature hydrogen environment, is evaluated using electrochemical charging method in combination with hydrogen desorption spectroscopy and various materials characterization techniques including scanning electron microscopy, focus ion beam, transmission electron microscopy, electron back scattered diffraction, etc. The effects of current density and charging duration on the formation of internal cracks and blisters on the surface were investigated. The morphologies, locations and density of cracks on the cross-section were examined in detail. The grain orientation characteristics and microstructures around the crack-tip were characterized. This enables us to clarify the crack initiation and propagation mechanisms. It was found that the cracks and blisters were easily initiated even at a very low current density (\<1 mA/cm2) and a small duration (\<30 min), when the specimens were charged in an electrolyte of 0.5 mol/L H2SO4. By increasing the current density and duration, the sizes and numbers of surface blisters tend to increase, but some of the specimens showed poor reproducibility when they were exposed to the exactly identical charging conditions. The typical morphologies and chemical compositions of inclusions were characterized, and the role of inclusions in the initiation of cracks and the formation of blisters are discussed. The HIC susceptibility of 2.25Cr-1Mo-0.25V steel clarified in the present study can provide guidance for those studies on the hydrogen embrittlement properties using electrochemical charging and also provide some implications for the explanation of room-temperature cracking phenomenon that has been encountered during the fabrication of reactors.


Effect of Electrochemical Charging on the Formation of Cracks and Blisters for 2.25cr-1mo-0.25v

Division / Sponsors: 
Pressure Vessels & Piping (PVP)


Paper Proceedings: https://asmedigitalcollection.asme.org/PVP/PVP2020/volume/83815

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