Hydrogen absorption in solution/mill annealed Alloy 600 at room temperature H2SO4 and high-temperature pressurized water

Solution/mill annealed Alloy 600 samples were cathodically polarized in a H2SO4 solution and 300 °C water. The effect of hydrogen absorption on the microstructure and oxides of the alloys was investigated. Carbon crystallization in the polarized mill annealed alloy reduced the solubility of hydrogen in this alloy and increased its mechanical strength. Hydrogen charging on the solution/mill annealed alloys at 300 °C pure water increased the oxide thickness. Compared to the uncharged alloys, in the 300 °C hydrogenated primary coolant hydrogen modified the oxides of the solution/mill annealed alloys to a Cr-rich inner/Ni-rich outer layer and a Cr-rich outer/Ni-rich inner layer oxide, respectively. ●Hydrogen decomposed the Cr23C6 carbide to form graphite in the mill annealed alloy.●Graphitization reduced the hydrogen solubility in the mill annealed alloy.●Graphitization improved the strength of the mill annealed alloy.●Hydrogen solubility in Alloy 600: solution annealed > mill annealed.●Mechanisms of oxide evolution at high-temperature solutions were introduced.