Temperature dependence of hydrogen depth distribution in the near-surface region of stainless steel

• The depth profile of hydrogen on a SUS was investigated at various temperatures.
• Hydrogen was predominantly distributed in the region shallower than 10 nm.
• Hydrogen was found to also exist in a deeper region (>30 nm).
• Both bulk and surface components gradually decreased as the temperature rose.
• The distribution of the desorption energy of the surface hydrogen was discussed.

The depth profile of hydrogen at a type 304 stainless steel surface was investigated with 1H(15N, αγ)12C nuclear reaction analysis at various temperatures. Hydrogen was predominantly distributed in the region shallower than 10 nm (surface hydrogen) with an area density of ∼1 × 1016 cm−2. Hydrogen was found to also exist in a deeper region (>30 nm) with a constant volume density of ∼4 × 1020 cm−3 (bulk hydrogen). While both bulk and surface components gradually decreased as the temperature rose, part of the intensities remained even at 975 K. From the temperature dependence of the amount of the surface hydrogen, the distribution of the activation energy for desorption is discussed.